RF ingress puzzle

[mdshunk]

I have a customer with a steel outbuilding and a steel home with very high levels of RF energy measured inside both buildings. All electrical power and all cable television feeds were removed, and the same RF measurements persist. All cell phones were turned off. I thought that the steel building would act like a Faraday cage, and preclude outside RF energies from entering. Is is possible that steel skinned structures can act like an RF "antenna" and bring in RF? The calibrated RF meters (Sencore and Bell) both are pretty silent outdoors, but go nuts inside both buildings. Any ideas on this one? I'm way out of my league on this one, but I'm in the home on other matters, and have been tasked with this RF issue also.

 

[LawnGuyLandSparky]

This will come as quite a shock if news of this leaks out to the tinfoil-hat wearers, that they're actually donning transmitter/ampifiers!

 

[RocketDoc]

Sounds like the buildings are serving as Omni-Directional antennas and receiving electromagnetic energy from microwave or radio frequencies. There are coating available on the market to block the signals if they need to be.

 

[dereckbc]

Could be anything, but I think you are overlooking the obvious, a source within the structure.

Does your meter have an attenuator on the input? If so keep adding attenuation until it is barely noticeable or gone, then walk around and find a peak signal. That is the source.

 

[zbang]

If the meters are quiet outside, there's got to be an RF source inside... Was -all- power really removed (and the leads earthed)? No computers running on UPS? Some cordless phone running on batteries? Any underground cables that might leak? Same readings outside all around the building (distant radar stations can do interesting things, but should only show up on one side)? What frequency(s) of RF?
If you know a local amature radio operator or radio/tv station engineer, they usually love tracking this sort of thing.

z is quite curious.

 

[wirenut1980]

Could be anything, but I think you are overlooking the obvious, a source within the structure.

Does your meter have an attenuator on the input? If so keep adding attenuation until it is barely noticeable or gone, then walk around and find a peak signal. That is the source.

I normally would agree, but the OP did say that all electrical power and cable TV feeds were removed to the house. Do try and attenuate the signal on your meter like derek suggested, and it may help in finding the culprit.

It does make you wonder how it is so strong inside, but not outside without there being any power on.

What is being affected? TV stations?

 

[mdshunk]

What is being affected? TV stations?

So far, nothing is being affected, except the occupant's health (so he claims :wink: ). Something about daughter's retardation and a sudden 30 lb. weight loss of the homeowner. That aside, I'm still inclined to solve this little puzzle. I haven't been back this week, so far. Last week, I even took batteries out of their garage door opener transmitters, cordless phones, and everything else I could think of that transmitted RF that might be in the home. I did try to attenuate the RF sniffers, and it was either "nothing" or "crazy". Home is all steel, and I think this is part of the issue somehow.

 

[marshallf3]

How far away are the local TV/Radio station antenna farms?

 

[ghostbuster]

Try contacting the local gov't group responsible for measuring "rogue "rf transmissions.In our area ,they have a van fully equipped with all the various antennaes and receivers to triangulate the source.We usually are able to identify the exact frequency and strength in db. for them before they arrive.

 

[mdshunk]

How far away are the local TV/Radio station antenna farms?

Miles and miles. Maybe more than 100. Cell phone tower within sight on a clear day, and a trucking concern down the road a bit. I'm headed back over there Friday to continue to sort out the EMF problem that I was originally called for that I can fix, then I'll work on the RF issue some more. RF matters are honestly over my head, but I'm willing to muddle through. The customer called one electrician previously, and when the man arrived and listened to his problem, he got back in his truck and drove off without so much as a single comment.

 

[mdshunk]

Try contacting the local gov't group responsible for measuring "rogue "rf transmissions.

Yes, I'd certainly be willing to do that, but I have no idea who that might be or how I'd even find out. I did think about contacting a local HAM radio club for a possible lead on such a sleuth.

 

[dbuckley]

The customer called one electrician previously, and when the man arrived and listened to his problem, he got back in his truck and drove off without so much as a single comment.

Probably a sound approach, as so far no problem has been identified.

When you say "very high levels of RF energy measured inside both buildings" what kind of levels are we talking about here?

If the customer has money and desperation, the first thing to do is to hire a spectrum analyzer, something from Agilent would do nicely. That will tell you what is really present.

 

[Psychojohn]

What frequency?
Even strength throughout the house.?
What is the field striength measured?

 

[Psychojohn]

Is the metal frame completly bonded and grounded?

 

[QES]

can this scope of yours isolate the frequency?

 

[tom baker]

Knowing a bit about radio and have used a commincations monitor (aligent), I would find a radio shop and see if they will check the noise floor with the monitor. It can quickly determine the rf level and frequency. The ones I use cost $20,000, and are very accurate. They are used to calibrate and set up radios.

 

[QES]

the frequency of a rf signal can tell you alot about there source of e.m. energy.

 

[robbietan]

how about high voltage lines outside?

the advice that you isolate the frequency is sound. what levels of EMF were measured