Unpowered reradiators with p25?

[Mycroft]

I've gotten conflicting information with regards to unpowered reradiators and p25 radios. Some people tell me that it won't work because of unspecified reasons, other people tell me it will work simply because it is literally reradiating a signal from one zone to another.

I only have a basic understanding of radio theory, and google isn't giving me much on this specific subject.

My problem statement is as follows:

I check in on a net every week and when I do so, I am generally in a metal building that stops radio signals cold. I started researching unpowered repeaters/reradiators and they appear to be a solution to this problem I am running into as I can set one of these up temporarily (and later permanently if the proof of concept works.) But sometime in the next year or so we are likely to move to p25+encryption.

Is there any reason p25/p25+encryption would fail in this circumstance I outlined? I'd like to know in advance before I spend any time/money on trying to make radio check-ins and training easier.

[Volunteer]

Mycroft,

As long as you have two resonant antennas for the band(s) used by your radio in the steel structure and use correctly built cabling you can achieve exactly what you're asking about. Here's a simple one line drawing of what I'm describing:

antenna-on-roof=[<==coax==>]=antenna-inside-building

I have done similar with broadcast television translators and could bend signals around terrain to add coverage to remote canyons. You need to be sure cabling length is minimized and match all impedances to reduce losses. Scala has some of the best antennas for your application. Your transmission modes and frequencies used don't matter much in your scenario as I understand it. I Use a product called "Stuf" to protect the coaxial connections against water incursion: http://www.atvresearch.com/stuf.aspx Quite a bargain at $5.00 / tube

Happy to add more if you need it.

V/R, Volunteer

I've gotten conflicting information with regards to unpowered reradiators and p25 radios. Some people tell me that it won't work because of unspecified reasons, other people tell me it will work simply because it is literally reradiating a signal from one zone to another.

I only have a basic understanding of radio theory, and google isn't giving me much on this specific subject.

My problem statement is as follows:

I check in on a net every week and when I do so, I am generally in a metal building that stops radio signals cold. I started researching unpowered repeaters/reradiators and they appear to be a solution to this problem I am running into as I can set one of these up temporarily (and later permanently if the proof of concept works.) But sometime in the next year or so we are likely to move to p25+encryption.

Is there any reason p25/p25+encryption would fail in this circumstance I outlined? I'd like to know in advance before I spend any time/money on trying to make radio check-ins and training easier.

[Hand]

I asked some ham buddies of mine about this yesterday, it brought quite a bit of interesting discussion. 2 technologies were mentioned - passive repeaters, bi-directional amplifiers.

Here is a link to passive repeater page: http://www.tntdiscount.info/passive_rep.php

And one for bi-directional amplifiers: http://www.wpsantennas.com/amplifier-repeater-bda.aspx

[Mycroft]

After the new year begins I'm going to give the unpowered solution a shot. I think I only need to send in a letter explaining what I'm doing to make that happen, whereas a powered solution will require a significant paperwork outlay, approval process, politics, and a fundraiser.

[Volunteer]

BiLinear amplifiers covering several bands work best in my experience with cellphone coverage in rural areas. I'm pretty sure the original question was for a single-band application, conventional radio scenario. Having said that, I also know BILinear amps can introduce unnecessary complexity and unless that's offset by a better signal to noise ratio your just making a bad problem worse. A spectrum analyzer would answer your questions as part of a site survey to make better informed decisions for your application.
Its also important to consider for the radio system you desire to communicate with that their engineering team is aware of what you intend to do. If you're not careful you run the risk of swamping the front-end of the distant radio system which negatively impacts anyone else attempting use the resource at that same point in time. The passive repeater link points in essence to what I originally mentioned. :o)

I asked some ham buddies of mine about this yesterday, it brought quite a bit of interesting discussion. 2 technologies were mentioned - passive repeaters, bi-directional amplifiers.

Here is a link to passive repeater page: http://www.tntdiscount.info/passive_rep.php

And one for bi-directional amplifiers: http://www.wpsantennas.com/amplifier-repeater-bda.aspx