Improve coverage in remote buildings

[prcguy]

I have to revise this answer. While I did manage to pull off a conversation from a portable at one point at around 10 miles form the repeater, that was making the call from an open area with a clear line of sight (mostly).
Under typical circumstances, these radios are used 4 miles out, at the most. Mostly are within half a mile. The remote buildings where I encounter the issues described in the original post are around 3-4 miles out. I went to one of these problematic locations myself, with a co-worker to conduct some testing (actually to do some work, and we took a pair of radios). We had success about 80-90% of the time, but occassionally no audio came through. This was in a campus area with some 2-story buildings constructed with concrete walls. Whenever there was a problem, the caller was indoors and on the first floor. This doesn't mean all calls failed from indoors on the first floor.

Anyways, really the issue at hand is to be able to make the radios hit the repeater antenna better in order to achieve a (close to) 100% success rate.
Don't really want to install another repeater at this remote site, and rely on the Internet to connect to the main site. That's overkill. Bigger stubby antennas on the portables? Or the suggested Commscope antenna at the repeater site?

Someone asked earlier if the problematic buildings are in all direction or are more in a certain direction. They are more or less in a certain direction covered by no more than a 30degree field of view.

The best antenna recommended so far is a directional DB-411 which is rated 2dB more gain than your current antenna. That would provide about zero benefit and may loose performance in directions other than where its pointed. There is the big DB-420 or a Commander Technologies Super Stationmaster, about the largest highest gain UHF omni's available at 10dBd but they are only rated about 3dB more than your current antenna and 3dB will not fix your problem.

I'm sticking with a minimum of 10dB more omni antenna gain than you have now to address the problem and that doesn't exist. Anything less than that will be lots of $$ spent for zero or barely noticeable improvement and will not provide reliable comms in the areas that don't work now. There are better antennas for handhelds but improvements will be a dB or two at most and will not even begin to fix the problem even with an upgraded repeater antenna. You need to look elsewhere for a solution.

If you were local to me (So Cal) I could loan you a 10dBd omni to temporarily replace your existing antenna to show that will not fix the problem. Unfortunately the antenna is too big to ship for any reasonable rate.

 

[RFI-EMI-GUY]

OP. The first thing I would ask the vendor is: Have you measured repeater desense ( duplex sensitivity) of the repeater and what value signal degradation. If it is 2DB or worse , higher, I would be asking what kind of duplexer, cheap notch type flat pack, or bandpass reject? Why is it so high, duplexer tuning or site noise? Frankly you want zero dB desense if you can attain it.

Is this a Mototrbo system? I think there is a voted RX option so you can put a remote receiver, on same frequency and time slots, at a remote area and connect back via the IPSC. no licensing mod required.

 

[ramal121]

To expand, this is how desense affects a DMR repeater. The portable on key up does a request to the repeater and drops. The repeater in turn keys up and completes the handshake. The portable now goes into transmit for as long as the button is held down. But, if the repeater suffers from any desense it will lose the weak signal from the portable and shut off. DMR usually has a hang time of several seconds so this may be construed as the portable transmitting with no audio when actually the repeater has just gone deaf. This is very specific.

A basic health check of the repeater should be done first to put everyone's mind at ease before you start barfing up $$$$ to throw at this thing.

 

[phadobas]

The best antenna recommended so far is a directional DB-411 which is rated 2dB more gain than your current antenna. That would provide about zero benefit and may loose performance in directions other than where its pointed. There is the big DB-420 or a Commander Technologies Super Stationmaster, about the largest highest gain UHF omni's available at 10dBd but they are only rated about 3dB more than your current antenna and 3dB will not fix your problem.

I'm sticking with a minimum of 10dB more omni antenna gain than you have now to address the problem and that doesn't exist. Anything less than that will be lots of $$ spent for zero or barely noticeable improvement and will not provide reliable comms in the areas that don't work now. There are better antennas for handhelds but improvements will be a dB or two at most and will not even begin to fix the problem even with an upgraded repeater antenna. You need to look elsewhere for a solution.

If you were local to me (So Cal) I could loan you a 10dBd omni to temporarily replace your existing antenna to show that will not fix the problem. Unfortunately the antenna is too big to ship for any reasonable rate.

Thanks for this. When I originally encountered this problem, what I had in mind is some sort of in-building repeater or BDA. Not a "repeater" as in "DMR Repeater", but as in a "RF signal repeater". They use those in the cell phone business and we have such a system, but not sure if there is this kind of signal booster or repeater for DMR.

My vendor recommended the Comscope, so I came here for a second opinion on that. The vendor is hardware vendor, not a local shop I could just call out to the site. So far what I got from these answers here is
a) The system is probably as good as it gets.
b) Bigger stubby antennas on portables or different rooftop antenna will not make much difference.
c) Get the system checked with by a professional shop to ensure there is nothing wrong with RF

So unless there is some sort of signal booster system exists for DMR, I'll get with some local shop to check the system for optimum RF performance.

 

[kayn1n32008]

Thanks for this. When I originally encountered this problem, what I had in mind is some sort of in-building repeater or BDA. Not a "repeater" as in "DMR Repeater", but as in a "RF signal repeater". They use those in the cell phone business and we have such a system, but not sure if there is this kind of signal booster or repeater for DMR.

