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Re: [Amps] SB-220 bias question

To: <gudguyham@aol.com>, <amps@contesting.com>
Subject: Re: [Amps] SB-220 bias question
From: "Joe Subich, W4TV" <lists@subich.com>
Reply-to: lists@subich.com
Date: Sat, 29 Aug 2009 18:02:32 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>

> 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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