Severe Inconsistency with TRBO Capacity Plus

[Firebuff880]

Since I don't actually install any longer just support all I can offer is a link that I have long had --

Antenna Downtilt Calculator

Pasternack's Antenna Downtilt Calculator (aka Antenna Tilt Angle Calculator) is used to determine the approximate downward angle, measured in degrees, that the transmitting antenna is to be positioned at for optimal signal strength and coverage.

www.pasternack.com

 

[ecps92]

The other thing to keep in mind, is interference from other users on your input frequencies or even the Output from another nearby DMR

Since Frequencies can be Analog, P25, DMR - there is no protection from any interference
just a WAG as we have really begun to see more simplex users on what (years ago) would have been called an input frequency. (+5)

We joked about putting all of our equipment atop one of the other mountains that sits about 5 miles due east of us. Wouldn't be a bad idea until the site needs maintenance.

 

[K4APR]

Another vote for antenna down tilt. I think this is a majority of your problem. Standard vertical omni's have a donut shaped pattern, unless it has rotatable bays for adjusting the pattern into an ellipse or something similar, but that still does not address the area close in and well below the pattern.

Do you have a tower top amp and base mounted multi-coupler on the RX side? Might want to check that TTA, if you have one. A bad TTA will greatly reduce your talk-in range.

 

[mmckenna]

Again, Downtilt is likely an issue, but it would not be the cause of intermittent signal levels at the same sites. That's looking more like an intermittent repeater issue or interference.

As for downtilt...
I've got a UHF site that I got stuck with that is at 2500 feet. Less than 1 mile away the ground level drops to sea level. It takes some wide beamwidth antennas with some serious downtilt to get coverage down to the users level.

Radio performance is consistent as the antenna pattern does not randomly change.

 

[sjaltavilla]

As for downtilt...
I've got a UHF site that I got stuck with that is at 2500 feet. Less than 1 mile away the ground level drops to sea level. It takes some wide beamwidth antennas with some serious downtilt to get coverage down to the users level.

Do you think that physically tilting the antenna to point downhill will work? After all, we only operate on the east face of the mountain.

 

[mmckenna]

Do you think that physically tilting the antenna to point downhill will work? After all, we only operate on the east face of the mountain.

I installed a Telewave ANT-450D that way at one of the sites.
I inherited this system, and have to maintain it pretty much as is. I would have preferred VHF for the location (and for interoperability), but sometimes we get stuck with what we have.
Anyway, a couple of sites with 10 watt UHF analog repeaters. The site was having a lot of issues. I had to replace a lot of poor quality components along the way.
One issue was "ham radio" grade antennas that were used. For some reason they went with 6dB gain omni-directionals. That blew a lot of power over the heads of the users. At two of the three sites, I replaced the antennas with the ANT-450D single bay folded dipoles. Both sites are at about 2500 feet elevation. Users could be anywhere from 4000 feet up on adjacent ridges to right down at sea level (actually -on- the beach). All this was within a few miles range (one site was one mile from the 2500' high repeater to seal level).
The wider beamwidth of the antenna helped put signal where it was needed, rather than blasting most of it out at the horizon.
At onne site which had a really steep slope, I installed the antenna on a pole and then mounted the pole over at about 15º so the antenna was looking down the slope. That greatly improved coverage.

The right antennas can make a big difference. I would have suspected a big company like Bearcom to do a better study of the application.
Often installers, and especially hams/hobbyists, will see antenna gain as "free power". That's great in some applications, but it can impact coverage in others. Sometimes lower gain, wider beamwidth antennas are what is needed to bring the pattern down where it does more for the users.

That absolutely sounds like some of your issue.

The intermittent coverage issues sounds like something else.

Combine those two solutions and you may see your issues go away.

 

[BMDaug]

+1 for the Telewave single bay folded dipole. I have a 150D (VHF) and love it! When the radio bonks, is it an OOR, or is it a busy bonk? If you’re getting an RSSI of -60 but it’s bonking, it doesn’t sound like OOR. It’s possible that the SU is receiving the CC fine, but is not heard by the site and therefore doesn’t receive a channel assignment. I don’t have experience with cap plus systems but you should note times of bonks and check logs to see if the site is even hearing the SU. If it’s not, it won’t matter how strong the CC is.

