Thank you to everyone who responded. All good suggestions. And thanks to
Frank KB4T for his continued voice from the front lines of day-to-day
experience.
*WG8S (Kim): *
- Failed capacitors.
- Neutral connection.
- Cutout with fuses to protect the capacitors, and
- lightning arresters. In other words, a whole "menu" of
possibilities. Most likely, lightning arrester(s) failure, then go through
the list.
*K8CN (Mike):*
- TIE WIRES - Older bell insulators with tie wires have been a chronic
problem in my neighborhood - the tie wires fracture and create perfect
spark gaps.
COMMENT: Maybe a spark gap in a fractured tie wire might be sensitive to
temperature. Perhaps a drop in temperature causes contraction of material,
which widens the gap and eventually keeps the charge from bridging across,
and stops the sparking.
- Have you noticed any reduction of arc noise intensity when there is
active precipitation at temperatures below 35F?
ANSWER: No. Below 35 F the intensity goes to its maximum (as measured and
recorded).
- Your local utility should acquire an ULTRASONIC DISH LOCATOR - it's
remarkable the pinpoint accuracy of this tool down to locating a hidden arc
on a bolt/nut junction.
ANSWER: The local utility does have the Radar Engineers Model 247-B
ultrasonic dish and Model 330 RFI locator. They purchased this gear 19
years ago upon my specific recommendation!
- Is there any change in RFI level after dark while temperature remains
close to the end-of-day temperature? The presence of the street lamp on the
suspect pole is the reason for the question.
ANSWER: I haven’t noticed that to be the case. But I will check for that as
sun goes down tonight.
*KB4T (Frank):*
- The most important consideration for the troubleshooting team is being
able to detect or hear the interference on some kind of receiver. If the
source can't be heard, how will the troubleshooting team know if the source
has been fixed?
ANSWER: The utility’s engineer (with RFI responsibilities) said he will
bring the ultrasonic dish and the Radar Engineers RFI locator. There is a
speaker on the locator. Also, in the past, I have been out there with my
FT-817 on 440 MHz with 7 el hand-held yagi. That has a speaker that is
audible to the linemen up in the bucket.
- Step one is to DIVIDE & CONQUER to determine if the source is above or
below the switch or cutout (if there is a switch or cutout present.) This
is done by opening the switch while listening to the receiver. If opening
the switch silences the source, the source is below the switch. If the
sources remains active, the source is above the switch.
COMMENT: I’ll watch to see if that is how they approach this. Otherwise, I
might casually mention this as an option.
- Poking/shaking/probing likely arcing sources is the next best step.
Monitoring the receiver for changes in the source behavior will reveal
which device is or houses the source.
COMMENT: This is how they have approached things before. But, I’ll be
interested to see if the ultra sonic dish yields any results.
- In my territory, LIGHTNING ARRESTERS are the #1 source of interference.
COMMENT: We have lots of lightning here too.
QUESTION: Does there need to be a lightning strike at or very near the pole
for a lightning arrestor to fail - and become a source of RFI? or, can they
just get old and break down and become a source of RFI?
- The STAPLES securing the BOND WIRE in place as it goes up the pole
often work their way out of a wooden pole creating a gap that is quite
capable of arcing and producing strong interference. I always ask the crew
I'm working with to hammer in all staples from the transformer up to the
top of the wire.
COMMENT: Thanks for the reminder. Again, I’ll keep my eye out to make
sure this is done - either to cure this RFI, or as preventive maintenance.
*W0LEV (Dave) & K9YC (Jim)*
- Don't neglect the STANDARD LIGHTNING SHUNTS on the poles.
ANSWER: I’ll ask about those too.
Again, many thanks to the RFI "brain trust."
73, ~ Alan K0AV
Colorado Springs
On Sun, Jan 28, 2024 at 2:45 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 1/28/2024 11:59 AM, David Eckhardt wrote:
> > They can and do become damaged by
> > shunting multiple lower-level discharges, much like MOVs.
>
> YES! Maybe ten years ago, AC0C alerted us to this, and sent me photos to
> add to my RFI tutorial. As I understand it, they get noisy when they
> start to fail.
>
> 73, Jim K9YC
>
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