Kachina_1_serv

Kachina_1_serv
 Kachina
Communications
6 METERS
| 65 WATTS
10 METERS
75 WATTS
3 The Kachina 1* is an Amateur Band SSB - AM all Solid State Transceiv-
3 er covering the entire 6 and 10 meter Amateur Bands. I
@ In addition to a highly selective 2.5 KHz Crystal Filter for SSB operation the
Kachina 1 provides a 6 KHz wide Crystal Filter for true AM Reception.
, m A Two Speed Dial Mechanism allows 1 MHz band coverage preventing con-
stant changing of the Bandswitch, yet easy tuning of SSB.
4% M The Kachina 1 has no RF Stage. Long ago, - m Low Frequency VFO, actually tuning from 5 MHz
В military receivers got rid of cross modulation pro- to 6MHz ensues low drift and a Treasceiver that
: a ducing, spurious “generating, RF Stages arid as a stays on frequency.
- result achieved a superior performance in orl m Very Small Physical Size. Only 8” wide, 3" high
= presence of strong: nearby transmitters. The per- + and 10%” deep. Leaves lots of room for the
= … formance of the Kachina 1 in this regard is | passenger s legs. Weight 8% pounds. 5
Je. .. Gutstanding. ВЕ и A m For Base Station operation an identically styled
| — | | DA a ; power supply is available,
| ~~ + * The KACHINA isa doll used by the Hopi Indians to illustrate the ~~ ES
D ‘communication of legends fi from. one generation to another. £ a
AMATEUR BAND SSB - AM TRANSCEIVER
-— SPECIFICATIONS
516-423-3614
General
All Solid State Transceiver using the latest in integrated circuits and broadband
transmitter circuits.
“28-30 Mz 26-30 MHz
50 - 54 MHz 50 - 54 MHz
(In 1 MHz bands. No-extra à crystals required) | |
SDR a <*--
MODES OF OPERATION AM Uses envelope detection and 6 KHz
wide crystal filter,
SSB Upper and Lower Sidebands u using
product detection and a 2.5 KHz
wide crystal filter.
POWER SUPPLY 13.6 volts nominal at a peak current of 8 amps.
* Negative ground only. Optional Power Supply
in matching cabinet available.
Transmitter a Receiver
MN POWER INPUT (Nominal) SIGNAL TO NOISE
6 Meters 65 watts PEP SSB. Better than 1 uv for 10 db S+N/N
16 watts average AM. E AUTOMATIC GAIN CONTROL
10 Meters 75 watts PEP SSB. | Within 10 db from 5 uv to 0.1 volts.
20 watts average AM. | E AUDIO OUTPUT
Mm SPURIOUS RADIATION More than 3 watts with no more than
Better than -50 db. Co 5% distortion. E
Mm CARRIER SUPPRESSION ” ~~ “= + “m SQUELCH |
Better than -40 db. Adjustable threshhold.
um ANTENNA IMPEDANCE E NOISE BLANKER ВЕ
50 ohms nominal. (The broadband transmitter RF pulse cancelling type
output circuitry allows considerable mismatch)
DISTRIBUTED BY:
PM ELECTRONICS
COMMUNICATIONS
© 410 OAKWOOD ROAD
PAT MARTINES HUNTINGTON STATION, N.Y. 11746
KACHINA 1 SSB TRANSCEIVER
THEORY OF OPERATION
The Kachina 1 Amateur Band Transceiver is a highly sophis-
ticated, state of the art, piece of communication equipment,
housed in the smallest of packages. Yet, the transceiver is
simple to an extreme when it is considered that not only does
it transmit and receive upper and lower SSB; but it also re-
ceives AM, using a special AM detector, and transmits double
sideband AM. The transceiver contains a noise blanker and squelch.
It covers from 26 - 30 MHz and 50 - 54 MHz in 1 MHz bands without
accessory equipment.
To make the explanation of the circuit as simple as pos-
sible, two block diagrams have been presented, one shows the
operation in the receive condition and the other shows the oper-
ation in the transmit condition. Asterics denote components
common to both the receive and transmit modes.
RECEIVE CONDITION:
Signal from the antenna is fed to the mixer through a hi pass
filter, L27, L28, 129, C127, C128, set of bandswitched bandpass
couplers, Ll through L4. (Shown as a single block in the block
diagram.) Here the signal is mixed with local oscillator voltage
provided by the oscillator IF amplifier chain, the output fre-
quency of which covers the range 38 - 42 MHz. When the signal
frequencies, 26 - 30 MHz are subtracted from the local oscillator,
output at 12 MHz IF frequency results. Conversely, when the local
oscillator frequencies are subtracted from the signal frequency,
50 - 54 MHz, a 12 MHz IF frequency also results. Thus by either
adding or subtracting the one set of local oscillator signals,
both the 6 and the 10 meter bands are covered.
