[AMRadio] WTB SB-220


Jim candela jcandela at prodigy.net
Sun Sep 26 15:28:04 EDT 2004



Cory,

    I have a Gonset GSB201 linear amplifier (GG 4-572B) where I use it on 75
/ 40 meters as an AM Linear. My GSB-201 only puts out about 800 - 900 watts
key down depending on drive and line voltage. I use an AM exciter that can
produce a clean 10 watt carrier, and this carrier if any stronger would over
drive the linear on AM. I get a clean 150 watts carrier output with this
setup with room for lots of upward modulation.

    I never had a SB-220 but these are nice rigs with lots of upgraded
circuitry available from various places. Now consider my situation where
much above 10 watts drive results in non-linearity as seen from a trapezoid
pattern when 100% modulating the drive on AM. I'd bet that with a SB-220 all
you need is 20 to 25 watts drive for 375 watts output. The Viking II cannot
run down there unless you modify it so that the final amp, and modulator run
off the low B+ (might be pretty extensive modification to make work right),
or run at about 80-100 watts output, and insert a 6 DB pad between the
Viking II output and SB-220 input. That might do the trick.

    Now for efficiency sake, AM linear is poor in that regard, but is
capable of being extremely effective, and linear. You can also run the legal
limit on AM and not worry about a big heavy modulation transformer. As a
bonus winter is coming, and a little air moving past those 3-500Z's will
certainly heat the shack!

Regards,
Jim

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net]On Behalf Of Cory Hine
Sent: Sunday, September 26, 2004 1:14 PM
To: amradio at mailman.qth.net
Subject: [AMRadio] WTB SB-220


Hey gang,

I am looking for a Heathkit SB-220 to run about 300 watts on AM using the
Viking II to drive it. Does anyone have a decent amp that they want to sell?
I would like pics if possible.

Thanks,

Cory/AD5QP


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