[RFI] Useful perhaps for others: audio correlation

[AA5CT]

Excellent work, Jim


Another way (or two?) popped into my mind reading your account -


(1) 2m or UHF Link (couple of HTs and a repeater, or maybe simplex)

Enlist another ham to 'relay' the noise heard on the station receiver via 2 meters
or UHF direct or using a repeater to your remote 'field' location with the
offending pole.

Almost 20 yrs back I used this technique with an intermittent noise coming
from a pole out of downtown Allen across from the big church along side
a busy thoroughfare. 

It boosted my confidence that "this was the pole" on account when the intermittent 
noise appeared at the pole it was also heard over the 450 link back to the station
receiver!

A few days later after making the report it was fixed. 'Dualy' tire tracks in the 
empty field next to the pole shows that Oncor had indeed been on site to take 
care of the issue. 

(2) 4G VoLTE Link (a "2 phone" (as in the wife's and yours) method)

20 years ago the 'vocoders' used in cellular pretty much bas***ed any sound
that was not not voice, but today's wider VoLTE (Voice over LTE) 'circuits' 
offer better fidelity, so VoLTE phone calls might be yet another way.

Notice that going with Verizon these days they require a phone capable of
VoLTE. I found this out when I signed up with Visible (which is owned by
Verizon and uses the Verizon network.) 

de AA5CT Jim


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On Saturday, August 21, 2021, 9:52:45 AM GMT-5, Jim Miller <jim at jtmiller.com> wrote: 





Yesterday I tried out my idea of correlating RFI heard at the pole with my
2m HT/Yagi with the RFI heard by my K4/7LFA on 6m.

I did this by running Chrome remote desktop on the PC in the shack and
Chrome remote desktop on my iPhone. Chrome remote desktop supports audio.

When testing in the shack make sure to turn off WIFI on the iphone so that
you're using the phone data plan as you will be when remote at the pole.

On the PC use Sound Card settings to enable "Listen to this device" on the
recording tab of the Radio sound card. Adjusting the PC volume will also
affect the level heard on the iphone. You may want to practice
muting/unmuting PC audio using the iphone chrome remote desktop cursor to
avoid driving whoever is at home crazy.

On my K4 I just put the radio in Test mode and CW and did a few dits to get
a feel for the delay to the iphone. It is very noticeable but less than a
second.

When listening to RFI I put the K4 in AM mode and turn up the PC audio.

I first tested this out in the shack to make sure of all the proper
settings then traveled to the suspected pole and was able to confirm that
any fluctuations at the pole site were heard in the iphone a fraction of a
second later.

I'll be repeating this test over the next few days in varying weather
conditions before calling the power company. RFI from this suspected
location varies from nearly non-existent to 20+db over the clean level. A
huge swing: affected by rain, morning fog, sunshine and wind which dry it
out.

73

jim ab3cv
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