Installation and Operation Manual for T-Pass

Installation and Operation Manual for T-Pass

Installation and Operation Manual for

T-Pass® Transmit Multicouplers

73-90-11 Series

Manual Part Number

7-9100

8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 [email protected] www.birdrf.com

Warranty

This warranty applies for five years from shipping date.

TX RX Systems Inc. warrants its products to be free from defect in material and workmanship at the time of shipment.

Our obligation under warranty is limited to replacement or repair, at our option, of any such products that shall have been defective at the time of manufacture. TX RX Systems Inc. reserves the right to replace with merchandise of equal performance although not identical in every way to that originally sold. TX RX Systems Inc. is not liable for damage caused by lightning or other natural disasters. No product will be accepted for repair or replacement without our prior written approval. The purchaser must prepay all shipping charges on returned products.

TX RX Systems Inc.

shall in no event be liable for consequential damages, installation costs or expense of any nature resulting from the purchase or use of products, whether or not they are used in accordance with instructions. This warranty is in lieu of all other warranties, either expressed or implied, including any implied warranty or merchantability of fitness. No representative is authorized to assume for TX RX Systems Inc. any other liability or warranty than set forth above in connection with our products or services.

TERMS AND CONDITIONS OF SALE

PRICES AND TERMS:

Prices are FOB seller’s plant in Angola, NY domestic packaging only, and are subject to change without notice. Federal, State and local sales or excise taxes are not included in prices. When Net 30 terms are applicable, payment is due within 30 days of invoice date. All orders are subject to a $100.00 net minimum.

QUOTATIONS:

Only written quotations are valid.

ACCEPTANCE OF ORDERS:

Acceptance of orders is valid only when so acknowledged in writing by the seller.

SHIPPING:

Unless otherwise agreed at the time the order is placed, seller reserves the right to make partial shipments for which payment shall be made in accordance with seller’s stated terms. Shipments are made with transportation charges collect unless otherwise specified by the buyer. Seller’s best judgement will be used in routing, except that buyer’s routing is used where practicable. The seller is not responsible for selection of most economical or timeliest routing.

CLAIMS:

All claims for damage or loss in transit must be made promptly by the buyer against the carrier. All claims for shortages must be made within 30 days after date of shipment of material from the seller’s plant.

SPECIFICATION CHANGES OR MODIFICATIONS:

All designs and specifications of seller’s products are subject to change without notice provided the changes or modifications do not affect performance.

RETURN MATERIAL:

Product or material may be returned for credit only after written authorization from the seller, as to which seller shall have sole discretion. In the event of such authorization, credit given shall not exceed 80 percent of the original purchase. In no case will Seller authorize return of material more than 90 days after shipment from Seller’s plant. Credit for returned material is issued by the Seller only to the original purchaser.

ORDER CANCELLATION OR ALTERATION:

Cancellation or alteration of acknowledged orders by the buyer will be accepted only on terms that protect the seller against loss.

NON WARRANTY REPAIRS AND RETURN WORK:

Consult seller’s plant for pricing. Buyer must prepay all transportation charges to seller’s plant. Standard shipping policy set forth above shall apply with respect to return shipment from TX RX Systems Inc. to buyer.

DISCLAIMER

Product part numbering in photographs and drawings is accurate at time of printing. Part number labels on TX RX products supersede part numbers given within this manual. Information is subject to change without notice.

Bird Technologies Group TX RX Systems Inc.

Manual Part Number 7-9100

Copyright © 2011 TX RX Systems, Inc.

First Printing: March 1993

Version Number Version Date

3

4

1

2

5

03/05/93

05/10/93

01/24/94

07/08/96

10/17/11

WARNING

Symbols Commonly Used

ESD Electrostatic Discharge

CAUTION or ATTENTION

High Voltage

Heavy Lifting

Bird Technologies Group

Hot Surface

Electrical Shock Hazard

NOTE

Important Information

TX RX Systems Inc.

Changes to this Manual

We have made every effort to ensure this manual is accurate. If you discover any errors, or if you have suggestions for improving this manual, please send your comments to our Angola, New York facility to the attention of the Technical Publications

Department. This manual may be periodically updated. When inquiring about updates to this manual refer to the manual part number and revision number on the revision page following the front cover.

Contact Information

Sales Support at 716-217-3113

Customer Service at 716-217-3144

Technical Publications at 716-549-4700 extension 5019

Bird Technologies Group TX RX Systems Inc.

Table of Contents

General Description ........................................................................................... 1

T-Pass Selectivity vs. Cavity Loss ....................................................................... 4

Unpacking ............................................................................................................ 4

Installation Overview........................................................................................... 4

Assembly.............................................................................................................. 4

Peg Rack Assembly ............................................................................................ 6

Cavity / Isolator Mounting .................................................................................... 6

Installation ........................................................................................................... 7

Intermodulation Considerations ........................................................................... 8

Multicoupler Checkout ......................................................................................... 9

Required Equipment .......................................................................................... 9

Procedure .......................................................................................................... 9

Measurement Accuracy..................................................................................... 9

Multicoupler Tuning .......................................................................................... 11

Tuning Specifics ................................................................................................ 11

Fine Cavity Tuning............................................................................................. 12

Procedure .......................................................................................................... 12

Coarse Cavity Tuning ........................................................................................ 13

Procedure .......................................................................................................... 13

Retuning System to all new Frequencies .......................................................... 14

Multicoupler Expansion .................................................................................... 14

Typical Expansion Channel Installation ............................................................. 14

Peg Rack Procedure ....................................................................................... 14

Relay Rack Procedure..................................................................................... 15

Setting Cavity Insertion Loss ........................................................................... 15

Cavity Loss Setting Procedure 1 ..................................................................... 17

Required Test Equipment .................................................................................. 17

Procedure for T-Pass Loop ............................................................................... 17

Procedure for BandPass Loop .......................................................................... 19

Cavity Loss Setting Procedure 2 ..................................................................... 20

Required Test Equipment .................................................................................. 20

Procedure for T-Pass Loop ............................................................................... 20

Procedure for BandPass Loop .......................................................................... 21

Maintenance....................................................................................................... 23

Isolators.............................................................................................................. 23

Table of Contents Manual 7-9100-5 10/17/11

Figures and Tables

Figure 1: Interconnect diagram of typical system ................................................ 1

Figure 2: Typical transmitter noise suppression ................................................... 3

Figure 3: Front view of 21 channel multicoupler ................................................... 5

Figure 4: Mounting rack detail .............................................................................. 6

Figure 5: Typical combiner installation ................................................................. 7

Figure 6: Measuring T-Pass channel performance .............................................. 8

Figure 7: T-Pass cavity fine tuning ..................................................................... 11

Figure 8: T-Pass cavity tuning controls .............................................................. 12

Figure 9: Coarse tuning a T-Pass cavity ............................................................ 13

Figure 10: Expansion channel installation .......................................................... 15

Figure 11: Top view of T-Pass cavity ................................................................. 16

Figure 12: Setting loop adjustment reference..................................................... 17

Figure 13: Setting T-Pass loop using step attenuators....................................... 18

Figure 14: Setting BandPass loop using step attenuators.................................. 19

Figure 15: Setting T-Pass loop insertion loss ..................................................... 21

Figure 16: Setting Bandpass loop insertion loss ................................................ 22

Table 1: Specifications .......................................................................................... 2

Table 2: Typical T-Pass channel insertion loss..................................................... 3

Table 3: Test data sheet ..................................................................................... 10

Table 4: Cavity insertion loss reference loop settings......................................... 16

APPENDIX A

800 MHz Isolators (Compact Style)

General Description .......................................................................................... 24

Installation.......................................................................................................... 25

Verifying Isolator Functionality ........................................................................ 25

Recommended Test Equipment ...................................................................... 25

Measuring Reverse Isolation (S12) ................................................................... 25

Measuring Insertion Loss (S21)......................................................................... 25

Figure A1: Verifying Reverse Isolation ............................................................... 26

Figure A2: Verifying Insertion Loss .................................................................... 26

Figure A3: Typical Reverse Isolation Waveform ................................................ 27

Figure A4: Typical Insertion Loss Waveform...................................................... 27

Table 1: Specifications ........................................................................................ 24

Table of Contents Manual 7-9100-5 10/17/11

GENERAL DESCRIPTION

The 73-90-11-NN Series T-Pass Transmit Combiners are designed to connect up to 21 transmitters to a common antenna. They use three-port bandpass filters (called T-Pass cavities) and ferrite isolators to provide low channel insertion loss, high isolation between transmitters, high antenna-totransmitter isolation, high intermodulation suppression, and excellent transmitter noise suppression.

