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MFJ 1708SDR Manual
SDR Transmit/Receive
Model MFJ-1708SDR
CAUTION: Read All Instructions Before Operating Equipment
300 Industrial Park Road
Starkville, MS 39759 USA
Tel: 662-323-5869 Fax: 662-323-6551
2017 M F J E NT E RP RI S E S , I NC.
MFJ-1708SDR Instruction Manual
Transmit/Receive Switch
Software Defined Radios are becoming commonplace, and often have to work
in conjunction with radio transceivers. Some means of protecting the SDR
input is required while the rig is transmitting. Not all radios have an RF out
(protected) jack, and those that do often require some sort of loopback
connection to completethe receive audio path. Radios with IF outputs do not
allow the full spectrum to be monitored. Some means of antenna sharing is often
required which will isolate the SDR during transmit operations. The MFJ1708SDR Transmit/Receive Switch will solve this.
The MFJ-1708SDR T/R switch uses a relay, which switches from transmit to
receive mode. When no power is applied to the unit, it is in the transmit mode.
Once power is applied the relay switches on and the unit is in receive mode.
When the unit senses RF or the control line is grounded from a keyer or PTT
switch, it switches the relay off and the unit is in transmit mode.
The delay adjustment allows you to change how fast the relay switches back to
the receive mode. It is adjustable from 0 to 2 seconds.
The MFJ-1708SDR T/R Switch requires 12 VDC or 110 VAC with MFJ-1312D
power supply.
Power……………2.1mm Coaxial power input jack with center pin positive and
shield negative
PTT….…………..RCA input jack
Delay…………….Controls time delay for switching
Radio….…………SO-239 Coaxial connector
Antenna………….SO-239 Coaxial connector
SDR….…………..SO-239 Coaxial connector
MFJ-1708SDR Instruction Manual
Transmit/Receive Switch
If you have any problem with this unit first check the appropriate section of this
manual. If the manual does not reference your problem or your problem is not
solved by reading the manual you may call MFJ Technical Service at 662-3230549 or the MFJ Factory at 662-323-5869. You will be best helped if you have
your unit, manual and all information on your station handy so you can answer
any questions the technicians may ask.
You can also send questions by mail to MFJ Enterprises, Inc., 300 Industrial
Park Road, Starkville, MS 39759; by Facsimile to 662-323-6551; or by email to Send a complete description of your problem, an
explanation of exactly how you are using your unit, and a complete description
of your station.
MFJ-1708SDR Instruction Manual
Transmit/Receive Switch
MFJ Enterprises, Inc. warrants to the original owner of this product, if
manufactured by MFJ Enterprises, Inc. and purchased from an authorized dealer
or directly from MFJ Enterprises, Inc. to be free from
defects in material and workmanship for a period of 12 months from date of purchase
provided the following terms of this warranty are satisfied.
1. The purchaser must retain the dated proof-of-purchase (bill of sale, canceled check,
credit card or money order receipt, etc.) describing the product to establish the validity of
the warranty claim and submit the original or machine reproduction of such proof of
purchase to MFJ Enterprises, Inc. at the time of warranty service. MFJ Enterprises, Inc.
shall have the discretion to deny warranty without dated proof-of-purchase. Any
evidence of alteration, erasure, or forgery shall be cause to void any and all warranty
terms immediately.
2. MFJ Enterprises, Inc. agrees to repair or replace at MFJ's option without charge to the
original owner any defective product under warrantee provided the product is returned
postage prepaid to
MFJ Enterprises, Inc. with a personal check, cashiers check, or money order for $10.00
covering postage and handling.
3. This warranty is NOT void for owners who attempt to repair defective units.
Technicalconsultation is available by calling the Service Department at 662-323-0549 or
the MFJ Factory at 662-323-5869.
4. This warranty does not apply to kits sold by or manufactured by MFJ Enterprises, Inc.
5. Wired and tested PC board products are covered by this warranty provided only the
wired and tested PC board product is returned. Wired and tested PC boards installed
in the owner's cabinet or connected to switches, jacks, or cables, etc. sent to MFJ
Enterprises, Inc. will be
returned at the owner's expense unrepaired.
6. Under no circumstances is MFJ Enterprises, Inc. liable for consequential damages to
person or
property by the use of any MFJ products.
7. Out-of-Warranty Service: MFJ Enterprises, Inc. will repair any out-of-warranty
product provided the unit is shipped prepaid. All repaired units will be shipped COD to
the owner. Repair charges will be added to the COD fee unless other arrangements are
8. This warranty is given in lieu of any other warranty expressed or implied.
9. MFJ Enterprises, Inc. reserves the right to make changes or improvements in design or
manufacture without incurring any obligation to install such changes upon any of the
products previously manufactured.
10. All MFJ products to be serviced in-warranty or out-of-warranty should be addressed
MFJ Enterprises, Inc.
300 Industrial Park Road
Starkville, Mississippi 39759 USA
and must be accompanied by a letter describing the problem in detail along with a copy
of your dated proof-of-purchase.
11. This warranty gives you specific rights, and you may also have other rights
which vary from state to state.
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