[Amps] SB-220 bias question

[Joe Subich, W4TV]

> 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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