T-Pass transmit combiners are broadband and easily adaptable to the most difficult duplex system design requirements.

An interconnect diagram of a typical transmit combiner is shown in Figure 1. The T-Pass filter passes one narrow band of frequencies and attenuates all others with increasing attenuation above and below the pass frequency. The T-Pass filter has a “dual-port” output loop plate which allows the filter to be easily connected to other T-Pass filters.

Connections between the filters are made with a

“thru-line” cable that behaves like a low loss 50

Ohm transmission line. The thru-line cables are individually optimized to their own channel frequency. No compromises are necessary to accommodate other channel frequencies. Each channel can therefore be anywhere in a very broad frequency range.

An isolator is added at the input to each T-pass channel to increase channel isolation. The ferrite isolators will isolate the transmitter from unwanted signals that enter the system via the antenna. The transmitter sees an excellent impedance match on its output, because the isolator absorbs reflected power that would otherwise enter the transmitters output stage. This improves the stability, spectral purity and long-term reliability of the transmitter.

The TX combiners can be expanded one channel at a time with factory-tuned, easy-to-install expansion channel assemblies. Expansion is usually accomplished without modifications to the existing system, and usually amounts to nothing more than placing a new channel assembly, or several, on top of the existing system. New channel frequencies can be above, below, or between existing channel frequencies.

The number of channels in the combiner is indicated by the last two digits of the model number in place of the NN designation. All of the information for both installation and expansion is included in this manual. The combiner is easy to install and

TX5

TX4

TX3

TX2

TX1

Transmitter Combiner (T-Pass)

S

Figure 1: Interconnect diagram of a typical Transmit T-Pass Combiner. Typical five channel system shown as an example.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 1

Specifications (Note 1)

Frequency Range (Note 2)

Cavity Type and Diameter

Max Continuous TX Power @ Tx-Tx Separation

Isolator Load Power (Continuous) (Note 3)

Minimum TX-TX Separation @ Cavity Loss

73-90-11-2C-nn 73-90-11-2D-nn

806 - 960 MHz

3/4-wave 6.625” (168 mm)

150 Watts @ 450 KHz

125 watts @ 250 KHz

5W / 60W 5W / 100W

450 KHz @ -1.25 dB

250 KHz @ -1.80 dB

See Table 2.

Channel Insertion Loss

Typical TX-TX Isolation @ Minimum Separation

Typical Antenna-TX Isolation

Typical TX Noise Suppression

Nominal Input Impedance, Ohms

Maximum Input Return Loss (VSWR)

Temperature Range

Connectors, Input and Antenna

Mechanical Mounting

Mounting Options (Notes 4 and 5)

-80 dB

-70 dB

See Figure 2.

50

-20 dB (1.22:1)

-30° to +60° C

N(F)

Peg Rack™ included with system

-MC: 14” H x 19” W rack-mount adaptor plates

-LR: System supplied without Peg-Rack

Maximum Number of Channels Per Rack

Dimensions (Note 6)

15

65.25” H x 24” W x 20.7” D

(1659 x 610 x 526 mm)

Weight, lb. (Kg)

Basic single-channel system:

Expansion channel assembly:

31 (14.0)

12 (5.4)

32 (14.5)

13 (5.9)

Notes:

1.-nn in model number represents number of channels.

2.Consult factory on T-Pass multicouplers for frequencies below 806 MHz or above 960 MHz.

3.Models available with 5W/25W loads. Same specifications as 60W and 100W models, except load power.

4. -MC option reduces maximum number of channels to 12 per pack.

5. -LR systems are tuned and tested on customer frequencies, then disassembled for shipping.

6. rack depth with cavity tuning rods at maximum frequency. Rod travel is approximately 2.2” (56 mm).

Table 1: Specifications.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 2

Tx-to-TX Separation

1 MHz

500 KHz

450 KHz

250 KHz

Cavity Loss (dB)

2

-2.1

-2.3

Channel Loss (dB) vs. Number of Channels

3

-2.3

-2.8

4

-2.4

-3.0

5

-2.5

-3.2

8

-2.8

-3.6

10

-3.0

-3.9

12

-3.3

-4.1

-1.25

-1.80

-2.4

-3.1

-2.9

-3.8

-3.2

-4.1

Table 2: Typical T-Pass Channel Insertion Loss.

-3.4

-4.4

-3.9

-4.9

-4.1

-5.2

-4.3

-5.5

Note regarding Table 2: The typical channel losses specified here are for equally spaced channels only. Channel loss may be higher or lower in multicouplers where separation varies from one channel to another. Contact TX RX Systems for T-Pass channel loss specifications based on your actual system frequency plan.

73-90-11-Series Systems

6.625" Diameter 3/4-Wave, Fo = 860 MHz

-35

-40

-45

-50

-55

0.01

-20

-25

-30

0

-5

-10

-15

IL = -1.25 dB

IL = -1.80 dB

0.1

1

Offset from Fo (MHz)

Figure 2: Typical Transmitter Noise Suppression.

10 100

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 3

has been factory tuned in most cases so that no adjustments are necessary. The specifications for the 73-90-11-NN family of T-Pass combiners are listed in Table 1 and the typical T-Pass channel insertion loss is shown in Table 2. The response curve shown in Figure 2 shows the typical transmitter noise suppression. Noise suppression depends on the cavity’s loss setting.

T-Pass Selectivity vs. Cavity Loss

As in the case of bandpass cavity filters, T-Pass filter selectivity depends on the coefficient of coupling of the cavity loops at resonance. Tighter coupling decreases insertion loss and selectivity while loose coupling increases them.

Although 800 - 1000 MHz T-Pass cavity loops can be set to approximately -0.8 to -3.0 dB insertion loss at resonance, TX RX Systems Inc. uses two standard cavity loss settings, -1.25 and -1.80 dB, that produce adequate selectivity for the majority of multicoupler applications in this range. The curves shown in figure 2 represent the lower selectivity side of the response curve of a typical 6.625 -inch diameter, 3/4 -wave 860 MHz T-Pass cavity filter.

Bridging loss in a progressive thruline T-Pass structure varies in the same general manner as bridging loss in a parallel junction bandpass structure; it decreases as cavity selectivity increases.

An optimal cavity loss setting exists that minimizes channel loss under a specified frequency plan and number of channels. See Tech-Aid No. 92002 (lit.

NO. D3001D93) for a complete set of selectivity and bridging loss curves for T-Pass cavities from

66 to 960 MHz.

UNPACKING

Most T-Pass transmitter multicouplers are shipped fully assembled in a cardboard crate. The cavities are usually mounted in a suitably sized Peg-Rack which is a patented design of TX RX Systems, Inc.

Other types of mounting may be supplied for custom tailored systems as specified at the time of order. In order to reduce shipping costs, some multicouplers are shipped partially assembled. In this case, customer assembly of the mounting rack and installation of the cavity channels may be required.

Accessories or other products ordered with the multicoupler will usually be found either already mounted in the rack or packaged separately as circumstances dictate. It is important to check the packing slip against the contents to make sure all parts are accounted for. Any shortages should be reported to TX RX Systems or its authorized representative.

It is important to visually inspect the system components for any shipping damage as soon as possible after taking deliver y. It is the customers responsibility to file any necessary damage claims with the carrier.

The transmit combiner is a very rugged device and is well packaged for damage-free shipping to any place in the world. However, a high impact during shipping can have a detrimental affect. A damaged shipping container is a sure sign of rough handling.

The most easily damaged parts of the combiner are the tuning rods. These rods are marked where they exit from the locking nut with a dab of red varnish or other color/type of paint. If this seal appears to be broken it may indicate that the system has been detuned in transit.

INSTALLATION OVERVIEW

Installation of a TX RX transmitter multicoupler consists of some or all of the following steps depending on how completely the unit was assembled at the factory:

1) Determine the exact mounting location for the multicoupler.

2) Assemble the mounting rack.

3) Install the cavities with isolators then install the

T-Pass Thruline cables and accessories into the rack.

4) Connect the transmitters and antenna(s) to the appropriate connectors of the multicoupler.

