[Top] [All Lists]

[RFI] 85 pulses per minute noise.

To: "rfi@contesting.com" <rfi@contesting.com>
Subject: [RFI] 85 pulses per minute noise.
From: Colman Ahern <Smokey@ziplink.net>
Reply-to: Smokey@ziplink.net
Date: Sat, 15 Dec 2007 15:04:23 -0800
List-post: <mailto:rfi@contesting.com>

Fairly often for several days at a time I get a very loud pulsing or 
pulsating noise anywhere from mid medium wave to upper HF.  It seems 
to pulse exactly at 85 beats per minute.

It's at its clearest right beside or almost on top of any broadcast 
station, the closer I tune to a station, the clearer and stronger the 
pulsing becomes.  Close to an adjacent broadcast its noise frequency 
is approx. one or two kHz per second, (using my ears).  Between 
broadcast stations it has a much lower sound, the rate of 85 beats per 
minute does not vary.

My antenna is outdoors, a very random length of wire about 30ft. high, 
the lead-in is coax.

Using a small am radio with whip antenna I can hear the noise by 
placing the antenna near the power outlets in my house, or the gas 
stove, telephone wiring, ground lead going to my receiver, a large 
towel rail in the bathroom, (which is about ten feet from my 
neighbours house), and from the metal case of my NRD-525 receiver, it 
dosen't matter if the NRD is switched on or not.  I can also hear it 
from the coax lead-in shield.  However, the am radio whip does not 
pick up this particular noise if placed on or near the actual 
shortwave antenna insulated wire.

Switching the power to my house off at the main circuit breaker and 
operating the NRD-525 from a battery makes no difference whatsoever, 
nor does removing the ground wire from the receiver.  With the power 
off I can still hear the noise on the am radio as above.

The best I can say is that it seems stronger on the power line outlets 
which are closer to my neighbour's house.

I've made a few recordings of the noise, one very slightly below 10mHz 
so it can be compared to the frequency rate of the time signal, also 
one made on lower SSB on approx. 9MHz, its somewhat mind numbing on SSB!

I have sent a couple of the recordings to the RFI Noise Website run by 
Ken Alexander, VE3HLS, and they should be posted there fairly soon.

In the meantime is it possible to email a sample as an attachment to 
the RFI list?  If not, and if anyone wants to hear it, I can send off 

The gas meter outside my house is bonded to the house wiring ground, 
as are water pipes, gas house heater, water heater, etc.  The antenna 
coax is also grounded to the house ground wiring where it enters the 
house.  The other end of the coax shield is not attached to ground but 
goes to one side of a binocular core antenna matching transformer as 
does the coax centre conductor. A five-foot copper pipe sunk in the 
back yard goes to one contact on the other side of the transformer, 
the antenna wire to the other.

Any and all thoughts and or help would be welcome. Where I live RFI 
noise levels can get pretty bad at times, this one beats all of them!

Thank you,

Colman Ahern.
Berkeley, Calif.

RFI mailing list

<Prev in Thread] Current Thread [Next in Thread>
  • [RFI] 85 pulses per minute noise., Colman Ahern <=