RFI Detective Work Needed

[SCPD]

So I guess it's now my turn for really bad RFI. I made a video of this to show what I mean. I get this 'splatter' from 1 thru 31 Mhz in AM or SSB. It's worst at 9 Mhz.

http://home.comcast.net/~cnick6/RFI.mov

In the video, the scope is set to a 200 khz spectrum. When I turn the scope to a 5 khz spectrum I'm seeing 15 peaks. The cycle is roughly at 333hz.

To me the signal seems too loud to be a small appliance or household device. This sounds more like a powerline issue.

One interesting thing is that when I use my vertical antenna the noise isn't as bad across the whole spectrum. The horizontal wire is completely wiped out however.

The RFI seems to be running 24 hours - another reason I don't think it's anything consumer level.

There are powerlines on my street and behind us running parallel to my horizontal wire.. (My antenna is at least 75ft from either one.)

I walked around with my Sony SW portable but the splatter is just about everywhere - so it's hard to get a fix on it. I'm going to go out later and see if I can't track it down again.

Any ideas?

 

[jim202]

So I guess it's now my turn for really bad RFI. I made a video of this to show what I mean. I get this 'splatter' from 1 thru 31 Mhz in AM or SSB. It's worst at 9 Mhz.

http://home.comcast.net/~cnick6/RFI.mov

In the video, the scope is set to a 200 khz spectrum. When I turn the scope to a 5 khz spectrum I'm seeing 15 peaks. The cycle is roughly at 333hz.

To me the signal seems too loud to be a small appliance or household device. This sounds more like a powerline issue.

One interesting thing is that when I use my vertical antenna the noise isn't as bad across the whole spectrum. The horizontal wire is completely wiped out however.

The RFI seems to be running 24 hours - another reason I don't think it's anything consumer level.

There are powerlines on my street and behind us running parallel to my horizontal wire.. (My antenna is at least 75ft from either one.)

I walked around with my Sony SW portable but the splatter is just about everywhere - so it's hard to get a fix on it. I'm going to go out later and see if I can't track it down again.

Any ideas?

Sounds like maybe the power company has put some broad band data on their power lines. Maybe you have some really bad computer cable leakage in your house. You can ask a bunch of questions. I would start with killing the cable TV modem box, kill the DSL and shut off all computers in the building including any hubs, routers or switches.

Jim

 

[SCPD]

This isn't local RFI as per my original post.

 

[sadatoni]

BPL? Horrors!

 

[mikepdx]

A cable modem's upstream operates between
5 MHz ~ 42 MHz

According to my cable modem's configuration manager,
my upstream is on 37.4 MHz

In your area, it could be on a lower freq.

If you have a Motorola Cable modem, try http://192.168.100.1/signal.html
other brands, you'll have to Google.

Leakage isn't alway local (in your home).
Leakage on the cable feeder often travels in lobes on the cable itself.
The feeder acts like a big horizontal antenna.
You may also have a line extender (cable co lingo for amp) near you.
That exacerbates the problem.

A possibility??

 

[datainmotion]

Nick,

A little red "x"? That's the interference you're getting?:lol::lol:

But seriously, as a possible alternative to BPL RFI, take a handheld scanner out and see if you get an odd "warbling" noise anywhere between 108 and 136 (pay close attention around 108.0054, 109.275, 114.0057, 115.275, 120.0060, 121.2625, 126.0063, 127.2625, 132.0066 and 133.2625).

I assume you know where to go from there if the CATV is the culprit.:wink:

Good luck,

Mike

 

[popnokick]

Just checking

I assume you've already tried this, but just to confirm....
What happens when you disconnect the antenna from your receiver? Noise gone? (I would expect it to be, since you said you are picking up the RFI on a portable receiver outside your location.) If the noise is gone when you pull the antenna, you can focus your detection activity on outside (maybe powerline/CATV) sources, rather than anything that is coming in via the AC power cord or something in close proximity to your receiver (computer, cable modem, etc.).

 

[Tommahawk]

From personal experience and my own RFI hunt have the Power company check their bolts to make sure that they are properly secured. You won't believe how much noise a loose bolt on a powerline can make.............

 

[lanbergld]

One interesting thing is that when I use my vertical antenna the noise isn't as bad across the whole spectrum. The horizontal wire is completely wiped out however.

Vertical antennas are more sensitive to local groundwave noise than are horizontal antennas. So this may suggest that the interference source is skywave propagated.


