This appears to be a problem only with a LPT keyer system on one band with
one antenna.
It probably relates to a combination of RF levels on one band and antenna,
and especially the poor design of simple LPT port keying systems where
keying transistors are not bypassed for RF or the port has a ground loop (as
you mentioned).
A little properly-placed low value resistor and bypass cap can do wonders.
----- Original Message -----
From: "J.D. "Dan" Weisenburger" <kw4t@comcast.net>
To: "Tom W8JI" <w8ji@w8ji.com>
Cc: "Carol Richards" <n2mm@comcast.net>; <CQ-Contest@contesting.com>
Sent: Wednesday, November 07, 2012 9:30 AM
Subject: Re: [CQ-Contest] RFI problem-Thank You
Along time ago I had a similar problem with LPT1. There were two grounds
causing a ground loop at some frequencies (actually gound loop was always
there) while others were clear. I made it a "Single" ground and all was
well
73 from Lake Moneysgone, Dan, KW4T
On 11/6/2012 5:57 PM, Tom W8JI wrote:
Thank you to all who responded. Just to clarify...I have no RFI problems
running 1kw on ssb. On cw, I have no rfi problems on 160,80,40m,20 or
10m as long as I use the monobanders. The problem manifests itself on
15m and when I use the TH6DXX. Normal day to day logging is done with
DX4WIN and no problems.My conclusion is that I am getting RFI through
the LPT1 cable. I will get some 31 mix cores and hopefully cure this
annoying probllem.
How far is the TX6 from the shack compared to other antennas?
Do you have a balun on it, and what type, and is the coax grounded at an
entrance panel or anyplace?
73 Tom
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