©1998 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 4/2/03
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GENERAL INFORMATION.
There are some jobs a transceiver
grade receiver just can't do, at least
not well. That's where reliable Ham-
tronics® commercial quality receivers
come in!
The R304 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, packet radio, and remote
control. The R304 was designed to
provide an alternative to our ac-
claimed R451 Receivers, offering in-
stant setup without lengthy waits to
obtain channel crystals. It is a single-
channel uhf fm receiver for reception
in the 440 MHz ham band or the ad-
jacent commercial bands.
The R304 is our 4th generation uhf
fm receiver, and it packs in features
you've told us are important to you
during our 35 years of designing re-
ceivers. It's up to the difficult jobs
you've told us you have.
The R304 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 0.2µV sensitivity.
The R304 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 continuous
output or 2 Watts intermittent output.
The receiver may be used with either
voice or fsk data up to 9600 baud us-
ing an external data interface unit.
An accessory TD-5 CTCSS Decoder
unit is available for subaudible tone
control.
The R304 features a new 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 frequency reference for the
R304 Receiver is a temperature com-
pensated crystal oscillator (tcxo). This
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 extended
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 60 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 nega-
tive 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-380N-8 ic directly to the board for
better 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).
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. When
HAMTRONICS® R304 UHF FM RECEIVER:
INSTALLATION, OPERATION, & MAINTENANCE
Table 1. Quick Specification Reference
Model R304-0
400.000 – 409.995 MHz
Model R304-1
410.000 – 419.995 MHz
Model R304-2
420.000 – 429.995 MHz
Model R304-3
430.000 – 439.995 MHz
Model R304-4
440.000 – 449.995 MHz
Model R304-5
450.000 – 459.995 MHz
Model R304-6
460.000 – 469.995 MHz
Sensitivity
(12dB SINAD): 0.2µV
Squelch Sensitivity:
0.15µV
Adjacent Channel Selectivity:
±12 kHz at -100dB!
Image Rejection:
60dB
Modulation Acceptance:
±7.5 kHz
Audio Output:
up to 2 Watts (8 ohms).
Operating Power:
+13.6Vdc at 60-200 mA,
depending on audio level.
Size:
4 in. W x 3-7/16 in. D (plus pot. shafts)
