Weird XTL5000 problem

[wyomingmedic]

Okay, I have multiple xtl5000s that are subscribers on a phase 1 system.

Recently, multiple radio on both the VHF and 800mhz side are having a problem with being in fringe areas.

They will be locked onto a site when signal strength is decent and WHAT I BELIEVE IS HAPPENING is the AGC kicks in to decrease signal strength. But, since we're in a fringe area, the signal strength drops once we get off the hilltop. Then, the radio seems deaf and struggles to receive traffic. Give it a few minutes and I BELIEVE THE AGC CATCHES UP, receiver becomes decent again, and signals pick up.

These radios all previously worked perfectly and continue to work fine in dense RF areas with high signal strengths.

Because if the sudden change across multiple radios, I am assuming this might be part of a trunking system upgrade. I have no part in system info, so I have no idea if an upgrade occurred.

Does this sound like an AGC issue? Would turning off the AGC alleviate this you think? Am I totally on crack and this is a different issue all together?

 

[DeoVindice]

When is the last time the problem radios were aligned? AGC is an audio parameter and has nothing to do with receive performance.

 

[GTR8000]

AGC is an audio parameter and has nothing to do with receive performance.

That is not correct. ASTRO 25 and APX series radios have Advanced RF AGC settings in the trunking and conventional personalities.

 

[DeoVindice]

That is not correct. ASTRO 25 and APX series radios have Advanced RF AGC settings in the trunking and conventional personalities.

I stand corrected. We only had a little bit of Astro25 hardware and have retired it.

 

[a417]

I stand corrected. We only had a little bit of Astro25 hardware and have retired it.

Yeah, take a common term like AGC and use it in various contexts, it gets confusing.

 

[wgbecks]

Recently, multiple radio on both the VHF and 800mhz side are having a problem with being in fringe areas.

They will be locked onto a site when signal strength is decent and WHAT I BELIEVE IS HAPPENING is the AGC kicks in to decrease signal strength. But, since we're in a fringe area, the signal strength drops once we get off the hilltop. Then, the radio seems deaf and struggles to receive traffic. Give it a few minutes and I BELIEVE THE AGC CATCHES UP, receiver becomes decent again, and signals pick up.

Does this sound like an AGC issue? Would turning off the AGC alleviate this you think? Am I totally on crack and this is a different issue all together?

There could be any number of reasons for the situation you’ve described that include individual radio alignment, antenna performance, or even the possibly issues with one or more of the RFSS covering those remote areas. However, I personally doubt this is a receiver AGC problem.

Instead, I would check the radios having weak signal coverage problems to to determine if any of them have “Full Spectrum Control Channel Scan” enabled. This feature seems novel but in many cases can be problematic, especially when operating in weak signal areas.

What can happen under these conditons is that the trunking logic fails to find a stronger control channel in the adjacent sites table and initiates scanning in search of a better signal (site) that can introduce a lap of sync with the system that gives the appearance of the radio having gone temporarily deaf, and is worth checking out.

 

[wyomingmedic]

Instead, I would check the radios having weak signal coverage problems to to determine if any of them have “Full Spectrum Control Channel Scan” enabled. This feature seems novel but in many cases can be problematic, especially when operating in weak signal areas.

What can happen under these conditons is that the trunking logic fails to find a stronger control channel in the adjacent sites table and initiates scanning in search of a better signal (site) that can introduce a lap of sync with the system that gives the appearance of the radio having gone temporarily deaf, and is worth checking out.

Interesting.. Yes, all radios have the full spectrum scan in place. I didn't cause problems in the past, but obviously something changed.

The fact that this is multiple radios suddenly developing the same problems, across bands, in areas they suddenly performed perfectly (and region wide. Not just with a site or two, but basically the whole state), I'm inclined to think something changed on the administration level.

But I will tinker with the full spectrum scan. That is an interesting point.

 

[wgbecks]

Interesting.. Yes, all radios have the full spectrum scan in place. I didn't cause problems in the past, but obviously something changed.

The fact that this is multiple radios suddenly developing the same problems, across bands, in areas they suddenly performed perfectly (and region wide. Not just with a site or two, but basically the whole state), I'm inclined to think something changed on the administration level.

But I will tinker with the full spectrum scan. That is an interesting point.

Be sure to populate all active primary and secondary CC's into the Astro 25 Control Channel list for the areas (sites) traveled
before disabling Full Spectrum Control Channel Scan.

