[600MRG] RFI identified

Paul N1BUG FN55mf paul at n1bug.com
Fri Jan 3 13:31:29 EST 2025


Thanks Brian. I will try the old fashioned cheater adapter. An isolation
transformer is out of the question unless I buy one so, being on a very
tight budget the probably unanswerable question is which is the more
likely to fix it... isolation transformer or line filter? I have nothing
to ground it to other than the electrical ground via one route or
another, unless I install an isolated ground. I've noticed line filters
that offer good attenuation at 2200m which is also of great interest,
are few. Fortunately there are those few.

Paul N1BUG



On 1/3/2025 12:13 PM, Brian Pease wrote:
> Experimenting is in order. One thing you could try, *with care*, is to
> plug in the fridge with a cheater adapter that isolates the frame from
> ground to see if that helps. As a next step, ground the frame to
> something other than the power line 3rd wire. Another thing would be an
> old school 60Hz isolation transformer, although I have found there tends
> to be too much capacitance between windings. A transformer with a
> groundable shield between windings might work. You could try a UPS if
> you had one large enough, but of course they can be their own source of
> RFI.  Then it is on to the line filter option.
>
>
> On 1/3/2025 11:47 AM, Paul N1BUG FN55mf wrote:
>> Since my return I have been plagued by periodic RFI that reduces S/N on
>> 630m by 10 to 15 dB, maybe more at times. It tends to cycle on for one
>> to three hours, then be off for a few to several hours. Audibly in AM
>> mode it is a somewhat rough 120 Hz buzz. Noise blankers don't touch it.
>> I can identify this RFI from below 10 kHz to above 500 kHz, but there
>> are several broad peaks and valleys across the range. The worst of them
>> is very broad centered approximately on 450 kHz but remaining almost
>> flat up to and across 630m. I have not tried to find the upper frequency
>> limit since I really don't care about anything above 500 kHz.
>>
>> Early this morning I found it the culprit. It is my refrigerator!
>> Perhaps a line filter will help, although my luck is rarely that good.
>>
>> I'm still chasing one, possibly two serious RFI sources affecting 2200m
>> but won't go into that here.
>>
>> 73,
>> Paul N1BUG
>>
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