RFI

[mgookin]

I'd like to be able to check a location for RFI. I'm thinking there's probably a way to hook an antenna up to a laptop and look at a live plot of frequency and magnitude where I can select my desired frequency range.

Does anyone know how this can be done?

 

[GoldDigger]

You will need to get a tuneable receiver with a computer interface. USB or other.

Tapatalk!

 

[hurk27]

I use an old AM transistor radio, the iron core antenna is very directional and for most RFI it will pick up any arcing RFI as well as the noise from the newer electronic ballast, back in the day we use to use them to find offending utility transformers that were causing havoc on the radio bands, another good item is a portable spectrum analyzer with a wide band front end, it will show you all the signals in an area and by using a small directional hand held loop antenna you can dial in on where a source is coming from, but you have to know the frequency of the RFI, a good toner receiver with a 60hz filter can also be used to find RFI, they have an AM detection diode on its front end and a speaker to hear the RFI.

I used this method to confirm that a very close AM broadcast transmitter was getting into the safety eye loops of a garage door opener which were digital encoded loops, as soon as I put the toner receiver pick up end next to one of the safety eye cables I could hear the modulation of the radio station, installed a phone RFI filter on them and never had another problem, it was a new Genie door opener, and even the tech from Genie could not find what was causing the problem, they had replaced the opener 4 times, then told me we had a wiring problem, it took me about 2 minutes to find it and maybe another 5 to install the filters, when I walked outside with the Genie tech and pointed to the towers about 1500' away his mouth just dropped open, he said he would have never thought it was that.

What kind of problem are you having and maybe I can point you in the right direction?

The newer electronic ballast operate at or around 20khz to 25khz, this puts the 6th and 7th harmonic right in the AM broadcast band, the lamp itself makes for a good antenna and I see no easy way to filter it out, I have no idea why the FCC has not required them to use RFI filtering to block anything above 30khz, install them in a building and forget listening to the AM broadcast band.

 

[kwired]

I use an old AM transistor radio, the iron core antenna is very directional and for most RFI it will pick up any arcing RFI as well as the noise from the newer electronic ballast, back in the day we use to use them to find offending utility transformers that were causing havoc on the radio bands, another good item is a portable spectrum analyzer with a wide band front end, it will show you all the signals in an area and by using a small directional hand held loop antenna you can dial in on where a source is coming from, but you have to know the frequency of the RFI, a good toner receiver with a 60hz filter can also be used to find RFI, they have an AM detection diode on its front end and a speaker to hear the RFI.

I used this method to confirm that a very close AM broadcast transmitter was getting into the safety eye loops of a garage door opener which were digital encoded loops, as soon as I put the toner receiver pick up end next to one of the safety eye cables I could hear the modulation of the radio station, installed a phone RFI filter on them and never had another problem, it was a new Genie door opener, and even the tech from Genie could not find what was causing the problem, they had replaced the opener 4 times, then told me we had a wiring problem, it took me about 2 minutes to find it and maybe another 5 to install the filters, when I walked outside with the Genie tech and pointed to the towers about 1500' away his mouth just dropped open, he said he would have never thought it was that.

What kind of problem are you having and maybe I can point you in the right direction?

The newer electronic ballast operate at or around 20khz to 25khz, this puts the 6th and 7th harmonic right in the AM broadcast band, the lamp itself makes for a good antenna and I see no easy way to filter it out, I have no idea why the FCC has not required them to use RFI filtering to block anything above 30khz, install them in a building and forget listening to the AM broadcast band.

I have been finding that when I install T5 HO luminaires they generally interfere with the FM broadcast.

I will have a radio playing while installing but once we energize them there is a lot of interference on the radio. And this is usually in shop buildings where people generally like to have a radio going quite often

 

[cadpoint]

I find this interesting and of course puzzling at the same time!

Hurk27, do you have to install a RFI filter at every light or could one just introduce
this product at the beginning of all the individual branch circuits? My assumption is that
it would need to be at each ballast?

I'll assume this individually would be required but you later state later in post #3 that it really doesn't matter because the RFI filter doesn't work against the stronger generation produced from within newer individual ballast! So only with correct detection tools would one know that in fact there is no correct action to be gained using a RFI Filter?

