©2009 Hamtronics, Inc.; Hilton NY; USA. All rights reserved. Hamtronics is a registered trademark. Revised: 8/10/11
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GENERAL INFORMATION.
The R306 is our 6th generation uhf nbfm
receiver. It is intended for demanding applica-
tions which require exceptional sensitivity and
selectivity. It is especially suited for repeaters,
audio and data links, and remote control.
The R306 uses triple-tuned circuits in the
front end and excellent crystal and ceramic fil-
ters in the i-f with steep skirts for close chan-
nel spacing 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 better than most transceivers. Low noise
fet's and surface mount parts in the front end
provide good overload resistance and 0.2µV
sensitivity.
The R306 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 frequency is programmed in at the
factory and is aligned to frequency; so you
have no adjustments to do at installation.
Volume and Squelch controls are trim pots on
the board for compact design. For those ap-
plications requiring adjustments on the out-
side of a cabinet, you may easily replace these
pots with suitable panel mount controls.
The frequency reference for the R306 Re-
ceiver is a temperature compensated crystal
oscillator (tcxo). This provides a temperature
stability of ±2ppm over a temperature range
of -30°C to +60°C without requiring a crystal
oven.
INSTALLATION.
Mounting.
Some form of support should be provided
under the pc board, generally mounting the
board with 4-40 screws and threaded stand-
offs to a chassis.
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 signals
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 capacitors used on the cabinet in
which it is installed. Be very careful not to
route the wiring near rf components on the
board, for instance underneath the board.
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.
Be sure to observe polarity!
Speaker.
An loudspeaker with an impedance of 8
Ω
or greater should be connected to E2 with
ground return through the mounting hard-
ware. 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 im-
pedances of repeater controller boards. There
is no need to load down the output to 8 ohms.
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 direct
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.
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 de-
pend 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
squelched.
If you need audio which is
squelched, take it from Repeater Audio termi-
nal E1. Level there is about 1V p-p.
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 R306 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. This adjustment is called “net-
ting”, which is a term going back to days when
all stations on a network would initially adjust
their VFOs to all be on the same exact fre-
quency before operating as a net.
The adjustment should be done using an
accurate service monitor or frequency
counter. Of course, make sure the test
equipment is exactly on frequency first by
checking it against WWV or another frequency
HAMTRONICS® R306 UHF FM RECEIVER:
INSTALLATION, OPERATION, & MAINTENANCE
Table 1. Quick Specification Reference
Frequency Range
:
can be supplied from 400 - 470 MHz
Sensitivity
(12dB SINAD): 0.2µV
Squelch Sensitivity:
0.15µV
Normal signal bw:
±5kHz deviation
Adjacent Channel Selectivity:
±12 kHz at -100dB! (narrower bandwidth
is available as an option)
Modulation Acceptance:
±7.5 kHz
Audio Output:
up to 1 Watt (8 ohms).
Operating Power:
+13.6Vdc at 38-100 mA,
depending on audio level.
Size:
4 in. W x 2.5 in. D
