GR1225 sql issue

[berkinet]

We have noticed that our GR1225 (40w, UHF running at around 15w) occasionally exhibits a problem when the receive carrier drops.
We operate with a PL tone on rx and tx and what we observe is when the receive carrier drops, the repeater continues to transmit white noise (open monitor) until the TOT has been reached, at which point it drops. We initially had Unmute/Mute Type set to AND/OR (supposedly the only option for a repeater). Things were fine for a few days, and then the problem started. We switched PL tones and the problem went away. However, this week we replaced our feed line with LMR400 and raised the antenna a few feet and the problem returned. This time we tried setting Unmute/Mute to AND/STD and that worked for 30 minutes or so, and then the problem returned again.

One more bit on information. The antenna and repeater are on a rooftop with A PV (Solar) system and the repeater is grounded to the same ground bus as the PV inverter. We do not recall having observed the problem late in the day or at night (but we can't be sure).

My questions: Could this be a sticky relay (or similar solid-state function) that is just not releasing when it should? Ir, could this be RFI from the PV system (though it is hard to imagine how it could generate the PL tone)?

Any ideas at all are most welcome. I'd be glad to provide any more information I can as well.

Richard

[Jim202]

We have noticed that our GR1225 (40w, UHF running at around 15w) occasionally exhibits a problem when the receive carrier drops.
We operate with a PL tone on rx and tx and what we observe is when the receive carrier drops, the repeater continues to transmit white noise (open monitor) until the TOT has been reached, at which point it drops. We initially had Unmute/Mute Type set to AND/OR (supposedly the only option for a repeater). Things were fine for a few days, and then the problem started. We switched PL tones and the problem went away. However, this week we replaced our feed line with LMR400 and raised the antenna a few feet and the problem returned. This time we tried setting Unmute/Mute to AND/STD and that worked for 30 minutes or so, and then the problem returned again.

One more bit on information. The antenna and repeater are on a rooftop with A PV (Solar) system and the repeater is grounded to the same ground bus as the PV inverter. We do not recall having observed the problem late in the day or at night (but we can't be sure).

My questions: Could this be a sticky relay (or similar solid-state function) that is just not releasing when it should? Ir, could this be RFI from the PV system (though it is hard to imagine how it could generate the PL tone)?

Any ideas at all are most welcome. I'd be glad to provide any more information I can as well.

Richard

I will stick my neck out here and suggest that you find someone with a spectrum analyzer to look at the input frequency. It may not be easy to see and you will have to do the looking at the time the problem is there.

If you think the problem is only during the daylight time when the solar system is charging the batteries, it could be from this equipment.

It is not a good idea to have your ground tied to the solar system inverter. You should be tied to the building steel beams. There is no telling what the solar system is grounded to. They may be tied to the building electrical system neutral. This is not the place to be grounded. You should conform to the National Electrical code for grounding an antenna system.

[berkinet]

Thanks for the quick response. I guess I need to add some additional info. When we first had the problem, the repeater was in another location in the house, and was not grounded. We only grounded it after moving it to the roof. The solar system does not charge local batteries, it just feeds back into the grid. I believe the solar panel frames, where we grounded the repeater, are tied to a separate grounding rod. I will verify that, and find another ground if necessary.

I will ask around about a spectrum analyzer. Good thought.

[fineshot1]

We have noticed that our GR1225 (40w, UHF running at around 15w) occasionally exhibits a problem when the receive carrier drops.
We operate with a PL tone on rx and tx and what we observe is when the receive carrier drops, the repeater continues to transmit white noise (open monitor) until the TOT has been reached, at which point it drops. We initially had Unmute/Mute Type set to AND/OR (supposedly the only option for a repeater). Things were fine for a few days, and then the problem started. We switched PL tones and the problem went away. However, this week we replaced our feed line with LMR400 and raised the antenna a few feet and the problem returned. This time we tried setting Unmute/Mute to AND/STD and that worked for 30 minutes or so, and then the problem returned again.

Which tone did this start with and what tone did you move to?

I ask because some PL tones have been known to false the reverse burst feature
such as 131.8 and 136.5 since the reverse burst uses 134.4 bits per second to
operate properly.

[berkinet]

Ah. Yes, we started at 131.8 and moved to 88.5.

[d119]

I ask because some PL tones have been known to false the reverse burst feature
such as 131.8 and 136.5 since the reverse burst uses 134.4 bits per second to
operate properly.

