[AMRadio] SB-200 on AM

Jim Wilhite w5jo at brightok.net
Tue Jun 10 14:51:54 EDT 2008

John, I used an SB 201 behind a Kenwood TS-430 for some years.  I 
didn't have any problems running about 125-150 watts carrier and 
modulating the Kenwood properly.  When I was using it, I didn't have 
my plate modulated stuff set up because of space limitations.  Just 
be sensitive to tune up and then set the carrier out to be within 
the parameters of the tubes in the amp.  About 125 to 150 is about 
all you would want to use.

With the Kenwood the thing to watch was setting the carrier low 
enough to make the collector current advance rather than fall.  It 
was tricky to get the carrier set then set the mic gain to give that 
meter indication.  Do it right and you will have a fine sounding 


----- Original Message ----- 
From: "John Lawson"

>   I have found (and hauled home) a slightly-ailing SB-200 amp that 
> I would like to use on AM...  I'll be driving it with an Alinco 
> DX-70 (40W AM/CW), into an ATR-15 tuner, thence by ladder-line out 
> to my "Sort-Of-NVIS Loop", the which system right now tunes 75 
> Fone down to 1.1:1 very stably and reliably.
>   Aside from the many pages of mods and tweaks, does anyone have 
> any comments/experiences - good-bad-ugly - ?
>   My previous AM rig was a Valiant - I've not had a separate 
> amplifier since I sold off all my S-Line gear back in the late 
> 80s.
>    Thanks in advance for any info or thoughts on the SB-200 in AM 
> service.
> Cheers
> John KB6SCO

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