Because a VFO running at 38 - 42 MHz would be highly un-
stable, a heterodyne system is used, in which; a VFO operating
from approximately 5 - 6 MHZ is beat with one of four crystals,
33 MHz, 34 MHz, 35 MHz and 36 MHz, to produce the sum frequencies
of 38 - 42 MHZ. A band pass amplifier system, 019 and Q20
selects only the wanted signals. The 5 - 6 MHz VFO Ql7, is
amplified and isolated by amplifier 018 and mixed with the out-
put of crystal oscillator 016 in the balanced diode ring mixer
D25 through D28.
In order to keep cross modulation products as low as pos-
sible, IF amplifier Ql provides only sufficient amplification to
overcome the losses in the balanced mixer and the crystal fil-
ter. (Filter insertion Loss = 4 db Maximum)
The crystal filter is internally diode switched from the
AM to the SSB condition when the mode switch is activated.
Integrated circuit amplifier ICI provides most of the gain
in the IF system and in addition provides approximately 90 db
of AGC control. The output of the integrated circuit is coupled
through an IF transformer to the product detector Q3 (used only
to detect SSB), and also through resistance coupled amplifiers
Q5 and Q6. The output from these amplifiers is then coupled to
the AGC detectors, the Am detectors and the squelch/S meter de-
tectors. DC amplifier Q7 amplifies the output of the AGC detector
and applies the control voltage to pin 5 of IF amplifier ICI.
DC amplifiers Q8 and Q9 amplify the DC voltage output from
the squelch detector and squelches first audio simplifier 04.
DC amplifier Ql14 amplifies the output from the squelch/S
meter detector and actuates the S meter.
The output from the AM detector directly feeds the first
audio amplifier 04.
Audio amplifier Q4 drives integrated amplifier IC2. The
volume control is connected between the two amplifiers.
Note that the audio output IC is directly coupled to the
speaker and no transformer is used.
In the SSB condition beat frequency oscillator Q12 provides
BFO voltage to the product detector through the emitter follow
013. The BFQ selects one of two crystals, a 12MHz crystal
(nominal) for the upper sideband operation and an 11.997 MHz
crystals are switched, the received frequency is also moved
and it is thus necessary to diode switch a small capacitor
across the VFO coil (not shown in the block diagram) to compen-
sate.
A noise blanker amplifier (IC, Q501) samples signal from
the antenna, detects the noise pulses, amplifies the pulses
(0502 and 0503), then applies the pulses to the transistor
switch Q15 (used as two diodes) to short the input to the crystal
filter during the pulse. Note that the noise blanker, to be
effective, must not be preceeded by highly selective circuits
and thus are often prone to cross modulation in the presence of
strong signals.
TRANSMIT CONDITION:
Refer to the transmitter block diagram. There are two mic-
rophone amplifiers, Ql0 and 011 which drive the double balanced
diode modulator D20 through D23. Carrier is supplied to the
modulator from the carrier generator Q12 and amplifier Q13 (BFO
in the receive condition). One of two crystals, 12 MHz (nominal)
or 11.997 MHz (nominal) are selected for either upper or lower
sidebands.
Carrier is balanced out in the balanced modulator (SSB mode)
and the resultant double sideband signal is fed into the crystal
filter where, in the case of SSB, the undesired sideband 1s re-
moved.
In the AM condition, the balanced modulator is unbalanced
by feeding into the modulator a DC voltage, via R63), thus allow-
ing carrier output. At the same time, the crystal filter is in-
ternally diode switched to a 6 KHz wide (nominal) band width,
allowing both sidebands and the carrier through.
Following the crystal filter is the IF amplifier ICI, fol-
lowed by diode gate D5 and diode mixer D1 through D4, which mixes
the IF signal with the VFO amplifier output to produce a signal
frequency in the 10 meter band or the 6 meter band dependent up-
on which tuned circuits are selected, Ll through L4. Output
from the tuned circuits in then fed through diode gate D30 to
the transmitter linear amplifiers Q201 through Q205.
The linear amplifier section is located on the large black
heatsink at the rear of the transceiver. Because transistors
at these frequencies fall off at approximately 6 db per octave,
their gain is considerable at the lower frequencies. A high pass
filter (not shown on the block diagram) is incorporated to atten-
uate all signals below the 10 meter band. This filter is sit-
uated between the tuned circuits and amplifier 0201. Transistors
0201, 0202 and 0203 are standard class A amplifiers followed by
two push-pull class B amplifiers Q204 and 0205. Output from
the final amplifiers is then fed to low pass filters (switched)
through the antenna relay to the antenna. 1.30, connected across
the antenna co-axial socket is part of the filter system.
RF is sampled from the output of the transmitter amplifier,
rectified and amplified by transistor Ql4 to activate the meter.
