Homemade repeater ideas

Looking for ideas to make a backyard repeater by using 2 mobile radios or one mobile and a handheld with an actual controller. Can anyone give me some examples and pictures would be nice.
Thanks

Pretty easy to do.
There are small basic repeater controllers on e-bay. There are kits you can build. If you don't need lots of bells and whistles, you can fabricate them on your own using a pair of mobile radios with the correct interfaces on them (16 pin Motorola's are easy).
Add a power supply, and mobile duplexer, and you'll get a basic small coverage area repeater.

The duplexer is key, as trying to run two separate antennas will require a lot of antenna separation to keep from the transmitter from overloading the receiver.

The Repeater Builder's Technical Information Page™

The controller I’m wanting to use is going to be a cat 260

wx5atx1 said:

The controller I’m wanting to use is going to be a cat 260

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If you own it already, then that will work. If you don't own it already, shop around and see what you can find.
I've never used the CAT-260, but I did inherit a couple of sites at work that are linked using their CL-100 & CH-100 links.

This Thread Sounds Real Close to the Thread He Started in the Motorola Forum on Making a Repeater

I'm sure you want to go a tad bit more elaborate, but I actually made a repeater out of two GP300's. I programmed one to scan, and beep when the scan stopped. I put the other on VOX and taped it's mike to the first one's speaker, with a TX delay. When the first one heard something, it would beep. That would open up the VOX on the second one. The audio was "all right". Not something I would put in service for a bunch of people. But it was fun to try.

Golay said:

I'm sure you want to go a tad bit more elaborate, but I actually made a repeater out of two GP300's. I programmed one to scan, and beep when the scan stopped. I put the other on VOX and taped it's mike to the first one's speaker, with a TX delay. When the first one heard something, it would beep. That would open up the VOX on the second one. The audio was "all right". Not something I would put in service for a bunch of people. But it was fun to try.

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Thats cool,is that what they call a poor man repeater....

Might not be exactly what you are looking for, but his one is about as easy and as cheap as it can get.

Cross Band Mini-Repeater Project:
Cross Band Mini-Repeater Project UV5R UV82

I’ve posted in other groups to because I have several commercial radios that I was seeing if I could make Into a repeater

Making a cross band repeater is easy, in band is another story and without a duplexer it will be hard to make it work. You can cobble things together and make an in band repeater work in front of you but the transmitting radio will blitz the receiving radio and you will not get any distance from it.

prcguy said:

Making a cross band repeater is easy, in band is another story and without a duplexer it will be hard to make it work. You can cobble things together and make an in band repeater work in front of you but the transmitting radio will blitz the receiving radio and you will not get any distance from it.

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A possible alternative is to use two antennas with proper horizontal and or vertical separation to create the needed isolation. Still, I prefer using a duplexer.

Depends on the band and spacing. I had a GE Master II repeater on 2m with a 1MHz split and vertical separated antennas and could not get it to work without a little desense. A pair of Baofeng radios would have no chance of working under those conditions.

vagrant said:

A possible alternative is to use two antennas with proper horizontal and or vertical separation to create the needed isolation. Still, I prefer using a duplexer.

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vagrant said:

A possible alternative is to use two antennas with proper horizontal and or vertical separation to create the needed isolation. Still, I prefer using a duplexer.

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Proper means lots of separation. Lots of separation is going to create lopsided coverage in most cases. Add in the cost of the coaxial cable, the losses associated with that, and then the limitations from using incorrect radios, it all adds up to poor performance. Might take a lot of work to get it to work halfway decent, but that money and effort might be better invested.
Not saying that dual antenna systems cannot work, just that it's not as easy as many think, especially with the closely spaced 2 meter offsets.

Even a mobile duplexer can work better.
At 2 meters, .600mHz separation usually needs some good duplexers if you want it to work well.
70cm is a bit easier with 5mHz of separation.

The real issue here in trying to cob together a simple repeater is the selectivity of the receiver your trying to use and just how clean the transmitter is.

To elaborate, the receiver is the most important part of the components your going to need. If the front end filtering is not sharp, you will never get rid of the noise and overloading RF from the transmitter. Plus it doesn't hurt to have good shielding on the receiver. Consider the shielding on the transmitter also.

Use of good shielded audio cables is a must. You might also consider putting in some audio bypass caps to try and eliminate any RF getting into the audio lines.

Another area to pay attention to is the coax cables you use. Use of double shielded coax cables for all the cables your going to need for your repeater package. What ever you do, don't use the cheap coax coax for CB use. The shield on that cable is junk and you will regret the effort it will cost you trying to get all the noise and receiver overload out of the package.

The duplexor is the key to a good repeater. It needs to have good isolation between the receiver port and the transmitter port. Just how much isolation required will depend on the transmitter power level.

On the transmitter power output, you need to keep a major point in mind. You can't turn down most solid state power amps below about 50% of their rated power. Going beyond that point you open up the possibility of it starting to generate crap noise and spurs. The use of a spectrum analyzer is a must to insure the transmit signal is clean.