5) Verify proper operation of each channel by measuring power output for each individual channel.

ASSEMBLY

An unassembled multicoupler will usually be broken down into the following general parts groups:

1) Peg rack assembly.

2) T-Pass cavities with mounting clamps.

3) Isolator & loads on mounting brackets with mounting clamps.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 4

Antenna connects here

First cavity has built-in short circuit.

Channel Number

TX 21

TX 20

TX 17

TX 16

TX 13

TX 12

TX 9

TX 8

TX 5

TX 4

TX 1

L21

L20

L19

L18

L17

L16

L15

L14

L13

L12

L11

L10

L9

L8

L7

L6

L5

L4

L3

L2

TX 19

TX 18

TX 15

TX 14

TX 11

TX 10

Tra n sm itte rs co n ne ct to type N connector on isolator.

TX 7

TX 6

TX 3

Isolator mounting clamp connector access hole on bottom for this bracket. Hole is on top for all other isolators.

TX 2

21 Cavity Peg-Rack

Model 93-00-10

Isolator mounting clamp connector positioned on bottom of cavity for this channel only.

Figure 3: Front view of 21 channel multicoupler showing cavity and cable layout. Multicouplers with fewer channels follow the same cavity stacking and cable pattern from the bottom up.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 5

4) T-Pass thruline cables and isolator to cavity cables.

Peg-Rack Assembly

If the unit was fully assembled then this step may be disregarded. A separate instruction sheet for the rack assembly is included with the rack.

Cavity / Isolator Mounting

After the Peg-Rack is assembled, the cavity filters are mounted. They are packaged separately from the isolator assemblies. The cavities have an identification tag attached indicating their frequency which is used to identify the cavity position in the system. A T-Pass THRULINE DATA SHEET is also included in the envelope with this manual for your multicoupler or expansion channel. This computer printout shows the position of each channel in the multicoupler and indicates its frequency. This information determines the position of the cavities in the rack. This data sheet also shows the position of critical-length Thruline cables.

The front view of a fully assembled 21 channel T-

Pass transmit combiner is shown in Figure 3. The location and assembly order are the same for any size multicoupler.

1) Mount the cavities for channel 2 (TX 2) on the right side of the rack starting with pegs 2 and 3.

The stainless steel clamps that hold the cavities

(part # 8-6212) on the right side should lay in the peg indentations closest to the vertical rails.

(Note that the 8-6212 clamps are also used for mounting the isolator assemblies.) The clamp always goes around 2 pegs. Orient the cavity as shown in Figure 4.

2) Identify the isolator assembly for channel 2. The isolators are labeled with the TX/Channel number and channel frequency. Mount the isolator assembly to the previously mounted cavity using two stainless steel clamps. See figures 3 and 4. The clamp connectors for the channel 2 isolator assembly should lie on the underside of the cavity. An access hole is provided in the isolator mounting plate edge to allow access to one of the hard to get at clamp connectors. It should face downward.

3) Mount each remaining cavity and isolator assembly for the right side (channels 3,6,7 etc.) following the order shown on the T-Pass thruline data sheet. The mounting clamps for these cavities will also lay in the peg indentations closest to the vertical rails. The isolator mounting clamp connectors and access hole should be on top for these channels.

4) Similarly mount the cavity and isolator assemblies for the channels on the left side of the rack starting with channel 1 and working up. The stainless steel clamps that hold the cavities

(part # 8-6212) on the left side should lay in the peg indentations closest to the center of the rack. Isolator clamps and access holes are on top for these channels also.

5) Connect the isolator to the T-Pass cavity as shown in figure 4, using isolator cable part #3-

1918 for each channel. Use pliers with rubber jaws (Utica Part #529-10) to tighten the connectors slightly more than finger tight. DO NOT

OVER TIGHTEN.

Figure 4: T-Pass cavity mounting rack detail.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 6

6) Similarly connect the T-Pass Thruline cables to the cavities using the THRULINE DATA Sheet and figure 3 as a guide.

Caution: The Thruline cables must be installed in the correct location for proper operation. Use pliers with rubber jaws to tighten these connections slightly more than finger tight.

This completes the assembly of the basic multicouplers. Any accessories should be mounted to the rack using the supplied mounting hardware and adapter plates.

Installation

The multicoupler should be located in a dry and level area, indoors. It is best if all transmitters are as equal in distance as possible from the combiners so that cable losses are the same for all channels. Figure 5 shows a suggested orientation for the equipment. Two points are important. First, a work area space should be left as illustrated so that the tuning controls are easy to access. This will facilitate tuning when channel frequencies are changed. Secondly, space is needed when adding expansion channels. If there is a lack of space to access the side of the combiner, then plan to allow the rack to be moved into the indicated work area to facilitate adding channels. This will require some slack in the cables that connect to the station transmitters.

Four, 17/64" (6mm) diameter mounting holes are provided in the base for attaching the rack to the floor using bolts or lag screws.

Each transmitter connects to its respective channel through an ‘N-style’ female connector on the isolator. We recommend using a high quality double shield or semi-flexible cable for this purpose. Rigid cable may be used but extreme care is needed to prevent damage to the connector on the multicoupler. High quality connectors should be used for all connections to the multicoupler. Connectors with gold plated center pins are preferred to minimize the generation of intermodulation distortion products.

The antenna connection is made to a female N connector on the last T-Pass cavity in the chain near the top of the rack. A flexible jumper of high quality coax is convenient for this purpose. This jumper should be rated to handle the total power output of all the transmitters combined. Since most transmitter multicouplers exhibit an average 3 dB loss, the actual total power output will be approximately 1/2 the total transmitter power. However, we recommend cable rated at twice the actual required power as a safety factor.

Direct connection to the hard line antenna cable is also possible but care should be exercised to prevent damage to the cavity connector due to excessive bending force created by misalignment of the hard line.

T-Pass

Transmitter

Combiner

Radio

Cabinet

Radio

Cabinet

Radio

Cabinet

Radio

Cabinet

Work

Area

Figure 5: The multicoupler should be positioned so that there is access for tuning and servicing.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 7

It is advised that the center pin on all mating N male connectors be checked for proper alignment before connection to the multicoupler. A cocked center pin in the male connector can permanently damage the mating female connector. In many cases, simple field replacement of the damaged connector is not possible and replacement of an entire subassembly may be required to make the unit operational.

This system is designed for use with separate transmit and receive antennas. For best operation, the transmit and receive antennas should be separated vertically by 20 feet with little or no horizontal offset between antennas. Lesser separations can be used but with an increased risk of harmful interference between radio systems. In most cases, it will be desirable to mount the receive antenna higher than the transmit antenna to maximize the talk-back range of low power portable radios.

Intermodulation Considerations

Following the previously mentioned antenna spacing recommendations will go a long way toward minimizing or eliminating intermodulation (IM) interference. IM is the result of a frequency mixing process that occurs when two or more RF signals are present simultaneously in the same circuitry where nonlinearity occurs. Product frequencies generated have frequencies that are determined by relatively simple mathematical relationships such as F(im) = 2F1-F2 and are normally determined by doing a computer intermodulation analysis for the antenna site. These products can be generated in

Wattmeter 2

T-Pass

Cavity Filter

50 Ohm

Load

Transmitter

Wattmeter 1

Single or Dual

Section

Isolators

Channel 3

Transmitter

UG27 Elbow Connector

& UG57 Male-Male

Adaptor

Channel 2

UG57

Male-Male

Single or Dual

Section

Isolators

Transmitter

Single or Dual

Section

Isolators

Channel 1

This T-Pass Loop requires a 3-1268 short circuit connector

Figure 6: Equipment hookup for measuring T-Pass channel performance.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 8

a corroded tower joint, metal-roofing, transmitter final amplifier or the receiver front-end.

Both cavity filters and ferrite isolators isolate the transmitters connected to the combiner from oneanother thus reducing intermodulation interference.

However in all transmitter combiners, intermodulation products are reduced in strength but never completely eliminated. They have to be reduced by an amount to meet the Federal Communications

Commission, 43 + 10 Log(Power Out) rule for spurious output reduction. Because of the limitations imposed by the tension and friction joints in connectors, IM products will be down 100 to 120 dB below carrier so they are still strong enough to cause problems if they fall on a near-by receiver frequency.

To avoid transmitter generated IM problems, do not put two channels on the same combiner that your IM software predicts will cause interference by generating either 3rd or 5th order IM products.

