Good points, Jim, but you still have to design the amp and a ready made one can
be left in the 20 meter position and drive reduced. To get the narrow phone
band only operation you would have to re-design the 20 meter filter. Why
bother to go through all of that work unless you just like designing
amplifiers. Then you can start out with a cheap CB amp. They don't have a
band switch.
________________________________
From: Jim Thomson <jim.thom@telus.net>
To: amps@contesting.com
Sent: Monday, October 8, 2012 3:37 AM
Subject: [Amps] 300 W single band mobile amp needed
Date: Sun, 7 Oct 2012 08:24:02 -0700 (PDT)
From: rick darwicki <n6pe@yahoo.com>
To: AMPS <amps@contesting.com>
Subject: [Amps] 300 W single band mobile amp needed
I have a friend that runs a motorcycle mobile on 20 Meters at about 100 watts.
He is looking for a schematic/info/link for a simple no tune amp of about 300W
that would just cover the SSB section of 20. Any help?
Thanks
Rick, N6PE
Going from 100 watts to 300w = exactly 4.77 db. That’s nothing to sneeze
at....and is enough to get the job done.
The duty cycle on SSB is such that there is no way in hell your buddy is gonna
fry his brains out on 20m band.
The average power is WAY too low... and so is the freq.
Any mono band amp has some advantages, only ONE LP filter required. Not only
that, you then also don’t have to worry
about band switching various LP filters. You just eliminated all the
switching! You also now have the luxury of designing the
combiner so it’s 100% optimized for 20m band. Then you get max eff.
Plan B might be to use a 11m cb amp, and install a 20M LP filter into
it..then retweak the bias a bit.
I would not worry about IMD on any mobile amp. With 300w pep,and a mobile
ant, you are not gonna be
loud enough to anywhere for anybody to start bitching about imd.
To supplement your battery-alternator setup, use a .5 to 1 farad cap across
the 12 vdc buss. The car stereo
guys use these caps all the time. They work damn good too. No more lights
blinking on heavy bass notes etc.
The 11m ops also use em for mobile applications.
Later....... Jim VE7RF
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