[600MRG] RFI identified

[Brian Pease]

If there is a light dimmer in the house it is a prime suspect and the 
only cure may be to get rid of it.

A great RFI tool is a battery operated AM radio tuned to the low end.


On 1/3/2025 1:40 PM, Paul N1BUG FN55mf wrote:
> Renee, same thing here. Old 1980s fridge never a problem. New 2024
> fridge big problem.
>
> My house is full of assorted LED bulbs, most of which appear to be no
> problem in that I cannot detect whether they are on or off on either
> 630m or 2200m. I do have one strange thing happening however. I've got a
> nasty RFI source on 2200m that is either in my ham shack or not on my
> premises. I'm not yet certain which, since my receiver is SDR I can't
> power down a lot of stuff here in the shack to check. The thing is, with
> my kitchen LED lights ON, that RFI drops 10 dB or more. With the lights
> OFF, out of the sockets, or the circuit breaker off, the RFI is 10+ dB
> stronger than when those lights are on. I don't know what is going on
> there. It's like those bulbs actually absorb RF! Also that source is
> reduced 2 to 3 dB with my microwave oven plugged IN vs. unplugged. Weird?
>
> Paul, N1BUG
>
>
>
> On 1/3/2025 12:49 PM, Renee K6FSB wrote:
>> I had same/similar issue extended up into HF and found a simple 20Amp
>> Line filter did the trick for me. I had found it in a surplus store
>> ( like in 2000) and had it for a rainy day....when I replaced the fridge
>> the issue started...old 1970 fridge = no issues , new 2005 fridge
>> needed filter.
>> same thing for some of the led replacement florescent bulbs, they may
>> need rfi proof...some companies cheap out..there is a place on their
>> board but no parts....
>> Renée, K6FSB
>>
>>
>> On 1/3/25 9:13 AM, 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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>>>
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>>
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