Larry Lanberg

Richmond Va

 

[SCPD]

Found the source. It's coming from a nearby utility pole that provides power, cable tv/modem and phone/fiber. There's a new "box" that I haven't seen before. This might be QWEST's new fibre-internet service.

I did drive around and look at similar utility poles. They have all the same boxes, etc. The other two poles that look identical to our pole are RF quiet.

I'm wondering if there could be a grounding problem with the pole.

I'm going to start with the power company first.

 

[E-Man]

If you could provide a picture of box/pole I should be able to identify.

 

[SCPD]

Leakage isn't alway local (in your home).
Leakage on the cable feeder often travels in lobes on the cable itself.
The feeder acts like a big horizontal antenna. You may also have a line extender (cable co lingo for amp) near you. That exacerbates the problem.

Yes as per my latest post, the source is coming from a utility pole with these services on it. It could be Comcast, Qwest or PSE (our power company.)

I'm going to call the power company and see if they can come check it out.

Obviously, this isn't normal. This RFI just started in the last 10 days or so.

 

[SCPD]

If you could provide a picture of box/pole I should be able to identify.

Sure, I'll get ya a photo tomorrow.

 

[popnokick]

Something might be slightly loose on the pole, too. I fellow ham I knew years ago used to go out of his house with a cheap AM portable radio tuned to a spot with no station and turned up loud enough to hear the noise. In his other hand was a baseball bat. When he got next to a pole suspected of being the noise source, he would swing the bat and soundly whack the pole. If the noise changed or stopped, he knew which pole was the source... and could demonstrate it to the power company.

 

[SCPD]

Sorry for the poor quality, but it's not bad. The new box I'm referring to is the lower right. I believe this is the fibre box that belongs to Qwest.

I've contacted the power company - just waiting for a response.

 

[datainmotion]

Yes - that box is definately a telephone company interconnect.

 

[E-Man]

And above the Phone is the CATV Tap, to the left what looks like a LE, and I cant tell from the Pic, where the Secondary is attached at, but it looks like you have Secondary going to a Service Drop? and Primary on the Cross Arm. Its hard to say, but I would be looking for a loose or broken Tie Wire, loose connections/hardware, bonding, unterminated ports. Hopefully someone will come out from the Power Company when you are home and check everything out soon.

 

[ab3a]

Nick, that's some really ugly looking pole work. I would call the phone company and the cable company to that pole and have them fix it on the general principle. If it looks that bad, it can't possibly last that long either.

As for Popnokick's suggestion: Some people used to do this. However, it can be very unsafe. The original reason for doing this was if there were some kind of intermittent arcing related to a broken insulator or some such thing on the pole you could figure out which pole had the bad insulator. The problem is that this is also a good way to bring that broken insulator down on your head, or to drop the high voltage lines to the ground. Use a portable radio to figure out which pole it is, get the pole number and then call the power company to fix it. Don't mess with it. If it is arcing, you had best get the people with the equipment and training to deal with this situation.

I'm sure that Nick Carr knows this, but if any of you other readers encounter this practice, please stop. It is not a good idea.

 

[radioman2001]

The cable amplifier box to the left of the pole could be the problem. I have run into numerous locations when I drive around where that style of cable box spews all kinds of garbage out. Mostly in the 46 mhz region.
Another thought is in the past I have a few instances where the primary power is leaking to ground causing a wide band noise. Enough to take out my television reception. Took me a month to find that one, the primary finally arced over leading me to it. I would call the power company and the cable company, if you don't get a response from them advise them you are going to notify the FCC. That usually gets them going.
I had an instance some years back where the cable box was actually rebroadcasting a computers CPU clock (the covers were off the computer to keep it cool) over their system, and was taking out the input to one of our fire ground repeaters over a mile away.

 

[SCPD]

Nick, that's some really ugly looking pole work. I would call the phone company and the cable company to that pole and have them fix it on the general principle. If it looks that bad, it can't possibly last that long either.

Well, it has seen quite a bit of weathering over the years. From wind to snow storms it has held up quite well considering.

Yes, I agree though it looks ugly. The box in the lower right is relatively new and those loose cables don't look particularly nice.

How do these amps get power? Are they tapped in from the power line? A loose wire here could cause problems I would think.

PS. Obtained a service order and the power company says it'll be checked out in next few days.