[Icom] Extra relay box to key amp

Tue, 26 Mar 2002 21:20:24 -0800

Larry,

In the hope of putting the "keying-relay debate" to rest, I have just placed
a new page entitled "Why do I need an external amplifier keying relay?" on
the QSL.NET Icom site. The new page is an excerpt from the IC-746 FAQ
compiled by Dana Hoggatt, KB9SSS, and  is accessible from the main page.
Select "On Keying Relays". The URL is http://www.qsl.net/icom/auxrelay.html
Dana's kind permission to me to use the FAQ material is gratefully
acknowledged.

I am confident that if the amplifier's keying-line voltage and current
parameters are within the safe operating area of the OMR-109F relay, taking
cognisance of the derating required for extended contact life, no auxiliary
relay will be required.

A prudent, conservative approach would be to use an auxiliary keying circuit
in all cases. To avoid hot-switching, as you described, the operate time of
the auxiliary relay (electromagnetic or solid-state) should be in the 1 to 5
mS range.

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Note new e-mail address:
mailto:[email protected]

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Larry Benko
Sent: Tuesday, March 26, 2002 18:35
To: [email protected]
Subject: [Icom] Extra relay box to key amp

I am not addressing this to anyone in particular.  However
for those who insist on using an additional relay/keying
circuit because they consider themselves to be cautious,
be careful that the inline interface does not have too
much delay.  I have measured 5 different Icom rigs
including the 746, 756, 756pro, 765, and the 706 and
all the rigs closed the send relay 9 to 10 milliseconds
before the beginning of the RF output.  If your interface
adds too much delay you will be hot switching the RF and
causing splatter to others on the band.  By the way most
medium sized relays have operate times in the 8 to 10
millisecond range.  Be cautious if you wish but please don't
be inconsiderate and interfere with others.

73,
Larry Benko, W0QE
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