HAMTRONICS R303 Owner's manual

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 1 -
GENERAL INFORMATION.
The R303 is the latest in a series of popu-
lar receivers for demanding applications
which require exceptional sensitivity and se-
lectivity. It is especially suited for repeaters,
audio and data links, and remote control. The
R303 was designed to allow the factory to set
it on frequency without lengthy waits to ob-
tain channel crystals. It is a single-channel vhf
fm receiver available in several models for re-
ception in the 144 MHz ham band, the 138-
175 MHz commercial band, or 216-230 MHz.
On special order, up to three frequencies can
be programmed into the receiver allowing
jumpers to change channels.
The R303 is our 9th generation vhf fm re-
ceiver, and it packs in features you've told us
are important to you during our 45 years of
designing receivers. It's up to the difficult jobs
you've told us you have.
The R303 retains all of the popular fea-
tures Hamtronics® receivers have been noted
for. It uses triple-tuned circuits in the front
end and excellent crystal and ceramic filters in
the i-f with steep skirts for close channel spac-
ing or repeater operation. The i-f selectivity,
for instance, is down over 100dB at ±12 kHz
away from the carrier, which is 40-50 dB bet-
ter than most transceivers. Low noise fet's in
the front end provide good overload resis-
tance and excellent sensitivity.
The R303 is designed for narrow-band fm
with ±5 kHz deviation. Other bandwidths are
available on special order.
The R303 features a positive-acting, wide-
range squelch circuit and additional output
terminals for low-level squelched audio and
discriminator audio as well as COS.
The audio output will drive any load as
low as 8 with up to 1 Watt continuous out-
put. Volume and squelch are adjustable with
trim pots on the pc board. For those applica-
tions requiring adjustments on the outside of
a cabinet, you may easily replace these pots
with suitable panel mount controls.
The receiver may be used with either
voice or fsk data up to 9600 baud using an ex-
ternal data demodulator unit. An accessory
TD-5 CTCSS Decoder unit is available for sub-
audible tone control.
There are several models, which have mi-
nor variations in parts and microcontroller
programming, to provide coverage as shown
in table 1. The frequency is programmed in at
the factory and is aligned to frequency; so you
have no adjustments to do at installation.
The TCXO (temperature controlled xtal os-
cillator) provides a temperature stability of
±2ppm over a temperature range of -30°C to
+60°C.
INSTALLATION.
Mounting.
Some form of support should be provided
under the pc board, generally mounting the
board with spacers to a chassis. The receiver
board relies on the mounting hardware to
provide the dc and speaker ground connec-
tions to the ground plane on the board; so
metal standoffs and screws should be used for
mounting.
Electrical Connections.
Power and input audio or data signals
should be connected to the solder pads on the
pc board with #22 solid hookup wire, which
can be attached to a connector or feed-
through capacitors used on the cabinet in
which it is installed. Be very careful not to
route the wiring near the components on the
left hand side of the board, which contains
sensitive loop filter and vco circuits which
could pick up noise from the wiring.
Power Connections.
The receiver operates on +13.6 Vdc at
about 100 mA peak with full audio. Current
drain with no audio is only about 38 mA. A
well regulated power supply should be used.
Be sure that the power source does not
carry high voltage or reverse polarity tran-
sients on the line, since semiconductors in the
receiver can be damaged. The positive power
supply lead should be connected to the re-
ceiver at terminal E3, and the negative power
lead should be connected to the ground plane
of the board through the mounting hardware
or the shield of the coaxial cable. Be sure to
observe polarity!
Speaker.
An 8-ohm loudspeaker should be con-
nected to E2 with ground return through the
mounting hardware. Use of lower impedance
speaker or shorting of speaker terminal can
result in ic damage. The receiver can also
drive higher impedances, such as the 1K to
20K input impedances of repeater controller
boards.
Antenna Connections.
The antenna connection should be made
to the pc board with an RCA plug of the low-
loss type made for rf. We sell good RCA plugs
with cable clamp. See A5 plug on website.
If you want to extend the antenna con-
nection to a panel connector, we recommend
using a short length of RG-174/u coax with the
plug and keep the pigtails very short.
