Starting a Trunked System?

[fogster]

I've always wondered about the 'backend' of trunked radio systems. While I know how trunking works in theory, I don't know much about the actual equipment used. Suppose I were to be setting up a basic trunked radio system. (Obviously, with my complete lack of knowledge, I'm not going to. I'm just curious.)

Exactly what equipment do I need? Does Motorola make a standalone device that has all the control equipment and repeater equipment in one, or does it require stringing together various stuff? Does this equipment turn up at hamfests/eBay/etc., or is it really rare/pricy? How much would it cost to set up a basic trunked system? (And has anyone ever built, say, an open-source repeater controller that runs on a PC?)

And, in the same vein, if I wanted to put the controller on a commercial tower, what's a ballpark monthly price to house the equipment and the requisite antenna(s)? (Obviously, prices will vary a lot. But are we talking $25 a month or $25,000 a month?)

Once again, I'm not actually doing this. I'm just awfully curious about how it all works.

[RadShop]

Somewhere between here, and HamSexy, a user made some trunking controller software.. Don't remember who though. Try searching for it, you might find it.

[wazzzzzzzzup]

look into LTR trunking. the controllers are made by alot of companys, you can start small, having a 1 channel LTR system (kinda like the old community repeaters where everyone had a PL or DPL, but more modern), and as your needs expand you can link other LTR controllers together. EBAYS got alot of it.


i have thought of starting one myself the LTR way.
wazz

[escomm]

Exactly what equipment do I need? Does Motorola make a standalone device that has all the control equipment and repeater equipment in one, or does it require stringing together various stuff? Does this equipment turn up at hamfests/eBay/etc., or is it really rare/pricy? How much would it cost to set up a basic trunked system? (And has anyone ever built, say, an open-source repeater controller that runs on a PC?)

The key is the controller. I've seen trunked systems using GM300s for their repeaters (pretty sure they aren't type accepted for that but given the network owner is worth more than $100mil I don't think he's too worried about the FCC coming after him) and Trident controllers. Seems Motorola has been pushing Trident controllers for a long time, but there are other products out there that have licensing from Johnson for LTR. Other formats will probably be a bit more pricey, as LTR is the "entry-level" standard.

And, in the same vein, if I wanted to put the controller on a commercial tower, what's a ballpark monthly price to house the equipment and the requisite antenna(s)? (Obviously, prices will vary a lot. But are we talking $25 a month or $25,000 a month?)

Location, location, location. Also, demand for rackspace will play into the equation as well. If you have a great site without space being occupied, you will probably get a better rate. I would say that $100-200 a month is a decent starting point for an "average" site with "average" occupancy. This will, of course, vary depending on location

edit: I'm sure one of the posters with more experience in infrastructure design, deployment, and management can provide some more-relevant insights to this as well.

[spareparts]

And, in the same vein, if I wanted to put the controller on a commercial tower, what's a ballpark monthly price to house the equipment and the requisite antenna(s)?

Place I work for charges $1200 a month for a full rack. What that buys:
80' HAT, with mounts provided by landlord
Private security on site 24/7
Life Safety Grade power system with N+1 standby
Telco Feeds available POTS, T1, PRI and RTNA
Internet Feeds Available.

Likely a bit high for a start up, but there are commerical carriers willing to pony up that ammount of money.

[N9LLO]

[quote="spareparts"

[Place I work for charges $1200 a month for a full rack. What that buys:
80' HAT]

80' feet? Are you sure you dont mean 800' HAAT? Hell I can piss 80'
800' HAAT will cost you about $400 a month around here for commercial stuff, my Ham stuff is free at 500'

Chris

[spareparts]

80' feet? Are you sure you dont mean 800' HAAT? Hell I can piss 80'
800' HAAT will cost you about $400 a month around here for commercial stuff, my Ham stuff is free at 500'

Chris,
What you get is the headache of not having to deal with the EPA for your genset, bonded security, 100 amps 3 phase power, and 24 strands of Verizon fiber already in place, The only thing higher in town is the water tower & that is loaded to capacity.

Like I said, there are commercial tennants already there. If the pricing was out of line, I'm sure they would bail in a heartbeat. (BTW, I have nothing to do with setting the price)

Martin

[AEC]

LTR is by far, the easiest trunking system to get operational, cost-wise as well.

For the E.F. Johnson LTR systems, you will need a 'few' things, I'll list them below..

1. LTR-10 code ID validator (keypad entry on R. panel)

2. Logic unit for control.

3. Receiver

4. Exciter(transmitter)

5. Power amplifer

6. Power supply(ferro-resonant type) H E A V Y!

That's just the basics, this does NOT include the C.W identifier

The ID code validator in this is programmed for all users.]

Next you will need receiver multicouplers and transmit combiners should you wish t add more channels.

The list grows from here, but you get the idea...it's not for the casual user to buy into something like this, even as low budget as LTR can get, it will still cost $$$.


I hope this helped.

[fogster]

Ooh, now you've got me convinced I should start an LTR system.

I've now got some more questions, though. (Thanks so far for the great answers!) I'm reading http://www.weavercomm.com/ltr.html and it mentions that all systems have 'equal access' to trying to get a channel. Which makes me wonder: can LTR be used in public safety? It doesn't seem to support an emergency call feature, since units can't go out and 'request' a channel until one is available.

The 1-channel LTR system sounds like a novel way to start, actually.

escomm, are the type-acceptance rules for trunked gear different? I don't understand your comment about the GM300s not being accepted. I'd think I could just throw some Mastr2's in if I wanted.

Is the ID validator necessary, or just if I'm concerned about abuse?

Perhaps a stupid question, but does each repeater in a multi-repeater LTR system end up with its own antenna, or is there an easy way to share one antenna across multiple transceivers? (I've never done anything involving more than one radio.)