Referring back to the VFO section, this part of the circuit
is identical with that described in the receiver section (Q17,
018, Ql6, Q19 and Q20).
Bias to the various transmitter amplifiers is provided,
using silicon, silver lead diodes which sample the heatsink tem-
perature and adjust the bias accordingly. In the case of the
push-pull finals a bias amplifier Q206, provides a stiffer source
than can be provided by the diodes alone.
II. DETAILED THEORY OF OPERATION
RECEIVE CONDITION
1.
Signal from the antenna is applied to the antenna
relay through one of two pi networks. (See transmit
section). When the antenna relay is not energized
the relay is in the receive condition and the sig-
nal is applied through the high pass filter, then
through diode gate D29 to the wiper arm of the band-
switch SW3. Transmit diode gate D30 15 in the OFF
position. SW3 selects one of two band pass couplers,
Ll and L2 in the 10 meter band section and L3 and LA
in the 6 meter band section. SW2 connects the out-
put to the diode mixer circuit at LS.
The mixer circuit, diodes D1 through D4, mixes the
local oscillator voltage, injected into potentiometer
Pl, with the signal, to obtain an IF frequency of
12 MHz. This signal is then fed through IF trans-
former L7, to amplifier Ql. Diode D5, used in the
transmit condition, is OFF.
Output from Ql is connected to the crystal filter
FLL.
Transistor gate Q2, used in the transmit condition,
is OFF.
The crystal filter is internally diode switched.
When an external voltage from the AM/USB/LSB selector
switch is applied to the filter through R12, the
filter switches to the SSB position. The same filter
10.
11.
is used on both sidebands. Sideband selection
takes place by changing the BFO crystal. (Des-
cribed later).
Output from the filter is connected to the inte-
grated circuit IC1 where most of the IF amplifica-
tion takes place. The IF transformer L9 then feeds
signal to the product detector Q3 for SSB operation,
and to the amplifier 05 and Q6 for AM operation.
Dealing first of all with the SSB operation, BFO
voltage from the BFO generator Q12 and amplifier Q13
is injected into gate 2 of (Q3 and mixing with the
SSB signal takes place.
The audio output from the product detector is fed
into the first audio amplifier Q4.
In order to prevent simultaneous operation of the
AM detectors D13 and D15, D13 is back biased with
a voltage from the AM/SSB selector switch, preven-
ting its operation. In AM operation the product
detector Q3 is rendered inoperative simply by
switching the BFO voltage off.
AM IF amplifiers Q5 and 06 also supply signal
voltage to the squelch detectors D14 and D15. (D15
also used to detect AM). The DC output form D14
also feeds the S meter amplifier Ql4.
In addition, output from Q6 supplies signal voltage
to the AGC detectors 010 ап@ 011. “Note that Dll is
connected to a voltage divider which applies approx-
12.
13.
14.
imately 3.5 volts to the anode of Dll, effectively
preventing rectification until the signal level is
sufficient to overcome the bias. This gives a very
necessary "knee" to the AGC characteristics, pre-
venting "pumping" of the SSB signal.
Output from the AGC detector D10 is applied to the
base of AGC DC amplifier Q7 and the AGC capacitor
C44.
Transistor Q7 is an emitter follower which drives
pin 5 of integrated circuit ICl giving more than
90 db of AGC control.
Capacitor C44 and resistor R42 determine the AGC
time constant. Transistor Q8 is a DC amplifier of
the rectified squelch voltage. Potentiometer P302,
on the front panel, reduces the positive voltage
derived from R51, so that the collector swings posi-
tive. This positive voltage is then used to in-
crease the current flow through DC amplifier Q9
causing its collector to swing negative, allowing
diode gate D12 to conduct. As the base voltage of
04 is normally about 1.2 volts above ground (due
to the drop across D32 and the Q4 base emitter
barrier potential) the saturated state of Q9 virtu-
ally grounds the base of Q4 and shuts off the audio.
However, when a positive DC voltage developed
accross the squelch rectifier, D14 is applied to
the base of 08, its collector goes nagative. This,
in turn, causes the collector of Q9 to go positive
15.
16.
17.
18.
and diode gate D12 is reversed or OFF.
The signal voltage which created DC output from
D14 is also applied to S meter amplifier, Q14,
which stage operates as an emitter follower and
drives the S meter.
Transistor 012 is a Colpitts type crystal oscil-
lator supplying BFO voltage to the product de-
tector 03 in the receive condition, and carrier
voltage to the balanced modulator in the transmit
condition. In the upper sideband condition, 12 MHZ
BFO voltage is developed and in the lower sideband
condition 11.997 MHz voltage is developed. In the
receive AM condition the BFO supply voltage is
turned off. In the transmit AM condition only the
12 MHz crystal is activated. Note that the two
quoted frequencies are approximate only, in actual
fact the BFO crystal frequencies may be adjusted
to be approximately 15 db down the filter slopes.
