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Radio Equipment Installation Forum Forum for discussing how to install radio communications equipment in Mobile, Base, Command Post, EOC, etc configurations.

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Old 02-28-2011, 10:18 AM
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Default In vehicle repeaters or????

My dept responds to some remote areas. Our portable radios do not reach back to the dispatch center and we need to relay thru the fire apparatus. I wanted to put repeaters or a extender in the apparatus so they would act like a repeater for the portables, Does anyone have a setup like this? Our Comm dealer doesn't like the idea, said it's expensive.
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Old 02-28-2011, 9:36 PM
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Sounds like you need a new communications contractor.......

In my department our dispatch is on VHF 159 area. Communications at our hosptial and some remote areas are inpossible. We use the Pyramid UHF-VHF Cross Band Repeater. Works EXCELLENT.

Here is the basic concept.

The pyramid interfaces between your mobile radio and handheld radio HT1250 for example. When you are out of your vehicle and the mobile radio is receiving a transmission, pyramid will repeat the signal your handheld. (Mobile radio must be on) You can then transmit back to the pyramid and the transmission will be repeated back to the mobile by the mobile radio extending the range and making communications possible where you thought it was impossible. I've used this system for years, Never had a problem

Last edited by gallagher073; 02-28-2011 at 9:44 PM.. Reason: update
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Old 02-28-2011, 9:50 PM
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notice the above poster said UHF/VHF, you do not want a VHF to VHF repeater because when the mobile transmits, it would likely blank the RX of the other mobile. so you will need to buy UHF radios for either handhelds or as the link back to the base.
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Old 02-28-2011, 10:34 PM
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Quote:
Originally Posted by davidgcet View Post
notice the above poster said UHF/VHF, you do not want a VHF to VHF repeater because when the mobile transmits, it would likely blank the RX of the other mobile. so you will need to buy UHF radios for either handhelds or as the link back to the base.
That's not true. VHF to VHF mobile repeaters work fine, it's all about separation. A local FD had a VHF to VHF mobile repeater system with 8 MHz separation and it worked fine.

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Old 02-28-2011, 10:48 PM
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I'll have to agree with VHF to VHF..it's doable...we had 110 watt UHF Spectras transmitting at 458.xxx..our PacRT's were at 465.xxx...but we also used half of a mobile duplexer tuned to the 465.xxx frequency that actually allowed us to use the PacRT and the Mobile radio as a repeater...465.xxx in and 460.xxx out. The three cavities of the duplexer rejected the near channel energy very well...
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Old 02-28-2011, 11:14 PM
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you could do VHF to VHF but we didn't want the problems and already had UHF handheld radios. I would crossband.......just my 2 cents. Find a contractor local to you who is knowledgeable about the pyramid system, they are not all that expensive.
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Old 03-01-2011, 10:30 AM
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VHF to VHF may or may not work, it all depends on your freqs, antenna seperation, and power levels. i've had 45W VHF mobiles blank out portables from 30ft away even when the TX/RX freqs were 3-4 mhz apart. why invest in getting the new freq license, equipment, etc and then find out it won't. UHF to VHF would guarantee no issues of blanking.

UHF to UHF does not have as severe an issue of RX blanking as VHF does, this is why you don't see many folks complain about it in UHF bands. the standard 5mhz seperation is enough to prevent it.
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Old 03-01-2011, 11:15 AM
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While a duplexer would be help full not putting both antennas on the same plane helps too. I have put the mobile antenna on the roof and the repeater antenna on the rear shelf of cars, there is a lot of RF separation between the roof and rear shelf. Don't run your coax's next to one another either use both sides of the car. Another thing is don't use portable radios for your repeaters, they don't have a good enough front end, unless you use a crystal version that has a real tunable front end. I use 170 mhz frequencies for repeaters on 155.00 and 153.00 channels. They are available in both the business and PS allocations.
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Old 03-02-2011, 11:16 PM
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I do like the Pyramid products. If you are considering an in-band repeat system, consult with them. They have the knowledge and the accessory equipment to make it fly. If it won't, they will tell you why not. I have a customer using a VHF-VHF in band vehicle repeater from them and NO problems whatsoever.
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Old 03-09-2011, 8:45 PM
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Talking Mobile Extenders

Georgia State Patrol uses them - they work great!

GSP operates on VHF 154-Mhz range.

Original extenders were UHF / 453 hand held to car / 458 car to hand held

Those original UHF extenders are still in use but now many GSP have a 700-Mhz extender.

Alabama State Troopers use 800-Mhz extenders with their VHF hi-band radios.

Years ago traveling in California, I heard CHP extenders on 154.905 while CHP operates on VHF lo-band.

They seem to work just fine. Kinda neat to be near or following a GSP cruiser down the interstate. I just lock my scanner on the trooper's mobile extender and listen to his radio as it scans. Good to about a 1/2 mile.

