VHF In-Vehicle Repeater

[bosco836]

Hi Everyone,

I am involved with a small volunteer medical-first-response agency that primarily does event medical standby. We currently use Kenwood VHF Portables in simplex mode to communicate with each other while at an event; however, have occasionally encountered events so large that our portables simply don't have the required range.

Having said that, we are starting to explore other options, such as in vehicle repeaters, and have some questions.

1. Would an in-vehicle repeater be an appropriate solution?
2. What sort of coverage/range could we expect?
3. What should we expect, cost wise in terms of the hardware (approx.)?
4. Occasionally, we will cover large events with 2 or 3 units. Having said that, if each unit had a in-vehicle repeater, would this create any problems? If so, is there a cost-effective solution to remedy said problem?
5. Are there particular brands/model numbers we should consider?

I would greatly appreciate any input.

Best regards,

 

[KAA951]

My .02 worth...

Usually, in vehicle repeaters systems are used to extend the range of portable radios at a scene (e.g. "extenders") so that you can talk to dispatch from greater distances. My former fire department installed UHF extenders systems in our ambulances that allowed us to hear and talk to dispatch on the 100 watt VHF simplex radio in the unit. My other agency used to carry VHF extenders portable radios tied to the low-band High power system in our cars.

It sounds to me as though you are looking for a tactical repeater system. IMHO you should look into buying a single trailer mounted repeater / generator / 50-75 foot portable tower that you can set up at your large events. This would give you much better site coverage than a roof mounted antenna on your med unit and would do away with the interference issue if several vehicle mounted repeaters are activated on the same incident. In addition, you would not have to worry about your vehicle with your repeater in it driving off with a patient in the middle of your event!

 

[code3cowboy]

Having been doing event EMS for a decade now, and radio stuff for nearly as long, Ill tell you the best bet is a portable repeater.

Get a small repeater, put it in a pelican case, get an antenna suitable for tactical placement, and put it on a building or hill or in a tall tree with a pair of large batteries, shore power, or a small Honda generator. I normally use a honda 750, it lasts for at least 10 hours, is very quiet, and does not put out much interference.

 

[N4DES]

You also wouldn't want to deal with the size and reliability issues in using a VHF duplexer in a mobile environment. Crossband (U to V) is fine but in-band can be an issue.

 

[bosco836]

Having been doing event EMS for a decade now, and radio stuff for nearly as long, Ill tell you the best bet is a portable repeater.

Get a small repeater, put it in a pelican case, get an antenna suitable for tactical placement, and put it on a building or hill or in a tall tree with a pair of large batteries, shore power, or a small Honda generator. I normally use a honda 750, it lasts for at least 10 hours, is very quiet, and does not put out much interference.

I like the idea of a portable repeater; however, have two concerns/issues that I hope you (or someone else) might have a solution for.

1. Living in southern Ontario, there isn't much in the way of hills around here. Everything tends to be pretty flat. Having said that, mounting it in a tree is likely going to be our only option - However, how does one get the antenna to the top of said tree? Is there a telescoping tripod available somewhere that would work for this application that is relatively portable? How high would it need to be for semi-respectable coverage?

2. Assuming the repeater is mounted in a remote location away from our unit/personnel, how do we ensure that no one tampers with and/or steals it?


I seem to get the impression that the mobile repeater install may not be the best solution in regards to coverage - however, if that ends up being our only option, what type of coverage should we expect? Would the coverage be improved if we had a mobile repeater that had an external telescoping antenna that could be hooked up to give us better coverage? Do such things exist? If so, where would we find one?



Once again, thanks to everyone for all the input this far. It is very much appreciated.

Best,

 

[n5ims]

You could also build a portable repeater along with a tower trailer where you simply drive up, level the trailer, crank up the tower, and flip the switch. Various government agencies have these that range from simple temporary command posts to complex mobile trunking repeater sites. Cell phone companies also have them to use when their existing tower may be damaged or out of service for some reason. Some communications companies also have them available as part of a package service for large events as well.

One group selling commercial tower trailers is here TowerWorx Mobile Tower Communications Solutions but several ham groups have had success building their own.

Other options are many:
* find a radio or TV station that has an old mobile remote van with an integrated tower that they may sell cheap or even be willing to donate.
* Get an old "Cherry Picker" bucket truck from a utility company, or other agency.
* Rent some scaffolding, a boom lift, sizzer lift, or bucket truck. Working with the event staff may find that they have one rented for setup and tear down that may sit idle for the duration of the event that may be available for your use during the event.
* Think out of the box a bit. Are there light poles, speaker scaffolding, or other tall items available at the event site for you to place your repeater? Just keep safety (of the installer, guests, and event staff) as a priority when mounting.

 

[bosco836]

You could also build a portable repeater along with a tower trailer where you simply drive up, level the trailer, crank up the tower, and flip the switch. Various government agencies have these that range from simple temporary command posts to complex mobile trunking repeater sites. Cell phone companies also have them to use when their existing tower may be damaged or out of service for some reason. Some communications companies also have them available as part of a package service for large events as well.

