Horrible Interference on repeater

[Foresigt]

Now that you have all of this input from the scanner guys, here is the information you need. Contact the FCC Operations Center at (202) 418-1122. They will be able to assist you. The FCC has teams that do field work to deal with interference to public safety frequencies and they have the authority to mitigate the interference and deal with the offender if needed.

 

[lenk911]

Not sure if the procedure remains the same but this will give you guidance.

A few years ago a public safety licensee in a major city reported to the FCC in Gettysburg that my client's radio system was interfering with them. The first action of the FCC was to notify the frequency coordinator for the service of the frequency reported. They contacted me as the engineer of the system.

My client's system was 250 miles away from the offended system. Their transmitter was on the same frequency as the offended's extensive voting receiver system's input. In the summer, my client was heard loud and clear even though both had different CTCSS tones. First thing I did was to verify my client's system was not emitting the wrong tone and it wasn't. Second, I requested the coordinator to have them verify their tone.

 

[lenk911]

Coordinators attitude as very parochial. This little rural system was wrong and the big city was right. First of all interference from 250 miles away was no brainer and the coordinator should have known better. Second of all, the big city's system had a tone squelch failure on a dominate site that they told nobody about. When I challenged the coordinator's conclusions he was going to report me to the FCC. I said bring it on!

Bottom lines:
1. The first investigator may have little qualification but play tough guy.
2. Make sure you're in the right before you report to the FCC.
3. Know your in the rights and know the FCC rules governing your system.
4. Never use a VHF base frequency as your input for a receiver voting system .

 

[AM909]

I'll bet 250 miles is well outside the designed protection radius of even the highest power of VHF stations.

As if interference on the input/output from/to distant mobiles wouldn't be bad enough, they go ahead and reverse the split and put bases transmitting up where only receivers should be.

 

[kayn1n32008]

Something I would suggest doing would be to take all of the transmitter frequencies on the site and pop them into the process for calculating related intermods…you may be surprised as a lot of this sort of issue are caused by either generation in the receiver, another transmitter on site or perhaps in rusty junctions in metalwork on site.

These calculations should be done for EVERY receive and transmit frequency, and include ALL sites with in at least a half mile. Possibly a mile for high power transmitters.

This includes broadcast and cellular centre frequencies.

 

[MTS2000des]

Now that you have all of this input from the scanner guys, here is the information you need. Contact the FCC Operations Center at (202) 418-1122. They will be able to assist you. The FCC has teams that do field work to deal with interference to public safety frequencies and they have the authority to mitigate the interference and deal with the offender if needed.

Yeah, I did that and all they did was write a letter to a building owner who's get her done BDA jammed my part 90 trunked radio system relied on by 4 PSAPs and 7,000 plus subscribers. The FCC is a joke. Better to engage local technical folks and track it down yourself, use local AHJ "tools" to gain compliance if resistance is encountered.

 

[G7RUX]

These calculations should be done for EVERY receive and transmit frequency, and include ALL sites with in at least a half mile. Possibly a mile for high power transmitters.

This includes broadcast and cellular centre frequencies.

Absolutely so, I spend a remarkable amount of my time doing exactly this while planning systems. The vast majority of intermod problems occur with very local systems although you are correct in that further ones can be the culprit; the nearby ones, being much higher PSD, will tend to dominate.

 

[speedway_navigator]

If yo uhave a network connection at the site a NUC or small PC with a RTL hooked to your multicoupler or RX port is a cool thing to have. Thats what I did at 2 sites so when the interfearance starts up I can get in and look at the signal remotely. I think I have $150 into each box. May be something to think about.

I thought tablets and NUCs were cool, then I bought a win 10 stick PC as Fry's called it, about $90. USB for power, I run quick books on it, carry it with me between summer and winter homes. It's about the length of a PC drive but half the width.

 

[jcefd10]

If yo uhave a network connection at the site a NUC or small PC with a RTL hooked to your multicoupler or RX port is a cool thing to have. Thats what I did at 2 sites so when the interfearance starts up I can get in and look at the signal remotely. I think I have $150 into each box. May be something to think about.

Send me some info on this please. I do I face have internet at both sites and a VPN set up between the 2.

 

[jcefd10]

It’s back pretty bad again today.
Sucks it wasn’t audible when the guys were here earlier this week. 🤦🏻‍♂️

 

[speedway_navigator]

with a RTL hooked to your multicoupler

Have you tried a tiny SA or RF explorer?
My RTL is still sitting on a shelf after umpteen years of "I"m going to try that real soon".

 

[JustinWHT]

I'll throw this in here. Could be either Miscellaneous Metallic Junction Intermodulation (MMJI) from a corroded metal.joint, or a defective transmitter or duplexer.

I had a paging frequency of 152.480 MHz and one of the two Denton, TX GTE VHF IMTS mobilephone channels (157.74 - 158.10 MHz) was going out on my 152.480. I did the frequency math and figured out which of their transmitters was at fault, stopped by their shop and they shut off that transmitter.

 

[WB5UOM]

actually a second harmonic filter on either would have solved that issue on 152.480...had that down here in east texas too

 

[speedway_navigator]

I had a paging frequency of 152.480 MHz

My cousin and I had that in Indiana years ago as Paging USA.
When I was installing IMTS phones in San Diego we only had 3 or 4 channels. I think LA and Vegas had them all.
I came on just after MTS went to IMTS.

 

[JustinWHT]

MTS phones in San Diego we only had 3 or 4 channels.
I came on just after MTS went to IMTS.

Remember Ironsides in San Franciso with Raymond Burr using an MTS phone in his s van?
SF wilh it's hills had receivers on telephone poles fed to a central voting system.
With exception in Abilene everything west of Fort Worth was manual MTS.

 

[sempai]

in my line of work, i am obliged to assume it's intentional. is there any equipment within 30 feet of your gear that you don't recognize or anything? is there any way somewhere else in the building or facility that anyone would be able to access that would give direct or indirect access to your own gear, or are you certain your equipment hasn't been tampered with?

i can think of a lot of reasons to intentionally interfere with EMS communications, and they're all terrible.

 

[jcefd10]

in my line of work, i am obliged to assume it's intentional. is there any equipment within 30 feet of your gear that you don't recognize or anything? is there any way somewhere else in the building or facility that anyone would be able to access that would give direct or indirect access to your own gear, or are you certain your equipment hasn't been tampered with?

i can think of a lot of reasons to intentionally interfere with EMS communications, and they're all terrible.

No sir. Nothing has changed. I'm all but certain its propagation. I was just up at the site and there was zero interference today.
I saw where the station I believe is causing it modified their license about 3 months ago, and that's when it started. I've been trying to dig in a little, but the FCC site is extremely slow if it works at all seems like.

 

[iowajm780]

Good luck getting the FCC to do anything. They will only help cell carriers with interferance that causes them problems. Even public safety agencies are given the cold shoulder when asking the feds for help.

 

[JustinWHT]

Good luck getting the FCC to do anything.

Because the FCC has priorities being with certifying Part 15 products.

FCC Priorities

/sarcasm mode on Now we know why it takes so long for FCC to investigate interference. They devote time on this!

forums.radioreference.com

 

[MTS2000des]

Good luck getting the FCC to do anything. They will only help cell carriers with interferance that causes them problems. Even public safety agencies are given the cold shoulder when asking the feds for help.

Yep. They could give two dumps less about PS interference. I can personally attest. Interference like crippling/degrading a major trunked radio system not some guy not being able to use his HT at home stuff either. They don't care. Get up, get down, FCC is a joke in your town.