[Dstar] Using the IC-2820H in x-band to pass DV to extend repeater coverage

[Nik Presser]

G'day all, 

After many sleepless nights, a message posted last year by our great home-brewer in Port Lincoln recently triggered an idea. With the view to build a couple of D-Star hotspots / DV node adapters, I've been thinking of an interim solution. It's not as flexible as a Hotspot but is an alternate solution all the same. 

Amongst a few recent experiments, including running a pair of IC-2820H's back to back via the packet connectors at 9600baud, it was obviously possible - from hotspot projects by others in VK3 & VK5 that DV could be passed through two RF ports configured for FM Narrowband. Now, whilst the IC-2820H will function in cross-band mode in FM mode, it will not work when one side of the rig is in DV mode - obviously because there is only one codec in this rig. 

Does it cross-band if both bands are in FM-Narrow? Yep. The left band needs to be in VHF and the right in UHF for the x-band function to work. 

So, if we use the left VHF band to access VK3RWN-C for example, but configured with the same freq split and in FM-N instead of DV mode and then having the right UHF band setup for a 70cm D-Star simplex frequency also in FM-N mode, I've found that we can pass a DV signal straight through the radio via x-band. Some work needs to be done with your low powered portable, such as the IC-92AD, on the local simplex freq. 

The RPT1 & RPT2 data doesn't seem to be sent in simplex mode, but if you activate the simplex frequency with -ve duplex mode and then set the repeater offset to 0 kHz instead of the usual 600 kHz or 5.4 MHz offset, it will trick the radio into thinking you're working duplex on DV and then send the RPT1 & RPT2 data, even though you're actually working simplex TX / RX. 

At home, I've got my IC-92AD running 100mW TX and the IC-2820H running 5w TX on both bands - it's all I need to access any of my local repeaters and it helps limit the simplex DV coverage to the Geelong area. 

Essentially this is a similar thing but different (??) to what's occuring on the RF side of the Hotspots... maybe... :-)

I'm going to refine the configs in the IC-2820H and IC-92AD but it's proven that this is a possible thing. And because the IC-2820H seems to run reasonably cool and uses less current compared to other rigs, it's an ideal radio to use. 

A handy use would be that if you were at your favourite campsite for the weekend. You mightn't have portable access into your favorite D-Star repeater but your vehicle radio could access it, then you could use the IC-2820H in the vehicle as the x-band link to transfer the DV signal between your IC-92AD and the distant D-Star repeater, using 100mW on your portable and enough RF power on your vehicle mounted IC-2820H to access the repeater. Much like using x-band in that old fashioned mode... err.. FM... :-)

And out of courtesy, perhaps it's a good thing to announce the other x-band freq when you announce your callsign every 10min, like the guys using the Hotspots do. Take precautions to limit your simplex range in order to prevent interference to fellow operators. If we all play nice, our world will be nice :-)

If you have any further enquires, wish to flame me or nominate me for a public flogging at dawn, please let me know off the list via vk3ba at wia dot org dot au

Cheers,

Nik Presser
VK3BA  (ex VK3NJP)
Geelong
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