CDM repeater researching

[nhfdcadet]

So heres the idea....portable deployable repeater that is either UHF or VHF
what i would like to do is take a pelican (or similar) box, and throw a VHF CDM on one side, and a VHF and a UHF CDM on the other side. 1250/1550 doesnt matter, just cdm of some sort.
What i am looking for is some way to interface the radios so that it can either be a v/u cross band, or a regular portable deployable VHF repeater.
idea being when we do either outbound mutual aid, or get mutual aid from somebody uhf, we can deploy this portable cross band repeater, OR we can use our own VHF repeater frequencies in a portable setting if ever needed, just a couple examples of the application for this project

so i talked to the ebay guy that makes those fancy CDM repeater interfaces, i dont know if i was explaining it right or whatever, he didnt want to get involved. nothing against him, I have one of his boxes between two mobiles in my truck, works great.

my idea for the concept was instead of having the switch mounted on the box like he makes, do it with a three position rocker switch, and just have one side be to activate the VHF radio, the other side to activate the UHF radio, or the middle position be off.

I have seen the boxes like NCS C250 or the Trident iOpt Comm-tac, havent been able to find any for sale online, and its a little out of my budget to buy new, which is what attracted me to the ebay ones, since i have seen them work in the past.

So i guess the final question is, (if you are able to understand the idea i am picturing in my head and this isnt all just crazy talk)
Is this something the can be done? and if so, does anybody have wire diagrams or anything that could help me out either try to make this myself, or have someone make it for me.

Please dont lecture me about licensing or anything, I am well aware it will be needed if this idea becomes reality, but right now this is in the very baby stages

 

[nhfdcadet]

If this helps to explain my concept at all.........

 

[mmckenna]

So i guess the final question is, (if you are able to understand the idea i am picturing in my head and this isnt all just crazy talk)
Is this something the can be done? and if so, does anybody have wire diagrams or anything that could help me out either try to make this myself, or have someone make it for me.

Not hard to do. Several repeater interfaces out there that will do what you want.
I'm not sure which e-bay guy you are referring to, though.
You want a repeater controller with a linking port. www.batlabs.com will give you a lot of info. So will repeater-builder.com

A couple of things to be aware of...
You —really— want to make sure you have time-out-timers set on the radios, or in the repeater controller. Be wary of the simple/cheap/no option repeater controllers. It's easy enough to wire two radios together, but you really want some stuff in the middle to manage things, like killing the repeater after a set amount of time.

You need good duplexers on the VHF side. Mobile duplexers will work, but they are not ideal. Good duplexers are large, and may not fit into a small case.
You also want lots of isolation between the VHF and UHF antennas. You don't want the UHF side overloading the VHF side, or vise/versa.

You want good coaxial cable. No RG-58. You also want good antennas on the end of that good coax. If the runs are short, 1/4" heliax superflex can work well. FSJ1-50A.
You also don't want to connect that directly to the back of the radio. Use a short jumper cable to get to the duplexer, then a jumper from the antenna port on the duplexer to the radio case. Put a chassis mount antenna jack on the outside of the Pelican case.

Heat can be an issue if it gets used a lot, so leaving the case open is important. If you want something you can seal up, you need a bigger box and preferably a fan.

 

[nhfdcadet]

Not hard to do. Several repeater interfaces out there that will do what you want.
I'm not sure which e-bay guy you are referring to, though.
You want a repeater controller with a linking port. www.batlabs.com will give you a lot of info. So will repeater-builder.com

A couple of things to be aware of...
You —really— want to make sure you have time-out-timers set on the radios, or in the repeater controller. Be wary of the simple/cheap/no option repeater controllers. It's easy enough to wire two radios together, but you really want some stuff in the middle to manage things, like killing the repeater after a set amount of time.

You need good duplexers on the VHF side. Mobile duplexers will work, but they are not ideal. Good duplexers are large, and may not fit into a small case.
You also want lots of isolation between the VHF and UHF antennas. You don't want the UHF side overloading the VHF side, or vise/versa.

