70cm portable "Suitcase Repeater"

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My 70cm Portable "Suitcase repeater"

Radios (programmed on the T-MARC shared non-protected pair 447.875 -offset):

Motorola Radius® M206 - 40 watt UHF (set for 18 watts) 6 channel radio (with a 135°F temperature controlled switch mounted on the heat sink).
Motorola Radius® M100 - 25 watt UHF (set for 15 watts) 2 channel radio (with a 135°F temperature controlled switch mounted on the heat sink).

Duplexer:

Motorola UHF mobile cavity duplexer purchased from Brinkley Electronics. Rated at 20 watts.

Controller:

NHRC-2 Repeater controller ("$60 repeater controller" featured in QST).

Power sources:

With commercial power available - 20 amp 12V supply.
Without commercial power available - Two 25Ah Gell Cell batteries (in parallel) backed up by the vehicle battery/alternator.
Power cable - 15 feet #10 red/black color coded 'zip cord' with 'fork' terminals on one end and 20 amp 'battery clips' on the other end.

Antenna:

Watson dual band (2M/70cm) antenna on a Larson "BSA" VHF ground plane kit. (5.5 Dbd gain on 70cm)

RF Cable:

50 feet of RG-8 with PL-259 connectors.

Antenna Support:

35 foot military surplus portable tower (with tripod adapter and guy ropes).

Carrying case:

U. S. Army surplus cannon shell shipping case for the radios, controller, and duplexer.
Two small 12Vdc fans.
Two 1 inch PVC pipe threaded elbows, short nipples, and unions with window screen covering the openings.
Short SO-239 'pass-thru'.

Programming of the radios:

Both radios transmit on 447.875 and receive on 442.875. In order to have on-site selectable CTCSS tones I came up with the following programming scheme:

M206 - Channel 1 TX tone 210.7 RX tone 123.0 Channel 2 TX tone 114.8 RX tone 100.0 Channel 3 no tone on either TX or RX

M100 - Channel 1 TX tone 123.0 RX tone 210.7 Channel 2 TX tone 100.0 RX tone 114.8

As you can see I have four RX tones available along with Carrier Squelch. It all depends on which radio (at which channel selection) is set up for receive! It is also possible to have a RX tone of 210.7 or 114.8 and not transmit any CTCSS! The 'truth table' looks like this:

210.7 tone - M100 in receive (Ch 1) and M206 transmitting (Ch 1 for the same tone or Ch 3 for no TX tone)

114.8 tone - M100 in receive (Ch 2) and M206 transmitting (Ch 2 for the same tone or Ch 3 for no TX tone)

123.0 tone - M206 in receive (Ch 1) and M100 transmitting (Ch 1)

100.0 tone - M206 in receive (Ch 2) and M100 transmitting (Ch 2)

No tone (Carrier Squelch) - M206 in receive (Ch 3) and M100 transmitting (any channel).

Of course the Microphone/RX audio cables connecting the radios to the controller and the RF cables connecting the radios to the duplexer may have to be swapped around for the different CTCSS configurations. I mounted a 'truth table' for the CTCSS tones and the necessary color coded cable connections inside the lid of the box.

The cannon shell shipping case was modified with "5 way" binding post feed-throughs for power (with the negative side grounded to the case), and two padlock hasps mounted on the corners of the front to keep the lid secured. An SO-239 "feed thru" for the antenna is mounted on the right "side" panel. The box is vented using 1 inch PVC pipe elbows on each end (both near the rear and facing down when the case is placed 'flat') with a small 12V fan exhausts through one elbow and another fan intakes through the other elbow. A temperature controlled switch is mounted on both radio heatsinks control both fans (saves battery life). Both PVC elbows have a piece of window screen on the outside to 'keep the critters' out . Lastly, the controller is mounted in a metal 'project box' inside the case and securely grounded to the case. To prevent disasters, there is a 20Amp DPST 'master power' switch after the 15 Amp 'master fuse' on the main +12V lead with a 'suicide diode' to blow the fuse in case of reversed polarity. There are appropriate fuses on both radio power leads and the controller in case something goes 'seriously wrong'. The controller is reverse polarity protected by diodes on both power leads.

I am trying to get a picture scanned for you to see what this 'thing' looks like..

E-Mail: [email protected]

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Last Revised - 06 May 2004