We do not recommend trying to use di-
rect coax soldered to board or another type of
connector. The method designed into the
board results in lowest loss practical. When
soldering the cable, keep the stripped ends as
short as possible.
We recommend you always use anten-
nas with a matching network which provides a
dc ground on the driven element to avoid stat-
ic buildup damaging the input stage of the re-
ceiver.
OPTIONS.
Repeater Use.
E5 provides a COS (carrier operated
switch) output which may be connected to a
COR module to turn a transmitter on and off.
The output level is about 5V unsquelched and
0V squelched. There is a resistor in series
with the output to limit current. Therefore,
the voltage that appears at the COR board will
depend on the load resistance at the input of
that board. For best results, be sure that the
input resistance of the COR board is at least
47K. If the input resistance is too low, no
damage to the receiver will occur; but the
squelch circuit hysteresis will be affected.
If your repeater controller uses discrimi-
nator audio, rather than the speaker output,
filtered discriminator audio is available at E4.
The level is about 2V p-p. Note that discrimi-
nator audio is not de-emphasized or squelch-
ed.
If your controller uses low level audio and
has a high input impedance (20K or higher),
HAMTRONICS
®
R303
VHF FM RECEIVER:
INSTALLATION, OPERATION, & MAINTENANCE
Table 1. Quick Specification Reference
Frequency Range: Can be supplied for any
frequency in range of 138-175MHz or 216-
230MHz.
Sensitivity (12dB SINAD): 0.15 to 0.2µV
Squelch Sensitivity: 0.15µV
Normal signal bw: ±5kHz deviation
Adjacent Channel Selectivity:
±12 kHz at -100dB (narrower bandwidth avail-
able as an option)
Image Rejection: 60-70dB
Modulation Acceptance: ±7.5 kHz
Frequency Stability: ±2ppm -30°C to +60°C
Audio Output: up to 1 Watt (8 ohms).
Operating Power: +13.6Vdc (+10 to +15Vdc)
at 38-100 mA, depending on audio level.
Size: 4 in. W x 2-1/2 in. D

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 2 -
squelched audio can be obtained from Re-
peater Audio terminal E1 independent of the
volume control.
Subaudible Tone Decoder.
To use our TD-5 Subaudible Tone Decoder
or a similar module, connect its audio input to
DISCRIMINATOR terminal E4. If you want to
use it to mute the audio (instead of inhibiting
a repeater transmitter as is normally done),
connect the mute output of the TD-5 to E1 on
the receiver.
Multichannel Operation.
The R303 may be programmed with more
than one channel. If you ordered this option,
you can change to the first alternate channel
by grounding E6 or the second alternate
channel by grounding E7. Grounding both
terminals selects the third alternate. Ground
terminals E8 and E9 are provided if you want
to use jumpers, or you can use an external
switch of some sort.
ADJUSTMENTS.
Frequency Netting.
All crystals age a little over a long period
of time; so it is customary to tweak any re-
ceiver back onto the precise channel fre-
quency once a year during routine
maintenance. Because modern solid state
equipment doesn’t require much routine
maintenance, many receivers don’t get their
oscillators tweaked as a matter of routine any
more, but they should.
The adjustment should be done using an
accurate service monitor or frequency coun-
ter. Of course, make sure the test equipment
is exactly on frequency first by checking it
against WWV or another frequency standard.
The channel frequency is trimmed pre-
cisely on frequency with a small variable ca-
pacitor, which is accessible through a hole in
the top of the shield can on the TCXO. The
proper tool is a plastic wand with a small
metal bit in the end.
To perform this adjustment, it is first nec-
essary to verify that the discriminator is prop-
erly adjusted. Do this by connecting a dc
voltmeter to E4. Connect a signal generator
set for 10.700 MHz to TP3, and set the level
for a relatively strong signal so there is very
little white noise. Adjust discriminator coil T3
for 2Vdc. Then, reconnect the signal genera-
tor to antenna connector J1, and set it for the
precise channel frequency. You can also use a
strong signal on the air if you are sure it is
right on frequency. Adjust the TCXO capacitor
for 2Vdc (to match the voltage obtained with
the 10.700 MHz signal).