There is much more to consider including the ability to set the TX deviation level from the RX input level. You really need to use a radio already set to the correct deviation as the input signal and a service monitor on the repeater transmitter. So the ability to have access to the required test equipment is a must to get the repeater to sound good.

Hope this gets you started in the right direction on your efforts to building a repeater. Walk slow on this project and don't cut corners. They will just bite you in the long run and create issues that can be very frustrating in trying to resolve.

I haven't even mentioned the antenna system. That is a whole other subject. What ever you do, use a good quality antenna and don't use any LMR coax. You will regret it in the long run.

Jim

mmckenna said:

Proper means lots of separation. Lots of separation is going to create lopsided coverage in most cases. Add in the cost of the coaxial cable, the losses associated with that, and then the limitations from using incorrect radios, it all adds up to poor performance. Might take a lot of work to get it to work halfway decent, but that money and effort might be better invested.
Not saying that dual antenna systems cannot work, just that it's not as easy as many think, especially with the closely spaced 2 meter offsets.

Even a mobile duplexer can work better.
At 2 meters, .600mHz separation usually needs some good duplexers if you want it to work well.
70cm is a bit easier with 5mHz of separation.

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I agree. There are also losses using a duplexer. Lopsided is dependent upon losses, TX output, attenuation, etc. as you know, whether single antenna or two. A mobile duplexer, along with its losses, is typically limited to the power output it can handle, ergo the potential for lopsided results you identified.

Dual antennas are an alternative that while not so friendly on VHF, as prcguy noted, can be suitable for UHF. An available pair is more likely for UHF as well.

What are the cost and loss differences between adding a coaxial cable and second antenna versus a duplexer? I am not really asking here. It is just more information for people to consider when thinking critically about what setup will work best for their situation. Options are good.

To the OP, I believe Yaesu is still selling their refurbished DR-1X repeaters to clubs for $400. Inside are two radios and a controller with a touch screen interface. 20 watts is the best you will safely get out of it due to its handling of heat. With that you could easily use a UHF mobile duplexer as mmckenna pointed out. While those things work directly from AC, you can also connect a battery and it will keep the battery topped up for backup purposes, should the mains go down.

Thank you all very much for the feedback. This is going to be a slow process and I will keep updated. Also I’ve herd conflicting story’s of the cheap Chinese duplexers. Is that what you are talking about would be safe with about 20watts or so?

wx5atx1 said:

Thank you all very much for the feedback. This is going to be a slow process and I will keep updated. Also I’ve herd conflicting story’s of the cheap Chinese duplexers. Is that what you are talking about would be safe with about 20watts or so?

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It's not just the power level, it's how well they notch out the other frequencies.

20 watts would probably be fine. The system I got stuck with at one of our remote sites is running about 10 watts, and they've held up OK. Not an outstanding system, but works well enough.

You haven't really talked about what frequencies you will be using. VHF/2 meter band will be more problematic. The duplexers tend to be larger, and they have to be of better quality since the normal repeater pair spacing is 600KHz. For a low power amateur system, 600KHz and <20 watts you can probably make it work OK. If you were trying to run more power, you'd need something better than the notch filters used in the mobile duplexers. That means adding quite a bit to your budget. Good ones can run $1500 and up, plus you need to tune them, which requires a spectrum analyzer with a tracking generator. Some sellers will tune them for you, but you are putting a lot of trust in a stranger that just might want your money.
Mobile duplexers are easier to tune, but still require the same gear.

70cm band, as mentioned, might be a better choice since the 5MHz offsets are a bit more favorable to less than ideal duplexers. You -could- get away with a lower end mobile duplexer on UHF and get a few miles coverage IF your antenna is in a good location.

Don't let any of this sour you on the idea of putting up your own repeater. It sounds like you are eager and willing to put in the work, that's good. Just be aware that some of us have done this before and learned a few lessons. Learning lessons that way on your own can be a good experience, but if we can save you a few headaches and a few bucks, it might be worth it.

The system I "inherited" at work is a set of 3 Bridgecom repeaters linked via IP to 3 separate hilltops. The Bridgecom repeaters are basically fancy ideas like what you are thinking of. 2 low end mobile radios in a box with a power supply and a basic controller. These had a mobile duplexer installed inside the box with the radios. Like I said earlier, not stellar performers, but I've got to work with what they have due to budget restrictions. With some careful work, they can work acceptably. You can do the same thing, a couple of basic mobiles, a controller, a duplexer and a power supply.
If I was building one from scratch, I'd probably use a pair of Motorola CDM-750's, you can score them for $50 - $100 each on e-Bay. A basic controller (you don't need much, just ID, and a way to kill the thing if it goes bonkers), and the rest.
I'd also probably put more money into the duplexer system and antenna/coaxial cable, since that makes a big difference in performance.
By going modular, rather than a pre-built box, you can upgrade modules as needed. Maybe start off with a mobile duplexer, upgrade later on if you want.

Either way, it'll be a fun project and you'll learn a lot.

And not one knowledgeable person on here wrote a word about getting frequency coordination, an especially problematic issue on 2mtr. in major metro areas like where the OP lives...SMDH...