[Amps] My conclusion: Re: Low SWR Input Amps

[Jim W7RY]

Here is what I use:

http://home.earthlink.net/~wd7s/TU-6B.htm

See it in action here (8877):

http://s900.photobucket.com/albums/ac206/w7ry/8877%20Amplifier/?start=0




And here (3CX800s):

http://s900.photobucket.com/albums/ac206/w7ry/3CX800%20Amplifier/

I use Arco mica compression variable caps for the input and output. 
Available at www.rfparts.com


73
Jim W7RY


--------------------------------------------------
From: "w3hvq" <w3hvq at frontiernet.net>
Sent: Wednesday, November 03, 2010 2:37 PM
To: <amps at contesting.com>
Subject: [Amps] My conclusion: Re: Low SWR Input Amps

> Friends,
>    The three responses received within a few hours after my posting are 
> greatly appreciated.  I have decided to scrap the idea of "no input 
> tuning" and immediately pursue using a switched-in tapped, tuned circuit 
> for each band.  I figure on initially setting the tap at the 60 percent 
> point from the bottom end of each coil (in the parallel LC circuit).   I 
> will adjust Q by adjusting the LC ratio so that it will work OK over each 
> band.   I was especially interested in the amps reflector response number 
> 9 which even included a suitable rule-of-thumb input resistor of 90 ohms 
> for realistic 4-1000 tests without applying any of the tube's voltages. 
> I'm sorry that I do not have time to supply any further information to you 
> guys, as I've already put my name in with about 90 others who expect to be 
> working the SSCW contest this weekend.
>    I can say that I originally built this amplifier in the days when all 
> transceivers were of the tube type.  That is, all had output tuning and 
> loading controls that allowed amplifier's SWR of 2 to 4 to be matched OK. 
> There was no consideration ever given to impedance matching within the 
> amplifier.
>    While I will eventually install tuned circuits for all six HF bands,  I 
> may omit 160m and 10m for this weekend's activity.  Go PVRC!
> Thanks my buddies,
> John, W8OHT
>
>
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