You want good coaxial cable. No RG-58. You also want good antennas on the end of that good coax. If the runs are short, 1/4" heliax superflex can work well. FSJ1-50A.
You also don't want to connect that directly to the back of the radio. Use a short jumper cable to get to the duplexer, then a jumper from the antenna port on the duplexer to the radio case. Put a chassis mount antenna jack on the outside of the Pelican case.

Heat can be an issue if it gets used a lot, so leaving the case open is important. If you want something you can seal up, you need a bigger box and preferably a fan.

Thanks for the advice. The guy on ebay was MRE1032, he builds these boxes that will interface 2 radios, like a RICK box, but very affordable. I have one of his boxes in my truck to cross my VHF and UHF, works great, he even wired in speaker leads to the connectors for me when i asked.
But he wasnt interested in this, which is fine, I just dont know where to even begin as far as this device between the radios.

Rule of thumb i always put everything on 60 second timeout.
As far as duplexers/antennas, optimally id like to do single antenna, just for ease of setup, but i think id get better performance by having a VHF and a UHF, and just add a duplexer between the VHF side.

This isnt going to be something in constant use, probably wont get much use at all, but one of those things where the time it gets used, its worth it.

I am in charge of communications for the ambulance i volunteer for, also on a regional rope rescue team that responds out of area a lot. So all of our stuff is VHF, lots of nearby areas are UHF, so i would love to have the ability if something happens like the rope team goes up into new york for a rescue (happened a few times in the last year) theyre all UHF, again all our portables are VHF, so before we go I pull this pellican box and a tripod out of my car, throw it in the truck, and we get on scene i connect our scene channel with their scene channel and there we go.
Thats only one application of all the ones i have thought of.

And for the VHF i likely would license some sort of itinerant vhf pair, or something to that extent

 

[mmckenna]

Thanks for the advice. The guy on ebay was MRE1032, he builds these boxes that will interface 2 radios, like a RICK box, but very affordable.

Yeah, I know his stuff. You probably want an actual controller in their to allow configuring the setup. You'll want some sort of ability to control traffic between the VHF - VHF side and the UHF side.

Rule of thumb i always put everything on 60 second timeout.

yeah, pretty easy to toast equipment if you don't. Mobile radios are not designed for long transmit times. Having a receiver go unsquelched, or someone tying the system up can cook them pretty quick. They are fine for short usage, but not for any high cycle sort of use.

As far as duplexers/antennas, optimally id like to do single antenna, just for ease of setup, but i think id get better performance by having a VHF and a UHF, and just add a duplexer between the VHF side.

Yes. You'd have a hard time finding a decent commercial quality dual band base antenna. You could use a diplexer and make it work, but more separation between antennas would be better. Give yourself enough coax to put a lot of space between the VHF antenna and the UHF antenna. That's what usually kill the interoperability systems that tie a bunch of portable radios together.

I am in charge of communications for the ambulance i volunteer for, also on a regional rope rescue team that responds out of area a lot. So all of our stuff is VHF, lots of nearby areas are UHF, so i would love to have the ability if something happens like the rope team goes up into new york for a rescue (happened a few times in the last year) theyre all UHF, again all our portables are VHF, so before we go I pull this pellican box and a tripod out of my car, throw it in the truck, and we get on scene i connect our scene channel with their scene channel and there we go.
Thats only one application of all the ones i have thought of.

And for the VHF i likely would license some sort of itinerant vhf pair, or something to that extent

A better approach is to have your agency licenses some of the DHS interoperability frequencies for this. That's what they are designed for. Any agency can license them easily. Most large agencies should have already done that and should have them programmed into their radios.

Setting up one of the VTAC33 through VTAC38 pairs would cover your VHF side and allow other agencies with VHF radios to use it.
On the UHF side, set up one of the UTAC41D through UTAC43D channels for the UHF simplex side.