[AMRadio] WTB SB-220


RJ Mattson rjmattson at hvi.net
Sun Sep 26 21:57:27 EDT 2004


If you can't get out consistantly with a Viking II, you need an antenna -
not an amp.
bob...w2ami
www.qrz.com/callsign/w2ami


----- Original Message ----- 
From: "Gary Blau" <gblau at w3am.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Sunday, September 26, 2004 9:22 PM
Subject: Re: [AMRadio] WTB SB-220


> I've always found more RF power, at least in significant iterations of
> ~100watts, can make a big difference on the air in cutting thru noise
> and band conditions.  But what's more important is full modulation.
>
> One potential benefit of running a -modified- Viking or Ranger, etc.
> into an amp like the SB220 is you can then concentrate on improving the
> modulation performance of the exciter xmtr.  This can in turn deliver a
> more effectively modulated signal thru the entire system and thereby on
> the air.
> Add that to the increased power ability of running a fully modulated
> ~400 watts carrier, and a case can be made that this is one of the
> easiest ways to get a big AM signal on the air.
> The easiest is to use a rice box for an exciter, but that's another fist
> fight.
>
> The Viking would have to be modified a good bit to optimize this
> approach.  The first problem being reducing the RF output to the 10-25
> watt level that the SB220 will want to see.  I've never had a VikingII,
> so I can't say for sure, but my first thought is to try a variable PA
> screen voltage scheme.  (I did this to good effect in my Ranger.)  You'd
> probably have to remove one of the 6146's in the Viking, and make other
> changes as well, but the idea is that not only will you be able to vary
> the drive to the amp, but it will also give the huge benefit of much
> higher positive peak modulation capability.  Positive peaks can easily
> go way beyond 100% as the PA now is operating well below its peak
> dissipation point.  Even if you're not a believer in hugely asymmetrical
> 'supermodulation', having an xmtr that can easily handle it will still
> be a big improvement over the 'stock' Viking.
>
> Loudness is where it's at to get thru on a noisy band, but having an
> extra 100-200watts as well makes a potent combo.
>
> g
>
>
> W4AWM at aol.com wrote:
> >
> > << I am looking for a Heathkit SB-220 to run about 300 watts on AM using
the
> > Viking II to drive it. >>
> >
> > Hi,
> >
> > If you are getting the full output from the V II into a good well
matched
> > antenna, a couple of hundred more watts is not going to make any
significant
> > difference on the receive end and will only serve to heat up the shack
and run up
> > your power bill.
> >
> > 73,
> >
> > John,  W4AWM
>
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