[RFI] Home RFI Hunting

Sun Sep 30 12:22:48 EDT 2018

Hey, thanks for the feedback Gedas. I don't have one handy but I may try 
another 31 as Jim states the add algebraically.

Thanks again and 73,
Dave W8FGU

On September 30, 2018 12:17:36 Gedas <w8bya at mchsi.com> wrote:

> 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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