Setting up Trunked Radio To VHF Simulcast

[brian86]

Ok first off I know that simulcasting would be simple if we used two mobile radios with accessory ports programmed for such however being a volunteer department we are trying to avoid spending $5,000 on a mobile P25 Phase II Radio.

We are a volunteer department that is in the process of obtaining a VHF transmit license so we can link our 700Mhz trunked radio system to a VHF Transmitter and simulcast transmissions from our trunked operations channel to our VHF operations frequency so volunteers in the county can monitor ops on their pagers. This is a one way repeat.

I want to use a PSR800 Scanner and an Orion VHF Front Mount Mobile to accomplish this task. The problem I am running in to is making the audio from the scanner activate the COS / COR on the Orion Front Mount VHF radio so the Orion radio will actually transmit the audio from the PSR800.

Is there a box or way to make the audio coming out of the PSR800 activate the COS / COR input on the Orion radio? Or do they make a box in the ham radio world that would do similar for say an HT to mobile?

Any suggestions or help would be great!

 

[ShawnInPaso]

While it would probably be a it of a mess in operation, you might be able to get by with one of these:
Micro Ham Radio Repeater Controller | eBay

As I understand your idea, you want the scanner audio to be re-transmitted on the Orion radio. Some of the issues you'll run into will involve the the Orion transmit signal completely ruining the scanner receiver if not properly configured (even then it can be iffy), and probably terrible audio quality if you get it to work okay. Of course you'll need to fabricate your connectors for each radio.

Then again, never hurts to try if the savings are good enough. I wonder if your county has a radio com shop; some of the folks there may be willing to help out and provide something a bit more robust.

 

[brian86]

Our County is 100% volunteer fire and ems, and the county does not help the volunteers in these regards at all. They would do anything for the sheriffs office tho.

 

[ShawnInPaso]

Well then lets hope they never need EMS or fire help....... :roll:

 

[krokus]

Why not use the accessory jacks on the two radios? You can use the base radio to provide keyline and received audio to be the VHF radio transmit audio. This setup should be more reliable and sound better.

I would avoid the PSR 800 for this use

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[n5ims]

Why not use the accessory jacks on the two radios? You can use the base radio to provide keyline and received audio to be the VHF radio transmit audio. This setup should be more reliable and sound better.

I would avoid the PSR 800 for this use

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Wouldn't the issue with that method be that the VHF listeners would hear everything but what was sent out using the base radio?

 

[phillydjdan]

If you are good with electronics and with a soldering iron, I bet you could pop open the case to that PSR800 and tap a signal voltage out of that LED on the top of the rig. Then you program it to light up upon transmission, and that could possibly give you the COR you need. I'm no expert, though, so maybe someone else can chime in and prove me wrong or elaborate on my theory.

 

[ofd8001]

What our fire department does is this: We have a system radio connected to a computer that does a Broadcastify feed for our fire channels. Our folks use their smart phones to monitor the channels. There is perhaps a 30 second lag time between transmission and smart phone reception.

There are a couple of other fire departments in our area doing the same thing.

Alternatively, if you have good reception and simlucast decode at the fire station, you can use a scanner in place of the system radio.

 

[brian86]

I don't have a base radio on the P25 Phase II System. We were trying to avoid spending $5k on a radio when the PSR800 we already have picks up the radio system flawlessly, The County P25 system is on our property.

I think what i need is a VOX activated COR. So when the scanner receives the signal it transmits the audio and somehow activates a relay to key the COR on the transmitting VHF Radio. Its late and i'm not thinking straight.

I will do some more research in the morning.

 

[krokus]

Wouldn't the issue with that method be that the VHF listeners would hear everything but what was sent out using the base radio?

True. The base radio might have the TX audio also routed to the accessory connector, which could also be fed to the VHF.

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[krokus]

I think what i need is a VOX activated COR. So when the scanner receives the signal it transmits the audio and somehow activates a relay to key the COR on the transmitting VHF Radio.

This can be done by tapping the audio, using a buffer amp, and rectifying the audio into a switching signal, to control the VHF transmit. (Using standard means of adjusting the level, as needed.)

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[jim202]

Have you tried talking to the radio shop that services the County radio system? Might be able to work out something with them. They might even have an old radio laying around that could be used.

I would also try sitting down with the County radio system manager. Never know what a one on one talk can produce for results. Having traveled all around the country working on public safety radio interoperability projects, I find most of these people are reasonable and for the most part very friendly. You might be surprised by what happens if you ask the right questions during one of these talks.

 

[brian86]

Have you tried talking to the radio shop that services the County radio system? Might be able to work out something with them. They might even have an old radio laying around that could be used.

I would also try sitting down with the County radio system manager. Never know what a one on one talk can produce for results. Having traveled all around the country working on public safety radio interoperability projects, I find most of these people are reasonable and for the most part very friendly. You might be surprised by what happens if you ask the right questions during one of these talks.

You need to come visit St. Mary's County.... talking to our public safety / I.T. / Communications / Emergency Management Director is difficult and it is always his way or no way. And before anyone asks he really is the Director of all these departments. Nice guy to talk to maybe, but accomplishing something useful is impossible.