One group selling commercial tower trailers is here TowerWorx Mobile Tower Communications Solutions but several ham groups have had success building their own.

Other options are many:
* find a radio or TV station that has an old mobile remote van with an integrated tower that they may sell cheap or even be willing to donate.
* Get an old "Cherry Picker" bucket truck from a utility company, or other agency.
* Rent some scaffolding, a boom lift, sizzer lift, or bucket truck. Working with the event staff may find that they have one rented for setup and tear down that may sit idle for the duration of the event that may be available for your use during the event.
* Think out of the box a bit. Are there light poles, speaker scaffolding, or other tall items available at the event site for you to place your repeater? Just keep safety (of the installer, guests, and event staff) as a priority when mounting.

We were thinking of something like this, recommended to us by someone on another forum. I'd be curious to see what everyone's feedback is.

VHF (136–174 MHz) Simple Repeater System ICOM F-121s on eBay.ca (item 120609292047 end time 14-Sep-10 01:55:00 EDT)

In addition that unit there, the seller has also offered us a Duplexer, a 3 Ft. Tripod, and a 17 Ft. Antenna.

According to his claims, we should see coverage of about 15-20 miles, in addition to having the capability to use the repeater as a base station.

(Note, the duplexer, tripod, and antenna will cost us approx. 275 dollars extra).

Does this sound like a reasonable setup?

 

[code3cowboy]

I like the idea of a portable repeater; however, have two concerns/issues that I hope you (or someone else) might have a solution for.

1. Living in southern Ontario, there isn't much in the way of hills around here. Everything tends to be pretty flat. Having said that, mounting it in a tree is likely going to be our only option - However, how does one get the antenna to the top of said tree? Is there a telescoping tripod available somewhere that would work for this application that is relatively portable? How high would it need to be for semi-respectable coverage?

2. Assuming the repeater is mounted in a remote location away from our unit/personnel, how do we ensure that no one tampers with and/or steals it?

Best,

You climb the tree and put the antenna into it. Or you put it on the roof of a building. You can also get a 20' type of tower. Or you can throw a rope over a branch or streetlight or some fiber mounted on utility poles and haul an antenna up.

You have a self contained repeater with everything integrated into your case. Then you chain the generator to the case and around some sort of solid object, like a tree radio tower fence or streetlight.

You will need a compact duplexer. Celwave makes one (I have one on a GR1225 that works really well)
Talley Inc. | Online Store - Search Results

I normally have a mag mount quarter wave with a metal plate for the ground plane, a two bay folded dipole and a decent ground plane antenna. Depending on where I set up and the area, I make a tenner choice.

What kinds of environments do you operate in normally?

 

[bosco836]

You climb the tree and put the antenna into it. Or you put it on the roof of a building. You can also get a 20' type of tower. Or you can throw a rope over a branch or streetlight or some fiber mounted on utility poles and haul an antenna up.

You have a self contained repeater with everything integrated into your case. Then you chain the generator to the case and around some sort of solid object, like a tree radio tower fence or streetlight.

You will need a compact duplexer. Celwave makes one (I have one on a GR1225 that works really well)
Talley Inc. | Online Store - Search Results

I normally have a mag mount quarter wave with a metal plate for the ground plane, a two bay folded dipole and a decent ground plane antenna. Depending on where I set up and the area, I make a tenner choice.

What kinds of environments do you operate in normally?

Thanks for the reply. I think we'd like to avoid our members climbing trees....we don't want to become patients ourselves.

I'm hoping the tripod/telescoping antenna option (as I mentioned in my previous post --> see above) will work well for our needs.

Having said that, we do stand-by medical coverage at a variety of events, ranging from hockey/football games, to carnivals, to events like the Amazing Race (where contestants travel between 3-4 towns trying to find clues). We are also a part of our county's emergency disaster response team.

A good portion of our events can be covered on our current VHF simplex system; however, we're starting to find that we're getting more and more "bigger" type events (i.e. Amazing race or large festival on our cities waterfront (~5-10 miles between different points) where the simplex system with 5W portables doesn't cut it.

Thanks again. I look forward to more feedback.

 

[RADIOUSER5]

Before buying anything, be sure you can get a license for the input frequency you plan to use; also, your repeater output frequency must be licensed for the antenna height and power that you plan to use. Also your portables will have to be programmed to use the repeater input and output. And you will want "talk-around" channels to bypass the repeater when it is not being used.

Duplexers must be tuned for the frequencies you plan to use. VHF is much more challenging that UHF or 800.

 

[bosco836]

Before buying anything, be sure you can get a license for the input frequency you plan to use; also, your repeater output frequency must be licensed for the antenna height and power that you plan to use. Also your portables will have to be programmed to use the repeater input and output. And you will want "talk-around" channels to bypass the repeater when it is not being used.

Duplexers must be tuned for the frequencies you plan to use. VHF is much more challenging that UHF or 800.

Thanks. I am currently in the process of figuring out what is required by industry Canada to obtain a separate license. As mentioned above, we already have a simplex VHF radio system (licensed by IC) and have the ability to program our current portables.

