RFI Detective Work Needed

[E-Man]

If my memory serves, there is a DC voltage on the Phone line, unknown origin. I believe the CATV Amps are feed from Power Supplies tapped to the Secondary. The Power Supply may be in the neighborhood, it may be a big box with Battery Backup mounted to the Pole.

I hope they find the problem.

 

[radioman2001]

The cable amplifier gets it's power from the coax itself. Somewhere nearby there should be another box roughly 18" cube, most are light green that has batteries in it and a power supply. There is usually a meter pan with meter below it. Those boxes also generate a lot of noise at times, don't know why.

 

[SCPD]

Minor update:

The local power company came out and checked the pole and their hardware. They didn't find a "problem" but I thought it was interesting that the tech noted that the pole was from the 1950s. This check was done on Wednesday afternoon.

Unfortunately, I wasn't home when they stopped by. They actually responded within about 5 hours of my initial call to them.

The customer service lady said that my Service Order was assigned to their "RFI investigator" on Friday morning.

I asked the lady to note my cell phone number on the order. I'm hoping the investigator will track this down and/or at least call me.

 

[SCPD]

Updated the utility pole picture with a better shot. You can clearly make out the mess of cables.

So, I got a phone call this morning from the RFI Tech that is going to come out and investigate. He didn't have a lot of details (he's not with power company) but he seemed certain that it was not powerline noise. He thought it was a consumer-level device. (He actually listened over the phone the noise it made. I later sent him the video of the issue.)

He is going to come out this week and he'll help track down the source.

 

[SCPD]

**update**

Had the RFI Techs out today. They were both very professional and within a very short time we had the problem tracked down.

It turns out my neighbor (who was on vacation for a short time) had an invisible fence installed. (A pet fence.)

In the garage, there's a pretty chunky transformer but it's powered by another device which plugs into the house AC system. (This is why it's a 24/7 source.)

We unplugged the power and sure enough, the noise stopped completely. The tech put his wand & rfi locator over the transformer and it was crazy loud.

The consensus is that it's likely a defective transformer. We called the company that installed the neighbor's unit and they are going to look at it tomorrow. So hopefully this will all be resolved soon.

I didn't think to look for the manufacturer but we were told this wasn't a cheap unit.

 

[E-Man]

Excellent, I was glad to hear they acted on your complaint, and pinpointed the problem.

Any info on the RFI Wand? Make etc. Sounds like a interesting device.

 

[SCPD]

Yeah here was the instrument he was using. (The top model.)

Radar Engineers; Radar Engineers, makers of RFI locators, ultrasonic locators, arc reflection radar, secondary fault locators and cable tracers.

I did a Google search on the probe/wand but I couldn't find anything similar. This was about an 12 inch by 2" metallic-black cylinder hooked up with a BNC cable to the above device.

 

[markclark]

I hope I'm not too late to be helpful here, but you may want to check out these links from a RFI noise investigation company and a utility trade magazine article on RFI.

A Smarter Approach to Resolving Power-Line Noise

RFI Services - Radio Frequency Interference and Power Line Noise

 

[SCPD]

Thanks Mark but it wasn't power line noise - at least not directly. The technicians speculate that this pet fence uses a poorly made transformer or switching power supply. This is in turn pushes RFI up thru the wire outgoing AC to the utility pole.

The tech noted that RFI can't get thru the big pole transformers which is why the noise has been somewhat limited (about 150 yards from source.)

 

[SkyPager]

The cable TV amps are powered by DC that is run between the center conductor and outer shield. If you look at the actual tap for the cable run to the house(s) you may find your problem there. I have found numerous locations in urban areas where people steal cable by removing the 75 ohm load and sticking just the center conductor of the RG-6 into the jack. The cable techs call this a "stinger". This creates an unbalance condition and enegrizes the whole cable run with RF. Cable companies use frequencies from 5 MHz to 1 GHz to transmit TV, on-demand programs and data. They are limited to 20uV leakage at 10 feet in the VHF air band. Not sure what they are limited to in other bands. I have found leaks as high as 100 uV.
Also since all of this stuff is outside, you will have wind, rain other companies working on the utility poles; they can be damaged by accident. The main trunk or feeder cable that attaches to the amp has a rigid metal outer shield. They are prone to radial cracks, or if there is a vertical run down the pole they can be kicked, pulled, smashed etc. The 2nd pix shows a stinger to the left of two normal connections. You might want to ask the cable provider to come and look for leaks or CLI (cumulative leakage index).

