G5 vs Band 14

[KevinC]

Not bashing, just passing along for reference as a possible cause of OOR or garbled audio...

This is with the Band 14 site about 1/4 mile away, signal level in the high -40's. The Unication only shows -94, but the trunked signal level was actually in the low -80's. I would intermittently go out of range, but had garbled audio the rest of the time in the area.

 

[mdsxfire]

Not bashing, just passing along for reference as a possible cause of OOR or garbled audio...

This is with the Band 14 site about 1/4 mile away, signal level in the high -40's. The Unication only shows -94, but the trunked signal level was actually in the low -80's. I would intermittently go out of range, but had garbled audio the rest of the time in the area.

View attachment 68667

I’m interested in why such a high error rate (hence the garbling)when u have a good signal, I’ve only seen error rates that high when I’m barely holding one bar.



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[KevinC]

I’m interested in why such a high error rate when u have a good signal, I’ve only seen error rates that high when I’m barely holding one bar.



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Interference from the band 14 site.

 

[mdsxfire]

Interference from the band 14 site.

Ok I’m sorry I just went back and re read the post and realized that’s what pointing out.


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[N6ML]

This is with the Band 14 site about 1/4 mile away, signal level in the high -40's. The Unication only shows -94, but the trunked signal level was actually in the low -80's. I would intermittently go out of range, but had garbled audio the rest of the time in the area.

I find this quite confusing. "signal level in the high -40's" - what signal? Observed how? "trunked signal level was actually in the low -80's" - what does "trunked signal" mean, and how was that observed?

Are you saying that this "Band 14" signal is desensing your G5 when you're attempting to monitor some other (trunked) system?

I've never seen a RSSI value higher than ~-94dBm on my G5 - it seems that their measurement "tops out" there, for some reason.

 

[KevinC]

I find this quite confusing. "signal level in the high -40's" - what signal? Observed how? "trunked signal level was actually in the low -80's" - what does "trunked signal" mean, and how was that observed?

Are you saying that this "Band 14" signal is desensing your G5 when you're attempting to monitor some other (trunked) system?

I've never seen a RSSI value higher than ~-94dBm on my G5 - it seems that their measurement "tops out" there, for some reason.

Band 14 LTE signal was measured in the -40 dBm range, trunked signal (what the G5 is receiving) was measured in the -80 dBm range (all measurements taken using a Antitsu S412E).

 

[N6ML]

Band 14 LTE signal was measured in the -40 dBm range, trunked signal (what the G5 is receiving) was measured in the -80 dBm range (all measurements taken using a Antitsu S412E).

OK, that clarifies a lot. I'm sure if would have been obvious to anyone familiar with LTE

 

[Astrak]

Yep, get a lot of interference when near cell towers here in Phoenix.

 

[mdsxfire]

Yep, get a lot of interference when near cell towers here in Phoenix.

I had heard that the LTE interference (along with LSM) is what gives a lot of the scanners with cheaper receivers problems receiving these system pretty much knocking the control channel from being picked up by the scanner.
Are the cell companies pumping more wattage out than the TRS? And how close are they in the freq range? And why would they dole out a spectrum to public safety and then throw out one so close to cell phones? Doesn’t make any sense from what I see/read.

I’ve brought my G5 right to the bottom of the cell tower with our counties TRS on it and this tower has all the major cell providers on it and thankfully there seems to be no interference or issue receiving


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[Thunderknight]

My G5 does that within a few hundred feet of a cell site (low mounted) in town. It does not have Band 14 on it, but I have not checked to see what other carriers it does have.
My APX is not affected in the same spot.

 

[Thunderknight]

I had heard that the LTE interference (along with LSM) is what gives a lot of the scanners with cheaper receivers problems receiving these system pretty much knocking the control channel from being picked up by the scanner.
Are the cell companies pumping more wattage out than the TRS? And how close are they in the freq range? And why would they dole out a spectrum to public safety and then throw out one so close to cell phones? Doesn’t make any sense from what I see/read.