 

[scover5555]

I see one problem with the setup your trying to do. You say you want to rebroadcast 700 MHz Ops over your VHF pager freq. Now what would happen if your rigged repeater was transmitting some Ops traffic while at the same time a page was going out to your department on the pager freq? I see trouble with this idea from a liability point of view.
If it was done properly at the paging control station so that when a page was being sent it would cut out the crossband repeat it would be fine but a second transmitter on the same freq, transmitting different traffic, is asking for trouble.

 

[SCPD]

I see one problem with the setup your trying to do. You say you want to rebroadcast 700 MHz Ops over your VHF pager freq. Now what would happen if your rigged repeater was transmitting some Ops traffic while at the same time a page was going out to your department on the pager freq? I see trouble with this idea from a liability point of view.
If it was done properly at the paging control station so that when a page was being sent it would cut out the crossband repeat it would be fine but a second transmitter on the same freq, transmitting different traffic, is asking for trouble.

If I'm correct there probably using 2 channel or so pagers and he's wanting to rebroadcast ops on the new channel there getting licenses for so one can be parked on primary page and scan the 2nd channel or channels the pager has or just be parked on ops if needed.

 

[DisasterGuy]

Brian- We do exactly what you describe on the Worcester and Somerset systems. I would not use a front mount Orion as your TX radio. You can do this fast, cheap or well but you have to pick 2/3.

The correct way to do this is as part of the system (the way Worcester and Somerset are done). The Somerset model wouldn't require any additional equipment from the county except for a license. The Worcester model is a bit more involved with an additional VHF MastrIII and combiner at each site.

If you attempt to do what you describe at a firehouse it will still be an expensive proposition even if you already have a tower. Figure the cost of a DB224-C (about $700) for your TX antenna, 7/8" heliax at around $4.50/ft), connectors/ground kit/polyphaser (another $250), tower contractor ($3000), and another $500-1500 for a continuous duty PA for the Orion.

As you can see, doing this right isn't cheap so either make a proposal for the Chiefs/Association to take to the county or prepare to spend quite a bit of money. Plan on using a proper donor radio like an XG-25m or XG-75m and a proper VHF station like the Mastr III, MSR2000 or even an old Quantar.


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[DisasterGuy]

Don't forget that your TX station needs to be capable of CW ID so even if you use something like an Orion you would still need to use a Repeater Controller to take care of this and COR where you wouldn't with an actual station for TX.


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[12dbsinad]

As stated in this post, doing it the "correct" way will require money to be spent. Using a scanner as the reciever (or scimping on any part) is something i'd only recommend to a hobbiest... not a Public Safety system.

With that said, what is the current setup at the station as far as other infanstructure such as a tower, antenna, feedline, grounding, etc? Do you get adequate coverage from the station on VHF for pager use? Also as stated, the VHF TX radio will essentially become a "repeater" as far as duty cycle because it sends out everything heard on 700, regardless if its only one way. Mobile rigs are not designed for high duty cycles at full power, and if it burns up it's money that is flushed down the toilet and could of been put towards the right set-up, which also means personel not hearing a call(s) if this does happen. I'd definently seek some sort of advise from a local radio shop or one that is contracted to work on the county system. I've seen cases where shops sometimes have things kicking around that may just fit the bill, and even hand-me-down equipment that would be just what the doctor ordered for reasonable costs.

 

[DisasterGuy]

Here is a bit of a budget to look at doing this right assuming you have a 100' tower with an appropriate building close or you can gain access to the tower you imply is available with an established shelter. This assumes that appropriate grounding is available at the site. The total comes to $13,131.70 and doesn't include the $3000-5000 you will pay the tower climber. Keep in mind that at 100' even this setup will have pretty limited range to a pager with a 250 watt ERP.

Quantity Part Unit Cost Total
1 XG-25m w/ P25 TDMA $2,325.00 $2,325.00
1 XG-25 Option Cable $90.00 $90.00
1 10A 12VDC PS $85.00 $85.00
75 LDF4-50 Coax $4.54 $340.50
1 Laird PC804N $32.00 $32.00
2 PolyPhaser IS-NEMP-C2 $103.00 $206.00
150 LDF5-50 Coax $8.36 $1,254.00
2 LDF4-50A Ground Kit $18.75 $37.50
3 LDF5-50 Ground Kit $17.87 $53.61
1 DB224-A $858.00 $858.00
3 1/2" N Male $23.50 $70.50
1 1/2" N Female $24.68 $24.68
1 7/8" N Male $36.02 $36.02
1 7/8" N Female $36.02 $36.02
1 FSJ1-50B N/TNC $62.87 $62.87
1 Mastr III VHF Station $7,570.00 $7,570.00
1 Rack Shelf $50.00 $50.00
$13,131.70

Run another way, this could be setup as a 4 site simulcast system for around $53,000 providing the same coverage as your paging system assuming dedicated Master III's with combiners into the current paging antennae. If done like Somerset (using each paging Mastr III to change channel to the rebroadcast frequency with paging having priority) it could be done for around $5,000.

 

[ofd8001]

Brian - I'm curious to know why you have discounted Broadcastify as a possible solution (noting that you do provide some feeds).

As a retired fire chief I can feel you pain from experience. When your dispatching service is provided by another entity, getting them to do things how you want and as quickly as you'd like them done can be frustrating. If things get real bad, everyone works for someone. Sometimes when the cause is just, correct and important, going over heads may be an option.