> The SB-220 is a compromise anyway as the Ep and Ip dont go
> to half on CW and drive has to be dropped for 1000W Input
> to maintain the same load impedance.
Not that it matters but you want Ep and Ip to go to 70% each
in order to reach half power (.7x.7= .5). By keeping them
in the same ratio, the plate load impedance remains the same.
If Ep and Ip sent to 50% each the power input would be 25%.
The 70% ratio is very typical ... 2800/2000V (SB-220),
3600/2500V (Henry, etc.) ... for the older amplifiers that
were designed for the old 1KW DC input (CW), 1500 W PEP
(output) SSB rules.
73,
... Joe, W4TV
> -----Original Message-----
> From: Carl [mailto:km1h@jeremy.mv.com]
> Sent: Saturday, August 29, 2009 7:24 PM
> To: lists@subich.com; gudguyham@aol.com; amps@contesting.com
> Subject: Re: [Amps] SB-220 bias question
>
>
> The SB-220 is a compromise anyway as the Ep and Ip dont go to
> half on CW and
> drive has to be dropped for 1000W Input to maintain the same
> load impedance.
>
> With 100W drive the typical key down output on CW is 800-900W
> and on SSB its
> 1200 and PS limited. This is when tuned to the maximum.
> Since the CW position puts less stress on the PS Id run it
> there for RTTY
> and digi.
>
> Now if you follow the manual, it says for CW/RTTY to advance
> the drive until
> the Ep is ( sags to) 2000 and Ip is 500 ma. Thats going to be
> way under 100W
> drive. You can also run 1000W PEP Input on SSB the same way
> as its still
> linear.
>
> Carl
> KM1H
>
>
>
>
> ----- Original Message -----
> From: "Joe Subich, W4TV" <lists@subich.com>
> To: <gudguyham@aol.com>; <amps@contesting.com>
> Sent: Saturday, August 29, 2009 6:02 PM
> Subject: Re: [Amps] SB-220 bias question
>
>
> >
> >
> >> NO WAY
> >
> > Absolutely "way" ... if you run the higher late voltage with lower
> > current and only 700 - 800 watts out in RTTY, the plate
> load impedance
> > of the tubes will be two to three times higher that the design
> > parameters of the pi network (higher voltage, lower current
> = higher
> > impedance).
> >
> > If the pi network will even tune with the higher PLI, the Q will be
> > much higher resulting in higher circulating currents, more
> loss, more
> > heat in the coils and stress on the capacitors. Since the
> pi-network
> > is already on the edge at 1500 W PEP, the added stresses of
> 100% duty
> > cycle RTTY may well cause premature failure.
> >
> > 73,
> >
> > ... Joe, W4TV
> >
> >
> >
> >
> >> -----Original Message-----
> >> From: amps-bounces@contesting.com
> >> [mailto:amps-bounces@contesting.com] On Behalf Of gudguyham@aol.com
> >> Sent: Saturday, August 29, 2009 1:17 PM
> >> To: df3kv@t-online.de; amps@contesting.com
> >> Subject: Re: [Amps] SB-220 bias question
> >>
> >>
> >> NO WAY
> >>
> >>
> >> To do so you have to modify the pi-net, as the output impedance of
> >> the tube will be much higher
> >>
> >> 73
> >> Peter
> >>
> >>
> >>
> >>
> >> -----Original Message-----
> >> From: DF3KV <df3kv@t-online.de>
> >> To: amps@contesting.com
> >> Sent: Sat, Aug 29, 2009 12:56 pm
> >> Subject: Re: [Amps] SB-220 bias question
> >>
> >>
> >>
> >> To do so you have to modify the pi-net, as the output impedance of
> >> the tube will be much higher
> >>
> >> 73
> >> Peter
> >>
> >> -----Original Message-----
> >> From: amps-bounces@contesting.com
> >> [mailto:amps-bounces@contesting.com] On
> >>
> >> My whole point is to run the tubes at higher plate voltage
> with less
> >> plarte and grid current for the same power output
> >>
> >> _______________________________________________
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> >> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> >
> > _______________________________________________
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>
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