It there an consideration made where one needs to consider checking that the correct Grounding of the structure that is in place and that it in effect, if not correctly grounded adds to the effects of RFI noise. I'm thinking of older structures and even older power applications of delta systems that do enter building UN-grounded.

Does adding this RFI filter add to any consideration to add some factor to non linear loading that are associated to florescent light usage?

I looked up RFIfilters, care to state which models you use? I realize they might be some different characteristic's of each but that you probably have a few favorites! I found it interesting that they had both parallel and what looked like inline or series equipment,
and others had in & out terminalson others!

With in-line in mind leads me to a presentation and a application I did on small refrigeration valves. Working for a refrigeration mechanic he told me to install a resister (blue) between the circuits because the signal was to strong to the littlevalves and this added in the valves life-span. I did not ask many questions about the resister and he was not much enlightenment, and just did what he stated! Frankly I'm not even sure it was a resistor!

Hurk would you ever install something like this on a light circuit? As I recall this was 120V
actuactors.

 

[GoldDigger]

That looks more like a capacitor.
It has a low enough value that the current from 60Hz is negligible but it is still a near short circuit to RF.

Tapatalk!

 

[hurk27]

I find this interesting and of course puzzling at the same time!

Hurk27, do you have to install a RFI filter at every light or could one just introduce
this product at the beginning of all the individual branch circuits? My assumption is that
it would need to be at each ballast?

I'll assume this individually would be required but you later state later in post #3 that it really doesn't matter because the RFI filter doesn't work against the stronger generation produced from within newer individual ballast! So only with correct detection tools would one know that in fact there is no correct action to be gained using a RFI Filter?

It there an consideration made where one needs to consider checking that the correct Grounding of the structure that is in place and that it in effect, if not correctly grounded adds to the effects of RFI noise. I'm thinking of older structures and even older power applications of delta systems that do enter building UN-grounded.

Does adding this RFI filter add to any consideration to add some factor to non linear loading that are associated to florescent light usage?

I looked up RFIfilters, care to state which models you use? I realize they might be some different characteristic's of each but that you probably have a few favorites! I found it interesting that they had both parallel and what looked like inline or series equipment,
and others had in & out terminalson others!

With in-line in mind leads me to a presentation and a application I did on small refrigeration valves. Working for a refrigeration mechanic he told me to install a resister (blue) between the circuits because the signal was to strong to the littlevalves and this added in the valves life-span. I did not ask many questions about the resister and he was not much enlightenment, and just did what he stated! Frankly I'm not even sure it was a resistor!

Hurk would you ever install something like this on a light circuit? As I recall this was 120V
actuactors.
View attachment 10029 View attachment 10030

The problem in filtering this kind of RFI is it would have to be at the output of the ballast, and within the oscillator circuit, building a band pass filter for the output which is around 800 volts @ 25khz, would require components that would not be cheap and also not affect the operation of the ballast, the other thing is I would believe that the oscillator circuit gets it's base frequency from the line frequency (60hz) which would save a few components, with this in mind when we install several of these fixtures in line in the same orientation they are all in phase for the most part, they will act as one large transmitter, I think most of us try to keep all the fixtures installed in the same orientation, but even if we did alternate every other one, it would make very little difference except for a radio that happens to be directly in between two fixtures, in which it would see a phase cancellation.

The problem with most off the shelf RFI or TVI filters is they are designed already for a set purpose, the RFI from these electronic ballast are a whole different animal and I have seen any type of filtering as of yet offered to connect to the output of a ballast, With the low current these ballast pull I do not see as much a problem on the line side of the ballast that any normally available line filtering should not have a problem with, but the 25hz is on the output side and I do not know of anyone building filters for this purpose, if would have to be a 30khz low pass filter that can handle the 800 volts HF AC.

The filters I used on the garage door eye circuit cables was an off the shelf phone filter with dip switch's to block different frequencies, I have been using them for years and since I save the telco many headaches, they keep me stocked (Most of the time), Radio Shack also has them and they are not too pricey

 

[hurk27]

I have been finding that when I install T5 HO luminaries they generally interfere with the FM broadcast.

