Horrible Interference on repeater

[N4DES]

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.

If you truly think that you found the offending user and it started about the time that they modified their license, reach out to the coordinator that did their license modification and advise them of the interference issue. If you do get through the FCC drama and find someone who is willing to work with you, the FCC will also engage the coordinator and if they made a mistake will want them to "work it out".

I had something similar with my HOA's Part 90 UHF repeater that I licensed and installed for them. It would get debilitating interference on the input frequency, a lot like yours, from a golf course irrigation system that was operating more than 4 times their licensed TX power output, no CWID, and antenna height higher than licensed. This is on the low power/low altitude part of the UHF spectrum, so the golf course's installation was totally illegal, but I brought them into compliance through the use of the coordinator.

 

[speedway_navigator]

In my early days of installing I put a base in the golf maintenance shop for the Lawrence Welk course in north county San Diego. A few weeks later I was in there for another task when one of the guys said every time they keyed it set off a sprinkler somewhere. I had not notice the sprinkler control was near where I ran the RG-8 (long before LMR400) and offered to move the install.

"oh no, we love to watch those old geezers run off the greens" was his reply.
Now I am one.

 

[jcefd10]

So, this reared it's head yesterday. So badly that we missed the tones for a structure fire. If we'd not had Active 911 to get the notification, nobody would have had any idea. 911 could not get into the repeater. They could hear our traffic, as the fire was maybe 1.5 miles from the tower so our radios could break the interference, but 911 could not talk to us for several hours.
The Fire Chief/EMA Director decided to contact GEMA yesterday, since they have a team for situations like this. (I didn't know that) and they are going to get with the state frequency coordinator and whoever else they need to involve and make a trip down from ATL to see if they can pinpoint where the interference is coming from. I guess I got this right, I'm just going off what I was told over the phone.

Guess we'll see.

 

[AM909]

Thanks for the update. Do let us know what happens. You're not the only one going through these problems on highband, and I'm sure we'd all like to see a successful resolution.

 

[JustinWHT]

highband,

Decades ago we called 37 and 42 MHz slices as low band and 152/157 MHz slices as high band.

I was replacing a fiberglass VHF antenna on a water tower. The gate key was labeled ... HI BAN.

 

[KB3KBR]

So, this reared it's head yesterday. So badly that we missed the tones for a structure fire. If we'd not had Active 911 to get the notification, nobody would have had any idea. 911 could not get into the repeater. They could hear our traffic, as the fire was maybe 1.5 miles from the tower so our radios could break the interference, but 911 could not talk to us for several hours.
The Fire Chief/EMA Director decided to contact GEMA yesterday, since they have a team for situations like this. (I didn't know that) and they are going to get with the state frequency coordinator and whoever else they need to involve and make a trip down from ATL to see if they can pinpoint where the interference is coming from. I guess I got this right, I'm just going off what I was told over the phone.

Guess we'll see.

has 911 thought of a microwave backbone to the repeater so that at least dispatches always go out?

 

[jcefd10]

Good news!
I got in contact with the county whom I thought was the offender's radio shop today. He verified that indeed they were using that frequency as one of the control channels. So why I monitored the repeater, he got the channel to transmit and behold, that was the cause if the interference.
For now, he has it disabled on his end, and we will go from there.
I got to give Evans a HUGE shout out on this, as he helped me nail it down just by the sound of the digital traffic I was receiving.
From here, their 911/EMA will decide whether or not to get a new frequency or take other actions. But we nailed it down! The guy from the GA Frequency Coordinators office didn't like my idea of it being in Alabama, but oh well.

 

[jcefd10]

has 911 thought of a microwave backbone to the repeater so that at least dispatches always go out?

Typically, they would. All ours uses is a directional antenna on their tower pointed back towards our repeater site.

 

[WB5UOM]

Yup...a control channel on almost any vhf frequency is gonna screw someone. As I think I said in an earlier post, I just went thru that exact same thing here. Hopefully, they wont switch back to my Customers rx freq..
and that was from 158 miles away

 

[KevinC]

Yup...a control channel on almost any vhf frequency is gonna screw someone. As I think I said in an earlier post, I just went thru that exact same thing here. Hopefully, they wont switch back to my Customers rx freq..
and that was from 158 miles away

I got ya beat. 400 miles, control channel output at 350' to a conventional repeater input at 300'. No ducting/weather conditions.

 

[speedway_navigator]

I got ya beat. 400 miles, control channel output at 350' to a conventional repeater input at 300'. No ducting/weather condition.

