[CQ-Contest] RFI problem-Thank You

[Tom W8JI]

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 at comcast.net>
To: "Tom W8JI" <w8ji at w8ji.com>
Cc: "Carol Richards" <n2mm at comcast.net>; <CQ-Contest at 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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>
>