Because moving the BFO frequency causes a simul-
taneous shift in incoming frequency (and transmit
frequency), a compensating network consisting of
diode switch D33, capacitor Cl07 and resistor R82,
moves the VFO frequency an approximate equivalent
and compensating amount when in the LSB position.
The voltage for this action is supplied by the side-
band selector switch (in the LSB position only).
The local oscillator frequencies are developed in
19.
20.
21.
22.
23.
10.
a heterodyning process hy mixing the VFO output
frequency (approximately 5 MHz to 6 MHZ), with one
of four crystals, 33 MHz, 34 MHz, 35 MHz and 36 MHz,
to obtain output frequencies of 38 MHz to 42 MHz in
1 MHz steps. This latter frequency is then mixed
in D1 through D4, with signals from either the 10
meter band or the 6 meter band according to which
tuned circuits are selected by the bandswitch, (See
II, 1.) and a 12 MHz IF frequency results.
017 is an FET, Colpitts, VFO, direct coupled to
emitter follower and isolating amplifier, Q18, which
drives diode balanced mixer D25 through D28, through
low pass filter L20 and Cl03.
. 016 is an overtone oscillator which supplies the
33MHz through 36 MHz crystal frequencies to the mixer.
Note that this oscillator does not use inductors to
obtain third overtone operation, and that its capaci-
tor/resistor values are critical to correct operation.
Both oscillator frequencies are added together in
the mixer and then fed to the band pass coupler Ll3
and Ll6, which removes unwanted signals before ampli-
fication by amplifiers Q19 and Q20. Output from Q20
drives the receiver mixer through IF transformer L17.
Because 019 and Q20 are wideband amplifiers, they
generate considerable white noise. Balance control
Pl is adjusted for balance so that the noise compo-
nent is minimized.
Audio output amplifier IC2 delivers more than 3 watts
24.
T RANSMIT
11.
of audio to the speaker. Note that the IC is a trans-
formerless amplifier. The extention speaker should
have an impedance of 3 ohms.
The noise blanker is located on the small "outrigger"
printed circuit board fitted to the "mother" board/ .
underside. Input from the antenna is fed into the
integrated circuit Q501 through step up transformer
L501 and high pass filter L27, L29. The amplified
signal is then fed to diode rectifier D501 through
transformer L502. The time constant of the recti-
fier output circuitry is very short, (C506, R505)
efficiently rectifying only pulses which are then
amplified by FET Q502 and bipolar transistor Q503.
The resultant pulse is fed to transistor Q15 on the
main printed circuit board. The function of Q15 is
unusual in that it operates as two diodes, formed
by the base emitter junction and the base collector
junction. Whenever a noise pulse arrives, the two
diodes conduct and short out the input signal to
the crystal filter for the duration of the pulse.
It should be noted that noise blanker circuits, be-
cause they must be preceded by little selectivity,
are prone to cross modulation, in the presence of
very strong signals.
CONDITION
25.
Microphone input is applied to audio amplifiers Q10
and 011. Q11 operates as an emitter follower sup-
plying low impedance audio to the balanced modulator
26.
27.
28.
29.
12.
(D20 through D23.)
Carrier voltage generated by transistors Q12 and
Q13, (See Sec. II, No. 16) is supplied to the
balanced modulator through the potentiometer P3.
The balanced modulator mixes the audio signal
with the carrier frequency and at the same time
allows the carrier to be suppressed. Controls
P3 and C70 allow a fine adjustment of the carrier
balance. The output of the balanced modulator is
double sideband suppressed carrier.
When the front panel SSB/AM selector switch is
in the AM position, an adjustable positive DC
voltage is applied to the diodes through resistor
R66 and causes a carrier unbalance allowing car-
rier output. The size of the carrier is adjusted
by pre-set potentiometer Р2.
The double sideband output from 112 is fed to the
crystal filter FL] through diode gate D24 and
transistor gate Q2.
In the transmit condition a positive voltage from
the control line (See Sec. II, No. 44) is applied
to the base of Q2 via R15, causing the stage to
saturate and conduct. The resultant DC voltage
developed across R14 forward biases the normally
open diode gate D24 and the double sideband signal
from the balanced modulator is applied to the crys-
tal filter through resistor R9.
30.
31.
32.
33.
34.
13.
In the transmit mode, transistor Ol is turned off
by applying a positive voltage from the control
line through D7 and R10 to the emitter. A positive
voltage at the emitter is the same as applying a
negative voltage to the base and the stage is ef-
fectively shut down.
For a discussion on the crystal filter see Sec. II,
No. 5. In the SSB mode the filter removes one
sideband of the double sideband signal, but allows
both sidebands to pass in the AM mode.
