Steve,
Be careful. I believe Doug used an old NRC R-175A plate choke. Check for
resonances before applying the juice!! His original intent with this article
and hence the selection of this specific choke was to convert the SB200 for
use as a LOW BAND amp only, ie 160/80/40 meters.
I just picked up a like new MFJ-259 swr analyzer and am anxious to do some
fun stuff. This coupled with my faithful Heathkit HD1250 GDO should let me
check most things.
Last time I checked Derek K7FF had some of these R-175As in stock.
GL and God Bless.
Lane
KM3G
San Diego
-----Original Message-----
From: Steve Lawrence <smlx@earthlink.net>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: Friday, September 25, 1998 7:07 PM
Subject: [AMPS] SB 200 on 160
>
>Doug DeMaw had an article on adapting the SB 200 for 160m in Sept. 1979
>QST. I utilized the input circuit only per the article to allow operation
>on all bands 80 through 10 including the WARC bands. The 15m position works
>for 17m and 12m while 30m works when the 40m position is selected. (Before
>you comment, it is perfectly legal to use the amp on 30m if the input is
>limited to 200W.) The article had a major error which doug confirmed. That
>is: the input and output connections of the broadband toroid are reversed
>as shown in the article. You'll get a 9:1 input SWR unless you correct it
>(reverse the connections to C16 and RL1). Although I haven't tried it, I
>have every reason to believe, based on Doug's typically fine work, that the
>mod for the plate circuit for 160 shown in the article will work. I've had
>the input circuit mod installed for over 18 years with zero problems. Nice
>to know that the plate choke isn't resonant in the WARC bands.
>
>73, Steve WB6RSE
>
>
>
>--
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>
>
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