The name of the fan is Tarzian, more modern name is Sarkes-Tarzian. Very
good fans!!
Joe W4AAB
----- Original Message -----
From: R.Measures <r@somis.org>
To: Harold B. Mandel <ka1xo@juno.com>
Cc: <wa4tt@nlamerica.com>; <n3ji@yahoo.com>; <amps@contesting.com>
Sent: Wednesday, August 25, 2004 7:37 PM
Subject: Re: [Amps] Centurion cooling improvement ideas for AM service
>
> On Aug 25, 2004, at 3:24 PM, Harold B. Mandel wrote:
>
> > Dear Sirs,
> > In reading about how the SB-220 will be used on AM I wonder
> > if any of the '220 users out there have connected a known-good 50 ohm
> > dummy load AFT of the amplifier and a known-good Reflected RF Power
> > meter between the exciter and amplifier and measured what the
> > amount of reflected power is with and without the amplifier on line.
> >
> > Is it not true that the SB-220 pass-through circuitry and the
> > input tuning circuitry sometimes displayed greater than ten percent
> > reflected power with the amplifier in STBY and an equivalent amount
> > of reflected power while keyed?
>
> Depends on what band. 10m is typically the worst on standby/bypass.
> Adding c. 30pF across the output connector will cancel the L in the
> relay. The SWR of the input can be corrected by raising the Q of the
> Pi tuned inputs to c. 2.
> >
> > In developing an A-M signal and worrying about the ability of
> > the amplifier to withstand prolonged keying, is it not wise to
> > determine
> > if an inherent defect of design is adding to the problem?
> >
> > An additional cooling option is available at Max-Gain on the
> > web.
> >
> > They sell a Tarzan fan that can be bolted to the exterior of the '220,
> > doing away with the internal fan altogether. The Tarzan fan is much
> > more
> > robust and coupled with the dual-level airflow in the '220/'221 series,
> > should provide more than adequate cooling for long key-down times.
> >
> > The only other issues to tackle are the anode and filament
> > transformer capabilities.
> >
> > Respectfully,
> >
> > Hal Mandel
> > KA1XO
> >
> >
> >
> >>>> Only problem is, my screen mod ARC-5 setup can
> >>>> only muster about 25 watts so I don't have any good way to tune
> >> up at the SB-220's full capabilities. -Charles
> >> Charles--- If you have a xcvr capable of 100w output, tune the
> >> final for full pwr out. Then switch to the Arc 5 and drive with the 25
> > w out
> >> from it. that will give you the 4 x head room normally required for AM
> >> operation. BUT you need to be sure the amp is robust enough to opr at
> > this level
> >> key down.------73 john WA4TT
> > _______________________________________________
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> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> >
> >
> Richard L. Measures, AG6K, 805.386.3734. www.somis.org
>
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