Output from the filter is amplified by integrated
circuit IC2 and fed into IF transformer L9. The
IF transformer feeds the product detector Q3 but
as the following audio transistor Q4 is shut down
in the transmit condition, no audio output results.
At the same time, output from L9 is conducted
through R19, C29, C15, D5 and Cl1 to balanced
mixer toroid input winding on L6. Although there
is also signal voltage on L7, Ql has been shut
down. (See Sec. II, No. 30)
The balanced mixer circuit D1 through D4 mixes the
signal with the local oscillator voltage and pro-
duces a signal output in both the 6 and the 10
meter bands. For a discussion of the local oscil-
lator system see Sec. II, No. 18 through No. 22.
As both € meter and 10 meter signals are available
at the output of the mixer a means must be used to
select the particular band required and this is
35.
36.
37.
38.
39.
40.
14.
done by band pass couplers L1 and L2 in the 10
meter bandswitch position, and L3 and L4 in the
6 meter position. These couplers are also used
in the receive condition and are discussed in
Sec. II, No. 1.
Qutput from the couplers are fed through diode
switch D30, the transmitter linear amplifier
module on the large heat sink at the rear of the
transceiver.
Diode switch D29, normally closed in the receive
condition is now open or OFF.
Due to the fact that the transistors used in the
linear amplifier module have a considerably higher
gain at the lower frequencies, especially around
14 MHz, than they have at 28 MHz and 50 MHz, it
was necessary to fit a high pass filter at the
input to the amplifier module. This filter con-
sists of the components C205, C206 and L207.
Signal from the filter is amplified by wideband
Class A amplifiers 0201, 0202, 0203 and Class B
push pull amplifiers Q204 and Q205.
The outputs of 0204 and 0205 is combined in the
output transformer L206.
Bias to the various amplifiers stages is set by
silver lead diodes, which diodes sense the tem-
perature of the environment and the heatsink and
adjust the bias accordingly. Similarly, if the
supply voltage is varied, the diodes maintain a
15.
constant bias voltage.
41. The Class A stage bias is controlled by diodes
D201 and D204, and the Class B stage bias 1s
controlled by diodes D203 and D204 together with
follower amplifier Q206. Bias to the final stages
is controlled by potentiometer P201, normally a
factory adjustment.
42. Output from the linear amplifier is fed by twisted
pair cable to either the 6 meter or the 10 meter
network sections, which effectively remove har-
monics generated in the amplifiers. As 2nd har-
monics are already considerably reduced by the
push pull operation of the final output transis-
tors, a simple single section pi network is suf-
ficient. L30 is part of the network system.
43. Output at the antenna socket is sampled by capa-
citor Cl14 and rectified by diode D31 and the out-
put then fed to the "S" meter amplifier Q14, which
in turn causes the meter to show a relative power
output condition. Note that the reading can only
be relative and will vary somewhat according to
the SWR of the antenna.
CONTROL CIRCUITS
44. When the microphone push to talk switch is actuated,
one end of the relay coil of Kl is grounded. As
the other end of the coil is connected to the po-
sitive supply voltage through polarity protect
45.
46.
47.
48.
16,
Diode D17, the relay closes. The moving arm of a
parallel set of relay contacts, normally grounded
in the receive condition, is connected to the positive
supply voltage; and a positive control voltage is
supplied to the following, turning them ON:
a. Entire linear amplifier module.
Ь. D30, D5, D24, 02, Q4 through D9, IC2 through
R94, Q12, Q13 and D13 via SW1 (only when in the AM
mode), Q6 through D6.
The following devices are turned OFF when the
control line is made positive:
D29, D8, D19, Ql via D7
The following devices are turned ON when the control
line is grounded (receive condition):
Ql, 04, Q6, D13, D29 D8
In order to prevent a certain amount of audio output
from the speaker due to leakage across. the chasses,
IC2 is turned off when in the Transmit condition.
Due to hetrodynim principle used in the Kachina 1,
the transceiver would be capable of operation on
both the 26 MHz and 27 MHz bands. However, in order
to comply with the law, transmission on these two
bands has been prevented.
SUPPLY VOLTAGES
49.
The nominal voltage which should be supplied to the
Kachina 1 is 13.6 volts. However, the transceiver
will not be damaged if voltages as high as 16 are
applied.
17.
Most of the stages in the transceiver are supplied
from a regulated 8.2 volts provided by the Regulator Circuit
D16 and R30. Because of voltage drop across the resistance
of the RF Choke L10, the voltage on the output side of
the choke will be a little lower than 8 volts. The
figure of 8.2 volts is nominal and may, in fact, vary as
much as 10% from this figure.
18.