I will have a radio playing while installing but once we energize them there is a lot of interference on the radio. And this is usually in shop buildings where people generally like to have a radio going quite often

Any radio receiver front end is made up of many frequencies, this is called super heterodyne, the cheaper the front end the more IF frequencies, or it may not be coming into the radio through the antenna at all, many of these cheap radios have un-shielded audio interconnect cables within the radio that can be subject to all kinds of RFI, Curtis Mathis TV's had this problem big time, as well as a few other poorly design TV's and radio's, the other way RFI can get into a radio is through the power system but if you are running a radio on batteries this can eliminate this as the source, also if you remove the antenna and it goes away then you know its coming in through the front end of the receiver, or at least through one of the IF sections, my Sony jam box picks up commercial jets over head because of the poor design of the IF section being close to the air craft frequencies.

 

[ghostbuster]

Here is another really good electrical interference (RFI) article link.

Hope it helps.

http://electricalbusiness.clbmedia.dgtlpub.com/2013/2013-04-30/home.php?page_view=24

 

[mgookin]

Thanks for all the contributions to everyone providing input.

Our product is an outdoor light control with onboard GPS radio receiver. The data it uses are date, time, lat & long.

One big customer has an upscale community about 20 sq mi and they have a dead zone where satellite radio won't work, cell phones won't work, etc. Our product does work there but I can tell by the time it takes to get a fix that reception is an issue. This area is wide open with no obstructions and it's just 1 sq mi in a very large community.

They asked me how to diagnose the source of the interference so I'm coming here asking where I can start.

I already have a satellite finder which I connect to a laptop via RS232. I use that when a customer has an odd installation to see if it will work or to find optimal installation location and orientation. I had this built by the company who did our prototyping and design files. We manufacture our own product. This device is specific to 1.575 GHz (1575 MHz) which is GPS L1 band.

What I'm looking for is something that will allow me to see a range of frequencies so I can diagnose this customer's situation and others as well. And of course I want to do it on the cheap! (doesn't everyone?)

Thanks.

 

[gar]

140331-1302 EDT

mgookin:

Enter
spectrum analyzer to laptop
in Google.

There may be one or more under $200 that cover 30 MHz to something higher. Whether the sensitivity you need is available in the low price range may be questionable.

You might actually have a dead spot rather than RFI. A comparison of signal strength close by in a working area may indicate whether it is RFI or just a low signal level.

.

 

[mgookin]

140331-1302 EDT

mgookin:

Enter
spectrum analyzer to laptop
in Google.

There may be one or more under $200 that cover 30 MHz to something higher. Whether the sensitivity you need is available in the low price range may be questionable.

You might actually have a dead spot rather than RFI. A comparison of signal strength close by in a working area may indicate whether it is RFI or just a low signal level.

.

Thanks gar. I'm finding all kinds of good stuff by Googling that phrase :thumbsup:

 

[Speedskater]

Find a friendly Ham radio operator. This is the kind of problem that they often face. Plus they have receivers that readout frequency and amplitude. They also have portable directional antennas.

This is a RFI Ham group.

http://lists.contesting.com/archives//html/RFI/

 

[hurk27]

140331-1302 EDT

mgookin:

Enter
spectrum analyzer to laptop
in Google.

There may be one or more under $200 that cover 30 MHz to something higher. Whether the sensitivity you need is available in the low price range may be questionable.

You might actually have a dead spot rather than RFI. A comparison of signal strength close by in a working area may indicate whether it is RFI or just a low signal level.

.

Dead spot for a GPS receiver???? in mountainous terrain sure, but in a state as flat as Florida I would never think you would have a dead spot for GPS reception.

1.5ghz is right next to several military and space bands 1.4ghz-1.6ghz, which GPS was originally designed for the military before it was allowed for civilian use, is this community located close to KSC or any other type of military bases especially an air-force base?, you could be hit with a jambing signal or something to prevent ease dropping on their bands, a spectrum analyzer that will hook up to a lap top that will cover these frequencies would be great if you can find one.

When I was on vacation in 2011 in Florida I never noticed any problems with my Garmin GPS and I was all over and around KSC as well as a couple air force bases, but you never know? it can pick up up to 12 GPS sats plus the WAAS stationary sat over the equator, as they have a 12 channel receiver plus the WAAS receiver, have you tried a garmin receiver in this area to see if it will work?

