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Re: [RFI] RFI detective story - with successful outcome and 30 dBm reduc

To: rfi@contesting.com
Subject: Re: [RFI] RFI detective story - with successful outcome and 30 dBm reduction of noise floor
From: Gary Smith <wa6fgi@steeltrails.net>
Date: Wed, 28 Feb 2018 14:37:09 -0800
List-post: <mailto:rfi@contesting.com>
Outstanding service form your local P & L.


On 2/28/2018 9:23 AM, Alan Higbie wrote:
In October 2017 I started to observe some spitting type broadband RFI noise
spikes. Within a week or so noticed that when outside temperature cooled in
evening the noise spikes would become constant.  Then noticed high winds
would cause more spikes in noise level.  Eventually the RFI became

This noise caused my normal noise floor (on P3 scope) of about -120 dBm to
increase by 30 dBm to -90 dBm.  The noise responded well to the NB on K3 -
but using the NB during contests also resulted in IM products and made
communications difficult.

*These are steps taken*:

1. Cut power at the panel of our house - K3 on battery power.  No change.
So coming from outside.  Had neighbors cut their power too. Eliminated them
as source.

2. Used National RF Vector Gun w/ loop - to DF the source.  Best used to
null off ends of loop. Initially hooked loop to Tecsun PL 660 set on 20
meters; then connect DF loop to KX2, then eventually set the P3 to run
ALONE as SDR receiver on 14.020 MHz (see page 25 of P3 Manual) (also
Instructions found at: http://www.g3tct.co.uk/P3.html ).  Connected the DF
loop to I.F. Input of the P3.  Ran on battery and carried around.

3. The P3 connected to the DF loop tuned to 14.020 showed noise signal
level only about 12 dB down from the strength shown on P3 when connected to
2 el. 40 mtr. yagi.

But using that portable set up allowed for making sure I was tracking same
noise signal that was bothering me in the shack.

4.  Before getting zero'ed in on the offending pole(s) - - it dawned on me
to try pinpointing noise source by carefully peaking the beam.  The P3
(with SVGA) may be configured to display signal strength in 1 dB increments
(spaced about 1 inch vertically) !!  And, I now have a digital readout on
my rotator indicator (Green Heron).  I spent about 20 minutes slowly going
back and forth. Finally determined that noise source peaked at 65 degrees
from my antenna.

5. Then, walked with P3 and National RF Vector Gun DF loop roughly along
the 65 degree line away from my house.  Eventually the signal got stronger
and stronger.  This was 1/3 mile away.

6. Then borrowed a friend's FT 817.  With that set for 220 MHz AM and a 7
element yagi (Arrow 220-7) - located which pole I thought it was.  But
wasn't completely sure - because the QRN/RFI signal was so strong - thought
it was one of two poles close to each other.  I should have inserted step
attenuator between beam and FT-817.

7. Having narrowed it down to two poles, I emailed the Colorado Springs
Electric Utility.   Mentioned that my FCC licensed station was now
essentially off the air because of RFI from the arcing and the utility's
power leak.  And mentioned that this was coming from 1/4 mile away.  I sent
along photos of the poles - with close ups showing pole numbers.  I also
sent a map and aerial photo (from Google Maps) showing my house, the 65
degree beam heading, distance, location of poles, handwritten pole numbers,

I went to the area at night - using binoculars - I looked for visible
arcing - but couldn't see any.

8.  A utility engineer emailed back - and he suggested we meet at the site.
But I suggested we first meet at my house.  He brought a lineman. I showed
them my shack and especially how the noise looked on the P3 scope - and
demonstrated what it should look like by flipping the SteppIR 180 degrees.
They could SEE my problem.

9. The engineer brought along the utility's Radar Engineers RFI locator
M330 !! (Yes, I told him I was happy to see they had followed my suggestion
of 12 years earlier - about buying one)  He also brought along a Radar
Engineers  MODEL 250 Parabolic Pinpointer Ultrasonic Locator.  (another
suggestion)  Note: This felt like I had dropped a hint about what I wanted
from Santa !!

10.  Triangulating around the immediate area - using that nifty gear - the
engineer  confirmed which pole supported the noise source.

11. The pole in question carried 7200 volt lines at lower level and 34,500
volt lines above that.

12. On the first day - the lineman went up and wiggled and tightened stuff
on the 7200 lines  But that made no difference.  Being by himself - with a
bucket truck which couldn't reach the upper wires - they suspended the
operation for the day.

13.  A week or so later - the engineer came back with a larger bucket truck
/ a crew of two lineman - and a foreman.

14. They couldn't quite zero in on exact source on the pole.  But they
started by de-energizing the 34,500 lines.  They sent me home to check my
noise in the shack.  Still the same.  None the less they tightened and
replaced hardware on those lines

15. The linemen came back down lower to the 7200 volt lines.  They wiggled,
tightened and disconnected stuff - until eventually they made the noise
stop on engineer’s RFI locator.  The source of this noise was a lightning
arrester which was failing.

16. They *replaced lightning arrestor* and the noise was gone on their RFI
locator - - but to be sure, they had me drive home to check noise level in
my shack - and yes, the particular noise had been eliminated

17. The replacement of the defective lightning arrestor reduced my noise
floor by 30 dBm (from approx. -90 dBm back down to -120 dBm.)

73, Alan K0AV

Colorado Springs
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