SECTION III
ALIGNMENT, ADJUSTMENTS AND TEST PROCEDURES
1. The Kachina 1 transceiver contains a lot of functions
in a small package. Yet the alignment and adjustment
processes are relatively simple. However, these adjust-
ments must be conducted with considerable care; and
good test equipment should be available. In particular,
a high-frequency oscilloscope should be available and
a VTVM for reading voltage across the dummy load in the
transmit condition. UNDER VOICE CONDITIONS, A WATTMETER
IS QUITE USELESS TO READ SSB POWER OUTPUT. Alignment
should be conducted in the following manner and in the
order given:
BFO
2. Connect a frequency counter to the emitter of 013.
With the Mode Switch on LSB, adjust the Trimmer Capacitor
C75 (nearest the rear) until the frequency reads 11997.00
kHz. Switch to USB, and adjust C74 (nearest front) until
the frequency reads 12000.00 kHz.
VFO Connect the counter to the emitter of Q18. Turn
the bandswitch to 27 MHz and the tuning capacitor fully
meshed. Adjust the coil slug L18 until the counter reads
4950 kHz. THIS IS A TEMPORARY ADJUSTMENT until the VFO IF
is aligned. Final adjustment is given in Paragraph 4.
3. Local Oscillator IF Amp.
Connect the oscilloscope to the output of R17, where
it connects to the 47 ohm Resistor Rl. Set the VFO Tuning
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19.
Capacitor to full mesh. Set the Bandswitch to 26 MHz,
and adjust IFT L15 for full output. (Rear IFT) Set the
Bandswitch to 29 MHz, and adjust Li6 for maximum output.
(Center IFT) Work back and forth (as there is inter-
action) until no further increase in output can be obtained.
Set the bandswitch to 28 MHz, and adjust L17 for maximum
(IFT nearest the front).
4. VFO Calibration
Remove the oscilloscope from the output of L17, above,
and connect the counter in its place. Set the dial to
Half Mesh and the Bandswitch to LSB. Set the Tuning
Capacitor to Full Mesh, and adjust the coil slug L18 to
read 39950.00 kHz. Turn the Tuning Capacitor fully out
of mesh, and adjust the Trimming Capacitor C105 until the
frequency reads 41010.00 kHz. It will now be found that
this latter adjustment upsets the first adjustment, so
the slug is again set to 39950.00 kHz with the Tuning
Capacitor Plates in full mesh. Repeat the high frequency
end adjustment, and continue back and forth until both
ends read correctly. This is a somewhat tedious operation
and msut be carefully perfcrmed if a linear dial reading
is to be obtained.
Set the Tuning Dial to a frequency of 40200.00 kHz,
then fit the dial drum so that the scale reads 200. The
Mode Switch should be in the LSE position for this
operation. When the drum is secured, check the dial
calibration against the Cursor Line. The reading should
be within 3 kHz. If the error is greater than 3 kHz--
but not excessively so--the drum may be turned a little
20.
to give, say, a smaller error over a greater part of
the scale. Remember that a 2 kHz error is about the
width of the window line.
Note that the plastic dial drum rides on 4 wires.
The drum must just touch these wires so that vibration
of the drum cannot take place in mobile operation or a
"warble" on the SSB signal will take place. The vibration
is actually causeing frequency modulation by moving the
VFO capacitor shaft. The wires must not be bent up too
high or they will cause drag of the tuning mechanism.
5. Crystal Oscillator
The Crystal Osciallator Ql6 needs no adjustment.
However, a check on proper operation may be made by read-
ing frequency of the local oscillator output at the out-
put of L17 and observing that the output changes in
1 MHz increments as the Bandswitch is rotated. The 50 MHz
to 53 MHZ positions will be a repeat of the 26 to 29 MHz
positions.
6. VFO Sidestepping
As outlined in Section 17, the VFO is sidestepped
when the LSB Sideband Crystal is activated. This may be
checked as follows. Connect the frequency counter to
the output of L17 and the junction of Rl. Turn the
Tuning Dial to approximately midrange. Set the Bandswitch
to any convenient position, and read the frequency with
the mode switch in the AM position. Now switch to the
LSB position. The frequency should read approximately
3 kHz lower in frequency. Switch to the USB position.
The frequency should be the same as that obtained on AM.
21.
7. IF Alignment
Connect the Signal Generator to the Antenna Terminal
and a meter across the speaker. Set the Mode Switch to
LSB. Set the Bandswitch and Dial to 28600 kHz. Advance
the Signal Generator until the signal can just be heard.
Adjust the IF Transformers L7 and L9 for maximum output.
Detune the Signal Generator, and adjust the Potentiometer
Pl (located at the front edge of the printed circuit board)
for minimum white noise output as read on the Output
Meter. Note that the minimum point may shift a db or so
from band to band, so other bands should be checked; and,
if need be, a compromise setting made. In any case, a
S+N/N of at least 10 db for 1 uv should be obtained.