I would imagine extenders are less expensive than repeaters and towers.
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Old 03-10-2011, 8:47 PM
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The provincial police up here use mobile repeaters too. 410'ish MHz handheld link and 141-143 MHz mobile to tower. The cost to implement a provincial repeater system that would provide handheld coverage was prohibitive.
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Old 03-11-2011, 3:08 AM
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Quote:
Originally Posted by mdulrich View Post
That's not true. VHF to VHF mobile repeaters work fine, it's all about separation. A local FD had a VHF to VHF mobile repeater system with 8 MHz separation and it worked fine.

Mike

I knew of a Public Safety agency that did VHF to VHF before they went UHF. Worked fine for them.

153 and 159 Mhz.

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Old 03-11-2011, 3:12 AM
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Quote:
Originally Posted by davidgcet View Post
VHF to VHF may or may not work, it all depends on your freqs, antenna seperation, and power levels. i've had 45W VHF mobiles blank out portables from 30ft away even when the TX/RX freqs were 3-4 mhz apart. why invest in getting the new freq license, equipment, etc and then find out it won't. UHF to VHF would guarantee no issues of blanking.

UHF to UHF does not have as severe an issue of RX blanking as VHF does, this is why you don't see many folks complain about it in UHF bands. the standard 5mhz seperation is enough to prevent it.
Antennas = County Sheriffs , State Police Agencys and Fire Depts..especially mobile command center all have their antennas in close proximity of each other when crossbanding and mobile repeating - SOOO
antenna space is no big deal. Low Band - VHF high - UHF or otherwise.

I dont belive they need a submit for a new freq license.

Any " Competant " radio service company can help them with this problem

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Old 03-11-2011, 5:13 AM
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There is an advantage to using the same band as your infrastructure frequencies. The need for only one set of portable radios.
Example: Say you purchase UHF portables for vehicular repeater use on your otherwise VHF network. Works fine when your vehicle is nearby and you are going through it. Now something happens and you are working well away from the vehicle (foot event, search in the woods) or the vehicle radio fails. You can't switch your portable to your VHF network and use it where VHF coverage does exist.

But the other posters are correct in that same band vehicular repeating does require enough seperate seperation and the proper cavities.
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Old 03-11-2011, 6:24 AM
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As was stated before consult a good dealer, or go with a manufacturers rep. They can point you to some one local who has do it before. Considering that the average cost of a mobile duplexer is around $100.00 and the repeater is $500.00, it's a lot less than putting up an actual repeater. If you have a field comm truck or chiefs car on scene equipped with one, you are all set. One thing is to make sure you have only one mobile repeater on at a time if they have the same input frequency or PL.
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Old 03-11-2011, 8:40 AM
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Quote:
Originally Posted by radioman2001 View Post
As was stated before consult a good dealer, or go with a manufacturers rep. They can point you to some one local who has do it before. Considering that the average cost of a mobile duplexer is around $100.00 and the repeater is $500.00, it's a lot less than putting up an actual repeater. If you have a field comm truck or chiefs car on scene equipped with one, you are all set. One thing is to make sure you have only one mobile repeater on at a time if they have the same input frequency or PL.
Look at the specs for the Pyramid, you can have two side by side on the same frq & same pl and one will only transmit.
From their website:
On-board logic control by the microprocessor ensures that only one vehicle will become active as the repeater, should several vehicles arrive at the same scene. The logic also handles cases where the priority vehicle leaves the scene (or fails), or another priority vehicle arrives from another scene.
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Old 03-14-2011, 11:30 AM
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For price and ease of installation going crossband is the way to go. That being said Pyramid and Vertex both make pre-selectors, filters, etc which will allow in-band repeating from your vehicle. If its done with success on a crown victoria you shouldnt have an issue on a pumper or other fire apparatus. 1 antenna on the trunk and the other on a fender bracket near the hood, works great as long as you have the proper filters etc

Its all in how much money you have. We just got a quote from a reputable dealer for around 2k for an in-band VHF-VHF system for our supervisor vehicle. This was using a Pyramid SVR-200v with filters and pre-selectors, and also included a new mobile radio with all the proper cables programming antennas etc

The question you have to ask yourself is what are the other agencies that you work with using in terms of frequency, is everyone in your area using VHF, are some on UHF or 800. The Missouri Highway Patrol is still using lowband and they use a VHF extender in their cars. Their troopers carry VHF-HI HT1250's. This works fine because most agencies in Missouri are still using VHF-HI. So if their mobile radio fails (or they get out of range) they can still talk to other agencies from their portable (they also have VHF-Hi mobiles installed as well but thats besides the point). They have the advantage of interop without the need for having multiple portable radios.

As far as anyone actually believing "the logic will handle multiple vehicles on scene" that just isn't true all the time. Frequently we get told by dispatch "multiple extenders keying up" or "we can't copy you there is interferance" because the logic in fact won't "always" handle multiple extenders being turn on in close proximity to one another. Does it happen all the time, no, but it does happen and it completely defeats your communication until the "logic" figures it out, or someone goes car to car turning off the extenders.

Either way you can do in-band or out of band and still have good success. Some agencies are also using the "stealth" or "phantom" antennas for their extender. They do provide a little more selectivity in the event you are using an in-band repeater.
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