any ideas?

Gocart878 · Post by **Gocart878** » Thu Jun 22, 2006 6:25 pm

Hello, i am in need of some help with what type of radios i need to purchase. my fire departments fire police squad uses ht750 radios in the 425mhz range, (yes we are close to Canadian Border). we are having problems communicating across the district which is approx. 4-8 sq miles. our units must be in range of approx half mile from the scene before they will be reached by a senior fire officer, whom is using either a ht1250 portable or mcs2000 mobile on the same freq. i need a higher watt portable something more than 4 watts(does motorola make anything like this) what about the mt-1000. as for the solution of our department rigs and protables, we utilize a repeater on the 424mhz split, however since were speaking of fire police, a repeater is totally out of the question. any input on what we can do whether it be antennas or better radios, please let me know. thankyou.

Rayjk110 · Post by **Rayjk110** » Thu Jun 22, 2006 7:00 pm

Well, using simplex UHF for about 4-8 miles is all you're typically going to get, and I thought about 3 was stretching it on average terrain. I believe some (HT600/MT1000) WILL take it up to 5, but that makes no more difference from 4 watts than taking a big step in one direction.

ALSO - Using the factory Whip antenna and not a stubby will help.

If they will mostly be used in vehicles, a Convert-A-Com will work great.

Al · Post by Al » Thu Jun 22, 2006 7:16 pm

4 watts transmit RF power output is the highest you're going to find in a portable whoever the manufacturer is because of the safety requirements imposed by the [FCC] U.S. Government. At 800 Mhz this maximum power output drops to 2 watts. The safety requirements were imposed because of the proximity of the portable's transmitting antenna to soft tissue in the human head.
Convertacoms would work if you could find ones made to take the HT Pro series radios....I don't believe they're made by M.
Would mobile radios with bluetooth mics work? You'd have to be within a couple hundred feet of your vehicle with the mobile radio in it and active to use bluetooth technology.

HLA · Post by **HLA** » Thu Jun 22, 2006 9:12 pm

what about an antennae adaptor and get the antennae outside of the vehicle. being inside a vehicle with a portable really restricts it's range.

Bruce1807 · Post by **Bruce1807** » Fri Jun 23, 2006 1:57 am

how about a pac/rt unit on the vehicles

fogster · Post by **fogster** » Fri Jun 23, 2006 7:25 am

Pick up the millions of 'government split' Sabers on eBay that no one else wants due to the split. You'll probably get 'em cheap.

The power won't be any better, but you could use a Convertacom with them.

I don't quite understand why you can't use a repeater. It sounds to me like a low-power repeater would cover the whole district nicely. If nothing else, maybe a vehicular repeater.

AEC · Post by **AEC** » Fri Jun 23, 2006 1:00 pm

Welcome to the 'border zone' with our Canadian buddies in the area known as 'LINE 'A''.

Simply, a repeater could be used and could also be set up so that your neighbors would never hear it either, even in operation.

I've used this 'trick' on LP repeaters in the past and it's always worked.

RX ant. 6-9 dB collinear

TX ant. (2) UHF 3-6 Elm. yagis, single cable, power splitter, angled in directions necessary to cover your area of responsibility(aor).

Due to line 'A' restrictions, and other compacts negotiated between the two nations within this region, local problems require local solutions, not international responses.

A GaAs FET preamp on the RX antenna, with good cabling/connectors for high signal/noise ratio, as well as a quality preamp with under 1dB NF.

The dual yagis on transmit, and vertaically separated by at least 10 feet, will keep the transmit signals out of the receiver, and create minimal desense for the receiver as well, PLUS, you get a cardioid patterned LP repeater that should not be heard on the other side of the 'great divide'.

If this is to be placed on a large structure, then I would angle both yagis to minimize polarization rotation, and refraction/reflection from large/multiple structres within the path of the signals.

I place the yagis in this pattern, and never had troubles with polarization,
attenuation or desense....\ /, and this angling also keeps the main lobe of the driven element away from the lobes of the collinear, and no coupling takes place to create a potential feedback loop within the repeater.

Also, you should keep the hang time removed, then the carrier will drop the moment you dekey and nobody would know.

Of course I didn't say 'don't ID' just don't ID the repeater, it's just a couple of HTs anyway with invisible users*cough*.

If you were looking for coverage, then I would worry about the ID, bu not for something this localized and as low powered as it will be on top of it all.

Really, when was the last time you heard any federal agency ID??
I don't get all worked up over 'the rules'..so what, I have a machine that has no IDer..big deal, the world still rotates, the sun still shines, but all I get is a small piece of anonymity because i refuse to ID a box of components.

Gocart878 · Post by **Gocart878** » Sat Jun 24, 2006 8:25 am

thanks for the input guys, as for now the convertacom sounds like the way to go. the cost of a repeater for a single freqeuency as well as reprogramming portables etc is just to much of a hassle for "fire police" the guys who direct traffic at an incident for those of you who dont know. anyways thanks again.

mike

AEC · Post by **AEC** » Sat Jun 24, 2006 10:32 am

Sounds like a minimalist way to overcome a problem, and good thing you can do so with the minimalist approach...that's great!

But all kidding aside, external antennas on any portable would be a vast improvement over use inside a vehicle with the radiating dunmmy loads all portables come with.