Cell site carriers are often hundred+ watts. And with LTE, the composite power depends on how active the site is (the more active the site, the higher the composite power).
This problem, somewhat caused by the FCC and somewhat caused by the fact there is a limited amount of desirable spectrum, goes back years...it's why we had 800 MHz rebanding. Some say the problem is just occurring all over again at 700.....
(Band 14 is 758-768, then a 1 MHz guard band and then public safety 700 spectrum starts at 769. The other major LTE bands, such as Verizon and AT&T commercial, are below Band 14).
Better receivers in PS radios are helping, but there is a limit to how much filtering one can cram into a portable radio.

 

[mdsxfire]

Cell site carriers are often hundred+ watts. And with LTE, the composite power depends on how active the site is (the more active the site, the higher the composite power).
This problem, somewhat caused by the FCC and somewhat caused by the fact there is a limited amount of desirable spectrum, goes back years...it's why we had 800 MHz rebanding. Some say the problem is just occurring all over again at 700.....
(Band 14 is 758-768, then a 1 MHz guard band and then public safety 700 spectrum starts at 769. The other major LTE bands, such as Verizon and AT&T commercial, are below Band 14).
Better receivers in PS radios are helping, but there is a limit to how much filtering one can cram into a portable radio.

So even with the 1mhz guard in between the frequencies are still close enough that they cause interference?


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[KevinC]

My G5 does that within a few hundred feet of a cell site (low mounted) in town. It does not have Band 14 on it, but I have not checked to see what other carriers it does have.
My APX is not affected in the same spot.

This was about a 100' rad center (pretty high for in town site) and none of my APX-series radios have an issue in this area either. The beamwidth must be pretty wide on these antennas as I couldn't really find any spots around the tower where it didn't cause an issue.

Again, not bashing, just putting it out there that this may affect others as well.

 

[Thunderknight]

So even with the 1mhz guard in between the frequencies are still close enough that they cause interference?

Yeah, if the receiver doesn’t have a real tight filter. In fact, a lot of the radios on the market today go down to 764 because that was the band segment until 2007. We will probably see newer models starting at 769 at some point. Same with 800, at some point the manufacturers will stop their radios at 862 (not 869) to avoid cellular interference. This is known as a near-far issue. The undesired cell signal is nearby and the desired LMR is far away.

I just checked the G5 spec sheet and it goes down to 763, so there is no hard filtering of the PSBB block. (Unless they use switchable filtering depending on the receiver’s active frequency)


(And I’ll just note that I still love my G5 anyway

 

[GTR8000]

It's worth noting that Band 13 (Verizon) starts at 777 MHz for the uplink (device transmit), which is close to the upper limit of the public safety narrowband segment of 769-775 MHz. While this really shouldn't have an adverse affect on reception, due to the low power of the LTE devices, it's probably good practice not to have your Verizon LTE device too close to a 700 MHz receiver.

 

[Thunderknight]

it's probably good practice not to have your Verizon LTE device too close to a 700 MHz receiver.

So it's bad to rubber band my Verizon phone to the front of my G5 and my FirstNet phone to the back?

 

[N6ML]

So it's bad to rubber band my Verizon phone to the front of my G5 and my FirstNet phone to the back?

Sounds like that would be ... sub-optimal

 

[APX8000]

One of the cell towers here will completely knock out the control channel on my GRE / Whistler scanners. G5 stays locked on the system but it will garble transmissions if I’m parked within a certain sector of the tower. APX, zero issues.

The GRE scanners have such a hot front end that it I couldn’t use it on analog trunked systems while mobile without any filtering. As far as the G5, it’s just that one tower and driving by it I don’t have an issue. Just parked in that one sector.

Just goes to show how you can’t beat a true subscriber.


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[KevinC]

Interestingly I was able to test a Uniden SDS100 in the exact same location I tested the G5. To my surprise the Uniden performed better, it still had issues but was able to stay locked onto the CC more reliably and pass most of the traffic.