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Message-ID: <199904160825.JAA07213@fm215.facility.pipex.com>
Date: Fri, 16 Apr 1999 09:27:15 +0100
To: rsgb_lf_group@blacksheep.org
From: "Walter Blanchard" <blanch@pncl.co.uk>
Subject: LF: LF Receive performance
In-reply-to: <199904151346_MC2-7224-194A@compuserve.com>
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Entirely agree with Dave's remarks re S meters etc.I'd written an almost
exactly similar email but hadn't got around to sending it.&nbsp;
Amazingly,&nbsp; in spite of&nbsp; the facts, DCB39 (or whatever it is)
is the same here;&nbsp; S9+20db; noise is S3; etc. However, I'm using an
ICOM 737 (which is completely useless on 136 straight-through) with a
26db gain VERY SELECTIVE (250 Hz) front-end ahead of it which transforms
its performance. It handles linearly the output from almost any length of
wire I choose to shove at it as an antenna because nearly all the
selectivity is applied <i>before the signal gets as far as the amplifier
grid.&nbsp; </i>&quot;Grid&quot; ???? - being an oldie and by definition
not knowing anything about modern wirelesses, sorry, electronics,&nbsp; I
built it using a device I DO know about - an E180F valve.&nbsp; Now all I
have to do is to get my old&nbsp; 4-400 HF linear retuned to 136 and
there'll be even more QRM.<br>
BTW, (what does that mean, by the way?)&nbsp; while attempting to
calibrate the 737 S-meter so I knew roughly what it meant I discovered it
has quite a temperature coefficient - between cold and warm it drifts 10
db.&nbsp; So probably many others do as well, since all these Japanese
rigs seem to be designed by a central design bureau and the only real
difference between them is the front panel design. Oops, shouldn't I have
said that?<br>
Walter G3JKV<br>
<BR>
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