Date: Fri, 30 Nov 2018 13:29:55 +0000 (GMT)
From: DAVE PICK <daveyxm@virginmedia.com>
To: paul@n1bug.com,
        "Discussion of the Lowfer (US, European, & UK) and MedFer bands"
 <lowfer@mailman.qth.net>,
        rsgb_lf_group@blacksheep.org
Message-ID: <2133457080.64533.1543584595217@mail2.virginmedia.com>
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References: <c0a5c460-47dd-1671-28fb-44590355a877@n1bug.com>
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Subject: LF: Re: [Lowfer] FET change, hmmm
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Paul

Try the Infineon IRFP260MPBF they are fast and reasonably priced. I use Ixys IXFH58N20 but they are expensive... they are the best though!
Can't find any FQA34N20 over here from reputable sources.

Dave G3YXM

> On 30 November 2018 at 12:58 N1BUG <paul@n1bug.com mailto:paul@n1bug.com > wrote:
> 
> 
>     Yesterday I replaced FETs in my 2200 meter amplifier. Since the
>     FQA34N20 is long discontinued I had no choice but to make a
>     substitute. I chose the FQA32N20C because I know of one active
>     station using them in the same amplifier with success.
> 
>     I notice drain ringing is significantly greater with the new FETs,
>     but maybe acceptable. I have little choice but to run the amp and
>     see how it goes.
> 
>     I also notice the gate voltage decay takes about twice as long as
>     the old FETs. According to the data sheets, turn off fall time on
>     the 32N20C is almost twice that of the 34N20. I suppose that is what
>     I am seeing. I *guess* this may be related to increased ringing, as
>     it appears one side is not fully off as the other begins to switch on.
> 
>     I would appreciate any comments or suggestions, including
>     suggestions for a FET which might leave a longer dead zone at the
>     phase transition. I'd think slow to turn on, fast to turn off would
>     be nice...
> 
>     Alternatively, if anyone has a stash of FQA34N20 purchased from a
>     well respected vendor (old stock) and would be willing to sell some,
>     I may be interested. I've already tried some which originated from a
>     Chinese source and am not interested in going down that road again. :-)
> 
>     73,
>     Paul N1BUG
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<!DOCTYPE html>
<html><head>
    <meta charset=3D"UTF-8">
</head><body>Paul<br><br>Try the Infineon IRFP260MPBF they are fast and rea=
sonably priced. I use Ixys IXFH58N20 but they are expensive... they are the=
 best though!<br>Can&#39;t find any FQA34N20 over here from reputable sourc=
es.<br><br>Dave G3YXM<br><blockquote type=3D"cite">On 30 November 2018 at 1=
2:58 N1BUG &#60;<a href=3D"mailto:paul@n1bug.com">paul@n1bug.com</a>&#62; w=
rote:<br><br><br>Yesterday I replaced FETs in my 2200 meter amplifier. Sinc=
e the<br>FQA34N20 is long discontinued I had no choice but to make a<br>sub=
stitute. I chose the FQA32N20C because I know of one active<br>station usin=
g them in the same amplifier with success.<br><br>I notice drain ringing is=
 significantly greater with the new FETs,<br>but maybe acceptable. I have l=
ittle choice but to run the amp and<br>see how it goes.<br><br>I also notic=
e the gate voltage decay takes about twice as long as<br>the old FETs. Acco=
rding to the data sheets, turn off fall time on<br>the 32N20C is almost twi=
ce that of the 34N20. I suppose that is what<br>I am seeing. I *guess* this=
 may be related to increased ringing, as<br>it appears one side is not full=
y off as the other begins to switch on.<br><br>I would appreciate any comme=
nts or suggestions, including<br>suggestions for a FET which might leave a =
longer dead zone at the<br>phase transition. I&#39;d think slow to turn on,=
 fast to turn off would<br>be nice...<br><br>Alternatively, if anyone has a=
 stash of FQA34N20 purchased from a<br>well respected vendor (old stock) an=
d would be willing to sell some,<br>I may be interested. I&#39;ve already t=
ried some which originated from a<br>Chinese source and am not interested i=
n going down that road again. :-)<br><br>73,<br>Paul N1BUG<br>_____________=
_________________________________________________<br>Lowfer mailing list<br=
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rget=3D"_blank">http://mailman.qth.net/mmfaq.htm</a><br>Post: mailto:<a hre=
f=3D"mailto:Lowfer@mailman.qth.net">Lowfer@mailman.qth.net</a><br>Post must=
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ed by: <a href=3D"http://www.qsl.net" rel=3D"noopener" target=3D"_blank">ht=
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=20
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