-B

 

[N5XPM]

Wow - thanks for all of the input overnight. Allow me to respond to as many questions as I can.



The old VHF setup consisted of four repeated channels. Our main site was located halfway up the mountain and housed four MTR2000's putting out 100 watts a piece. Each repeater had it's own antenna and duplexer. Our secondary (receive only site) was at our satellite base area (about 2 miles down the road from the main base lodge/ski village. We had many issues talking out from that side of the hill before we installed that equipment. Over at that site, we only had two MTR's since we only needed the ski patrol and lift maintenance channels over on that side. The old network ran like a charm - almost no dead spots anywhere.



This is one of the main conclusions we have come to. We are considering moving everything to mid-mountain in an attempt to balance the coverage area.



Any good recommendations on antennas? Do you think physically tilting the antenna 30 or so degrees downhill will help?



GPS updates are not set to a data revert channel. I considered doing this, but I was afraid that dedicating one repeater to be data-only would reduce our talking capacity dramatically. Our GPS updates are being handled by a PC with software - we use Elcomplus SmartPTT. Note that only about 40% of our subscriber radios are GPS capable.



Considering I can hit the repeater from 40 miles out, I would hope so.



Thanks for the recommendation - we currently don't have any monitoring software (I know, I know) but it is certainly a much-needed investment.



We have a brand-new combiner unit, so we only use one antenna.



Trunking operation works flawlessly when we are well within the coverage area. No bonks until you make it halfway down the mountain.



Tell me about it. The one that was sent to us originally was terrible. I ended up reworking the entire thing and had to manually touch each unit on property since Bearcom didn't set us up with Radio Management originally. What a time to be alive lol.



Funny enough - we have an analog simplex channel that we use in case of system failure. We can pretty much cover the entire main face of the mountain on 4 watt simplex. Yet the 55 watt repeater has problems. Go figure.



This is a really good thought. I might have to take a closer look at this. Since we are at the top of the mountain, we have had interference from the west of us (NY)...

You have provided some helpful information.
It is not a trivial effort, but I would consider reducing the repeater transmit power to 25 watts or so and doing some testing. If your portables are 4 watt anyway, it "matches" the power of the repeater paths more closely.
I think you have multiple issues, but a reduction in power may help reduce repeater receive defense and improve consistency in performance. It it helps, it might suggest a combiner retune is in order.
I agree with others with the benefit of reducing antenna gain and working on downtilt.
This type of problem is extremely frustrating to figure out, but you are working through many of the right potential issues and will resolve it eventually.

 

[sjaltavilla]

When the radio bonks, is it an OOR, or is it a busy bonk? If you’re getting an RSSI of -60 but it’s bonking, it doesn’t sound like OOR. It’s possible that the SU is receiving the CC fine, but is not heard by the site and therefore doesn’t receive a channel assignment.

Its almost never an OOR bonk, rather a bonk that occurs when the subscriber cannot reach the repeater after a couple of tries. Now looking back at the logs, I can see that we have a load of collisions happening because of ARS and GPS data. I'm starting to think that not having a data revert channel is screwing up our ability to talk in.

 

[sjaltavilla]

I would consider reducing the repeater transmit power to 25 watts or so and doing some testing.

We tried 30 watts for a day or two and it was utterly abysmal. I think we were totally below the beamwidth angle of the antenna. Just ordered a Telewave ANT-450D and also a better mount. Should be showing up in a couple weeks so I will advise what we find out with that.

 

[N1GTL]

If the system is not too active, turn two of the repeaters off and test. If everything works great, try the same with the other repeaters, one at a time. It may take a while if the interference is occasional. You may find one repeater is giving you the OOR. Leave that one off for a day or two and let the system operate with the other two. If it works fine, you found the repeater being interfered with. Your new antenna MAY help attenuate that. If not, a little testing with a couple HT's can help you determine what RSSI level you should program into the repeater.

