Topband: Another take on power line noise hunting

[Pete Smith N4ZR]

Or, since you don't really need a calibrated result, build a simple 
variable attenuator.  Just about anything works so long as you can vary 
the sensitivity as you approach the power line.

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 1/5/2013 1:17 PM, donovanf at starpower.net wrote:
> Hi Paul,
>
> You would helpful a step attenuator, in 1 dB steps, to be a valuable addition to your tool bag.  There are situations where it helps isolate to an individual pole.  Its much more accurate than an S-meter.
>
> Something like this, or many other alternatives:
>
> http://www.ebay.com/itm/Coaxial-RF-Step-Attenuator-Set-1-dB-steps-to-70-dB-total-DC-to-1-GHz-/200866468929?pt=LH_DefaultDomain_0&hash=item2ec4931441
>
> 73
> Frank
> W3LPL
>
> ---- Original message ----
>> Date: Sat, 05 Jan 2013 11:44:08 -0500
>> From: N1BUG <paul at n1bug.com>
>> Subject: Topband: Another take on power line noise hunting
>> To: Topband <topband at contesting.com>
>>
>> I've been following this discussion with interest. I spent the
>> summer tracking down more than 20 sources of power line noise. As an
>> offshoot of that I've made it my mission to help clean up RFI in my
>> little corner of the world. I've been slowly drifting away from
>> DXing and this has turned out to be my new area of interest.
>>
>> Since this topic is perhaps of interest to topbanders, and since my
>> experiences seem to vary somewhat from the typical reported here so
>> far, I thought I would take a moment to share some observations. I
>> should probably note I was dealing with a mix of 13.2 kV
>> distribution lines and 46 kV transmission lines. My hunt was made
>> more challenging by the fact I had multiple sources in a relatively
>> small area and could often hear more than one at a time even with
>> directional antennas and attenuation.
>>
>> My tools this summer were 135 MHz AM receiver with 3 element yagi
>> and step attenuator; LF/MF/HF/VHF/UHF AM receiver with DF loops for
>> low bands and 7 element yagi for 445 MHz; ultrasonic receiver with dish.
>>
>> Low frequencies, eg. AM BC or 160 meters were *occasionally* useful
>> in locating a general source area. Sometimes the area identified
>> turned out to be an area of *radiation* but the noise was
>> *generated* elsewhere. Often the relatively close proximity of
>> multiple sources made low frequency tracking useless.
>>
>> VHF was always useful in finding a source area, 80% of the time
>> resolving it to a single pole. The sharp, deep null at exactly 90
>> degrees off axis of the yagi proved very useful for confirming a
>> source structure. Poor resolution/accuracy of signal strength
>> metering was perceived as a problem.
>>
>> UHF was very helpful in a few areas where the noise was particularly
>> strong at VHF and/or signal strength so close over a span of several
>> poles that VHF could not pick the source pole with high confidence.
>> So far, experience indicates this is more likely to happen on the
>> transmission lines. They're a bear. Again, poor or no signal
>> strength metering (signal below AGC threshold) was perceived as a
>> problem.
>>
>> The first ultrasonic unit tried was a waste, finding something at
>> only 10% of RF noisy poles. The second unit was able to hear
>> something from about 60% of the same 21 poles. The figures are
>> averages over more than 10 runs with each unit. The two were also
>> tested on a spark signal range under somewhat controlled conditions.
>> These things are definitely not created equal!
>>
>> To date I have identified and had the power company fix almost
>> everything I have worked on. The remaining open case involves a
>> short section of a 46 kV transmission line which is extremely
>> perplexing due to the specific nature of the issue (details on
>> request). Just when I starting thinking I was getting good at this,
>> I came up against this one.
>>
>> If I were doing this strictly for myself these tools would be more
>> than adequate. Since I'm not and I only have so many hours in a day
>> I have several upgrades on my wish list:
>>
>> HF/VHF/UHF AM receiver with wider bandwidth better signal strength
>> metering
>>
>> Log periodic dipole array covering ~100 to ~900 MHz for frequency
>> agility while maintaining some directional properties
>>
>> Portable oscilloscope for observing noise signatures in the field
>> (I'm hoping it helps sort out overlapping source radiations)
>>
>> Yet another upgrade of the ultrasonic unit.
>>
>> Comments are welcome, even if it's to tell me I'm clueless!  :)
>>
>> 73
>> -- 
>> Paul Kelley, N1BUG
>> RFI Committee chair,
>> Piscataquis Amateur Radio Club
>> http://www.k1pq.org
>> _______________________________________________
>> Stew Perry Topband Distance Challenge coming on December 29th.
> _______________________________________________
> Stew Perry Topband Distance Challenge coming on December 29th.
>