Having at least two transmitter combiners allows maximum flexibility in dealing with transmitter generated IM.

Multicoupler Checkout

Fully assembled multicouplers are factory tuned and ready for routine operation after properly connecting the transmitters and antenna(s) as outlined previously. The components used in systems that require partial assembly have been fully intercabled and tuned so they will not require tuning. However, it is recommended that the performance of the multicoupler be checked initially and data recorded for future reference. This is done by measuring the input and output power of each channel and recording the data. Figure 6 shows the equipment hook up.

REQUIRED EQUIPMENT

If a power monitoring system is not installed along with the multicoupler, two Bird Model 43 thruline wattmeters or equivalent can be used. They should be equipped with elements for the frequency band of interest and rated for the expected transmitter power output. The use of two wattmeters eliminates errors that can occur from changing cable lengths. The measurements should only be done one channel at a time because most wattmeters cannot accurately measure the total power of two or more transmitters simultaneously. A pocket calculator with Log functions makes for easy calculation of power loss in dB using this measured data.

PROCEDURE

Start with channel 1 at the bottom of the rack and proceed to the next higher channels. The two wattmeters should be connected to the equipment as shown in figure 6. Note that the use of the elbow and/or male-male connectors allows the shortest connections and negligible hook up loss. Longer cable lengths will tend to increase measurement error.

It is important that the same wattmeters and wattmeter elements be used in the same position throughout the tests. The serial numbers of the wattmeters should be recorded for future reference. Wattmeter elements may not have serial numbers so they need to be labeled or otherwise keyed to a specific wattmeter to assure repeatability of the measurements.

A convenient data sheet is included in Table 3 and may be photo copied. After entering the data and calculating the power losses, it should be retained for future reference. A column is provided for entering the factory measured loss from the T-Pass

Thruline Data sheet that was included in the envelope with this manual. The factor y data was obtained with a laboratory network analyzer having an accuracy ±0.05dB. The readings obtained using the wattmeter method outlined may vary considerably from the factory values and this difference is explained in the next paragraph.

MEASUREMENT ACCURACY

The Bird thruline wattmeter has a measurement accuracy of +/- 5% of full scale. When using a 100 watt element in this meter, the measurement error can be as great as + or - 5 watts.

As an example of the actual dB loss readings that might be produced using the wattmeter method, consider a T-Pass channel that has a factory measured loss of 3.0 dB. We would expect that a 100 watt transmitter would produce 50 watts out of this channel but the actual wattmeter reading for the input power could measure as low as 95 watts to as high as 105 watts. The measured output power could run from 45 to 55 watts. It is possible that the output reading may be 5 watts low while the input reading is 5 watts high or just the opposite. These two extremes would yield the following dB loss values:

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 9

For a Power Out (P

O

) of 45 watts and a Power

Input (P

I

) of 105 watts:

Loss (dB) = 10 Log

10

(45/105)

Loss (dB) = -3.7

For a P

O

of 55 watts and P

Loss (dB) = 10 Log

10

Loss (dB) = -2.4

I

of 95 watts:

(55/95)

So the calculated loss for this channel can run from

-2.4 to -3.7dB and be acceptable considering the measurement error factor. The actual error could be much greater if a 250 watt element was used; the measured values could vary by as much as +/-

12.5 watts. So using a wattmeter element with the smallest possible rating is important for accuracy.

Use of between series adapters or UHF type connectors for making connections to the wattmeters, device under test or loads, could make this error even worse due to the additional impedance mismatch that these connectors can cause.

Transmitter Combiner Test Data Sheet

8

9

6

7

4

5

2

3

Combiner Model Number:

Serial / Job Number:

Date: Technician:

Wattmeter #1 Serial Number:

Wattmeter #2 Serial Number:

Channel

Number

1

Power Input

(Pi) in Watts

10

11

12

13

14

15

Power Output

(Po) in Watts

Power Ratio

Po / Pi

Table 3: Test Data Sheet.

Calculated

Loss (dB)

Factory Measured

Loss (dB)

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 10

MULTICOUPLER TUNING

T-Pass transmitter combiners are pre-tuned at the factory and usually require no adjustment. T-Pass expansion channels are also pretuned but may require fine tuning after being installed in an existing system. Channels that are close in frequency

(adjacent channels in the multicoupler) to the expansion channel may also benefit from fine tuning due to the slight interaction that occurs with the new channel. The procedures that follow may be used at any time to verify that any or all channels are properly tuned or to correct any misalignments.

It is interesting to note that T-Pass filters, bandpass filters and cavity filters in general can act as impedance transformers as well as filters. It is for this reason that many field service personnel claim that they can always tune a filter better than the factory.

What isn't generally realized is that their tuning efforts are usually producing better impedance matching between transmitter and antenna which can be improved by the transforming action of filters. Since the filters are usually tuned using laboratory grade 50 ohm loads, the tuning adjustment that produces this improved match will be slightly different than the factory adjustment. While this tuning may produce slightly greater power output readings, it will rarely produce any discernible change in system performance.

It is our recommendation that channel tuning only be attempted under the previously mentioned conditions or when it is suspected that the combiner has been tampered with or subjected to extreme shock in shipping or installation. This condition is indicated when the channel loss is in excess of that expected from actual measurement of power input and output.

Tuning Specifics

Tuning the multicoupler consists of tuning the individual T-Pass channels. T-Pass channel tuning involves cavity filter tuning. For multicoupler models used at 800 MHz and above, isolator tuning is

never required because these isolators are fixedtuned at the factory for specific frequency bands and have no user adjustments.

Transmitter

Fine

Tuning

Two Single Section or One Dual Isolators

Input Output

50 Ohm

Termination

Coarse

Tuning

T-Pass

Cavity Filter

To Other

Channels

To Other

Channels

Wattmeter

Output

Section

Termination

Figure 7: Using a Wattmeter for T-Pass cavity fine tuning.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 11

Fine Cavity Tuning

Figure 7 shows a hookup suitable for fine tuning any channel under power while installed in the multicoupler. The term fine tuning here refers to cavities that have already been tuned to frequency and may only require adjustment of the fine tuning control (+/- 50 KHz). The transmitter is used as a signal source and the cavity is adjusted for minimum reflected power.

Procedure

With the transmitter keyed, the cavity fine tuning control is adjusted (pushed in or out) to obtain a minimum meter reading. See Figure 8 for a detail of the cavity tuning controls. If a minimum meter reading is obtained with the fine tuning rod fully in or completely out, do the following:

1) Set the fine tuning rod so that about 1/2 its length is inserted into the cavity.

NOTE

When tuning a cavity that has been in service for some time it is not unusual to find the main tuning rod hard to move in or out. This occurs because

TX RX uses techniques borrowed from microwave technology to provide large area contact surfaces on our tuning plungers. These silver plated surfaces actually form a pressure weld that maintains excellent conductivity. This pressure weld develops over time and must be broken to move the main tuning rod. This is easily accomplished by gently tapping the tuning rod with a plastic screwdriver handle or small hammer so that it moves into the cavity. The weld will be broken with no damage to the cavity.

When adjusting the coarse tuning rod, it is easy to put the cavity far off resonance and cause most of the transmitter power to be reflected back into the isolator output section load. This load should be capable of dissipating this power or damage could result. If in doubt about the loads capability, follow the coarse tuning procedure outlined below. It is based on the use of a spectrum analyzer and frequency generator which avoids the need to consider power levels.

2) Loosen the coarse tuning rod locking screw (5/

32"/4mm Allen/HexKey wrench required) and move the rod in or out slightly to obtain minimum meter reading. Small movements of the coarse tuning rod are facilitated by tapping the rod with the handle end of a screw driver while gently pushing or pulling the main tuning rod.

Tighten the coarse tuning locking screw.

3) Adjust the fine tuning control for a minimum meter reading.

4) Tighten the fine tuning locking mechanism.

Coarse Tuning Rod

Coarse Tuning Lock

10-32 Cap Screw

Cavity Resonator

Input/Output Port

Loop Plate

Hold Down Screws

Loop Plate Assembly

Calibration Index

Fine Tuning Rod

Input/Output Port

Loop Plate Assembly

Calibration Mark

Calibration Index

Fine Tuning Lock

Knurled Thumb Nut

Figure 8: T-Pass cavity tuning controls.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 12

Spectrum Analyzer

Bird SignalHawk

Signal Generator

RLB - 150 Bridge

T-Pass

Cavity Filter

LOAD

50 Ohm Load

3-1268

Short Circuit

Connector

Figure 9: Equipment hookup for

T-Pass cavity coarse tuning.

