On Tue, 07 Oct 2003 23:48:06 -0400, Kelton Joyner
wrote:

My SSB radio requires 30 amps transmitting. With the other loads in the
boat ( fans, lights etc.) the load approaches 50 amps. I limit transmit
time to 10 minutes in order not to have to run the engine to recharge

It was great up to here^^. SSB puts out 150 watts PEAK ENVELOPE
POWER. The linear amp is about 65% efficient, these days of IC
bricks. Idle current is so low the brick amp is connected directly to
the power source, whether the radio is on or off. It's simply cut off
electronically.

A properly voice-modulated 150WPEP transmitter draws about 5A of
"average" current. You'll see the lights dim on PEAKS of voice
modulation, but in between words it draws 0 amps when it's putting out
0 watts. If you were operating AM, your average load would go up
quite a bit as there is always a carrier being transmitted, modulation
or not, but that's not the case on SSB which is very efficient.

I'm a ham, obviously. My 650W mobile SSB rig, a Yaesu FT-900
transceiver driving a highly modified TenTec Hercules II 12V linear
amp, which is actually FOUR linear amps in parallel, draws a peak load
of about 120A from its Mercedes diesel starting battery in parallel
with a 130AH deep-cycle boat battery mounted next to the radio and
linear in the trunk of my 1973 Mercedes 220diesel (which is the ideal
ham car with ZERO electronics). The mobile will still start after
operating a contest all day at this level. My average current drain
is about 20-25A while transmitting voice. RTTY or PSK31, our new ham
radio digital mode, which runs full power at 100% duty cycle, is
another matter altogether. For the mobile data mode, I prefer packet
radio's burst transmissions at 300 baud. I've operated 650 watts as a
mobile, cross-band (VHF to HF), packet repeater at hamfests for
years....great fun working the world from a 1W walkie talkie and
simple notebook computer.

Your fans and lights are a MUCH HIGHER average load than your SSB
radio ever was.....



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?