P25 Mobile Repeaters?

[JethrowJohnson]

Hi everybody and Happy Easter,
I know there are analog repeaters that use a separate channel to act as a bridge from the portable radio to the P25 talkgroup, but are there digital repeaters that are always on (or on when the engine's running) that act just like another tower so that it doesn't need a separate channel? Or would that not work for some reason?

 

[mrsvensven]

I think you may using the terms "analog" and "digital" when what you mean is "conventional" and "trunked".

A mobile repeater can use either an analog or P25 conventional channel to repeat on-scene communications back to a wider area channel, which can be either analog, digital, conventional, or trunked.

I think you're asking if it's possible to bring a full trunked radio site to a scene. Many big (statewide or large city) systems will have one or two deployable trunked radio sites attached to a communications vehicle or tower trailer. These are big, expensive, and take an hour or more to set up. It's not typically done for anything less than a really long duration incident, or something planned in advance.

 

[nd5y]

Maybe I don't understand the question. For something to "act just like another tower" would require backhaul connectivity to the network. That's not what vehicular repetaters (sometimes called extenders) do.

 

[JethrowJohnson]

Sorry, I meant can it just retransmit what it receives from the towers to the radio(s) and vice versa to boost the signal without anyone having to switch to the Repeater channel like my department does with their analog one? And I'm not asking for advice on getting any or anything like that, I'm just curious.

 

[Deziel0495]

We're looking into a DVRS for this exact reason. We want to improve in building coverage for our operations which take place on TMR. We'd still be required to switch to a conventional repeater but that would be connected back to our main Ops talkgroup so traffic from both could be heard back and forth.

At least that's what I'm being told will take place.

 

[JethrowJohnson]

Yeah, that's what my department has, except it's analog. I was wondering if there were any that looked and acted like a regular mobile radio antenna that also retransmits anything it receives on the same talkgroup.

 

[mmckenna]

Sorry, I meant can it just retransmit what it receives from the towers to the radio(s) and vice versa to boost the signal without anyone having to switch to the Repeater channel like my department does with their analog one? And I'm not asking for advice on getting any or anything like that, I'm just curious.

Pyramid's SVR-P250 P25 - Pyramid Communications

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Pyramid's SVR-P255 P25 EVRS - Pyramid Communications

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Pyramid's SVR-P252 Full Duplex P25 EVRS - Pyramid Communications

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[JethrowJohnson]

Okay. The way the EMS Captain explained it to me is that all of the trucks had MARCS repeaters on them, and if there were enough of them to line up from California to New York they would all still hear each other because the signal would go from the towers to a truck repeater to the next one in line, then the next one, etc. and the way I understood, I thought they were just on all the time and everyone could just stay on FD84GLEN or whichever channel they were using and the repeaters would just boost the signal to make sure everyone else had coverage. A few weeks ago, I found out that's not exactly how it works for us, we have analog repeaters and in order to use them you have to switch to REPEATER on the radio. I was trying to figure out if what I had originally thought was even possible. Now it sounds like it isn't.

 

[mmckenna]

Okay. The way the EMS Captain explained it to me is that all of the trucks had MARCS repeaters on them, and if there were enough of them to line up from California to New York they would all still hear each other because the signal would go from the towers to a truck repeater to the next one in line, then the next one, etc.

He's thinking of a mesh network.
That's not what mobile repeaters/extenders do.

If the radios have LTE capability (some Motorola and Harris radios do), then hopping on the LTE or WiFi networks would permit them to connect back into the trunked system from anywhere with a connection.

 

[JethrowJohnson]

He's thinking of a mesh network.
That's not what mobile repeaters/extenders do.

If the radios have LTE capability (some Motorola and Harris radios do), then hopping on the LTE or WiFi networks would permit them to connect back into the trunked system from anywhere with a connection.

Oh okay. Thank you. 👍 Is it possible to get radios to work that way though if the manufacturers would make them that way?

 

[mmckenna]

Is it possible to get radios to work that way though if the manufacturers would make them that way?

Yes, like I said, it's called mesh networking.
problem is, spectrum and licensing. Mesh networking is usually done in the GHz bands where there's lots of room to do that sort of stuff, and licensing is a bit easier.

 

[JethrowJohnson]

Yes, like I said, it's called mesh networking.
problem is, spectrum and licensing. Mesh networking is usually done in the GHz bands where there's lots of room to do that sort of stuff, and licensing is a bit easier.

Nice! Thanks again

 

[speedway_navigator]

Some agencies use a VHF simplex channel for fireground even if they are on a trunked system. In those cases the truck repeater is probably going to take your simplex audio and send it to the trunked repeaters by using a mobile radio on 700/800 MHz. It might be a conventional repeater to a 2nd VHF freq but I have not seen that.