 

[a417]

The fact that this is multiple radios suddenly developing the same problems, across bands, in areas they suddenly performed perfectly (and region wide. Not just with a site or two, but basically the whole state), I'm inclined to think something changed on the administration level.

This.

This is the thought process I like to see. And since it's reproducible on more than one unit, you can go to the appropriate contacts and say "...so what changed on your end...?"

 

[wyomingmedic]

Currently reaching out now. Not sure if I'll get an answer, but some folks are saying that they did a recent update to the GTR stuff from Quantar. Not sure if that's it, bit will dig a bit deeper.

 

[KevinC]

Interesting.. Yes, all radios have the full spectrum scan in place. I didn't cause problems in the past, but obviously something changed.

The fact that this is multiple radios suddenly developing the same problems, across bands, in areas they suddenly performed perfectly (and region wide. Not just with a site or two, but basically the whole state), I'm inclined to think something changed on the administration level.

But I will tinker with the full spectrum scan. That is an interesting point.

Unless RF AGC is much different in the APX vs the XTS it wouldn’t take minutes for it to recover.

My guess from over 1.000 miles away is you switch to a distant site on the mountain top. When you’re back at ground level you can no longer see that site so you have to look for a good site. And since that site was distant it doesn’t have any local sites in it’s ACL so it takes a little longer.

I’d question if the ACL’s on sites were monkeyed with.

But that’s just my guess.

 

[xmo]

If they changed the base stations from Quntar to GTR, it is possible the outbound modulation format was changed from C4FM to LSM in which case, you could try changing your mobile receiver format.

 

[NVAGVUP]

From a system level, it is possible something isn't correct with adjacent site tables. Basically if radio is affiliated to Site A, the radio will start looking for/move to other site # (Per control channel) if signal strength is 2 levels below other sites in adjacent site list. (If I recall correctly) But if those adjacent sites are not built correctly, radio will first look at your control channel list, and if it does find what it is looking for, it will revert to Full Spectrum Scan. (If box is checked).

An unrelated test. How do you know signal strength is less? Do you have a RSSI button? If so, use that as a reference.

Since Wyolink is primarily VHF trunked, I don't have a good feel on talk in/talk out coverage balance/performance vs 800 trunked.

 

[hitechRadio]

Get rid of full spectrum scan, unless the radios travel a wide area like an entire state, not needed.

Manual enter the the CC's needed, and order them top down. The CC scan starts from Top Down if it cannot find an Adj. Site. and the radio resorts using CC list. It can take awhile if your main site/s are at the very bottom of the list of a large CC Channel list.

Additionally check Adj. site list, or you can do it your self with SDR trunk. In addition make sure a specific TG is allowed at the adj. sites in your area that you require, which only a sys admin can change all of this.

If you set up you preferred site list, double check that also. It is in Trunking personality.

Also enable, under Display>General Enable All to display or display&alert (your preference),, ORI, SSI, ICI, STI and SRI. This is for trouble shooting for the most part.
I would also add RSSI to the menu on a Mobile or a button on a portable.

 

[wyomingmedic]

An unrelated test. How do you know signal strength is less? Do you have a RSSI button? If so, use that as a reference.

Yup, RSSI button is available, which is how I watch the received signal strength. Coupled with my general knowledge of how the sites cover, I can compare that to historical coverage patterns.

 

[wyomingmedic]

If they changed the base stations from Quntar to GTR, it is possible the outbound modulation format was changed from C4FM to LSM in which case, you could try changing your mobile receiver format.

Already at CQPSK, so I don't think it's a modulation issue.

 

[n3obl]

When the last time the radio been bench tested and aligned?

 

[RFI-EMI-GUY]

Why would anyone still be using the RF AGC?

 

[tunnelmot]

Why would anyone still be using the RF AGC?

For those of us not on the inside( example: NAS, ham use, etc ), why not? Genuinely curious.

 

[RFI-EMI-GUY]

For those of us not on the inside( example: NAS, ham use, etc ), why not? Genuinely curious.

Because while in theory it reduced off channel interference/blocking, it did not actually improve the receiver dynamic range or off channel rejection performance. The logic required to switch it in and out does not follow varying real world conditions of strong interferer(s) and having a weak desired signal. It made weak desired signals even weaker.

It perhaps fixed sporadic problems in the strong desired signal area but killed the fringe. It was at best a hastily concocted band aid for the NEXTEL problem which actually required eventual segregation (800 MHz transition plan) of the NEXTEL band by several MHz.