Coaxial Cable Management for Rovers



Coaxial cabling can be bulky, heavy and lossy.

Problem: During my Jan. 2011 rove the antenna crosstalk from 6, 2, 1.25 and/or 0.7 meter 100W amplifiers managed to zap my Yaesu FT-857D causing a $300 repair and took out the pre-amp of my external 0.7 meter amplifier.

Solution: During the January 2013 rove I tried to manage the antenna crosstalk and cabling issues by implementing a simple multiplexing arrangement. Rather than separate LMR-400UF individual cables for each of the 4 bands, I shared a 22 ft. LMR-600UF cable for all 4 bands. This was possible through the use of two, 4 pole Transco coaxial relays.











Loss Reduction Calculator: At 432 MHz my 22 ft. cable attenuation was reduced from 0.7 to 0.4 dB (not including connectors) for a savings of approx. 0.3 dB on 70 cm.

Weight Reduction: Four, 22 ft. LMR-400UF cables weigh 6 lbs. versus one 22 ft. LMR-600UF cable weighs 2.9 lbs. plus one 4-pole relay weighing 0.8 lb. = 3.6 lb. for a savings of approx. 2.4 lb. (not including connectors).

Bulk Improvement: Routing 4 separate LMR-400 cables down the telescoping mast with sliding antenna booms is a real headache. They end up catching the yagi elements and shorting out the RF capture areas when the antennas are "nested" (mast retracted).

Related Issues: (the devil is in the details)

- Coax relays can be sensitive to weather when use in outdoor environments. Up to 90 MPH winds (TX Hwy. 130 toll way), rain, dew, thermal cycles, etc. cause premature failure.

- Long duty cycles when dissipating up to 5.6 watts (28 VDC @ 0.2 amps) can over heat the relay solenoids in a confined space and/or when heated by direct sunlight on a warm (>100' F) Texas summer day.

- Shock and vibration when traveling on the highways and/or bumping down gravel roads

- Providing a reliable,  low RFI emission, source of 28 VDC power within a rover can be challenge.

- Yes, good low-loss and high-power coax relays aren't cheap (at least don't buy the cheap ones). As the length of your coax run increases the economics get better. My push-up mast extends up to 22 ft. (in order to get good 6 meter ground-bounce performance and raise my rover yagi stack over nearby obstructions, when necessary).

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