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Re: [Amps] Drake L4B to 6 Meters Help

To: "Michelle" <michelle_melt@windstream.net>,<amps@contesting.com>
Subject: Re: [Amps] Drake L4B to 6 Meters Help
From: Paul Baldock <paul@paulbaldock.com>
Date: Mon, 12 Dec 2016 10:07:29 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I have converted an SB220 and a TL922 for 6M. Both will produce 1300W PEP 6M.
( FYI I have converted an SB200 and that gave 600W PEP)

A stock L4-B will easily produce 1KW PEP on 10m and should do the same on 6M.

Note:
You need to ground the grids directly.
You should use a PI (not T) on the input with the PI output cap right next to the cathode. I use compression trimmers. You should reduce the turns on the plate choke and cathode choke to about 1/3 of what they were originally. You should use an L-PI on the output. The L is necessary to overcome the output cap of the tubes. I used the original TUNE cap with most of the plates removed, and a new LOAD cap. The open frame antenna relay should work fine. You will need to add a little cap, maybe around 10pF, on the normally closed path to compensate for the relay inductance when the amp is bypassed.

- Paul  KW7Y

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