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Re: [Amps] setting trimmer caps on amp RF in/out

To: John Keating <>
Subject: Re: [Amps] setting trimmer caps on amp RF in/out
From: Jay Sturtevant <>
Date: Fri, 21 Feb 2020 00:40:41 -0500
List-post: <>

Did you need info for a QRO HF 2000?


On Thu, Feb 20, 2020, 11:26 PM John Keating <>

> I'm looking for a procedure/recommendation on proper setting of the
> trimmer caps on the RF input and output of a QO HF 2000 amp. They are
> located right at the SO-239s. The input cap is in circuit (to ground) all
> the time; the output cap is in circuit (to ground) when the amp is not
> keyed (so the two are in parallel in that condition). I checked the input
> with the antenna analyzer and the output into 50 ohm dummy load, it's not
> wildly off 50 ohms across the HF band but it does vary -- 50 -j0 ohms at 4
> MHZ, 51 +j4 ohms at 7MHZ, 56 +j5 ohms at 10MHZ, 60 +j0 ohms at 14MHZ, 58
> -j8 ohms at 18MHz, 53 -j10 ohms at 21MHZ, and 43 -j4 ohms at 28MHZ. That
> makes the "bypass" condition SWR 1.25 in spots.
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