This lets audio be recorded at dispatch and gives users who are not in simplex range access to your radio traffic. This helps if a 2nd alarm is called by giving the offsite folks a common operating picture before they show up.

Having a bunch of these truck repeaters in a long line won't work. If 2 are on site they need a way to sync so only one is operating,
kind of a "quite you numskulls I'm broadcasting" situation.

 

[BMDaug]

Having a bunch of these truck repeaters in a long line won't work. If 2 are on site they need a way to sync so only one is operating,
kind of a "quite you numskulls I'm broadcasting" situation.

This is exactly what the ESP feature in a Pyramid SVR250 does. It’s auto-designates a priority unit between transmissions.

When interfaces with a modern multiband mobile like a Harris XG100M, you can easily patch analog conventional or P25C portables and mobiles to a trunked or conventional system.

-B

 

[JethrowJohnson]

Some agencies use a VHF simplex channel for fireground even if they are on a trunked system. In those cases the truck repeater is probably going to take your simplex audio and send it to the trunked repeaters by using a mobile radio on 700/800 MHz. It might be a conventional repeater to a 2nd VHF freq but I have not seen that.

This lets audio be recorded at dispatch and gives users who are not in simplex range access to your radio traffic. This helps if a 2nd alarm is called by giving the offsite folks a common operating picture before they show up.

Having a bunch of these truck repeaters in a long line won't work. If 2 are on site they need a way to sync so only one is operating,
kind of a "quite you numskulls I'm broadcasting" situation.

Yeah, that's what our repeaters do. Almost everyone still has analog radios, so when they were using FD84GLEN on MARCS, everyone who couldn't use MARCS just used the REPEATER channel. It doesn't work like mesh networking like I had thought at first.

 

[speedway_navigator]

Back in my Bearcom days we got the contract for the San Jose grand prix. Along with the 2 way rental for the track officials we got the contract for the ticket seller's IP network to connect the ticket booths spread out across the track.
We had been using Motorola Canopy 2.4 GHz gear at other events but had recently been contacted by Firetide about using their mesh network.

We got our mesh nodes in place and immediately found out they would not talk to each other. We worked a couple of 16 hour shifts after figuring out the Firetide units had about .25 mile range where we had assumed it was close the Canopy's 2 miles. We finally patched the system together but found out the network would drop and the sync up again.

The downside was the ticket agency was using a VPN, when the network dropped out the VPN did not resync even thought the Firedtide IP network did.

After the race the techs in the Garland office had Firetide engineers come in and test units in the shop. They put one mesh node on the bench and the second on a cart. As soon as the cart got about 50' from the bench the carrier dropped for about 50 ms and then resynched. They repeated this a number of times.

I heard Firetide did a firmware update after seeing the problem.

As if that wasn't enough of a major fiasco we had RFI problems too. Since I had worked from 0700 on Thursday all night into Friday by boss told me to go back to the motel and get a nap about 1000 on Friday. By 1130 the local office manager was banging on my door telling me I needed to meet the city's RF engineer at our temp repeater site to prove our system was not causing problems to their PD channel.

I grabbed a quick shower and went to the roof of the Marriott where we had our repeaters. I turned off each one while he did testing, the RFI was still there, it was not any of our equipment.

 

[mmckenna]

We got our mesh nodes in place and immediately found out they would not talk to each other. We worked a couple of 16 hour shifts after figuring out the Firetide units had about .25 mile range where we had assumed it was close the Canopy's 2 miles. We finally patched the system together but found out the network would drop and the sync up again.

Off topic a bit, but it's been a long time since I did network stuff. Glad I don't mess with it too much anymore.
I've noticed that many networking companies, many large networking -C-ompanies, release products as their form of beta testing and let the end user discover all the problems. The "gee, I guess we need to send out an update" seems to be a stuck record. It's amazing the issues we used to discover that made it plainly obvious it was not a finished product.
Seems to be "get the money first, then will sort out the product issues".

 

[wa8pyr]

Yeah, that's what our repeaters do. Almost everyone still has analog radios, so when they were using FD84GLEN on MARCS, everyone who couldn't use MARCS just used the REPEATER channel. It doesn't work like mesh networking like I had thought at first.

The Pyramid SVR200 is very popular with MARCS users. Relatively inexpensive, simple to operate, and is available in UHF.

They're "smart" repeaters in that they will not allow more than one repeater on the same "repeat" frequency to operate at the same incident at any one time. The first truck on the scene turns on their repeater, and if another truck shows up and activates their repeater, the first repeater senses the new one and shuts off. This prevents "feedback loops" which cause radios to go into transmit and stay that way.

We've used them for years and they work just fine.