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Re: [Amps] AL811, AL811H or AL572 mods to 6m

To: dezrat@copper.net, Peter Voelpel <df3kv@t-online.de>
Subject: Re: [Amps] AL811, AL811H or AL572 mods to 6m
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Wed, 2 Aug 2006 21:39:04 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Bill said:
>As I mentioned, this technique is covered in any recent ARRL handbook
in the HF amplifiers chapter.<

That deals nicely with the output side. But 811s and 572s have very long grid 
leads, which make them awful bloody things at 30, let alone 50MHz. So 
personally, I wouldn't touch them with a barge pole (as the saying goes) on 6. 
I suppose you could series tune the grids to resonance, but I have doubts about 
the resulting efficiency at the end of the day. The spacing is enough for, I 
suspect, transit time to start coming into play, as well as the gain dropping 
because of cathode lead impedance.
73
Peter G3RZP
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