 

[mgookin]

Dead spot for a GPS receiver???? ...

Not a dead spot. The device works which is proof of reception of GPS signals. There is definitely some interference there though. Either a (intentional) transmitter or something (unintentionally) radiating. A spectrum analyzer will be useful.

 

[dereckbc]

Workied at a utility for 10 years and did a lot of RFI. Also a ham radio operator. Best tool for RFI is a simple 9-volt transistor radio on the AM band works great. With a little practice you can walk right to the source of interference.

 

[K8MHZ]

Workied at a utility for 10 years and did a lot of RFI. Also a ham radio operator. Best tool for RFI is a simple 9-volt transistor radio on the AM band works great. With a little practice you can walk right to the source of interference.

For on the cheap, that's the ticket. Also, you can use your body as a shield and get some idea of a direction of the RFI.

 

[dereckbc]

For on the cheap, that's the ticket. Also, you can use your body as a shield and get some idea of a direction of the RFI.

For power line interference I do not know of any better tool at any price level that is better. Now once you get to say a power pole with a bad isolator we had what was called the BIG EAR to identify which isolator on the pole it was. The Big Ear was a ultra sonic microphone on a parabolic reflector. But to find the pole or box just an AM transistor radio and sledge hammer is all it took.

Now for VHF and higher with IM then you need a spectrum analyzer and directional antenna to find the source transmitter. But for power, just an AM radio tunned in between station on the lower end of the band around 550 to 600 Khz. Just avoid 1.55 Mhz as you will be chasing your tail all day because that is what Telephone T1 circuits use.

 

[hurk27]

For power line interference I do not know of any better tool at any price level that is better. Now once you get to say a power pole with a bad isolator we had what was called the BIG EAR to identify which isolator on the pole it was. The Big Ear was a ultra sonic microphone on a parabolic reflector. But to find the pole or box just an AM transistor radio and sledge hammer is all it took.

Now for VHF and higher with IM then you need a spectrum analyzer and directional antenna to find the source transmitter. But for power, just an AM radio tunned in between station on the lower end of the band around 550 to 600 Khz. Just avoid 1.55 Mhz as you will be chasing your tail all day because that is what Telephone T1 circuits use.

Oh yea the little cheap AM radio was or is one of my favorite tools for RFI, back when I did some RFI tracking for the FCC out of Chicago, I used these and a few other tricks I mentioned in post 3, The last one I had I found at a yard sale for a buck, it was a fancy 9 transistor Philco, remember back in the day it was how many transistors that was the selling phrase they used:lol:, many of us knew that a better radio depended upon the design of the front end as well as the filtering in between each IF section, the better front end radios that had good filtering would not make a good RFI tracker, for what its worth car radios had some of the best front ends and filtering as they had to deal with not only the power lines they drove under but the ignition system, so forget using a car radio for a RFI tracker:happysad:.

But to the OP keep in mind that power lines around salt water mist and spray can have tracking noise very badly, and good luck trying to get the POCO to do something about it, the FCC can issue a cease and decease notice to then but many times it doesn't get you very far, also I would have a hard time expecting that a problem from the power lines or a transformer is affecting the front end of a GPS receiver at 1.5ghz??? but anything is possible???

 

[mgookin]

Thanks for the 411 on the salt water. This is a gulf front community. Lots of salt.

I'm not so concerned about the affect the RFI has on our product there because our product does work there. These guys tell me they can't use satellite radio, cell phones, etc. and that's significant in an upscale community of this caliber. Our business relationship would skyrocket if I solved the RFI issue out there. Consider it a personal challenge for me to solve not only to impress a customer but so that in the future I can show up on a site and pinpoint issues they may be having.

We do get customers from time to time doing crazy installs, like inside a building mounted to the ceiling pointing down at the floor, and it still works! But it takes seemingly forever to get a fix and that's not how we tell customers to install it. Optimal installation occurs when the device is installed in an upright position with unobstructed exposure to the horizon, as is the case when installed atop a cobrahead on a highway.

Thanks again for all the education, pointers and opinions. This venue in invaluable.