Someone mentioned using a 0db gain antenna. This could also be contributing by receiving the distant signals. I have an amateur repeater with a 10db station master. It will not cover areas of the town it is in but it covers 20 miles away great. Not the ideal situation. I've been setting up TRBO systems for 13 years and this should not be too hard to troubleshoot for an experienced tech. This is really not a difficult or uncommon issue with TRBO systems.

 

[BMDaug]

Was this resolved?

I think they’re still waiting on the Telewave folded dipole, but I’m interested to see how they plan to mitigate collisions. I don’t know much about cap plus… is it possible to do a TDMA CC and put CC on slot one and data on slot two? If so, you wouldn’t need to dedicate an entire repeater to ARS/GPS, but TDMA CC is relatively new tech and I don’t know if that system supports it.

-B

 

[N1GTL]

I think they’re still waiting on the Telewave folded dipole, but I’m interested to see how they plan to mitigate collisions. I don’t know much about cap plus… is it possible to do a TDMA CC and put CC on slot one and data on slot two? If so, you wouldn’t need to dedicate an entire repeater to ARS/GPS, but TDMA CC is relatively new tech and I don’t know if that system supports it.

-B

I have done 3 or 4 systems with GPS. It really depends on the number of subscribers as to whether or not you need a dedicated data repeater for GPS.

 

[sjaltavilla]

I think they’re still waiting on the Telewave folded dipole, but I’m interested to see how they plan to mitigate collisions. I don’t know much about cap plus… is it possible to do a TDMA CC and put CC on slot one and data on slot two? If so, you wouldn’t need to dedicate an entire repeater to ARS/GPS, but TDMA CC is relatively new tech and I don’t know if that system supports it.

We are waiting on the Telewave antenna. I am likely going to switch one of our three repeaters to an enhanced GNSS data revert channel. This is a feature that requires two time slots so that the subscriber units can communicate with the repeater and vice versa to eliminate GPS packets being sent at the same time, therefore reducing collisions (at least that's what I understand). This will leave us with four timeslots for pure voice traffic, and based on watching our system in peak winter season, no more than three talkgroups are ever used simultaneously. I think this is the most viable solution, but I could very well be wrong.

 

[sjaltavilla]

I have done 3 or 4 systems with GPS. It really depends on the number of subscribers as to whether or not you need a dedicated data repeater for GPS.

We have about 100 GPS subscribers all sending packets once every 60 seconds. Now that I say it out loud, that is most certainly one of our problems.

 

[N1GTL]

You need a dedicated GPS repeater for that number.

 

[sjaltavilla]

You need a dedicated GPS repeater for that number.

That's the conclusion that I've come to. Wish our vendor thought of that before setting up our system- because now I have to go around and reprogram all 220 units before winter. Thank god for OTAP (which I had to set up of course, our vendor didn't think of that, either)

 

[wa8pyr]

That's the conclusion that I've come to. Wish our vendor thought of that before setting up our system- because now I have to go around and reprogram all 220 units before winter. Thank god for OTAP (which I had to set up of course, our vendor didn't think of that, either)

Bearcom? I'm not surprised. Some of my subscriber agencies used them as their radio shop so I had to deal with them from the system end; it was not a happy experience.

 

[sjaltavilla]

Bearcom? I'm not surprised. Some of my subscriber agencies used them as their radio shop so I had to deal with them from the system end; it was not a happy experience.

Yup - and we only went with them because they bought out our old vendor, Wells Communications.

 

[NVAGVUP]

The DB 633 is a good 3 db gain antenna. A unity gain antenna does provide a little better downtilt, but not enough to make a night/day difference.

Has the combiner been evaluated? What are the freqs? What is the predicted insertion loss per freq? (TX and RX) Is each repeater balanced for insertion loss? (So each channel is equal)

Also run a desense test on antenna system. Not with just one repeater active, but all repeaters. (Run same test into dummy load) (This is probably the most important test to help point you in the right direction!)

Yes you can use repeater from distance, but are other repeaters keyed during this anecdotal test? Plenty of variables. Don't use the "dart board approach". Methodically start eliminating items. (IE Above RF testing does NOT care about DMR, analog or other protocols. RF is RF.)