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Voltage required for proper radio operation

N4XEO wrote:

Most of the radios are rated for 13.8 volts now a days. With the parts 
getting smaller and smaller they just can't run on less than that.

W9AE replies:

The VCO, LO, and mixer circuits in ham radios are generally powered by a regulated internal voltage.  Usually 9.6 Volts or less.  It's not obvious to me why a late-model ham transceiver shouldn't have stable frequency when operated at 13.0 Volts.  Maybe some of us are using DC power supplies that have poor load regulation?  Or maybe the DC power cable has too much resistance or poor connections?

I have used a lawn tractor battery to power my FT-847 at max UHF CW output power, with no noticeable instability of TX Sat VFO frequency.  The lawn tractor battery voltage was approximately 13.0V.  But my 12-gauge DC power cable is only 4 feet long - less than half the length of the original cable set.  And of course the lawn tractor battery voltage doesn't drop when I draw 12 Amps on transmit because it is designed for high current engine starting.

Wayne Estes W9AE
Mundelein, IL, USA
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