800 MHz?

 

[KevinC]

800 MHz?

VH&F

 

[JustinWHT]

I got ya beat. 400 miles,

I got ya beat. Late '60s, Brazilian railroad 3,300 miles away on 42 MHz, the repurposed TV ch 1 to LMR 40-50 MHz. Sunspot related.
Radio shop had VHF simplex radio network in surrounding counties for oil rigs, that used 40-50 MHz crossband control point repeaters.
System retired in '74 and moved to UHF repeaters.

 

[WB5UOM]

Well on my problem..the interfering transmitter was low power at 300ft..
but...the ground elevation was 1000ft.
the receiving end is a 160ft tower at about 400ft elev...

 

[N6JPA]

Good evening all.
I have a very general question here. Here recently we have been having some pretty bad issues with interference on one of our repeaters. We have 5 in the same hut, and only 1 is getting the interference.
We are running NXDN in 12.5 spacing at the moment at this site.
Something is transmitting on our FD/EMS repeater input frequency. It is such a strong signal, that the portables cannot key over it to key the repeater. Mobiles can, but only for a very limited distance. The other day when it was at it's worst, I think you could still get the repeater if you were no more than 6-8 miles from it. With my NX5200, I was standing at the base of the tower and was barely able to talk over it. Any more than .5 miles away, portables were useless. Our 911 could not talk over it either. They have a yagi on their tower around 150' pointed directly towards this repeater site so they usually have zero issues. We noticed it very badly last Thursday and I was hoping it was only atmospheric conditions, but again this morning it reared its head. I just made a quick run by the repeater to see if we were having the interference again and as suspected, we are. I was able to get a video of what is coming across, if that would help make sense of it all. All i can hear on it is some digital in the background. The foreground noise I have no idea.

I've contacted a couple of radio shops to see if any of the technicians could tell what was being received. We've searched the FCC site for anyone that may be within a distance to where the signal would be strong enough to keep us from being able to use our radios. We traced it down to 3 agencies in GA and one in AL so far that "MAY" be close enough to cause the interference. We contacted the closest of the ones and asked if they still had repeaters online using that frequency and they did not. I have programmed the input frequency in both digital and analog in both my portable and mobile radios with carrier squelch and you cannot hear the traffic from the ground, or at least I have not yet anyway. It never goes away completely it seems, just eventually gets weak enough we can talk over it for a while without interference.

Now the main question. How do I go about contacting the FCC to report the interference? I wasn't sure if there was a specific group you contact there, or a certain number to call for situations like this. Typically, I know nothing would need to be said or reported as some interference is expected, but this is leaving us pretty much dead in the water when the signal is coming across at its peak.


Apologies for such a long post! Thanks to anyone who stuck around to read completely. I would have not posted here but I'm out of ideas.

You should hire someone to do direction finding and use a spectrum analyzer. This sounds like a good ole intermod problem.

 

[AM909]

You should hire someone to do direction finding and use a spectrum analyzer. This sounds like a good ole intermod problem.

Look up just a few posts. It was a good old frequency-coordinator-failing-to-protect problem, putting a neighboring base station transmitter directly on the victim's base receive frequency.

 

[jcefd10]

It’s been a week today, and we have had zero issues since they disabled that channel.

 

[speedway_navigator]

What was the ERP limit on the other user's license? I've seen licenses where it was less than TPO due to issues like this where the coordinator did the path loss calcs but the install crew left the transmitter at full power.

Did you run any of the coverage prediction programs on the web?
I have some sites listed here.

why are you reading way up here?

If anyone has some to add let me know.

 

[10-43]

Had a similar issue many years ago when working in a local hospital. The patient telemetry system was getting knocked out on a couple of frequencies. We located the area the signal was coming from but could not find an FCC license for it. Contacted the FCC field office who had a remote receiver in our area. They monitored it too. FCC engineer suggested a spurious emission.
Turned out to be a local paging transmitter that had spurious emissions that was the 3rd harmonic of the primary transmitter frequency, wasting their power in the 400 Mhz business band.

 

[speedway_navigator]

I have some spurious emission FCC violations in this list.

Index of /FCC/

It's interesting to see how the feds decide who gets a fine and who slides by, in my opinion race had a factor in at least one case.
How would someone know a transmitter had spurs without a complaint? I doubt any of the NOVs were intentional.

It's been a few years since I checked a radio on a service monitor but when I did I was looking at a narrow bandwidth, not 100-500 MHz for a VHF freq.