Setting Channel Frequency.
The channel frequency is determined by
frequency synthesizer circuits, which use a
microcontroller which is programmed at the
factory. If you need to change frequency,
contact the factory to get another micro pro-
grammed for the new frequency settings.
ALIGNMENT.
General Procedure.
A complete alignment is needed when-
ever the frequency is changed by more than 1
MHz. Alignment ensures that the frequency
synthesizer is optimized at the center of the
vco range and that all stages are tuned to res-
onance.
Equipment needed for alignment is a sen-
sitive dc voltmeter, a stable and accurate sig-
nal generator for the channel frequency, and
a regulated 13.6Vdc power supply with a 0-
200 mA meter internally or externally con-
nected in the supply line.
The slug tuned coils in the Receiver should
be adjusted with the proper tuning tool to
avoid cracking the powdered iron slugs. Vari-
able capacitors should be adjusted with a
plastic tool having a small ceramic or metal
bit. (See A1 Tuning Tool on our website.) All
variable capacitors should be set to the center
of their range. Turn them 90° if they have not
previously been aligned (except on the op-
tional TCXO).
Note: Meter indications used as refer-
ences are typical but may vary widely due to
many factors not related to performance, such
as type of meter and circuit tolerances. Typi-
cal test point indications are for the 144 MHz
band unit and may differ for other bands.
a. Set the SQUELCH pot fully counter-
clockwise and the VOLUME pot just a little
clockwise.
b. Connect speaker and +13.6 Vdc. You
should hear white noise.
c. Connect voltmeter to TP1. Adjust vco
coil L1 for +2.0Vdc. (Although the vco will op-
erate over a wide range of tuning voltages
from about 0.5V to 4.5V, operation is opti-
mum if the vco is adjusted to 2.0V.)
d. Connect voltmeter to TP2. Adjust
buffer coil L3 for a peak, typically about
+0.35V.
e. Connect signal generator to TP-3.
Use a frequency counter or synthesized signal
generator. Set generator to exactly 10.7000
MHz. Set level just high enough for full quiet-
ing. At 1 uV, you should notice some quieting,
but you need something near full quieting for
the test (about 20µV).
f. Connect dc voltmeter to Discrimina-
tor terminal E4. Adjust discriminator trans-
former T2 for +2Vdc.
 Be careful not to turn the slug tight
against either the top or bottom because the
winding of the transformer can be broken.
The tuning response is an S-curve; so if you
turn the slug several turns, you may think you
are going in the proper direction even though
you are tuning further away from center fre-
quency.
g. Connect signal generator to J1 using a
coax cable with RCA plug. Adjust signal gen-
erator to exact channel frequency, and turn
output level up fairly high (about 1000µV). Ad-
just frequency trimmer in TCXO (if necessary)
to net the crystal to channel frequency, indi-
cated by +2Vdc at E4.
Note: There are two methods of adjusting
the mixer and front end. One is to use a volt-
meter with test point TP-4. The voltage at this
point is proportional to the amount of noise
detected in the squelch circuit; so it gives an
indication of the quieting of the receiver. With
SQUELCH control fully ccw, the dc voltage at
TP-4 varies from -0.5 Vdc with no signal (full
noise) to +1 Vdc with full quieting signal.
The other method is to use a regular pro-
fessional SINAD meter and a 1000 Hz tone
with 3 kHz deviation
In either case, a weak to moderate signal
is required to observe any change in noise. If
the signal is too strong, there will be no
change in the reading as tuning progresses; so
keep the signal generator turned down as re-
ceiver sensitivity increases during tuning.
h. Connect fet dc voltmeter to TP4 or
observe sinad meter. Set signal generator for
relatively weak signal, one which shows some
change in indication. Alternately peak RF am-
plifier and mixer coils L4-L8 until no further
improvement can be made.
When properly tuned, sensitivity should
be about 0.15 to 0.2µV for 12 dB SINAD.