My vendor recommended the Comscope, so I came here for a second opinion on that. The vendor is hardware vendor, not a local shop I could just call out to the site. So far what I got from these answers here is
a) The system is probably as good as it gets.
b) Bigger stubby antennas on portables or different rooftop antenna will not make much difference.
c) Get the system checked with by a professional shop to ensure there is nothing wrong with RF

So unless there is some sort of signal booster system exists for DMR, I'll get with some local shop to check the system for optimum RF performance.

You pretty much have it right.



While there are BDA solutions for analogue and P25, I'm not sure if there are the same type of solutions for DMR.

Depending on the brand of repeater you are using, you may be able to network in remote receivers and have a voted system

 

[prcguy]

Thanks for this. When I originally encountered this problem, what I had in mind is some sort of in-building repeater or BDA. Not a "repeater" as in "DMR Repeater", but as in a "RF signal repeater". They use those in the cell phone business and we have such a system, but not sure if there is this kind of signal booster or repeater for DMR.

My vendor recommended the Comscope, so I came here for a second opinion on that. The vendor is hardware vendor, not a local shop I could just call out to the site. So far what I got from these answers here is
a) The system is probably as good as it gets.
b) Bigger stubby antennas on portables or different rooftop antenna will not make much difference.
c) Get the system checked with by a professional shop to ensure there is nothing wrong with RF

So unless there is some sort of signal booster system exists for DMR, I'll get with some local shop to check the system for optimum RF performance.

You have around 100w ERP from the repeater to the field radios. The handhelds in the field might be 2 or 3w ERP getting back to the repeater. A BDA would be designed to hear the repeater better at the remote buildings via handhelds but it will do nothing for the handhelds getting back into the repeater. Any repeater system is a bit lop sided with the repeater having much more potential range than the handhelds trying to get back to it. You need a new site or an extender repeater at the remote buildings.

A hired RF company will probably tell you to feel lucky with the range you have and get a better site or an extender repeater at the remote building area.

 

[RFI-EMI-GUY]

Thanks for this. When I originally encountered this problem, what I had in mind is some sort of in-building repeater or BDA. Not a "repeater" as in "DMR Repeater", but as in a "RF signal repeater". They use those in the cell phone business and we have such a system, but not sure if there is this kind of signal booster or repeater for DMR.

My vendor recommended the Comscope, so I came here for a second opinion on that. The vendor is hardware vendor, not a local shop I could just call out to the site. So far what I got from these answers here is
a) The system is probably as good as it gets.
b) Bigger stubby antennas on portables or different rooftop antenna will not make much difference.
c) Get the system checked with by a professional shop to ensure there is nothing wrong with RF

So unless there is some sort of signal booster system exists for DMR, I'll get with some local shop to check the system for optimum RF performance.

From your previous posts I am assuming you have a Hytera system. I have attached two systems planners which may or may not be current due to software licensing issues and legal problems in the US. That said, these may give you some ideas about the optional typologies for their systems.

A signal booster for UHF conventional would have to be a channelized (Class A) signal booster. You can boost signal to and from a portable radio within a building. The booster would have to be registered with FCC database. Because of filtering (<75 KHz) there could be potential problems in that there will be two-way delay of the TDMA signals which may have the effect of transmitting from the portable outside the desired TDMA time slot. Also that same delay will create a simulcast like interference zone on the immediate periphery inside and outside the structure where the booster is installed.

DMR coverage problems are best solved with the installation of additional base stations linked via IPSC and utilizing the roaming capabilities of the radio. You would have to coordinate and license an additional channel pair in most cases.

MotoTrbo (Motorola) alludes to receiver satellite voting which would be RX only, and not require additional coordination or licensing. I don't know if Hytera offers this, but they talk about simulcast which would employ voting.

http://leon880314.com/wp-content/uploads/2017/08/Manual-De-Usuario-Hytera-DMR-Convencional-Radio-Planificador-De-Sistemas.pdf

http://leon880314.com/wp-content/uploads/2017/08/Manual-De-Usuario-Hytera-DMR-Planificador-De-Sistemas.pdf

 

[freddaniel]

Adding a second voted receiver would be the best solution. All cellular base stations use two receivers and separate antennas. That allows very low-power [0.1 watt] handhelds like iPhones, with no external antenna, to work well indoors or outside at several miles range. Most DMR vendors offer a satellite receiver solution. The second receiver and antenna can offer up to 16 dB improvement on inbound handheld range.

 

[RFI-EMI-GUY]

Adding a second voted receiver would be the best solution. All cellular base stations use two receivers and separate antennas. That allows very low-power [0.1 watt] handhelds like iPhones, with no external antenna, to work well indoors or outside at several miles range. Most DMR vendors offer a satellite receiver solution. The second receiver and antenna can offer up to 16 dB improvement on inbound handheld range.

That is very true. Doing diversity RX even at the existing repeater site will aid in talkback.

 

[MUTNAV]

Is there an obvious down-tilt from where your antenna is to where the buildings are?

Thanks
Joel