Out of curiosity, what exactly makes VHF more challenging than UHF or 800?

 

[RADIOUSER5]

The size and tuning of the cans or duplexers - standard separation for amateur radio 146 MHz repeaters is 600 KHz; standard UHF is 5 MHz and 800-900 is 30-45 MHz. The greater the separation, the easier it is to design a filter that will keep the transmit from overloading the receive or desensing.

 

[bosco836]

In communicating with one of our potential repeater dealers, he advised that we should be okay with so long as we had a 3.5mHz minimum between our Tx and Rx and that he would ensure our duplexer is capable of fulfilling our requirements.

I still have not had any formal communication with IC (hopefully tomorrow) short of browsing their website, but if we can get a frequency in the the low 150 range for Rx and something in the low 160 range for Tx, presumably we should be problem free?

Would it make sense (or even help) to use different PL tones on transmit / receive frequencies?

 

[code3cowboy]

The size and tuning of the cans or duplexers - standard separation for amateur radio 146 MHz repeaters is 600 KHz; standard UHF is 5 MHz and 800-900 is 30-45 MHz. The greater the separation, the easier it is to design a filter that will keep the transmit from overloading the receive or desensing.

Hams use 600Khz on VHF, the rest of us like to space things out. I try to go with 5-6Mhz spacing minimum. Several agencies go with 8 or 9 Mhz splits. The more the merrier.

In communicating with one of our potential repeater dealers, he advised that we should be okay with so long as we had a 3.5mHz minimum between our Tx and Rx and that he would ensure our duplexer is capable of fulfilling our requirements.

I still have not had any formal communication with IC (hopefully tomorrow) short of browsing their website, but if we can get a frequency in the the low 150 range for Rx and something in the low 160 range for Tx, presumably we should be problem free?

Would it make sense (or even help) to use different PL tones on transmit / receive frequencies?

Not being sure where you are frequency wise, I would advocate looking 4-8mhz above and below your frequency. The more separation the merrier, but you will still want a duplexer.

Using different PL tones really is a matter of the guy setting everything up. On one hand you are able to simplify and have one tone for everything, but you can run into "technical" issues when doing that. On the other you can run different input and output tones and have some other "technical" pluses and minuses.

Since you are affiliated with the county already, you should talk to the county comm people and see what they already have available. Often there is something set up for a county OES or county public health agency that you can use "after hours" or that sits there and you can have free reign of. Nothing like exercising a cache and having a repeater system that already covers the county.

 

[bosco836]

Hams use 600Khz on VHF, the rest of us like to space things out. I try to go with 5-6Mhz spacing minimum. Several agencies go with 8 or 9 Mhz splits. The more the merrier.



Not being sure where you are frequency wise, I would advocate looking 4-8mhz above and below your frequency. The more separation the merrier, but you will still want a duplexer.

Using different PL tones really is a matter of the guy setting everything up. On one hand you are able to simplify and have one tone for everything, but you can run into "technical" issues when doing that. On the other you can run different input and output tones and have some other "technical" pluses and minuses.

Since you are affiliated with the county already, you should talk to the county comm people and see what they already have available. Often there is something set up for a county OES or county public health agency that you can use "after hours" or that sits there and you can have free reign of. Nothing like exercising a cache and having a repeater system that already covers the county.

As much as I would love to get on the county radio system, the cost of upgrading all of our radios is simply cost-prohibitive (as our current radios are VHF Conventional only, where EMS is on a VHF trunked, city fire is on 800mhz P25 along with PD, and county fire on a UHF LTR System.)

The other issue becomes that we sometimes assist with coverage of events outside of our county; thus, facilitating the need for a mobile/portable setup. However, I appreciate the suggestion.....if only we had the money for new XTS-5000 portables.....

 

[kcleave]

Vehicular Repeater

The answer to all your questions is a vehicular repeater.I am with a Volunteer fire Dept in northern Alberta,the research I have done so far have found Midland,Maxon,Relm,Vertex and pyramid the range from 2 watts up to 100 watts.Prices range from about $1600 up.Our EMS uses a system like the midland with a satellite phone system the cost of this system is about $20000 per unit.The one problem that you can have is, if two equipped units are at the same scene,some systems have software to correct this problem it's all in the specs.It's an inexpensive way to correct a big problem the repeaters are always with the units responding.Hope this helps answer most of the questions.

 

[ElroyJetson]

I would highly recommend an Icom FR-5000 repeater module with a duplexer for use as a vehicular repeater. It's very compact, about 9 inches square and 2.5 inches tall, plus the duplexer, and runs
on 12 volts. Power output is up to 50 watts and can be tuned to any desired lower power level.
I can easily provide a packaged repeater that's ready to connect to an antenna and power for under 1000 dollars.


Elroy

 

[gunz2000]

hello, bosco836 could you email me at aelcich@bell.net there is a few things i would like to ask you about the group you belong to, i also belong to a volunteer group in southern ontario
thanks
Andrew