I would like to get in touch with some folks in British Columbia that
built a DD repeater from a pair of ID-1 radios. That repeater, unlike
the "official" Icom DD repeater, was full duplex (because it used the
novel concept of a full time receiver and a full time transmitter).

I *know* they existed... I just can find ANY mention of them online.

ANY pointers appreciated, even if just from memory of people or names.

Thanks,

Steve Stroh N8GNJ

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Steve Stroh N8GNJ (he / him / his)
Editor
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I'd like to see any info on the BC repeater too.

To expand on Erik's reply, our system still uses the Icom DD 23cm digital repeaters as a central hub for all the ID1 radios within range. Each user ID1 is assigned two IP addresses when it connects to the repeater. At the repeater we have a WRT54GL router with a modified version of Open-WRT+OLSR to route the data packets back out of the repeater to its destination ID1. Our local data network does not rely on the Icom Gateway software and is based on "non-routable" network paths that are configured in our routers. When we operate during the Marathon, we can add an external connection into our network from the Internet.

This system has worked perfectly for connecting multiple ID1 radios into a wide area multi-point network from the first. The only trouble I recall is during initial attempts, a Linux system would connect to the network using DHCP to the repeater just fine, but the Windows boxes would not. Peter had to make some minor changes to the OpenWRT+OLSR firmware in the WRT54GL router to solve the DHCP problem. So at this time, any computer we connect to the ID1 is able to get an IP address via DHCP from the repeater. I use a router on my ID1 so I can have multiple loggers at my net control station. The only issue that I've had since then is remembering how to configure the ID1 with the proper frequency and repeater callsign.... :-)?

I always considered the Icom DD 23cm "repeater" operates more like a store and forward packet node. I do not know if it is actually running full duplex data on the RF. I could definitely see how it can be sending data from a previous packet while the next packet is coming from a different station, but I don't think it is operating as a "bit regen" full duplex repeater.

When I first looked at the "Bent Pipe Repeater" document, it didn't seem to provide an advantage. But just consider, the ID1 radios basically setup a RF "wire" connection between two IP networks. The standard ID1 firmware can only connect to one other station at a time with its half-duplex link. But the DD repeater uses two radios. What do you get if you put the *repeater* callsign in both ID1 radios and use one exclusively for RX and the other for TX? The RX radio will pass along anything matching its callsign. The TX radio puts its own callsign on every transmission.? The router you put at the repeater site would use two ports, one for RX and one for TX, with the router passing data between them. In this configuration you should be able to have a different packet coming in on the RX side while a previous packet is being TX. But I'm not sure this will work unless the remote ID1 radios do NOT incorporate a TX-inhibit when the RX is hearing a signal. There are probably some problems with this option to build a DD repeater, too much depends on the ID1 firmware. Needs to be tested. Two ID1 radios and a router will certainly work to link two DD repeaters on separate frequencies but we're using Part 15 for that.??

73, Doug Reed, N0NAS.

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Hi Ed.

No, I don't believe "full duplex" in the DD repeaters either. In the old days, a full duplex 9600bd packet repeater required a bit-regen sync detect board on the receiving TNC which then fed the delayed data stream into the transmitter and keyed the PTT until the data sync was lost. TAPR used to make a PCB for the G3RUH modem boards and we had one here in Minneapolis on 2M. That was a real full duplex bent pipe repeater that acted as a piece of wire between any two stations. All it wanted was sync detect to begin transmitting. The actual TNC on site was mostly for sending an ID. But that is not how the Icom DD repeater works.

When we played with ID1 radios 20 years ago, we (I?) believed the ID1 could only make a one-to-one point-to-point link. It could not do a one-to-many multi-point link. Multi-point seemed to be the magic part of the DD repeater. So the main difficulty with using a single ID1 as a half duplex repeater is the need to be able to support more than one user at a time. I could possibly accept a "duplex" DD repeater where the RX and TX are decoupled from each other so that it can be receiving a packet from one user while transmitting data to another user on the output frequency. That is more or less what I was suggesting by using two radios and a router to handle the data between ports and users. This becomes a "full duplex" repeater in the same way that an Ethernet connection is full duplex. Packets are flowing both ways at the same time, but they are each "store and forward" in the controller or router.

I just don't know if the ID1s can be programmed to RX and TX without a known destination programmed into the radio. I think that is where some experimenting is needed. We just never tested it back then.... It sounds like maybe Vancouver did....

73, Doug Reed, N0NAS.

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Yes, I was mixing the DD with the DV which is two mobiles in one box. It was annoying that we had to replace the internal coax because Icom didn't seem to use double-shielded cable in the original DVs. And adding an extra pass cavity in the RX line helped improve the out-of-band rejection considerably.

I don't think I ever considered using CQCQCQ as an all-call because when I used it with a DV repeater nothing happened until the ID was sent after I unkeyed. I never tried to see what would happen with ID1 DD radios. If that works for one-to-many broadcasts, then connecting a properly programmed router to the ID1 would probably make it a DIY repeater. Sounds like an easy option if it works.

73, Doug Reed, N0NAS.