8. Front-End Alignment
This process is best done in the transmit condition
because the tuned circuits 11, L2 and L3 and L4 are con-
nected between the exciter proper and the linear amplifier
when in the Transmit mode. The adjustment will then be
correct for the receiver mode. However, a preliminary
adjustment should be made by setting the dial to approxi-
mately 28200 kHz and aligning L1 and L2. Then set the
dial to 50200 kHz and align L3 and L4 for maximum output.
See Section 15.
9. Checking the AGC
There are no adjustments to be made to the automatic
gain control system. However, proper operation of the AGC
System is dependent upon proper operation of other parts
of the circuit. A quick check may readily be made by
22.
measuring the DC voltage at the Emitter of Q7. This point
is labeled AGC on the bottom of the printed circuit board,
on the lefthand edge near the 1000 mfd 10 volt electrolytic
capacitor. With no signal, the voltage should read around
4 volts DC. As the signal level is increased, the voltage
will also increase. As a further check, the Audio Meter
should be connected across the speaker and the Generator
set to 5 uv. The audio gain control should be set to a
level well below audio amplifier overload. Advance the
Signal Generator output and read the audio increase. The
increase should not be more than 12 db from 5 uv to
0.1 volts.
10. Checking the Squelch
There are no internal squelch adjustments. However,
proper operation is dependent upon the proper operation
of other parts of the circuit. A check may be made as
follows: Set the Mode Switch to LSB and, with the Signal
Generator Output fully attenuated, adjust the Squelch
until muting just occurs. It will be found that there
is a little backlash in the squelch point, and the control
should be advanced carefully back until the audio is just
beginning to unsquelch. This is a most sensitive point.
Now advance the Signal Generator output. The Squelch
should open on less than 1.5 uv of signal. Note that if
there is any BFO voltage getting into the front end of
the receiver this will open the Squelch, and a larger,
opposing Squelch voltage will be required, and thus a
larger signal to overcome to voltage. This may be simply
checked by operating the Squelch in the AM position when
23.
when the BFO is turned off. Note that if the balanced
modulator is badly out of balance, BFO voltage may be
sufficient to overcome the normally shut off Q2 and enter
the IF amplifier system. In all but early models of
the Kachina 1, a diode--D24--has been placed in series
with the emitter of Q2 giving increased isolation from
the BFO when in the Receive position.
11. S Meter, Receive Condition
There are no adjustments to be made to the S Meter
system. However, proper operation of the S Meter is
dependent upon other parts of the circuit. As the S
Meter circuit shares components common to the AM and
Squelch Detection systems, a defect in any one part of
the system may well affect the S Meter system. For
example, BFO voltage leaking into the IF system will not
only affect the Squelch operation but will also affect
the AGC system and cause the S Meter to read when no
signal is being received. It is normal, however, to
have the S Meter show up to an S1 signal when in the
SSB modes.
12. Sensitivity
A simple check on receiver sensitivity may be per-
formed as follows: Set the Bandswitch to 28 MHz and
the dial to approximately 600. Connect the audio volt-
meter across the speaker and the signal generator output
to the antenna socket. Set the generator output to 1 uv
and measure the voltage develcped across the speaker
when the Audio Gain Control is fully advanced and the
Mode Switch is set to LSB. The voltage across the
24,
speaker should measure between 0.5 and 1 volt. Note that
this measurement--alone--is quite meaningless and could well
be a measure of how good the receiver operates as a noise
generator. However, if the signal to noise reading is
satisfactory, then the reading is a good measure of satis-
factory operation. Note if the receiver will not make
the sensitivity measurement, then it is highly unlikely
it will make the AGC test,
Switch the Signal Generator to 30% modulation and
the Kachina 1 to AM. Output across the speaker should
be better than 0.5 volts, typically 1 volt.
13. Signal to Noise Ratio (5+N/N)
Connect the Signal Generator and set the Receiver
Mode Switch to LSB. set the Generator to 28200 kHz--
no modulation--and tune in the signal until a beat note
of about 1 kHz is obtained. Set the Receiver Audio Gain
Control until an audio output meter connected across
the speaker shows no more than 1 volt. Detune the
receiver until no beat note is heard, and note the drop
in meter reading. The meter should have dropped at
least 10 db, typically 15 db.
Turn the Kachina 1 to AM and the Generator Modula-
tion to 30% at 3 u volts output, and note the reading on
the Audio Output Meter. Turn off the modulation. The
output should drop at least 10 db, typically 14 db. This
measurement measures the signal and the noise against
the noise. Note that this reading may drop slightly
after the front end tuned circuits are broadbanded.
25.
TRANSMITTER
14. Band Pass Coupler Alignment
Connect the dummy load and set the Mode Switch to
AM. A VTVM such as the Hewlett Packard 410B should be
connected across the dummy load and set to the 100 volt
scale. A high-frequency oscilloscope should also be
connected across the dummy load. Turn down the microphone
gain control, and press the microphone Push-To-Talk Switch.