Coarse Cavity Tuning

Wh en a T-Pass c avi t y f r equ enc y has t o b e changed by over 50 KHz, adjustment of the main tuning rod is required. Large frequency changes are more easily observed when using a tracking generator and a return loss bridge to give a swept display of the return loss curve. The return loss curve is a very precise indicator of T-Pass cavity tuning. The test equipment hookup for doing this is illustrated in Figure 9 and uses the following equipment;

1) Spectrum Analyzer that covers the frequencies of interest such as the Bird Technologies “Signal Hawk ™”.

2) Signal generator capable of producing the frequencies of interest.

3) Eagle Return Loss Bridge (35 dB directivity).

Model RLB150N3A.

4) Double shielded coaxial cable test leads

(RG142 B\U or RG223/U).

5) 50 Ohm load with at least -35 dB return loss

(1.10:1 VSWR).

6) Shorting stub from holder at top of T-Pass rack

(Part # 3-1268).

Procedure

1) Set the spectrum analyzer for the desired channel frequency (display center) and vertical scale of 10 dB/div. Set the signal generator for the desired center frequency.

2) Connect the return loss bridge to spectrum analyzer and signal generator as shown in figure 9 but do not connect it to the cavity. Leave the test port (called the load port) on the bridge open.

3) Set up the 0 dB return loss reference display on the spectrum analyzer. Then connect the return loss bridge.

4) Loosen the fine tuning rod locking nut and set the fine tuning rod so that 1/2 its length is inserted into the cavity.

5) Loosen the main tuning locking screw and move the main tuning rod in or out to obtain maximum return loss at the desired frequency.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 13

Small movements of the main tuning rod are facilitated by tapping the rod with the handle end of a screw driver while gently pushing or pulling the main tuning rod.

6) Lock the Main and Fine tuning rods and reinstall the cavity in the system. Use the previously outlined fine tuning procedure to verify proper tuning under power.

Retuning System To All New Frequencies

When retuning the combiner to all new frequencies perform the following procedure in a step-by-step fashion;

1) Determine new thruline cable lengths for the new channels and the specific stacking order in the rack. TX RX Systems Sales engineers will assist by making the calculations using their design software. Due to variations in coaxial cable characteristics and assembly techniques, factory supplied cables are recommended.

2) Use the Coarse Tuning procedure as outlined earlier in this manual to tune each cavity channel to the new transmitter frequencies.

3) Connect the channels according to the new

Thru-line cable chart.

4) Fine tune each channel using the fine tuning procedure as outlined earlier in this manual, starting with channel 1 and proceeding to the next higher channel. After tuning all channels, repeat this step a second time to verify that there is no more channel interaction.

5) Verify channel losses if desired using the multicoupler checkout procedure outlined previously.

MULTICOUPLER EXPANSION

Expansion channels for your multicoupler may be ordered directly from TX RX Systems or its authorized representative. The systems engineer will help you select the right model and any required options.

The expansion channel and options are shipped with mounting instructions and a new T-Pass

Thruline cable sheet which shows the exact mounting location of the new channel in the existing system. In most cases, this channel will be added directly to the next topmost position in the rack and the antenna connection will then move to this cavity. A new thruline cable will connect this channel to the existing cavities.

The system engineer may also advise that the cavity insertion loss on some of the existing channels needs to be changed in order to accommodate a new channel. This can be necessary when the new channel is much closer in frequency separation to existing channels than that previously encountered. This usually means increasing the cavity loss for all close spaced channels which provides the increased selectivity required. Cavity insertion loss values are shown on the T-Pass Thruline cable sheet.

Typical Expansion Channel Installation

The following text is a procedure for adding expansion channel components to a typical T-Pass

Transmitter Multicoupler. Please keep in mind that instructions shipped with the expansion components supersede these procedures.

Typical Parts Included

(Quantity and Description)

(1) T-Pass Cavity Assembly.

(1) Single/Dual Isolator w/load on Mounting Plate

(1) 9.4" Isolator to Cavity Interconnect Cable

(4) Stainless Steel Band Clamps

(1) T-pass Thru-line Cable

(1) T-pass Thruline Chart.

PEG RACK PROCEDURE

1) Determine the location of the Expansion Channel in the rack by consulting the new

THRULINE cable chart.

2) Mount the cavity in the peg rack using two (2) stainless band clamps, refer to Figure 10.

3) Rotate the cavity body so that the connectors are orientated the same as those on the other cavities and that no cavity-end cap screws are preventing a flush fit with a mounting peg.

4) Tighten the cavity mounting clamps.

5) Attach the isolator mounting plate to the cavity using two (2) band clamps. Clamp screws

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 14

should be positioned as shown in figure 10. Do not tighten the clamps.

6) Rotate the isolator mounting bracket so that the isolator is in the vertical plane as illustrated, forming a smooth line in relation to the other channels in the rack.

7) Due to the limited space, tightening may require the use of a 5/16" open end wrench. Tighten both clamps securely.

8) Connect the isolator-to-cavity cable. Use a pair of cable pliers to tighten-up the connectors.

9) Connect the new channel to the multicoupler using the proper length T-Pass Thruline cable.

Use a cable pliers to tighten these connections.

NOTE

The required length thruline cable and new cabling chart has either been factory supplied or is to be determined and fabricated by the customer as determined at the time of order. Use

T-Pass THRULINE design sheets supplied by the factory.

10) If necessary, reset cavity insertion loss of adjacent channels as noted on the Thru-line cable sheet. Follow the procedure outlined under

Setting Cavity Insertion Loss.

11) Fine tune the T-Pass cavity of the expansion channel according to the procedure outlined earlier.

Figure 10: Expansion channel installation.

RELAY RACK PROCEDURE

Because of their width, 6.625” cavities

NOTE are mounted on relay racks in a horizontal orientation on cavity deck plates.

1) Determine the location of the expansion channel in the rack by consulting the new

THRULINE cable chart.

2) If necessary install an empty cavity deck in the rack using 4 Phillips screws. If there is room on an already existing cavity deck then skip this step of the procedure.

3) Mount the cavity on the deck by laying the cavity onto the “V” shaped cavity bracket.

4) Rotate the cavity body so that the connectors are oriented the same as those on the other cavities in the system. Secure the new cavity to the brackets using (2) stainless band clamps.

5) Tighten the cavity mounting band clamps.

6) Connect the black isolator-to-cavity cable using a pair of cable pliers to tighten-up the connectors.

7) Connect the new channel to the combiner using the proper length T-Pass Thruline cable. Use a pair of cable pliers to tighten these connections.

NOTE

The required length Thruline cable and new cabling chart has either been factory supplied or is to be determined and fabricated by the customer as determined at the time of order.

Use T-Pass Thruline design sheets supplied by the factory.

8) If necessary, reset the cavity insertion loss of the adjacent cavities as noted in the Thruline cable sheet. Follow the procedure outlined below under Setting Cavity Insertion Loss,

9) Fine tune the T-Pass cavity of the expansion channel according to the fine tuning procedure outlined earlier.

SETTING CAVITY INSERTION LOSS

It is sometimes necessary to reset the insertion loss of a T-Pass cavity filter in order to change its selectivity. Increasing the loss will increase the

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 15

cavity selectivity which may be necessar y to accommodate more closely spaced channels.

Changing the loss is accomplished by rotating the coupling loops to change the coefficient of coupling. Both loops are normally adjusted for a given insertion loss setting. Most T-Pass cavities have a

Calibration Index label beside both loops that gives a relative indication of their settings (see Figure

11). In actual practice, these marks are not accurate enough for setting loss values consistently.

Calibration

Mark

Bandpass

Loop

Loop Locking

Screws (6 places)

T-Pass

Loop

Figure 11: Top view of T-Pass cavity.

Two procedures are offered for setting the cavity loss. Both procedures take advantage of the fact that when a tee connector is placed on a single bandpass or T-Pass loop, a rejection notch can be observed across the tee. The depth of the rejection notch is directly related to the loop's coefficient of coupling.

