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Re: [Amps] What are the drawbacks of using a tube running, relatively lo

To: Manfred Mornhinweg <manfred@ludens.cl>
Subject: Re: [Amps] What are the drawbacks of using a tube running, relatively low voltage and high current?
From: Roger <sub1@rogerhalstead.com>
Date: Fri, 08 Jan 2010 02:31:55 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>

Manfred Mornhinweg wrote:
> Roger,
>
>   
>> How does this negatively affect the components in a Pi-L network for say 
>> 160 through 10, 6 meters, or say a strip line on two?
>>     
>
> I would say that using a lower plate voltage affects these components 
> POSITIVELY! Since the tube's capacitance stays the same, the lower load 
> impedance resulting from the lower voltage and higher current makes the 
> tube's capacitance less important, comparatively to the plate load 
> impedance. This allows you to use a lower Q for the tank circuit, which 
> is often advantageous for cutting down losses or reducing size. Note 
> that a lower voltage does not FORCE you to use a lower Q! It only gives 
> you more range of freedom to choose the Q that's optimal for your 
> intentions!
>   

I'm building up one rig using a pair of FU-728s, but have been thinking 
about playing around with the obsolete Russian GU73B if I can find a 
pair. One to use and a spare.Amateur power levels would allow the tube 
to loaf along with a reasonable amount of air even if the FU728s are 
probably more practical.

73

Roger (K8RI)
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