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From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <CABP+t7a4HJpEJhtih2HLchjFeXaM_HX0THRdVaL4tFCytzbuRw@mail.gmail.com> <4F101646.3040400@iup.uni-heidelberg.de> <Pine.LNX.4.64.1201130849450.31496@plato.ucs.mun.ca>
Date: Fri, 13 Jan 2012 13:08:38 -0000
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Subject: Re: LF: TA condx last night
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Hi Joe you need to be careful with the 4427 as well. If you remove the drive
from some of this family the output all go permanently high. So the "two
Dave's" keyed their designs by keying the supply to the 4427.

Alan

----- Original Message ----- 
From: <jcraig@mun.ca>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, January 13, 2012 12:27 PM
Subject: Re: LF: TA condx last night



On Fri, 13 Jan 2012, Stefan Schäfer wrote:

> There are a few possible reasons why the PA blows up. I am more and more
> convinced that it comes from the drive stage. Late in the night i got the


I've been thinking along these lines too.  I fried an IRF640, replaced it
with an IRFP260, and was heartbroken when that fried too. I put another
260 in and half-fried that one -- it still puts out a bit of RF, but the
input is a triangle and not a square so the gate impedance is way down.

The TX is a  class E driven with a juction transistor totem pole.  The
plan is to replace this with a fet driver eg: 4427.

73
Joe VO1NA
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