wrote in message
...
On Sat, 24 Feb 2007 14:20:12 -0500, "Jimmie D"
wrote:


I was tired when I made the post and for got to say that this would be a
mbile unit. antenna mounted on my tool box in the bed of my pickup. It was
really just a thought about mounting the amp in the tool box since room in
my little Nissan is scarce. From there I made the leap to thinking since
the
feed point impdance of the antenna is already going to fairly low and feed
line length practically 0 why step it up to 50 ohms just to drop it back
down again. More realistically I am thinking a short antena on 20M may be
more like 10 ohms wich would be a 5:1 SWR and I dont think my amp would
like
that much. At best I am thinking the 10M antena I am planning on using
will
have the 25 ohm impedance you metioned, 15 and 20 m antennas would have
even
a lower impedance.so an output impedance of say 15 ohms might be a good
thing.

Jimmie

One reason to go from whatever andtenna feed impedence to 50 ohms is
on receive you still need a 50 ohm match so using standard amp design
with 50ohm output makes life easier for that. Also for testing life
is easier (got a 10 ohm load?) as then everything is standardized
at 50 ohms. Also at low impedence the I^R losses go up as the
magnitude of I gets very large

Allison.




Found an old CB amp in my junk box today. Spec plate on the amp says it will
cover 80 thru 10. I plan on doing some mods improving the bias.and add some
filtering I think this may give me what I want. I forgot I bought a 5 galon
bucket of these amps at a hamfest years ago and still have a few around.