[Amps] Amplifier Input Circuit Consultation

[k7rdx]

A pair of 4-1000`s in gg (screens,grids grounded) cathode impedance looks 
close to 50 ohms but still needs pi tuned input networks for each band. I 
did this way back in the early 70`s and an impedance transformer is not 
required. A pair drive very easily,especially with 6-7kv from a well current 
rated hvps..It`s a good idea to run seperate adjustable bias to balance the 
tubes and prevent one tube from pulling more zsac than the other..GL,73 
Jim..K7RDX..
----- Original Message ----- 
From: "Paul Kraemer" <elespe at lisco.com>
To: <n1wr at chesapeake.net>; <amps at contesting.com>
Sent: Thursday, October 23, 2008 12:18 PM
Subject: Re: [Amps] Amplifier Input Circuit Consultation


> Sounds fantastic to me!
> Of course, there is an option---use two 4-1000 in paralell, that lowers 
> the
> input impedance to 50 ohms.
> It has been done.
> Paul K0UYA
> ----- Original Message ----- 
> From: <n1wr at chesapeake.net>
> To: <amps at contesting.com>
> Sent: Thursday, October 23, 2008 12:03 PM
> Subject: [Amps] Amplifier Input Circuit Consultation
>
>
>>I continue to work on the design/construction of my 4-1000 amplifier.  I'm
>> working on the input network details.
>>
>> The 4-1000 has a generally accepted input impedence of 100 ohms.  So I am
>> planning on using a 2:1 step up unbalanced to unbalanced balun followed 
>> by
>> a parallel tuned circuit, Q of 2-3, for each band.  Taking this approach 
>> I
>> will need only one relay contact per band to switch each tuned circuit 
>> (as
>> opposed to two needed to switch a pi network).
>>
>> In all of my reading and research I haven't seen this approach taken. 
>> The
>> grid compartment is under construction.  Before I go ahead and construct
>> the input this way - can anyone come up with a reason this won't work?
>>
>> I thoroughly enjoy this list and faithfully tune in to the goings on.  I
>> really appreciate the help and support that is provided.
>>
>> Wayne N1WR
>>
>>
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