©2005 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 5/17/05
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GENERAL INFORMATION.
The R302 is the latest in a series of
popular receivers for demanding ap-
plications which require exceptional
sensitivity and selectivity. It is espe-
cially suited for repeaters, audio and
data links, and remote control. The
R302 was designed to provide instant
setup without lengthy waits to obtain
channel crystals. It is a single-
channel vhf fm receiver available in
several models for reception in the
144 MHz ham band, the 148-174 MHz
commercial band, or 216-226 MHz.
The R302 is our 8th generation vhf
fm receiver, and it packs in features
you've told us are important to you
during our 40 years of designing re-
ceivers. It's up to the difficult jobs
you've told us you have.
The R302 retains all of the popular
features 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
spacing or repeater operation. The i-f
selectivity, for instance, is down over
100dB at ±12 kHz away from the car-
rier, which is 40-50 dB better than
most transceivers. Low noise fet's in
the front end provide good overload
resistance and excellent sensitivity.
The R302 is designed for narrow-
band fm with ±5 kHz deviation. The
audio output will drive any load as
low as 8
Ω
with up to 1 Watt continu-
ous output. The receiver may be used
with either voice or fsk data up to
9600 baud using an external data in-
terface unit. An accessory TD-5
CTCSS Decoder unit is available for
subaudible tone control.
The R302 features a positive-
acting, wide-range squelch circuit and
additional output terminals for low-
level squelched audio and discrimina-
tor audio as well as COS.
There are several models, which
have minor variations in parts and
microcontroller programming, to pro-
vide coverage as shown in table 1.
Channel frequency is controlled by a
synthesizer with DIP switch channel
setting.
The TCXO (temperature controlled
xtal oscillator) 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, gener-
ally mounting the board with spacers
to a chassis. 3/8-inch holes should
be provided in a front panel for the
bushings of the SQUELCH and VOL-
UME controls. After sliding bushings
through panel, washers and nuts can
be installed on the outside of the
panel. Be sure to provide support for
the board; do not rely on the controls
to support the board, since that could
cause a break in the pcb solder con-
nections.
The receiver board relies on the
mounting hardware to provide the dc
and speaker ground connections 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 sig-
nals should be connected to the solder
pads on the pc board with #22 solid
hookup wire, which can be attached
to a connector or feedthrough capaci-
tors 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 200 mA peak with full audio.
Current drain with no audio is only
about 45 mA. A well regulated power
supply should be used.
Be sure that the power source does
not carry high voltage or reverse po-
larity transients 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
connected to E2 with ground return
through the mounting hardware. Use
of lower impedance speaker or short-
ing 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. There is no need to
load down the output to 8 ohms.
0
Note that the audio output ic is
designed to be heatsunk to the pc
board through the many ground pins
on the ic. When running moderately
low audio levels as most applications
require, it is no problem to use an ic
socket; so we have provided one for
your convenience. If you will be run-
ning high audio levels, check to see if
the ic is getting hot. If so, you should
remove the ic socket, and solder the
LM-386 ic directly to the board for bet-
ter heatsinking.
Antenna Connections.
The antenna connection should be
made to the receiver with an RCA plug
of the low-loss type made for rf. We
have them available if you need one.
If you want to extend the antenna
connection to a panel connector, we
recommend using a short length of
RG-174/u coax and a good RCA plug
with cable clamp
(see catalog).
When
soldering the cable, keep the stripped
ends as short as possible.
We do not recommend trying to
use direct coax soldered to board or
another type of connector. The
method designed into the board re-
sults in lowest loss practical.
0
We recommend you always use
antennas with a matching network
which provides a dc ground on the
driven element. This reduces chances
of static buildup damaging the input
stage of the receiver as well as provid-
ing safety for the building and other
equipment.
HAMTRONICS® R302 VHF FM RECEIVER:
INSTALLATION, OPERATION, & MAINTENANCE
Table 1. Quick Specification Reference
Model R302-1
138.000 - 148.235 MHz
Model R302-2
144.000 - 154.235 MHz
Model R302-3
154.200 - 164.435 MHz
Model R302-4
164.400 - 174.635 MHz
Model R302-5
216.000 - 226.235 MHz
Model R302-6
220.000 - 230.235 MHz
Sensitivity
(12dB SINAD): 0.15 to 0.2µV
Squelch Sensitivity:
0.2µV
Adjacent Channel Selectivity:
±12 kHz at -100dB!
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 45-200 mA, depending on audio level.
Size:
4 in. W x 2-7/8 in. D (plus pot. shafts)
