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Re: [TenTec] amp keying loop weirdness

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] amp keying loop weirdness
From: Robert & Linda McGraw K4TAX <RMcGraw@Blomand.Net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 23 Feb 2006 10:08:52 -0600
List-post: <mailto:tentec@contesting.com>
High speed I/O devices are known to be affected by capacitive loading.  Some 
drive long lines better than others.  The long cable probably did it.  The 
short cable fixed it.  For those making your own cables, pay attention to 
the "pf per ft" numbers.  Lower is better.  Usually this is a factor not 
considered to be a concern in audio cables as most drivers are quite low Z 
devices.  On the other hand, inputs with a high Z will experience HF 
roll-off with high capacity type cables.

Bob, K4TAX

> Re the QSK probs with amps some are having, FWIW, I recall having some 
> kind
> of QSK amp keying loop weirdness problem a couple of years ago (can't
> clearly recall what it was--the amp either didn't key, or hung or 
> something
> like that) and it turned out the problem was somehow related to my use of 
> a
> really long keying cable.  I used a 10 or 20 foot long phono cable--the 
> kind
> RS sells with the black jacket that costs around 3 dollars with the phono
> plugs on the ends, and when I switched to a much shorter cable, around 5
> feet or so, the problem went away.   The continuity of the long cable was
> fine--no shorts; no opens.  Of course with the Orion QSK thing it sounds
> like a rig control problem but if you ever encounter anything odd with the
> amp keying and you have real long key lines try shortening them.

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