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Improve coverage

Posted: Thu Nov 08, 2018 10:24 pm
by phadobas
I'm about to deploy over a 100 Mototrbo radios, with a repeater. We have a campus with many buildings across many city blocks, including a warehouse 4 miles out. My vendor gave me a test repeater and 2 radios for site-survey. I got 100% coverage in most buildings on the campus and also out at the warehouse, but there is a small area with 2 buildings that are in a lower area then the rest, and coverage for those 2 buildings is spotty at best with many dead spots.
My vendor suggested installing a "receive-only" repeater, assuming that a portable radio would still be able to hit the repeater on its own from these deadspots. I restested that theory and found that I wasn't able to key the repeater from those spots.
After this, I brought up maybe using radiating coax through these areas, which the vendor said might be ok.
What other - fairly simple - solutions exist to cover such areas?
The roof of the trouble-building will get very good signal. Can't we just network a repeater in the trouble-building to the 1st repeater? Or they would interfere with each other being so close? They are about half a mile apart, but as I said the building is in a low laying area, so most of it is a dead-spot. But the roof is good.
I'm new to the dmr subject (i've been in wired voice industry for 20 years, but never dealt with radios) so I don't know how multiple repeaters would work together to extend coverage. I have computer network between the 2 buildings with gigabit speed so we could definitely network repeaters if that would solve the issue.

What could we do here?

Re: Improve coverage

Posted: Fri Nov 09, 2018 12:52 am
by RadioRookie
1/2 a mile , even indoors for handhelds, should be more than close enough to hit a repeater. What kind of antenna is on the repeater? Is it located inside or outside? What band are the radios. You have alot of networking options with DMR.

Re: Improve coverage

Posted: Fri Nov 09, 2018 12:55 am
by RadioRookie
I would also be curious to know the wattage on the handhelds.

Re: Improve coverage

Posted: Fri Nov 09, 2018 4:00 am
by phadobas
The antenna for the repeater is outdoors, and is a long white stick antenna. About 5ft long. I hope this is a scientific-enough description :) This antenna is installed on the roof of a 10-story tall building, which is pretty good.

The test radio is UHF and is Motorola XPR7550 so I believe it outputs 4W.

The problem I think is that between the repeater's antenna and the radio is 3 concrete industrial buildings, the trouble building is also at the bottom of a small hill (if you can call anything a "hill" in Florida), and I was in the basement of that building when I couldn't hit the repeater.

Re: Improve coverage

Posted: Fri Nov 09, 2018 3:17 pm
by Firebuff880
So I see two things you could do --

First, your could use a MOTOTRBO SLR-1000 as a second / additional site and put it in the offending location with the system set up in Multi-site / wide area mode. MOTOTRBO also supports Satellite receive only repeaters but this can be costly depending on how many repeaters are in the prim site as you need one for one.

Your other option is to just place a Bi-Directional Amplifier system (BDA) in the offending location - with a directional antenna feed pointed at the prime site.

Re: Improve coverage

Posted: Fri Nov 09, 2018 5:24 pm
by Notarola
I was going to suggest a BDA but a potential cheaper faster fix may be to change from an Omni to a 3 element yagi. Point the yagi at the bad coverage area. a 3 element is not directional enough to radically cut down the coverage on the main campus but is directional enough to bring up the weaker coverage in the 2 buildings.

Re: Improve coverage

Posted: Fri Nov 09, 2018 5:59 pm
by phadobas
Thanks for these suggestions. Both the SLR1000 and the 3-directional yagi sounds good. We will do some field tests with the vendor and determine the best route.

Re: Improve coverage

Posted: Sat Nov 10, 2018 6:06 pm
by Notarola
let us know what you find.

I have also used a passive indoor outdoor antenna system to improve marginal coverage in a building like a warehouse/garage. Usually a single floor. The passive antenna is simply a 6-8 element yagi outside the building pointed at the system and an omni or 3 element inside connected with a good SHORT cable. If that doesnt work then your all set for a BDA by just coupling in an amp and filters.

Re: Improve coverage

Posted: Mon Nov 12, 2018 6:14 pm
by phadobas
I've done BDA for cell phones before so I understand the basic concept: 1 roof antenna where signal is good, connected to an amplifier in some closet, from where, you run coax and install some dome antenna(s) where needed. In fact, this is already in place in that specific building for cell phones. So with that in mind, what is the make and model of an amplifier I would use to tie into this existing system?

Re: Improve coverage

Posted: Tue Nov 13, 2018 4:56 pm
by Notarola
Unless its a 800 system you cant piggy back on it. Even then the amp modules are probably band passed.

Again you have the concept right. The outside antenna is split into a RX and TX path. On UHF this would be EG 451. RX and 456 Tx for the portables. The protables Tx on 456 this is picked up by an internal antenna(s) fed through a band passed amplifier and coupled to the outside antenna. The outside antenna picks up the 451 signal puts it through a second band passed antenna and couples that to the internal antenna(s) for the portables to RX.