Excuse the brain fart! That was the same voltages that the NCL-2000 used
back in 1963. However holding a SB-220 to a KW input still requires that the
drive be reduced or the amp improperly loaded. Id prefer reduced drive.
Carl
KM1H
----- Original Message -----
From: "Joe Subich, W4TV" <lists@subich.com>
To: "'Carl'" <km1h@jeremy.mv.com>; <amps@contesting.com>
Sent: Saturday, August 29, 2009 8:48 PM
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.
>
> 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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>> >>
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>> >
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>>
>
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