 Crystal filter trimmer coils T1 and T2
normally should not be adjusted. They are set
at the factory. The purpose of the adjustment
is to provide proper loading for the crystal fil-
ter, and if misadjusted, ripple in the filter re-
sponse will result in a little distortion of the
detected audio. If it becomes necessary to
adjust T1 and T2, tune the signal generator
accurately on frequency with 5kHz fm devia-
tion using a 1000 Hz tone. In order of prefer-
ence, use either a SINAD meter, an
oscilloscope, or just your ears, and fine tune
T1 and T2 for minimum distortion of the de-
tected audio.
THEORY OF OPERATION.
The R303 is a frequency synthesized vhf
fm Receiver. Refer to the schematic diagram
for the following discussion.
Low noise dual-gate mos fet’s are used for
the RF amplifier and mixer stages. The output
of mixer Q5 passes through an 8-pole crystal
filter to get exceptional adjacent channel se-
lectivity.
U4 provides IF amplification, a 2nd mixer
to convert to 455 kHz, a discriminator, noise
amplifier, and squelch. Ceramic filter FL5 pro-
vides additional selectivity at 455 kHz. The
noise amplifier is an op amp active filter
peaked at 10 kHz. It detects noise at frequen-
cies normally far above the voice band. Its
output at pin 11 is rectified and combined
with a dc voltage from the SQUELCH control

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 3 -
to turn a squelch transistor on and off inside
the ic, which grounds the audio path when on-
ly noise is present. Inverter Q6 provides a dc
output for use as a COS signal to repeater
controllers.
The injection frequency for the first mixer
is generated by vco (voltage controlled oscilla-
tor) Q1. The injection frequency is 10.700
MHz below the receive channel frequency.
The output of the vco is buffered by Q2 to
minimize effects of loading and voltage varia-
tions of following stages from modulating the
carrier frequency. The buffer output is ap-
plied through a double tuned circuit to gate 2
of mixer Q5.
The frequency of the vco stage is con-
trolled by phase locked loop synthesizer U2. A
sample of the vco output is applied through
the buffer stage and R1 to a prescaler in U2.
The prescaler and other dividers in the syn-
thesizer divide the sample down to 5kHz. A
reference frequency of 10.240 MHz is gener-
ated by a TCXO (temperature compensated
crystal oscillator). The reference is divided
down to 5 kHz. The two 5kHz signals are
compared to determine what error exists be-
tween them. The result is a varying dc tuning
voltage used to phase lock the vco precisely
onto the desired channel frequency.
The tuning voltage is applied to varactor
diode D1, which varies its capacitance to tune
the tank circuit formed by L1/C15/C16. C12
limits the tuning range of D1. The tuning volt-
age is applied to D1 through a third order low
pass loop filter, which removes the 5kHz ref-
erence frequency from the tuning voltage to
avoid whine. In order for the synthesizer to
lock, the vco must be tuned to allow it to gen-
erate the proper frequency within the range
of voltages the phase detector in the synthe-
sizer can generate, roughly 0.5Vdc to 4.5Vdc.
Serial data to indicate the desired channel
frequency and other operational characteris-
tics of the synthesizer are applied to synthe-
sizer U2 by microcontroller U1. Everything
the synthesizer needs to know about the
band, division schemes, reference frequency,
and oscillator options is generated by the con-
troller. Information about the base frequency
of the band the receiver is to operate on and
the channel within that band is calculated in
the controller based on information pro-
grammed in the eprom on the controller.
Whenever the microcontroller boots at power
up, the microcontroller sends several bytes of
serial data to the synthesizer, using the data,
clock, and /enable lines running between the
two ic’s. Terminals E6 & E7 allow alternate
frequencies to be selected for those receivers
programmed to use that feature.
+13.6Vdc power for the Receiver is ap-
plied at E3. Audio output amplifier U5 is
powered directly by the +13.6Vdc. All the
other stages are powered through 5V regula-
tor U6 for stability and to eliminate noise.
Additional filtering for the vco and buffer
stages is provided by capacitance amplifier
Q3, which uses the characteristics of an emit-
ter follower to provide a very stiff supply,
eliminating any possible noise on the power
supply line.
