DTR Repeater Revisited

I know this topic has been kicked around for awhile. It seems that only the Cane company has offered a somewhat viable commercial DTR repeater.
With more Motorola DTR radios showing up on eBay it seems like interest is growing for a functional “Home Brew” repeater.
The fundamental problem of no repeater frequency split/shift in the programming of these radios is well known. So my question is, has anyone reading this come up with a reasonably functional solution to extend the useful range of the DTR handhelds?

It is just not practical to try to set up a repeater unless you have the version that uses internals from two radios. (Hence, the high cost.) The DTR cannot receive on one frequency and transmit on another because the “channels” are not individual frequencies, but are a pre-programmed algorithm of frequencies that it hops from one to another quickly.

Some users have tried cables that tie the headphone jacks of one to another, but they have never worked well. Most of those cables have been withdrawn from the market. The problem with using two radios tied to a cable is that you needed to block the signal coming to the transmitting radio or it would just not transmit. Some users have tried putting one radio very high up in a tree and the other very low down, tied together with the special cable. This only worked if the DTR was at its very limit of reception area, so that the high one would pick up the signal while the low one wouldn’t. As far as I know, no one has ever been able to resolve how to prevent the transmitting radio from also receiving the signal.

The other issue is that the DTR has about the best range of any two way radio on the market, and there has been less need for repeaters. It is not really designed for wide area coverage, because those radios would be licenced business radios. The DTR is a licence-free radio.

I am also interested in this, and perhaps I could help. Seems like the dtr radios are based on the iden 900MHz of Nextel. Perhaps one of these T6737A iden 900MHz quad base transceiver systems on eBay could be repurposed to significantly extend the range of the DTR systems on private internet networks?

I’m a wireless / network / systems architect (read: hobbyist) that has been interested in these dtr/iden PTT systems for some time now.

The DTR system really isn’t geared up for repeaters. It’s frequency hopping - picking the clear ones dynamically as required. This means that the fundamental operation of a repeater is compromised. They must have sharp filters that stop the output making the input desensitise. You can get smallish cavities that work fine with an 8Mhz split in frequencies, and you can get even sharper and more expensive cavities that can do less than a Megahertz split. With the Motorola system as far as I can see there’s no way to make the things NOT frequency hop. The analogue idea of linking two radios would still work, but as soon as one fired up, the other would be swamped by RF and even with frequency hopping, it wouldn’t cope.

You can do repeaters with two radios on DMR and while you can’t do it without opening the radios and using a discriminator feed, it works. I can’t see how a frequency hopping radio can work back to back.