I need to correct some of my last statements on this topic (thanks to
Dave AB9CA/4 for pointing them out).
I apparently was thinking of other battery chemistry than lead-acid
batteries. A check with wikipedia reveals that full charge voltage,
open-ckt, is 2.1v per cell (12.6v for auto battery). Fully
discharged open-ckt voltage per cell is 1.95v (11.7v) and 1.75v
(10.5v) when loaded.
Matt was seeing full RF output with 12.2v at the amp.
But that was with his engine running (alternator charging) which
ought to deliver higher voltage to the amp (if cable losses are low -
something like 0.5v drop if wiring is 8-awg). Alternators run at
14.2v in full charging. They have a voltage regulator that drops
this when battery reaches full charge (not sure what voltage that is
but seems I've seen >13v).
I do not recall what gauge of dc wire was run to the 100w Motorola
VHF trunk-mount radios we used to install for police and fire, but
they held power pretty well with engine off (with fresh battery
charge). I am thinking the wires were 12ga awg and 17-foot long
before cutting to length in each install.
The rest of my suggestions for testing and connections are still good.
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[email protected]
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