[Boatanchors] SB-220 in AM service

[jeremy-ca]

Hmmm, maybe 200W of plate dissipation and 500W out on AM? Id love to see 
that on a spectrum analyzer!

Carl
KM1H


----- Original Message ----- 
From: "RAY FRIESS" <rayfrijr at msn.com>
To: "Jim Wiley" <jwiley at alaska.net>; "rbethman" <rbethman at comcast.net>
Cc: "Boatanchors Mail List" <boatanchors at mailman.qth.net>; 
<ke7kk at earthlink.net>
Sent: Wednesday, March 12, 2008 6:18 PM
Subject: RE: [Boatanchors] SB-220 in AM service



That's one good thing about the old Palomar amps ... like the 300.   6 sweep 
tubes (two driving 4) and
you can get almost 500 watts out AM with only 40 or 50 watts drive.
A little "redoing" to prevent spurious emissions and it's a great sounding 
half KW.





> Date: Wed, 12 Mar 2008 14:09:00 -0800> From: jwiley at alaska.net> To: 
> rbethman at comcast.net> Subject: Re: [Boatanchors] SB-220 in AM service> CC: 
> boatanchors at mailman.qth.net; ke7kk at earthlink.net> > I use an old Drake 
> L-4B in AM service, and have used it for more than 20 > years, with no 
> failures - and the same set of tubes. I usually set it > for about 350 
> watts unmodulated carrier output (the max allowable is > 375 watts, which 
> which with modulation equals 1500 watts PEP). I tend > to be long winded, 
> but the L-4B is a continuous duty rated amp, and was > built properly. It 
> has a pair of 3-500Z tubes, a squirrel cage blower, > chimneys on the 
> tubes, tube sockets in a pressurized plenum, plus a > separate power 
> supply that can really take some guff. > > > The SB-220 should be OK at 
> 250 watts or so out, as long as you limit > continuous talk time to 10 
> minutes or less , with no more than a 50% > overall duty cycle. Keep your 
> eye (or nose?) on the transformer - if it > starts to smell hot, back off 
> on the talk time. For a test, I ran the > L-4B on 20 meters at 1000 watts 
> output for a hour into a dummy load - > other than the power supply 
> starting to smell a bit warm, and the tubes > getting sort of orange, no 
> problems.> > > Before the rules for AM changed, I used to run it at about 
> 400 watts > carrier output, mostly on 10 meters AM, also with no problems. 
> However, > I did manage to unsolder the connections inside an external 
> low-pass > filter doing that. > > > Good luck. Maybe I will hear you on 
> the band once I get my 10-meter > antenna back up. > > > - Jim, KL7CC> > > 
>  > >>> Greetings Anchor People> >>>> >>> The Heath SB-220 in the shack is 
> seldom used and I would like to use > >>> it in> >>> AM linear mode with 
> low power exciters such as the Heath DX-60, Knight> >>> T-60, HT-32 / 37, 
> HX-500, WRL DSB-100 etc. As its rated for 1KW CW > >>> RTTY> >>> (10 Min 
> max) I thought that 250W input on AM should not stress the > >>> power> 
>  >>> supply or tubes, in the low power position (graphite tubes) At 60%> 
>  >>> efficiency that should be approx. 150W rf output. Any thoughts from > 
>  >>> others> >>> who have used the Amp on AM ? Thanks for your input Bill 
> KE7KK SD> > Bob Bethman/NØDGN/BC-610/Northern Radio SP-600 Manassas, VA - 
>  > > MultiBand Dipoles> >> > 
> _______________________________________________> >> >> 
> ______________________________________________________________________________________________