TROUBLESHOOTING.
General.
The usual troubleshooting techniques of
checking dc voltages and signal tracing with
an RF voltmeter probe and oscilloscope will
work well in troubleshooting the R303. DC
voltage charts and a list of typical audio levels
are given to act as a guide to troubleshooting.
Although voltages may vary widely from set to
set and under various operating and measure-
ment conditions, the indications may be help-
ful when used in a logical troubleshooting
procedure.
Current Drain.
Power line current drain normally is about
38 mA with volume turned down or squelched
and up to 100 mA with full audio output.
If the current drain is approximately 100
mA with no audio output, check to see if volt-
age regulator U6 is hot. If so, and the voltage
on the 5V line is low, there is a short circuit on
that bus somewhere and U6 is limiting the
short circuit current to 100mA to protect the
receiver from damage. If you clear the short
circuit, the voltage should rise again. U6
should not be damaged by short circuits on its
output line; however, it may be damaged by
reverse voltage or high transient voltages.
Audio Output Stage.
Note that audio output ic U5 is designed
to be heatsunk to the pc board through the
many ground pins on the ic.
If audio is present at the volume control
but not at the speaker, the audio ic may have
been damaged by reverse polarity or a tran-
sient on the B+ line. This is fairly common
with lightning damage.
If no audio is present on the volume con-
trol, the squelch circuit may not be operating
properly. Check the dc voltages, and look for
noise in the 10 kHz region, which should be
present at U1-pin 11 with no input signal.
(Between pins 10 and 11 of U1 is an op-amp
active filter tuned to 10 kHz.)
RF Signal Tracing.
If the receiver is completely dead, try a
10.700 MHz signal applied to TP-3 using coax
test lead. Set level just high enough for full
quieting. At 1 µV, you should notice some
quieting, but you need something near full
quieting for the test.
You can also connect the 10.700 MHz test
lead through a blocking capacitor to various
sections of the crystal filter to see if there is a
large loss of signal across one of the filter sec-
tions. Also, check the 10.245 MHz oscillator
with a scope or by listening with an hf receiver
or service monitor.
A signal generator on the channel fre-
quency can be injected at various points in the
front end. If the mixer is more sensitive than
the RF amplifier, the RF stage is suspect.
Check the dc voltages looking for a damaged
fet, which can occur due to transients or re-
verse polarity on the dc power line. Also, it is
possible to have the input gate (gate 1) of the
RF amplifier fet damaged by high static charg-
es or high levels of RF on the antenna line,
with no apparent change in dc voltages, since
the input gate is normally at dc ground.
Synthesizer Circuits.
Following is a checklist of things to look
for if the synthesizer is suspected of not per-
forming properly.
a. Check the output frequency of the
vco buffer with a frequency counter.
c. Check tuning voltage at TP1. It
should be about +2.0Vdc. Actual range over
which the unit will operate is about +0.5Vdc
to about +4.5Vdc. However, for optimum re-
sults, the vco should be tuned to allow opera-
tion at about +2.0Vdc center voltage.
d. Check the operating voltage and bias
on the vco and buffer.
e. Check the TCXO at pin 1 of the syn-
thesizer ic. A scope should show strong signal
(1.5 Vp-p) at 10.240 MHz.
f. The data, clock, and latch enable lines
between the microcontroller and synthesizer
ic’s should show very brief and very fast activ-
ity, sending data to the synthesizer ic shortly
after the power is first applied or a dip switch
setting is changed. Because this happens very
fast, it can be difficult to see on a scope. Use
1mSec/div, 5Vdc/div, and normal trigger.
Microphonics, Hum, and Noise.
The vco and loop filter are very sensitive
to hum and noise pickup from magnetic and
electrical sources. Some designs use a shield-
ed compartment for vco’s. We assume the
whole board will be installed in a shielded en-
closure; so we elected to keep the size small
by not using a separate shield on the vco.
However, this means that you must use care
to keep wiring away from the vco circuit at
the right side of the board. Having the board
in a metal enclosure will shield these sensitive
circuits from florescent lights and other strong
sources of noise.