The software program for a controller sounds very nifty, although was unable to find it. Is such a program even legal, or is LTR still proprietary/patented?

Edit: Is it possible to have a computer 'listen' to the bus between repeaters and, say, generate graphs on which repeaters are active at a given time? I like graphs.

[escomm]

escomm, are the type-acceptance rules for trunked gear different? I don't understand your comment about the GM300s not being accepted. I'd think I could just throw some Mastr2's in if I wanted.

It's got more to do with the radio not being type accepted for continuous duty as could be the case with the GM300s. I could also be wrong on this entirely because /\/\ makes a repeater kit using GM300s.

Anyhow, the point I was trying to make with this is that you could use a radio as "old" and "simple" as a GM300 to get your system up and running. I imagine you could probably get the Mastr2's to work, but I'm not too familiar with GE gear so I couldn't tell you for sure.

Perhaps a stupid question, but does each repeater in a multi-repeater LTR system end up with its own antenna, or is there an easy way to share one antenna across multiple transceivers? (I've never done anything involving more than one radio.)

They will each need their own antenna and feed line unless you use a combiner. A combiner will let you hook up multiple feed lines to one antenna.

The software program for a controller sounds very nifty, although was unable to find it. Is such a program even legal, or is LTR still proprietary/patented?

I have to imagine that it is, as I know Motorola (and everyone else offering an LTR solution) paid royalties to EF Johnson for use of the format, and probably still pay royalties for their usage of it.

[AEC]

(quote)Is the ID validator necessary, or just if I'm concerned about abuse?(/quote)

A validator is used to ensure 'subscribers' of the system are the only users, but with LTR, many times one can key the system up durign a conversation, but it will dump you after the valid user stops transmitting.

You can always forego the ID validator, but then you run the risk of your system being wide open to any user that knows your channel assignments and IDs for your home system, such as LTR is 'logic' trunked, you have set channels to steer onto, and they hop from one to another, unlike Type II or IIi systems Circle-M sells.

When a specific channel is available, the LTR system automatically makes that channel available to users, and the first keyed, is the first priority on the heirarchy, all else being second and so on.

A four channel LTR system will have four receivers, four transmitters, and it's the job of the control logic to properly assign each channel in the queue according to a preset priority.

If channel 1 is in use, channel 2 is next in line for use and so on..

[bellersley]

Using LTR for a Public Safety system would be bad. There are no individual radio ids, no emergency, and the like. Passport addresses some of there issues, but it would still be a bad idea.

[escomm]

Most of the current /\/\ mobiles & portables will do both MDC1200 encoding and decoding in LTR modes. But you're right-- there's no QCII in LTR operations afaik (only conventional).

[fogster]

Oh, another question: if the LTR data is subaudible (150 Hz, IIRC), then I'd imagine that use of PL tones is impossible in an LTR setup? (Not sure why PL would be necessary anyway, given that the squelch is basically data-controlled, but, once again, I'm a curious fella )

They will each need their own antenna and feed line unless you use a combiner. A combiner will let you hook up multiple feed lines to one antenna.

Is this setup (single antenna with several radios and a combiner) the norm, or do most people just run multiple antennas?

Anyhow, the point I was trying to make with this is that you could use a radio as "old" and "simple" as a GM300 to get your system up and running. I imagine you could probably get the Mastr2's to work, but I'm not too familiar with GE gear

My reasoning for mentioning that Mastr 2s was the same, then--old and simple. (I'm not too familiar with GE gear either, it just seems to be a real common choice for repeater setups. This being Batlabs, there's probably not a lot of doubt as to what brand radio I'd be using. )

Using LTR for a Public Safety system would be bad. There are no individual radio ids, no emergency, and the like.

My understanding is that each unit has a number it transmits. Or is this just the talkgroup ID? I was under the impression that it was a unique ID, but my understanding is obviously not rock-solid. (My question about public safety usage was based on my understanding of other trunking methods, where using the emergency button gets priority access, possibly even commanding a currently-transmitting unit to dekey. But then again, a conventional setup would have the same limitation as LTR in this case....)

[bellersley]

An LTR talk group consists of 3 parts: Area, Home Repeater and Group. A typical group would look like 0-5-121. This means it's in area 0, home repeater 5 and group 121. All radios on this talk group are programmed the same, so there is no unique radio id.

[thebigphish]

Using LTR for a Public Safety system would be bad. There are no individual radio ids, no emergency, and the like. Passport addresses some of there issues, but it would still be a bad idea.

:cough:
some people around here are doing it
:cough:

[Bob W]

Using LTR for a Public Safety system would be bad. There are no individual radio ids, no emergency, and the like. Passport addresses some of there issues, but it would still be a bad idea.

:cough:
some people around here are doing it
:cough:

Around here too...

(I was gonna comment, but....)

http://www.radioreference.com/modules.p ... 868&nopt=1

[Bruce1807]

Why would anyone use LTR for public safety.
The big issue is that if your home channel dies you are history.
Where as Motorola trunking the home channel is the control channel of which there is usually four.
Any channel failure on a Mot system merely increases the risk of busies, not total lockout and that's a single site system.
We won't even talk about failsoft and redundant controllers.
And let's leave SmartZone alone for now.

[Bob W]

As I said, I was gonna comment, but.....

[RocketNJ]

Another disadvantage of LTR trunking for public safety is no call priority level on a talkgroup basis.

[Pj]

Using LTR for a Public Safety system would be bad. There are no individual radio ids, no emergency, and the like. Passport addresses some of there issues, but it would still be a bad idea.

:cough:
some people around here are doing it
:cough:

And I think you have the only system in the state that worked somewhat properly out of the box...

I am sure Bloomfield, East Windsor and Windsor all love the bill they paid for Passport that they are not able to use...