[RFI] Chasing RFI

Charlie Gallo Charlie at TheGallos.com
Sun Oct 18 13:30:57 EDT 2015

On 10/18/2015 Jim Brown wrote:

> On Sun,10/18/2015 8:51 AM, Charlie Gallo wrote:
>> Any ideas how to proceed from here?

> Some questions to help you think about it.

> As you tune around a band, especially the lower bands, are there peaks
> of noise, with a center that sound like a growly tone? If yes, this 
> noise is not power-system related, its an electronic source. And, of 
> course, you could have both kinds of sources. Many of us do.

Tuning  around  is how I found the secondary source (along with the P3
waterfall)  -  the  rest  is  broad  band  - basically flat, no peaks,
demising  as  you  go up the bands - less on 28Mhz than say 160m (with
big antennas) - with the hand held - max on 40m, flat across the band

> A great way to figure this out is to look with a spectrum display, 
> especially one with a waterfall. Electronic sources will show bumps of
> noise, spaced 10-20 kHz across a band, and if they drift, they're 
> switching power supplies. If they don't, they're running on some sort of
> clock, usually associated with a microprocessor. They will show up as 
> straight vertical lines on a waterfall, wiggly if they're a switcher. 
> Power line noise is impulse noise, and will show up as horizontal lines
> on the waterfall.

> Listening with the 660, how far have you walked?  More than a block or
> two? Have you tried driving around listening between stations for the 
> noise on an AM radio?

Walked about 8 blocks, drove with stops around a mile, seems to center
around  the  area  of  the  pole  2  blocks from W2IRT's house  - that
general area is the ONLY place I could hear it on 10m

> If you never heard it on the Aircraft band, you were probably not close
> enough to the source. In other words, it could be a lot farther away. 
> The reason that an AM VHF RX is so useful is that the noise at these 
> higher frequencies doesn't travel far on the power system wiring, but is
> radiated by wiring close to the source.

OK  -  but the fun was I could only hear it on 10m in the general area
of  that  pair  of poles, got more than 1/2 block away, NOT audible on
10m,  but  never  was able to hear it on Aircraft - which is why I was

> 73, Jim K9YC

73 de KG2V - Charles Gallo
Quality Custom Machine-shop work for the radio amateur (sm)


More information about the RFI mailing list