[RFI] Home RFI Hunting

[Gedas]

Dave, wind one core with the appropriate number of turns, followed by 
your second core 3" to 4" away wound with it's own turns. The choice of 
77 core may not help as your typically want resistive loss of the RFI 
but if you have it handy try it. Never know. 73

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 9/30/2018 11:31 AM, Dave Van Wallaghen wrote:
> First, thanks to all of you who replied on the list and privately. I 
> appreciate all the advise.
>
> I just wanted to follow up on this as I tried a few things and I 
> sheepishly bring the solution to my buzzing noise problem on the low 
> end of the AM band and 600m in case anyone else runs into my situation.
>
> I did run a separate AC ground back to the panel physically separating 
> my shack circuit from my problematic AV/TV circuit. This had no effect 
> what so ever. So while pondering why this noise is so prominent if my 
> antenna or rig is connected to the AC ground system, my inexperience 
> waned enough that I finally figured out what was going on. In my first 
> email, I failed to mention that the antenna I was using is a 80-10m 
> multi-band end fed from MyAntennas. This seemed like a logical choice 
> since it is resonant on all of the ham bands I wanted to test and does 
> fairly well on 160m and 600m as well.
>
> So yes, the coax shield of the feedline of the antenna acts as the 
> counterpoise for this antenna, and in effect, everytime I connected 
> the AC ground to the rig or antenna ground, it was coupling the noise 
> directly to my antenna system and rig. Several turns of the feedline 
> through a #31 core at the rig end greatly reduces the buzzing. It 
> reduced the noise for S9+5 to a respectful S5-6 which is what I was 
> seeing when I floated the ground of the rig and antenna. I still have 
> a little noise between 380-480Khz that I will tweak and see if I can 
> eliminate all together.
>
> This leads to my next question: I was thinking of using a #77 mix core 
> in series with the #31 to help here as the #77 has a higher impedance 
> in the lower frequencies. I may have missed it in Jim, K9YC's RFI pdf, 
> but does series mean the two cores together with the cable passing 
> through them simultaneously? Or two separately wound cores? I 
> apologize if this is a dumb question. I've learned a great deal 
> throughout this process and I might just be a little overloaded at the 
> moment ;-)
>
> 73,
> Dave W8FGU
>
>
>
>
> On September 13, 2018 14:23:44 Jim Brown <jim at audiosystemsgroup.com> 
> wrote:
>
>> On 9/13/2018 10:36 AM, Dave Van Wallaghen wrote:
>>> So, my questions are: as the largest portion of this noise comes from
>>> my TV plugged into the AV circuit, would running separate grounds for
>>> my AV and shack circuits back to the panel help alleviate some of the
>>> noise that I find on my shack circuit ground? Or do you think most of
>>> it is being physically coupled? I would have tried this myself, but
>>> while certainly doable, it will be a little work to make it happen.
>>
>>
>> Several thoughts on this.
>>
>> First, RF noise from defective/poorly designed equipment OFTEN travels
>> on the green wire, so yes, separate green wires is a good thing.
>>
>> Second, chokes to kill noise currents need to be tuned to the
>> frequency(ies) where you are bothered by the interference. While PROBING
>> for noise sources at lower frequencies can be effective, there's no need
>> to choke those frequencies unless you use your radio there.
>>
>> Third, if the TV is a noise source, I would choke every cable connected
>> to it, starting with those that are likely to be the most effective
>> radiators, first the power cable and coax feeding it, then audio and
>> video cables if there are any.
>>
>>>
>>> I also read on the Polamar website about using #75 mix Clamp On cores
>>> for use on frequency ranges down to 200 kHz. Is this something
>>> applicable to my problem?
>>
>> Only if you need to kill noise on the new 630M band, and only if you
>> wind a lot of turns. Simply clamping one or more of them onto cables is
>> unlikely to do much.
>>
>> I'm surprised that you're hearing a lot of noise coming from an LCD TV.
>> The most likely source would be a poorly filtered switch-mode power
>> supply built into it. I would also look for other sources around the TV,
>> like switch-mode wall warts for various equipment, or built into other
>> equipment.
>>
>> 73, Jim K9YC
>>
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>
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