[Amps] SB-220 bias question

[Carl]

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 at subich.com>
To: <gudguyham at aol.com>; <amps at 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 at contesting.com
>> [mailto:amps-bounces at contesting.com] On Behalf Of gudguyham at aol.com
>> Sent: Saturday, August 29, 2009 1:17 PM
>> To: df3kv at t-online.de; amps at 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 at t-online.de>
>> To: amps at 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 at contesting.com
>> [mailto:amps-bounces at 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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