Uh, what? Reverse burst is a phase shift of the PL tone in use used to silence the far end. DPL operates at 134.4 BPS as it's standard operating speed. DPL uses 134Hz as it's "Turn off code" which is significantly different than reverse burst, albeit they perform the same essential function.

I've never heard of 131.8 or 136.5 falsing anything.

Additionally, for the OP, I never recommend LMR400 for use in a duplex (repeater) environment. As the cable ages, the dissimilar metals in the shielding tend to begin to generate noise.

There is some information on this on the internet.

[berkinet]

I had heard to avoid lmr400 inside the case, but not to avoid at all. Thanks for noting that. It is only a 12 foot run, so we can switch next time we lower the mast.

[jackhackett]

I would also check the duplexer tuning, and as with all GR1225s, check the PA solder joints.

[fineshot1]

I ask because some PL tones have been known to false the reverse burst feature
such as 131.8 and 136.5 since the reverse burst uses 134.4 bits per second to
operate properly.

Uh, what? Reverse burst is a phase shift of the PL tone in use used to silence the far end. DPL operates at 134.4 BPS as it's standard operating speed. DPL uses 134Hz as it's "Turn off code" which is significantly different than reverse burst, albeit they perform the same essential function.

I've never heard of 131.8 or 136.5 falsing anything.

Additionally, for the OP, I never recommend LMR400 for use in a duplex (repeater) environment. As the cable ages, the dissimilar metals in the shielding tend to begin to generate noise.

There is some information on this on the internet.

THIS IS A WELL KNOWN ISSUE to which i suggest you make yourself aware of!

[fineshot1]

I ask because some PL tones have been known to false the reverse burst feature
such as 131.8 and 136.5 since the reverse burst uses 134.4 bits per second to
operate properly.

Uh, what? Reverse burst is a phase shift of the PL tone in use used to silence the far end. DPL operates at 134.4 BPS as it's standard operating speed. DPL uses 134Hz as it's "Turn off code" which is significantly different than reverse burst, albeit they perform the same essential function.

I've never heard of 131.8 or 136.5 falsing anything.

Additionally, for the OP, I never recommend LMR400 for use in a duplex (repeater) environment. As the cable ages, the dissimilar metals in the shielding tend to begin to generate noise.

There is some information on this on the internet.

I was not attempting to create a sub thread and completely describe the use of reverse burst.
I simply wanted to make the OP understand that the use of certain tones can be un-advantagious
when reverse burst is used.

Perhaps better described below:

http://batboard.batlabs.com/viewtopic.php?t=3713

https://en.wikipedia.org/wiki/Continuou ... lch_System

[berkinet]

Thanks to all so far for some interesting ideas. However, one thing still puzzles me: How can the "noise" (or whatever it is that holds the repeater up) do so without the PL tone being present? And, if the PL tone is actually present in the noise, why doesn't it activate the repeater by itself?

[jackhackett]

How can the "noise" (or whatever it is that holds the repeater up) do so without the PL tone being present? And, if the PL tone is actually present in the noise, why doesn't it activate the repeater by itself?

This is why I suggested checking the duplexer. If the TX leaks back through strong enough it would have the same PL (assuming you programmed TX and RX PLs the same) and could keep the repeater keyed. Likewise, bad solder joints could cause the PA to be spurious, putting out wideband noise that could also contain the correct PL. Or, some form of intermod could be causing the TX signal with the proper PL to mix with some external signal creating a signal on the RX frequency.

[berkinet]

Thanks for the explaination. So, if if the problem is being caused by the types of issues you note, turning PL off on tx would stop the symptoms I described above, right? That is an easy test.

BTW, I doubt it is the duplexer, that was professionally tuned and I have the screenshots of the results. But, after two days of sun, it is pretty clear the problem is related to solar radiation. Though, it may not be from the roof where the repeater is mounted.

Off to test.

[d119]

How can the "noise" (or whatever it is that holds the repeater up) do so without the PL tone being present? And, if the PL tone is actually present in the noise, why doesn't it activate the repeater by itself?

This is why I suggested checking the duplexer. If the TX leaks back through strong enough it would have the same PL (assuming you programmed TX and RX PLs the same) and could keep the repeater keyed. Likewise, bad solder joints could cause the PA to be spurious, putting out wideband noise that could also contain the correct PL. Or, some form of intermod could be causing the TX signal with the proper PL to mix with some external signal creating a signal on the RX frequency.