The first procedure uses precision rotary attenuators, a signal generator and an RF millivolt meter to provide very accurate results. The actual loss setting obtained when this procedure is carefully followed will be within one tenth of a dB of the desired value and the return loss will be 20 dB (1.25:1) or better.

The second procedure uses a spectrum analyzer and frequency generator and produces slightly less accurate results. When this procedure is carefully followed, the loss settings will be within two tenths of a dB of the desired value and the return loss will usually be -15 dB (1.5:1 VSWR) or better. The advantage of this procedure is that it is much faster to do, does not require precision attenuators and will yield acceptable results in most cases.

Table 4 shows a reference chart for setting T-Pass cavity loss with either procedure. The chart shows the desired cavity loss settings and the reference setting for both the T-Pass and bandpass loop assembly. The reference notch depth for a given loss is that which can be observed across a tee connector connected to either loop assembly. Note that the reference notch depths are slightly different when the T-Pass loop assembly has a built-in

Cavity Loss (dB)

1.25

1.25

1.80

1.80

Built-in Short

Circuit

No

Yes

No

Yes

Coupling Loop Type

T-Pass

Bandpass

T-Pass

Bandpass

T-Pass

Bandpass

T-Pass

Bandpass

TX RX Systems

Part Number

3-3721

3-2294

3-2292

3-2294

3-3721

3-2294

3-2292

3-2294

Table 4: Cavity insertion loss reference loop settings.

Reference Notch

Depth (dB)

-9

-17

-9.6

-16.7

-6.6

-14.6

-7.2

-13.9

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 16

short circuit. This loop is only used once in the bottom cavity of the T-Pass stack. Detailed procedures and illustrations follow on the next few pages.

CAVITY LOSS SETTING PROCEDURE 1

This procedure uses precision rotary attenuators, a signal generator and an RF Millivolt meter.

Required Test Equipment

1) Signal generator capable of producing a CW signal level of at least -10 dBm with variable output level capability at the frequency of interest.

2) An RF voltmeter with a 0.001 Volt (-50 dBm) scale and a 50 Ohm input adapter. Helper

Instruments RF millivolter used for this example.

3) Rotary Attenuators, [email protected] 0-1 dB in 0.1 dB increments. [email protected] 0-10 dB in 1.0 dB increments. [email protected]

0-70 dB in 10 dB increments. JFW Industries model 50BR-017.

4) Two 10 dB fixed attenuator pads with BNC connectors. JFW Industries model 50F-010.

5) UG-914/U, BNC(F)-BNC(F), union. TX RX Systems' part # 8-5805.

6) UG-28A/U, N(F), N(F), N(F) tee.

7) UG-57B/U, N(M)-N(M) coupling.

8) Two, UG-201A/U BNC(F)-N(M) adapter. TX RX

Systems' part # 8-5814.

9) 50 ohm coaxial cable test leads with BNC male connectors (high quality cable).

A spectrum analyzer may be used in place of the

RF voltmeter. However, the personnel doing the work should fully understand the procedure and understand the use of the analyzer for this application. We have found it convenient to use test cables with BNC connectors. They allow for more convenient connection to test equipment and to small attenuator pads. UG-201 BNC to N adapters are used when connections to N connectors are needed.

Procedure for T-Pass Loop

1) Set the signal generator for the desired operating frequency (within 1 MHz of operating frequency) and for an output signal level of approximately -10 dBm. Set the rotary attenua-

Modulated

Signal Source

0 0 0 0 0 0 0 0

UG914/U

Female-Female

Connector

All cables are 50 Ohm coaxial. Double shielded cables preferred.

0.1 dB/Div.

RF Voltmeter

1

2

3 4 56 7 8 9

10

3

ZERO

SET

1.0 dB/Div.

50 Ohm Adaptor

10 dB/Div.

10 dB Attenuator Pads

Rotary Attenuators

Set to Loop Reference Settings

Figure 12: Setting loop adjustment reference level.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 17

tors for the Reference Notch Depth Value shown in the chart (table 4) for the desired insertion loss and T-Pass loop part #.

2) Connect the test leads together through the female union, as shown in Figure 12, and adjust the range switch and the zero set on the voltmeter for a convenient reference level (A

level of 2 on the 0 to 3 scale for example) on the meter. The generator output level may also be adjusted slightly if necessary.

3) Remove the bandpass loop from the cavity and insert it, connector end first, back into the cavity and tighten all 3 screws securely. See Figure

13.

4) Set all three attenuators for 0 dB but leave them in the circuit.

5) Connect a UG-28A/U Tee connector and UG-

57B/U coupling to the T-Pass loop as shown in figure 13. Then connect the test leads as shown. Make sure to install the short circuit stub

(part # 3-2330) from the top of the T-Pass rack if the loop does not have an internal short.

6) Loosen the main tuning rod locking screw and slowly slide the tuning rod in or out to obtain a dip (minimum voltage) in the meter reading which indicates cavity resonance. Use the fine tuning control to maximize the dip (the fine tuning rod should not be full in or out which would indicate that slight adjustment of the main tuning rod is necessary). Note the meter reading.

7) If the meter reading is greater or less than the reference level from step 3, the T-Pass loop rotation will have to be adjusted. If the meter

Modulated

Signal Source RF Voltmeter

UG-28A/U

UG-57B/U

T-Pass

Loop

50 Ohm Adaptor

Short Circuit Connector

3-1268 from top of rack

10 dB Pad 10 dB Pad

0.1 dB/Div.

1.0 dB/Div.

10 dB/Div.

Rotary Attenuators

Set to Loop Reference Settings

Bandpass Loop turned upside down with connector inserted into cavity.

Loop visible and screws tight.

Figure 13: Setting the T-Pass loop using step attenuators.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 18

Modulated

Signal Source

10 dB Pad

RF Voltmeter

UG-28A/U

UG-57B/U

Bandpass

Loop

50 Ohm Adaptor

10 dB Pad

0.1 dB/Div.

1.0 dB/Div.

10 dB/Div.

Rotary Attenuators

Set to Loop Reference Settings

Small Circle on Bandpass Loop indicates ground end of loop and should be oriented as shown.

Previously calibrated T-Pass Loop 3-1268 short circuit removed.

Figure 14: Setting the Bandpass loop using step attenuators.

reading is greater than the reference level, the loop will have to be rotated so that the calibration mark on the loop points to a slightly higher number on the calibration index label. Conversely, if the meter reading is less than the reference, the loop will have to be rotated so that the index mark points to a slightly lower number on the calibration index. Loosen the three loop locking screws and rotate the loop so that the index mark is moved to the next higher or lower calibration tag number as needed and tighten the 3 locking screws. Note that tight screws are necessary for accuracy.

8) Repeat steps 6 and 7 until the minimum meter reading is equal to the reference level from step

3. Rotation of loops will change the cavity frequency slightly.

9) The Bandpass loop should be installed with the connector up and the ground point circle oriented toward the center of the cavity as shown in Figure 14.

10) Remove the short circuit stub from the T-Pass loop.

Procedure for Bandpass Loop

1) Maintain the previous signal generator settings and set the rotary attenuators for the proper setting as shown in table 4 for the Bandpass Loop.

2) Connect the test leads together through the female union and adjust the range switch and the zero set on the voltmeter for a reference level (A level of 2 on the 0 to 3 scale is conve-

nient) on the meter. See figure 12. The genera-

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 19

tor output level may also be adjusted slightly if convenient.

3) Set all three attenuators for 0 dB but leave them in the circuit.

4) Connect a UG-107 Tee and the UG-57B/U to the Bandpass loop as shown on figure 14. Then connect the test leads as shown. Make sure the short circuit stub has been removed from the T-

Pass loop.

5) Loosen the main tuning rod locking screw (see figure 8) and slowly slide tuning rod in or out to obtain a dip (minimum voltage) in the meter reading which indicates cavity resonance. Use the fine tuning control to maximize the dip (the fine tuning rod should not be full in or out which would indicate that slight adjustment of the main tuning is necessary). Note the meter reading.

6) If the meter reading is greater or less than the reference level from step 2, the bandpass loop rotation will have to be adjusted. If the meter reading is greater than the reference level, the loop will have to be rotated so that the calibration mark on the loop, points to a slightly higher number on the calibration index label. Conversely, if the meter reading is less than the reference, the loop will have to be rotated so that the index mark points to a slightly lower number on the calibration index. Loosen the three loop locking screws and rotate the loop so that the index mark is moved to the next higher or lower calibration tag number as needed and tighten the 3 locking screws. Note that tight screws are necessary for accuracy.

