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Re: [Amps] 160 meter tuned circuit

To: "Larry" <>
Subject: Re: [Amps] 160 meter tuned circuit
From: Bill Turner <>
Date: Thu, 18 Mar 2004 07:05:29 -0800
List-post: <>
On Tue, 16 Mar 2004 17:52:15 -0600, Larry wrote:

>Hi guys, I recently recieved a home brew 4-1000a amplifier. Amp is tapped for 
>160 only and running just 1 tube. High voltage is near 5000. This amp has no 
>tuned input circuit and Im not a very good builder. Does anyone have a 
>schematic or know where I can get a tuned circuit for this one band amp? My 
>Yaesu tunes to abt 1.6 swr on auto tuner and antenna standing wave is less 
>than 1.5.   


You can use a simple pi-network on the input.  For a Q of 2 and assuming
input and output impedances of 50 ohms, the values are 1768 pF for both
capacitors and 4.42 uH for the coil.

I would recommend using compression type trimmers for the capacitors,
since the impedances are rarely ever exactly 50 ohms at each end.  500
volt rating caps should be fine.

If you have Excel installed on your computer and you want to experiment
with different values of R and/or Q, VA3UX has an online calculator
available at

Click on "Improved Pi Calc's".  You can either run this online or save
it as a file on your computer to run offline.

73, Bill W6WRT
QSLs via LoTW

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