I think Jack is right on the money with this one. You could test the desense/spur theory by momentarily changing the transmitter PL to something different than the receiver, putting a portable or mobile in monitor mode, and seeing if the problem persists. If it doesn't, you've identified it. If it does, something else is wrong.

Keep in mind these repeaters are getting long in the tooth, much like their predecessors (The R100/MCR100) they can and will develop issues as they age. For the 1225 series, the PA has always been the popular source of contention.

[motorola_otaku]

Additionally, for the OP, I never recommend LMR400 for use in a duplex (repeater) environment. As the cable ages, the dissimilar metals in the shielding tend to begin to generate noise.

Having run into the same issue with the same hardware I can almost 100% guarantee this is where your issue lies. You are generating IMD products in the coax, and since the generated signal source has a CTCSS tone matching your input that's what's causing your receiver to lock up.

Replace with Heliax using new non-tarnished connectors and your problem will most likely go away. If you have any PL259s or adapters in your feed line run you need to eliminate those as well. Ideally your jumpers between the repeater and duplexer should be made with RG142/400 cable using new non-tarnished connectors as well.

When was the duplexer last serviced? How was it tuned to your frequency?

You also didn't mention what kind of antenna you are using. Comet/Diamond/Tram and other cheap hammy antennas can also generate IMD products due to poor solder joints on the elements, in addition to the elements not being properly secured and insulated inside the fiberglass tube. Any good commercial-grade Telewave, Andrew Decibel, Sinclair, or Celwave antenna will work fine as long as the connectors are clean, and in the case of folded diploe arrays the individual elements are in good shape, the insulators aren't cracked, and the connections to the elements are clean and free of corrosion.

Sorry if any of this is noob-level entry stuff to you, but I've been down this road more times than I can count with hams and their repeater setups.

[berkinet]

I have some news to report. We switched to CSQ on tx and we have not observed the problem again. Of course, listeners who are using Tone receive no longer hear the "over beep." Depending on the capability of radios in use on the repeater, we may try to use a different PL on tx. Seems most "modern" radios allow rx and tx ctcss to be specified separately (Not including my Yaesu ft-8800).

The noise source seems very likely to be the PV inverters located nearby. However, today it was a little cloudy when I got "on site" and the problem was not occurring. So, I could not shut them off to test.

Next steps: Change the coax. Since it is so short we may just use RG214 or RG393. The antenna IS a Comet UHF cut to frequency. Our budget is pretty limited (This is a neighborhood CERT system on GMRS) so buying something better right now is not an option. However, I did examine the antenna when I cut it to length and the solder joints looked good. For the time being, we are going to trust the duplexer, at least until we have addressed other issues first. BTW, the internal coax connectors are all RG400 with quality N connectors and NO adapters.

Thanks for all the help and advice (noob level and otherwise).

[d119]

Well using different TX and RX tones permanently does not solve the problem, it merely masks it. I would not consider that a permanent solution, at all.

214 would certainly be better from a metallurgy standpoint than LMR 400, but 214 is considerably more lossy than 400. This is why people are advising you to use heliax.

I've never seen or heard of a Comet base station antenna that can be "cut to length". Are you using a mobile antenna with a "ground plane" base adapter????

Something sounds very wrong about this all of a sudden...

[jackhackett]

I've never seen or heard of a Comet base station antenna that can be "cut to length". Are you using a mobile antenna with a "ground plane" base adapter????

They make a 440-512 tunable antenna, model CA-F72GF.

[d119]

Yikes... Not anything I would ever use...

[motorola_otaku]

I've only bought Andrew Decibel antennas new a couple of times... the rest were hamfest or Ebay finds, usually $50 or less. A 30-year old DB antenna will beat the pants off a brand-new Comet antenna.

[KE7JFF]

I've only bought Andrew Decibel antennas new a couple of times... the rest were hamfest or Ebay finds, usually $50 or less. A 30-year old DB antenna will beat the pants off a brand-new Comet antenna.

Amen to that...and don't forget tower site junk piles....its where I got a folded dipole that all it needed was some TLC on the bracket!

[Karl NVW]

Speaking from 40+ years of experience, if you want to get rid of the PL noise issue, get rid of that braided shield cable. BOTH the antenna feedline AND the Tx jumper into the duplexer need to be solid shield. 1/4" Superflex makes a great Tx jumper, use something larger for the main line up to the antenna. The receive cable isn't carrying any power, so braided shield there is USUALLY acceptable, provided that you have a solid RF, DC, and lightning ground for the duplexer and GR1225 mounting rack.