7) Repeat steps 5 and 6 until the minimum meter reading is equal to the reference level from step

3. Rotation of loops will change the cavity frequency slightly.

8) Make sure that all the loop locking screws are tight. The cavity loops are now set and the cavity should now be tuned to the desired frequency as outlined elsewhere in this manual.

CAVITY LOSS SETTING PROCEDURE 2

This procedure uses a spectrum analyzer, signal generator, and fixed attenuator pads.

Required Test Equipment

1) Spectrum Analyzer and a signal generator.

2) Two 10 dB fixed attenuator pads with BNC connectors. JFW Industries model 50F-010.

3) UG-914/U, BNC(F)-BNC(F), union. TX RX Systems' part # 8-5805.

4) UG-28A/U, N(F), N(F), N(F) tee.

5) UG-57B/U, N(M)-N(M) coupling.

6) Two, UG-201A/U BNC(F)-N(M) adapter. TX RX

Systems' part # 8-5814.

7) 50 ohm coaxial cable test leads with BNC male connectors (high quality cable).

We have found it convenient to use test cables with

BNC connectors. They allow for a more convenient connection to test equipment and small attenuator pads. UG-201 BNC to N adapters are used when connections to N connectors are needed.

Procedure for T-Pass Loop

1) Remove the screws that hold in the bandpass loop assembly; remove the assembly; invert it and place it back into the cavity. The coupling loop will be visible. Install and tighten the three locking screws.

2) Connect the test leads to the spectrum analyzer; turn it on and let it warm up for at least 30 minutes.

3) Connect the 10 dB attenuator pads to the test leads. They will remain connected for all subsequent measurements.

4) Note the Reference Notch Depth value for the

T-Pass loop assembly to be adjusted from the chart, see table 4.

5) Set the spectrum analyzer for the frequency of the channel of interest (within 5 MHz of actual operating frequency)

6) If the Reference Notch Depth is 8 dB or less then set the display for a vertical range of 2dB/ div otherwise set it for 10dB/div.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 20

UG-28A/U

UG-57B/U

T-Pass

Loop

10 dB Pad

Short Circuit

Connector 3-1268 from top of rack

Signal Generator

10 dB Pad

Spectrum Analyzer

Bird SignalHawk

Figure 15: Setting a T-Pass loop for a specific cavity insertion loss.

Bandpass Loop turned upside down with connector inserted into cavity.

Loop visible and screws tight.

7) Temporarily connect the test leads from the spectrum analyzer together through a UG-914

BNC union to set the zero reference.

8) Connect a UG-28 tee and a UG-57 coupling to the T-Pass loop as shown in Figure 15.

9) Connect the test leads from the spectrum analyzer to the tee connector as shown in figure 15.

10) Adjust the cavities main tuning rod so that a rejection notch appears in the center of the display.

11) Loosen the three loop locking screws and rotate the loop to obtain the reference notch depth from step 4.

NOTE

The tightness of the locking screws affects the depth of the rejection notch slightly. It is usually necessary to rotate the loop for a notch depth that is slightly less than the reference.

The Notch depth will tend to increase slightly as all three locking screws are tightened.

12) Remove the bandpass loop and place it back into the cavity with the connector-end up.

Procedure for Bandpass loop

1) The Bandpass loop should be installed with the connector up and the ground point circle oriented toward the center of the cavity as shown in Figure 16.

2) Connect the test leads, with 10 dB pads attached, to the spectrum analyzer; turn it on

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 21

Signal Generator

UG-28A/U

UG-57B/U

Bandpass

Loop

10 dB Pad 10 dB Pad

Small Circle on

Bandpass Loop indicates ground end of loop and should be oriented as shown.

Previously calibrated

T-Pass Loop 3-1268 short circuit removed.

Spectrum Analyzer

Bird SignalHawk

Figure 16: Setting a Bandpass loop for a specific cavity insertion loss.

and let it warm up for at least 30 minutes if this has not been done.

3) Note the Reference Notch Depth value for the

Bandpass loop assembly to be adjusted from table 4.

4) Set the spectrum analyzer for the frequency of the channel of interest (within 5 MHz of actual operating frequency).

5) If the Reference Notch Depth is 8 dB or less then set the display for a vertical range of 2dB/ div otherwise set it for 10dB/div.

6) Temporarily connect the test leads from the spectrum analyzer together through a UG-914

BNC union to set the zero reference. Make sure to use the 10 dB pads which should remain on the test cables for all measurements.

7) Connect a UG-28 tee and a UG-57 coupling to the bandpass loop as shown in figure 16.

8) Connect the test leads from the spectrum analyzer to the tee connector as shown in figure 16.

9) Adjust the cavities main tuning rod so that a rejection notch appears in the center of the display.

10) Loosen the three loop locking screws and rotate the loop assembly to obtain the reference notch depth from step 3.

NOTE

The tightness of the locking screws affects the depth of the rejection notch slightly, it is usually necessary to rotate the loop for a notch depth that is slightly less than the reference.

The Notch depth will tend to increase slightly as all three locking screws are tightened.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 22

11) Tighten all loop locking screws. The cavity loss is now set. The cavity will have to be tuned to its operating frequency following the procedures outlined earlier in this manual.

MAINTENANCE

Because T-Pass transmitter multicouplers are composed of mostly passive components, they will continue to operate without any maintenance for years and there is no recommended maintenance period. We do feel, however, that it is wise to check multicoupler performance by measuring channel loss periodically and this may be done at any convenient time along with other radio system maintenance.

ISOLATORS

Isolators perform two important functions. Their primary function is to keep unwanted RF frequencies out of the transmitter so that intermodulation products cannot be generated. Isolators have a substantial amount of reverse isolation. They also ensure that the transmitter never sees any significant reflected power so it will always operate with maximum stability at full-power output. Isolators prevent energy from getting into the transmitters output by dumping any RF energy entering the output of the isolator into a dummy load. The model

73-90-11 series of T-pass transmit combiners will use either single section or dual section isolators at the input to each T-pass channel.

Single-section isolators have one load port. A properly sized load capable of dissipating the maximum expected reflected power that might be encountered should be used. Dual section isolators have two load ports, one for each section. Although loads of equal power rating may be used for both ports, it is customary to use an output load capable of dissipating the maximum expected reflected power that might be encountered. A small load (5 watts) is usually factory installed on the first section of the isolator where high reflected power is not a factor. Refer to Appendix A for a further discussion of isolators.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 23

Appendix A

800 MHz Isolators (Compact Style)

GENERAL DESCRIPTION

Isolators perform two important functions. Their primary function is to keep other RF frequencies out of the transmitter so that intermodulation products cannot be generated. Isolators have a substantial amount of reverse isolation. They also insure that the transmitter never sees any significant reflected power so it will always operate with maximum stability at full-power output. Isolators prevent energy from getting into the transmitters output stage by dumping reflected RF energy entering the output of the isolator into a dummy load.

The 800 MHz (compact style) isolators available from TXRX Systems are broad-band and do not require tuning. The isolators are available as either single section or dual section models. Dual section models consist of two single sections mounted in the same case with a load permanently attached to the load port of the first section. Table A1 lists the

800 MHz isolators available from TX RX Systems along with their performance specifications.

TXRX

Systems

Part #

3-22223P

3-22224P

3-22225P

3-22226P

3-22227P

3-22228P

3-22229P

3-22230P

Freq

Range

(MHz)

764 - 776

794 - 806

806 - 824

851 - 869

870 - 894

925 - 935

935 - 940

940 - 960

Isolation

(dB)

(min)

50

50

50

50

50

50

50

50

Insertion

Loss

(dB) (max)

0.50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

3-22223PL 764 - 776

3-22224PL 794 - 806

3-22225PL 806 - 824

3-22226PL 851 - 869

3-22227PL 870 - 894

3-22228PL 925 - 935

3-22229PL 935 - 940

3-22230PL 940 - 960

50

50

50

50

50

50

50

50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

TXRX

Systems

Part #

Freq

Range

(MHz)

3-22223PLA 764 - 776

3-22224PLA 794 - 806

3-22225PLA 806 - 824

3-22226PLA 851 - 869

3-22227PLA 870 - 894

3-22228PLA 925 - 935

3-22229PLA 935 - 940

3-22230PLA 940 - 960

Isolation

(dB)

(min)

50

50

50

50

50

50

50

50

Insertion

Loss

(dB) (max)

0.50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

3-22223PLB 764 - 776

3-22224PLB 794 - 806

3-22225PLB 806 - 824

3-22226PLB 851 - 869

3-22227PLB 870 - 894

3-22228PLB 925 - 935

3-22229PLB 935 - 940

3-22230PLB 940 - 960

50

50

50

50

50

50

50

50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

0.50

Table A1: Specification for 800 MHz Isolators (Compact Style).