Because the frequency of a synthesizer
basically results from a free running L-C oscil-
lator, the tank circuit, especially L1, is very
sensitive to microphonics from mechanical
noise coupled to the coil. You should mini-
mize any sources of vibration which might be
coupled to the receiver, such as motors. In
addition, it helps greatly to prevent the mold-
ed coil from vibrating with respect to the
shield can. Both the coil and can are soldered
to the board at the bottom, but the top of the

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 4 -
coil can move relative to the can and there-
fore cause slight changes in inductance which
show up as frequency modulation. Therefore,
the factory cements the top of the coil to the
can.
Excessive noise on the dc power supply
which operates the receiver can cause noise
to modulate the synthesizer output. Various
regulators and filters in the receiver are de-
signed to minimize sensitivity to wiring noise.
However, in extreme cases, such as in mobile
installations with alternator whine, you may
need to add extra filtering in the power line to
prevent the noise from reaching the receiver.
To varying degrees, whine from the 5kHz
reference frequency may be heard on the sig-
nal under various circumstances. If the tuning
voltage required to tune the vco on frequency
is very high or low, near one extreme, the
whine may be heard. This can also happen
even when the tuning voltage is properly near
the 2.0Vdc center if there is dc loading on the
loop filter. Any current loading, no matter
how small, on the loop filter causes the phase
detector to pump harder to maintain the tun-
ing voltage. The result is whine on the signal.
Such loading can be caused by connecting a
voltmeter to TP1 for testing, and it can also be
caused by moisture on the loop filter compo-
nents.
Typical Dc Voltages.
Tables 2-4 give dc levels measured with a
sensitive dc voltmeter on a sample unit with
13.6 Vdc B+ applied. All voltages may vary
considerably without necessarily indicating
trouble. The charts should be used with a log-
ical troubleshooting plan. All voltages are
positive with respect to ground except as
indicated.
Use caution when measuring voltages on
the surface mount ic. The pins are close to-
gether, and it is easy to short pins together
and damage the ic. Try to connect meter to a
nearby component connected to the pin un-
der question.
Typical Audio Levels.
Table 5 gives rough measurements of au-
dio levels. Measurements were taken using
an oscilloscope, with no input signal, just
white noise so conditions can be reproduced
easily.
Table 2. Typical Test Point Voltages
TP1 Tuning V. Normally set at 2V
TP2 Buffer approx. 0.3 – 0.6V
TP3 Test Input (No reading)
TP4 Sig. Level With SQUELCH control
fully ccw, varies from -0.3
Vdc with no to +0.9 Vdc
full quieting.
E4 Freq. Varies with frequency of
input signal. Voltage at
this point normally is ad-
justed for +2Vdc with a
signal exactly on fre-
quency. Can vary a little
without being a problem.
Table 3. Typical Xstr DC Voltages
Xstr Stage E(S) B(G1) C(D) G2
Q1 vco 0.9 1.6 3.8 -
Q2 buffer 0 0.7 2.4 -
Q3 dc filter 4.1 4.8 5 -
Q4 RF ampl 0 0 4.6 2.3
Q5 Mixer 0 0 4.9 0
Q6 sq. open 0 0 5 -
sq. closed 0 0.65 0.14 -
Table 4. Typical IC DC Voltages
U2-1 2.4
U2-2 2.4
U2-3&4 5
U2-5 0 – 5V
(~2V tuned)
U2-7 5
U2-8 1.6
U2-9 0
U2-10 0
U2-11 0
U5-1 1.4
U5-3 0.01
U5-5 6
U5-6 13.6
U5-7 7
U5-8 1.4
U4-1 5
U4-2 4.4
U4-3 4.8
U4-4 5
U4-5 3.8
U4-6 3.8
U4-7 3.8
U4-8 5
U4-9 2 (aligned)
U4-10 0.8
U4-11 2
U4-12 0.6 (with
squelch just closed)
U4-13 0 (sq open)
7.5 (squelch closed)
U4-14 0
U4-15 0
U4-16 1.8
Table 5. Typical Audio Voltages
Audio Test Point Normal Level
U4-9 (Discriminator) 3V p-p audio
E4 (Disc Output) 2V p-p audio
E1 (Repeater Output) 1V p-p audio
U4-11 (noise ampl) 3V p-p noise
CW lug of Vol cont. 400mV p-p audio
U5-3 (af ampl input) 0 to 200mV p-p
U5-5 or E2 (speaker 0 to 7V p-p audio
ampl output)

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 5 -
PARTS LIST FOR R303
RECEIVER.