Note the carrier output on the VTVM. On the 10-meter band,
this should be approximately 30 volts. Now check the
output on 28, 29 and 30 MHz. If the voltage is very
uneven, align L] and L2 as follows: Set the Bandswitch
to 28 MHz and the Dial to O. Adjust L2 (the rear metal-
cased coil under the Bandswitch) for maximum output. Set
the Bandswitch to 29, and set the dial to 500. Adjust
L1 (the metal-cased coil nearest the front under the Band-
switch) for maximum. As there is some interaction between
the settings, work back and forth until the output is as
even as possible. It is normal to have as much as 4 volts
difference between the ends. Repeat the operation on 50
and 53 MHz, this time adjusting the uncased coils L3 and L4.
Note that is one particular part of the band is favored,
the coils may be aligned at that frequency. It is assumed
that the Carrier Balance Controls and the AM Carrier
Controls had previously been adjusted.
15. SSB Carrier Balance
Connect the dummy load, the VTVM and the oscilloscope
as indicated in the last paragraph. Turn the Mode Switch
to SSB. Turn the Microphone Gain Control completely down.
26.
Press the Push-To-Talk Switch. Turn up the VTVM and Scope
Gain. If the carrier is greater than 0.1 volts peak-to-
peak, adjust the Carrier Balance Controls C70 and P3. The
controls are located right at the rear of the main
printed circuit board and are screened CAR BAL on the
board. Turn first the Potentiometer for a minimum output.
Then turn the Capacitor for minimum. Return to the Poten-
tiometer. If the control will not reduce the output
further, turn the shaft slightly so as to double the output
and go back to the Capacitor. The output should decrease.
If not, return to the Potentiometer and set it on the
other side of minimum and null the Capacitor again. Work
back and forth until the absolute minimum is obtained.
Check the USB position; and if the carrier increases, go
through the operation once more. IMPORTANT NOTE: If
the carrier balance is not complete, some distortion of
the AM signal may become apparent when using AM. See
next paragraph.
16. AM Carrier Level
The AM Carrier Reinsertion Potentiometer is right
alongside the SSB/AM Mode Switch and is screened AM CAR
on the board. This control sets the amount of carrier
when in the AM mode. IMPORTANT NOTE: The Kachina 1 uses
low-level modulation, therefore only % of the SSB power
should be transmitted in the form of carrier, or distortion
will result. Increasing the carrier level beyond the
correct amount will actually decrease the intelligibility
of the signal for the modulation will be all negative
27.
and have no positive excursions. The Carrier Level is
normally set to 30 volts on the VTVM, which is 18 watts
on the dummy load. Advance the microphone gain to about
9 o'clock, and whistle while observing the oscilloscope.
The RF voltage should double in amplitude on the peaks
and drop to Zero in the valleys. If the Carrier Level
is too high, the amplitude will not double on peaks;
and it will be necessary to reduce the Carrier Level.
If the Microphone Gain is advanced too far, note that
the valley in the waveform will begin to fill in and
"double hump." This indicates too much audio gain.
To an AM listener, too much microphone will turn the
signal into Sideband, and he will claim it is distorted.
However, were he to switch his receiver to S5B, he would
find that it was 100% copy. IMPORTANT: IF THE
CARRIER BALANCE CONTROLS ARE ADJUSTED AFTER THE AM
CARRIER LEVEL IS SET, DISTORTION OF THE SIGNAL WILL
RESULT, AND IT WILL BE FOUND IMPOSSIBLE TO OBTAIN NEGA-
TIVE MODULATION on the OSCILLOSCOPE. Imbalance due
to misadjustment of the Carrier Balance Controls AND
the deliberate unbalance in order to create carrier
will cause a phase shift of the carrier and conseguent
distortion of the signal. In addition, adjustment of
the Carrier Level Controls AFTER the Carrier Level has
been set will cause a change in the Carrier Level.
Therefore, adjust the Carrier Balance before setting
the AM Carrier Level, and then do not touch the Carrier
Balance Controls afterward.
28.
17. Final Amplifier Bias
To make this adjustment, 1t 1s necessary to remove
the linear amplifier section from the rear of the radio.
Open the supply to the RF Choke L211, which supplies
voltage to the collector of the amplifiers, and insert
a milliampere set to the 500 ma scale. Make certain
that the Mode Switch is on SSB and that the Microphone
Gain Control is down. There must be no signal coming
through the amplifier. It is a good idea to remove the
voltage from Q201--the first amplifier stage--to be sure
that there is no signal coming through the amplifier.
Then adjust the Bias Potentiometer, located at the front
end of the linear amplifier module, for a Collector
Current of 75 ma. It will be necessary to adjust
the Push-To-Talk Switch.
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