Line Noise Follow-Up
Steve_Fraasch at ATK.COM
Tue Aug 3 13:46:32 EDT 1993
Last winter, I queried the field for help fixing a high tension power line
noise problem. Thanks. My problem was mid-voltage distribution out of a sub-
station. I've had a lot of experience working with the utilities with this
stuff, so I thought I would pass on my lessons from the school of hard knocks.
The true offending source was not on the REALLY BIG lines 4 miles away (I don'
t know the KV), but on the intermediate lines running out of a sub-station 1.5
miles away. There were three sets of LAPP bell insulators that were arcing
across through the ceramic glue that holds the tie stud (I hate those bell
insulators). Sure enough, these were old insulators made in 1954, and 1960.
I finally discovered this noise in April, after 4 months of casual hunting.
The crew replaced the bells with a one piece design that did not use the
series bell pin and clevis attachment. They tightened hardware, and replaced
the line disconnect, but the "bells" were the offenders (as they have always
been for me at other QTHs). There is a star washer available to insure
continuity from pin to clevis, but my crew did not have them. The new, one
piece insulator is preferred.
Here is an after-action report of lessons learned:
- Use a 2 meter or other VHF receiver w/ am noise detector, 4 - 6 element yagi
and hunt the source YOURSELF. Work from your qth, and work out omni from
ground zero. Do not discount your own, or neighbors' homes (My experience is
10% are from noisy appliances). I use a modified Heath HW-202 w/ am and
homebrew 6 el W2PV yagi design. I have a 1 dB NF LNA, but I seldom need it.
The yagi is cumbersome, but with it, not only can I find the pole, but
sometimes I can find the exact piece of hardware through careful triangulation.
I've never been wrong on a pole; sometimes I get the piece of hardware right.
- Check over time, and correlate that the source is indeed the one you're
hearing. This is not hard if an actual arc or hiss is seen or heard, but
small, inaudible arcs will be low amplitude. If the pole is in a distribution
network about your QTH, it could very well be the one, but be sure before you
cry wolf. I know that inaudible arcs can go 2 miles, but that's about it.
- If you're positive, call it in. Give the exact location, and a pole number
if available. There should be no need to get FCC, or others involved.
- Fixing power line noise is somewhere between re-stocking the employee pop
machine, and removing "lost dog" signs from power poles. You must be patient,
but be persistant. I reported my problem in late April, but the problem was
not fixed until 2 Aug. My service guy followed up every 3 weeks or so. He
told me up front it would be a while; the ground has been extremely wet in MN,
and he did not want to stick the truck. If nothing happens after 3 months and
numerous calls, then you need to write letters (utility management, copy FCC,
and BBB). I've never had to write and involve others, but, another ham in St.
Paul did to fix REALLY BIG lines. Tact was not this fellow's strongpoint,
- Know the day the work is sched. Check the day of their arrival to make sure
noise is present. If the noise is intermittant, and it rained a day before,
the noise could be gone, and your credibility is shot. If it's there, BE AT
THE SITE w/ DETECTOR IN HAND. If you want to guarantee the problem won't be
fixed properly, don't bother showing up when the crew arrives.
- Troubleshoot in this order: insulators, disconnects, lighting arrestors,
line components. Insulators arc thru and are either solid, or intermittant;
lightning arrestors usually arc interally and are continuous. The tech will
most likely have a 300 Mhz "super snoop" noise detector, whose 3 el yagi is
too broad to locate a specific piece of hardware. They will then use a
portable "snoop," IR, or ultrasonic detector from inside the bucket crane, and
check all pieces close-up. Use your 6 el to help. My guy chucked is snoop
and used my HW-202 because I had a S meter. I've not used a 440 rig, but I
think this with a 12 el yag would be great.
- Once they have fixed the first problem, keep kicking the pole, or guy wire
until the line is quiet. In my case, there were 3 sets of bell insulators
that were noisy. When done, you could kick that pole to death and not hear
- A letter of thanks to the crew's boss after successful completion goes a
long way. Can you think of a more thankless job?
As of 3 Aug, things are quiet. It was fun to hear summer EUs again from black
hole land on 75m, as well as weak, puny VK sidebanders oblivious to DX. I've
even managed to make Mark, K0KX, jealous which is a change in status quo.
"It's only a hobby," Steve, K0SF.
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