[NLRS] 6m and up noise

[Gerald]

On Wed, 2006-01-25 at 08:28 -0600, Brad Johannes wrote:
> 
> Thanks Al,
> I'm still in the investigation stage. I did some more net searching about 
> the topic yesterday after I posted this and drove home last night with the 
> AM radio on in the truck, on a high unused freq. That was pretty enlightening 
> itself. I'm in a newer development in town with no overhead power lines, at 
> least nothing within a few blocks that I've noticed. There is a string of 
> them along the highway about 1/4-1/2 mile away and as I drove home along 
> them the noise on the radio picked up, not as much as some areas of St. 
> Cloud I drove thru, but it was still something. I got home however, and 6m 
> was quiet. Next time I notice the noise on 6 I'll get some good bearings on 
> it and go drive around town.
> >From what I read on the net, power companies are helpful as long as you are 
> civilized, have logs, recordings and data to support yourself, and go thru 
> their proper channels.
> I think there is only 1 or 2 TV broadcasts from St. Cloud, ch13 and 19 if I 
> remember. Ch2 is in the Twin Cities, and I think the twin cities is also the 
> closest HDTV transmitters.

Power line noise radiates from the lines quickly at VHF so when you hear
the noise (I like to use my TM-261 on AM for finding noise) you are
close. At 2m the peaks are often less than a pole span wide. Essentially
inaudible at greater distances. At the BC band the two wire (or three
wire) transmission line spacing is such a small fraction of the
wavelength that there isn't as much radiation and you can follow power
line conducted noise for literally miles and often find the peak noise
is at the end of a radial line due to the SWR build up from the end of
the line. About all listening at 1700 will tell is that there is a noise
source on that line somewhere between the ends and the substation (not
to say the arc can't be at the end or in the substation). It takes
listening at VHF to locate the noise source. Work up in frequency from
BC through HF bands to 6m and then 2m, maybe 432 (I've not had UHF
mobile often to compare yet). A couple feet of 432 yagi on a portable AM
or SSB receiver makes a good locater that can point out how high up the
pole the noise source is when listening 40 or 50 feet away from the
pole.

Power companies can be defensive about line noise because lots of
"noise" can come from industrial sources as well as from things like
power line home digital networks. Many a power line noise source has
been traced to a home door bell transformer thermal protector or a
thermostat on an aquarium heater. Power companies often are defensive
because they don't hear noise in their FM radios in their line trucks
and don't understand AM vs FM vs SSB reception. They sometimes don't
understand that while they don't hear noise on FM, they also sometimes
don't hear signal because of the noise. In bad cases, when the noise can
be shown (with the hand held UHF yagi) to be coming from power poles
uniquely and the power company doesn't cooperate, the FCC can get
involved and power companies have been known to have been cited by the
FCC for excessive noise. Though that doesn't seem to work for BPL.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson