Portable Radio Coverage

[RADIOGUY2002]

Here are some tech specs in order to better answer this question and or suggestions.

I am in the process of putting up an antenna and repeater system up higher then what it is at currentily at now. The utimnate height will be at 100 ft, plus a 10 ft antenna with 6 to 7 db gain. The repeaters will tx out at 50 watts (TPO) the erp would be higher, clearily. The run will be down with lmr-400 or better. What can I expect for portables radio coverage at 5 watts out. I'm not to consider with mobiles as they tx at 50 watts and would be more then able to get in, in retrospec.

Any ideas on calculations?

 

[KC8RFE]

Just a guess but probably reliable coverage will be around 5-10 miles my guess but that's still dependent on other factors like terrain and buildings.... There are some programs out there that will give very very good detailed coverage patterns.

Another thing what frequencies. UHF will differ from VHF.

 

[Josh]

There are still a number of variables left to uncover.

50 watts TX, out of the radio will equate to significantly less out of a duplexer, unless you are using two antennas with vertical separation, which will alter your TX pattern. A duplexer will also decrease RX sensitivity as well by a few decibels, depends on the model and quality of the duplexer, of course.

Second, what band are we talking here? UHF or VHF? UHF will have significant loss using LMR400 and your saying "5 watt portables" implies VHF, but ya never know. If I were setting up a repeater, however, at 100' I would want to have heliax on that. LMR400 is prone to some issues in repeater use- I don't recall exactly how it panned out off-hand but info is out there, something about TX power being reflected and making RX audio sound staticy.

 

[SkipSanders]

If it's GMRS, welcome to the FCC's mixed up rules. Currently, there IS no legal way to have a repeater (fixed) station with an antenna more than 6.1 meters above ground or a tree or building on which it is mounted, and the power (ERP) can be no more than 5 watts. The rules allow for fixed base stations with up to 15 watts output, but, uh, gee, the FCC requires those to be specifically described on your license application... and the application no longer gives you any way to submit the info. Catch-22.

Mobiles can have up to 50 watts. Note that I'm not saying it makes SENSE, the FCC rules for GMRS are in a total mess and have been for years.

(f) Each base station and each control
station with an antenna height
greater than 6.1 meters (20 feet) must
be separately identified on Form 605.
See §§ 95.25 (d) and (e) and 95.51 of this
part.

 

[RADIOGUY2002]

Update

Thanks so far,

It's currentily located at hgt to tip at 46ft and it making it out on mobiles at 17 miles, somedays are better. But thats pretty consistent, now the portables current are beteen 5 to 7 miles typical and do exceed 9 miles. As if you have not firgured out already it's not gmrs and yes the 5 watt thing shown have been a dead give away that its vhf. But, yes I know not always the case. As their are selected few radios in uhf that are 5 watt. As I have one myself.

Yes, its a duplexer and it was installed at the factory by Icom direct. If that helps at all. Any additional info I will try to suppily if I can located in answer for it. Its also 12.5 khz step for the migration already.

 

[RADIOGUY2002]

No ideas? No additional updates?

 

[Josh]

double height will mean 3db additional gain/range, which won't be a whole lot, but noticeable. It may also allow the system to snare in those portable radios a bit better from height alone.

Won't know for sure until it's installed