 

[comsec1]

Nickcarr, I had the same experience with one of those hidden fences. I hope the person who owns it understands better than the one I ran into.
I had to go the route of a FCC complaint which the ARRL handled very well. I did all the good neighborly things even offered to repplace their whole unit with a model that does not cause RFI.
The model in question in my case was made by a company called INNOTEK and was installed by a company on rt10 in randolph. you will probably find out it is not a bad transformer but the way the thing is engineered to work. It wiped out from 0 up to about 7.5 Mhz.
When I finally got to talk to the company they advised that the installation directions advises that if interference occurs to radios to not use it and install a filter.
I purchased the recommended filter from NEWARK IN ONE electronics for $15.00 back in 05 for the person who owned the fence but they did not want to fix it.
I "hear" these things all over the place while driving around and wonder how the FCC ever allowed such a piece of junk to be sold.
If you need any info on the filter I still have all my invoices and logs, which I reccommend you start in case the owner becomes uncooperative and you have to go the next step.
Good luck and keep us updated

 

[comsec1]

Nick, just noticed you are out in WA so it can't be the same installer as the one local to me used. Let me know if it was an INNOTEK.
thanks

 

[SCPD]

Not sure of the brand exactly, but I did read up on the model you are talking about. I'll try to get the manufacturer info next time I'm there.

The techs work for our local power company (consultants) and have sent a formal letter to the company that installed the fence. The tech got them to admit that they have had this "problem" before. The company will install a filter to quiet the RFI.

My RFI was from roughly 2-32mhz on my wire antenna. A quality "noise blanker" can get most of it but forget about AM. My vertical did okay with the NB which allowed me still operate somewhat. The vertical wasn't as bad probably due to the nature of the antenna.

It's funny how we take for granted the clear airwaves when something like this happens.

My neighbor is being very cooperative. (Frankly, I think she got way overcharged for this installation. I mentioned to her for the money she paid -- the fence had better work flawlessly.)

 

[comsec1]

Glad to hear your neighbor is cooperative, Mine took almost 2.5 years to resolve and several letters from the FCC to convince the guy, they finally moved.

 

[poikaa]

Any updates on this?

poikaa

 

[SCPD]

The company that did the installation of the pet fence installed a filter. Unfortunately, I wasn't around at the time, so I didn't see the exact specifics.

The RFI was cut almost entirely. The center freq of the RFI dropped down to roughly 8 Mhz (instead of 9 Mhz) and while it's still present, it's far less of a nuisance than before - since it's out of the broadcast band at 9 Mhz.

I think they probably should have doubled up on their filter chokes but I'm not going to make a fuss. I'm back to 95% of normal conditions.

 

[poikaa]

One of my neighbors had a electric fence and was told that it was illegal to have one in this area because of kids. He removed it and 90% of my noise stopped. I you are in a rural area you may be stuck with it.

poikaa

 

[SCPD]

One of my neighbors had a electric fence and was told that it was illegal to have one in this area because of kids. He removed it and 90% of my noise stopped. I you are in a rural area you may be stuck with it.

Just to be clear, this isn't an electric fence. The pet fence uses a wire around the house property and the unit transmits an ultrasonic frequency to a receiver shock collar. If the pet goes near the antenna wire, then the pet receives a "humane" electric shock.

This antenna wire is buried around my neighbor's yard. The 'transmitter box' is hooked into house AC wiring.

These transmitters are made in China and are not very well regulated (even though they received FCC Part 15 certification.)

Technically, I could file a complaint with the FCC but as I said, it's not worth starting a war over it.