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 24

INSTALLATION

The isolators can be mounted on most types of surfaces but should not be physically located where they will not be exposed to moisture or very high humidity. TXRX Systems isolators are well shielded magnetically and may be mounted on steel cabinets or panels.

The isolators can get quite hot during operation. This can occur when an antenna system component fails causing high reflected power which is then dissipated by the isolator load. These loads can get hot enough to burn skin so use caution when servicing these systems.

VERIFYING ISOLATOR FUNCTIONALITY

If you suspect there may be a problem with an isolator you can verify the functionality of the device by measuring its reverse isolation and insertion loss. It is important to electrically remove the isolator from the system before testing. This is easily accomplished by disconnecting the input and output cables.

WARNING:

Do not make or break cable connections to the isolator while the circuit is under transmit power. Shut down the transmitter before servicing.

RECOMMENDED TEST EQUIPMENT

The following equipment or it’s equivalent is recommended when verifying isolator functionality.

1) Spectrum Analyzer. Bird Technologies Signal

Hawk.

2) A pair of double shielded coaxial cable test leads (RG142 B/U or RG223/U).

3) 50 Ohm load with at least -35 dB return loss

(1.10 : 1) VSWR.

Measuring Reverse Isolation (S12)

The reverse isolation of your isolator can be verified by performing the following procedure in a step-by-step fashion.

1) Make sure the transmitter associated with the isolator is turned off.

2) Disconnect the input and output cable to the isolator.

3) Connect a spectrum analyzer and tracking generator to the input and output ports of the isolator respectively, as shown in Figure A1.

4) Make sure that a 50 Ohm load is connected to the load port of the isolator. If you are testing the isolator on the bench make sure you connect a load. If you are testing the isolator while it is still mounted on the system rack/cabinet leave the existing load connected.

5) Inject a test signal (-10 dBm) from the tracking generator into the output port of the isolator.

The test signal should sweep across the operating bandwidth of the isolator.

6) Compare your displayed waveform against the example shown in Figure A3 as well as the specification listed in table A1.

Measuring Insertion Loss (S21)

The insertion loss of your isolator can be verified by performing the following procedure in a step-bystep fashion.

1) Make sure the transmitter associated with the isolator is turned off.

2) Disconnect the input and output cable to the isolator.

3) Connect a tracking generator and spectrum analyzer to the input and output ports of the isolator respectively, as shown in Figure A2.

4) Make sure that a 50 Ohm load is connected to the load port of the isolator. If you are testing the isolator on the bench make sure you connect a load. If you are testing the isolator while it is still mounted on the system rack/cabinet leave the existing load connected.

5) Inject a test signal into the input of the isolator from the tracking generator which will sweep across the operating bandwidth of the isolator.

The strength of the test signal should be -10 dBm.

6) Compare your displayed waveform against the example shown in Figure A4 and the specification listed in table A1.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 25

Spectrum Analyzer

Bird SignalHawk

Spectrum Analyzer

Bird SignalHawk

Tracking Generator

Tracking Generator

50 Ω Load

Figure A1: Verifying Reverse Isolation.

50 Ω Load

Figure A2: Verifying Insertion Loss.

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 26

Figure A3: Typical reverse isolation waveform.

TX RX Systems Inc.

Figure A4: Typical insertion loss waveform.

Manual 7-9100-5 10/17/11 Page 27

Celsius to Fahrenheit Conversion Table

CELCIUS FAHRENHEIT

77

76

75

74

81

80

79

78

85

84

83

82

89

88

87

86

69

68

67

73

72

71

70

93

92

91

90

97

96

95

94

101

100

99

98

105

104

103

102

177.8

176.0

174.2

172.4

170.6

168.8

167.0

165.2

192.2

190.4

188.6

186.8

185.0

183.2

181.4

179.6

163.4

161.6

159.8

158.0

156.2

154.4

152.6

206.6

204.8

203.0

201.2

199.4

197.6

195.8

194.0

221.0

219.2

217.4

215.6

213.8

212.0

210.2

208.4

CELCIUS FAHRENHEIT

38

37

36

35

42

41

40

39

46

45

44

43

50

49

48

47

30

29

28

34

33

32

31

54

53

52

51

58

57

56

55

62

61

60

59

66

65

64

63

107.6

105.8

104.0

102.2

100.4

98.6

96.8

95.0

122.0

120.2

118.4

116.6

114.8

113.0

111.2

109.4

93.2

91.4

89.6

87.8

86.0

84.2

82.4

136.4

134.6

132.8

131.0

129.2

127.4

125.6

123.8

150.8

149.0

147.2

145.4

143.6

141.8

140.0

138.2

CELCIUS FAHRENHEIT

-1

-2

-3

-4

1

0

3

2

5

4

7

6

11

10

9

8

-9

-10

-11

-5

-6

-7

-8

15

14

13

12

19

18

17

16

23

22

21

20

27

26

25

24

37.4

35.6

33.8

32.0

30.2

28.4

26.6

24.8

51.8

50.0

48.2

46.4

44.6

42.8

41.0

39.2

23.0

21.2

19.4

17.6

15.8

14.0

12.2

66.2

64.4

62.6

60.8

59.0

57.2

55.4

53.6

80.6

78.8

77.0

75.2

73.4

71.6

69.8

68.0

CELCIUS FAHRENHEIT

-40

-41

-42

-43

-36

-37

-38

-39

-32

-33

-34

-35

-28

-29

-30

-31

-44

-45

-46

-47

-48

-49

-50

-24

-25

-26

-27

-20

-21

-22

-23

-16

-17

-18

-19

-12

-13

-14

-15

-32.8

-34.6

-36.4

-38.2

-40.0

-41.8

-43.6

-45.4

-18.4

-20.2

-22.0

-23.8

-25.6

-27.4

-29.2

-31.0

-47.2

-49.0

-50.8

-52.6

-54.4

-56.2

-58.0

-4.0

-5.8

-7.6

-9.4

-11.2

-13.0

-14.8

-16.6

10.4

8.6

6.8

5.0

3.2

1.4

-0.4

-2.2

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 28

Return Loss vs. VSWR

Return Loss

30

25

20

19

18

17

16

11

10

9

15

14

13

12

1.43

1.50

1.57

1.67

1.78

1.92

2.10

VSWR

1.06

1.11

1.20

1.25

1.28

1.33

1.37

TX RX Systems Inc.

3

2.5

2

1.5

1

.5

50

25

28

32

35

40

45

75

38

42

47

53

60

67

Insertion Loss

Input Power (Watts)

100 125 150

50

56

63

71

63

70

79

88

75

84

95

106

79

89

99

111

119

134

Output Power (Watts)

200

100

112

126

142

159

178

150

220

460

860

940

1920

Free Space Loss

Distance (miles)

.25

68

71

78

.50

74

77

84

.75

78

81

87

1

80

83

90

2

86

89

96

5

94

97

104

10

100

103

110

83

84

89

90

93

94

95

96

101

102

109

110

115

116

90 96 100 102 108 116 122

Free Space Loss (dB)

Free space loss = 36.6 + 20log D + 20log F

Where D = distance in miles and F = frequency in MHz

Manual 7-9100-5 10/17/11

250

125

141

158

177

199

223

Watts to dBm

Watts

300

250

200

150

100

75

50

3

2

5

4

25

20

15

10

44.0

43.0

41.8

40.0

37.0

36.0

34.8

33.0

1 30.0

dBm = 10log P/1mW

Where P = power (Watt)

dBm

54.8

54.0

53.0

51.8

50.0

48.8

47.0

15

104

107

113

119

120

126

300

150

169

189

212

238

267

Page 29

8625 Industrial Parkway, Angola, NY 14006 Tel: 716-549-4700 Fax: 716-549-4772 [email protected] www.birdrf.com

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