 Note: Values which vary with freq. band are
shown in a table below. Resistors and capacitors
are 0805 or 0603 smt type unless noted otherwise.
 Caution: IC’s are static sensitive. Use ap-
propriate handling precautions to avoid damage.
Ref Desig Value (marking)
C1 0.1µf
C2 100pf
C3 0.1µf
C4 100µf electrolytic
C5 0.15µf mylar (red)
C6 .01µf
C7 .001uf
C8-C9 100µf electrolytic
C10 0.1µf
C11 390pf
C13 100µf electrolytic
C14 390pf
C17 7pf
C18 390pf
C21 3pf
C24-C25 390pf
C32 4pf
C35 .033µf
C36 7pf
C37 4pf
C38 7pf
C39 .001uf
C40 1µf electrolytic
C41 0.1µf
C42-C43 .001µf
C44-C45 .033µf
C46 0.1µf
C47 4.7µf electrolytic
C48 0.1µf
C49 100µf electrolytic
C50 68pf
C51 220pf
C52-C54 0.1µf
C55-C56 100µf electrolytic
D1 BB132 varactor diode
D2 MMBT5179 (used as diode)
D3-D4 MMBT3904 (used as diode)
FL1-FL4 10.7MHz crystal filter
(matched set of 4)
FL5 LT455DW ceramic filter
J1 RCA Jack
J2 6 pin header
L2 0.33µH RF choke
(red-sil-orn-orn)
L3-L8 2½ t. ,slug tuned (red)
Q1-Q2 MMBT5179
Q3 MMBT3904
Q4-Q5 BF998 MOS FET
Q6 MMBT3904
R1 180
R2 27
R3 10K
R4 47K
R5 27
R6 1K
R7 27
R8-R10 10K
R11 180
R12 47
R13 10K
R14 3.9K
R15 470
R16 1meg
R17 1K
R18 10
R19-R20 100K
R21 27
R22 47K
R23 27
R24 330K
R25 100K trim pot
R26 47K
R27 100K
R28 15K
R29 2meg
R30 47K
R31 510K
R32 4.7K
R33 680
R34 1K
R35 22K
R36 100K
R37 100K trim pot
R38 47K
R39 10
T1-T2 10.7MHz IF xfmr
(T1005)
T3 455kHz IF xfmr
(T1003)
U1  MC9RS08KA1CP µP
U2  LMX1501A PLL
U3  10.240 MHz TCXO
U4 MC3361BPD IF ampl
U5 LM386N-1 AF output
U6 78L05ACD regulator
XU1 8 pin ic socket
Y1 10.245 MHz crystal
Values which vary with frequency band:
R303-1 is 138 - 144 MHz
R303-2 is 144 - 154 MHz
R303-3 is 154 - 164 MHz
R303-4 is 164 - 174 MHz
R303-5 is 216 - 230 MHz
Ref -1 -2 -3 -4 -5
C12 10 10 10 10 8
C15 20 15 12 10 8
C16 68 68 62 47 47
C19 43 39 30 27 12
C20 82 68 62 62 33
C22 30 27 22 20 8
C23 82 68 62 62 27
C26 22 20 18 15 6
C27 0.5 0.5 0.5 0.5 0.3
C28 22 22 18 15 8
C29 0.2 0.2 0.2 0.2 n/u
C30 22 20 18 15 7
C31 3 3 3 3 1
C33 39 33 27 22 10
C34 82 82 68 62 27
L1 2½t
(red)
2½t
(red)
2½t
(red)
2½t
(red)
1½t
(brn)

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 6 -

©2012 Hamtronics, Inc.; Rochester NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 2/14/16 - Page 7 -