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Old June 15th 06, 07:29 AM posted to rec.aviation.homebuilt
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Default Jim Weir - Radio Receive Current


those first-generation solid-state radios really that inefficient?



Around 1978, I was given the job of modifying a Motorola Land Mobile (FM
~150MHz) repeater for use on a mountaintop repeater site where we were
installing solar power. The idea was to see how much current we could save
with simple modifications.

I found that when you turned the speaker off with the little plastic slide
switch provided, it actually SHORTED the output of the audio transformer.
Shut the thing up - sure did! So 90% of the standby rx current was being
drawn by audio circuitry - just because the design people had been too cheap
or lazy to do it right. And this was on a fairly modern (by aviation
standards) radio that was worth $5000 or so, even back then.

I moved the switch so that it cut power to the audio instead of just
shutting it up - and the size of the panels needed dropped by half!

You said they didn't care about current draw. That may have been an
understatement!