Friday, June 12, 2009

More D-Star experimentation (and reading)

With the ID-1 hooked up to a temporary indoor antenna, I was hoping to hear some activity on one of the two local repeaters.

The closest repeater is only about 8.5 miles away, but Google Earth strongly suggests that its antenna is not line-of-sight from my QTH. Despite being at almost 1300', and the VE7RAG repeater being at 2700', the southern flank of Mount Fromme comes between the two locations and so this repeater is masked (though this might not necessarily be entirely 'fatal').

The next closest repeater is VA7ICM. As far as I can tell, this should be completely line of sight to my QTH. Google Earth seems to indicate this is the case, though an attempt to verify this with binoculars this afternoon was rather stymied by the haze caused by the hot weather and the results of the wildfire burning near Lilooet. Hopefully the air will clear soon and I can retry the exercise. This repeater lies some 18.3 miles to the SE, but really ought to be perfect given the LOS.

I have not yet tried to fire up either repeater yet, but leaving the ID-1 on for a few hours while surfing for information about how to 'drive' a D-Star rig I heard nothing. This isn't a huge surprise, and I suspect it's mostly likely because I'm on 23cm, the least popular D-Star band (though the one I'm interested in because of its novelty and also the high speed data mode). Also, I imagine my temporary indoor mobile vertical on a mag mount isn't going to perform terribly well - though I simply don't have any experience to draw on at this point as to whether it would be completely useless.

I have decided to erect a Comet CYA 1216E antenna and point it at VA7ICM if all goes well. I'll measure the likely length of required LMR-400 tomorrow - I'm told this will do as a feed line, though obviously it has fairly large losses at 23cm.

My research in how to actually use D-Star to initiate (route) a call has turned up some useful references. It appears that it is generally accepted that Icom's manuals are pretty woeful when it comes to edifying the new users in this regard, so most repeater groups have some sort of "getting you going" notes on the subject. Here's a summary of what I've learnt (CAVEAT LECTOR: I could still be barking up the wrong tree on some of the details!).

To route a call, there are 3 requisite fields, aside from MYCALL, which in my case is never changed as I'm the sole operator. These are UR (your call), RPT1 (uplink repeater) and RPT2 (downlink repeater).

UR is the field that addresses a particular call sign on the network (at the last heard repeater) if set to a station call. This can be set to CQCQCQ to address any station on the destination repeater(s) or on the simplex frequency (essentially to operate like an analogue radio).

If the RPT1 field is set, then this specifies the uplink repeater call. This is composed of the call sign, plus the special band/port ID always at the 8th character position. Thus, if the callsign is shorter than 7 characters, there will be spaces to pad the string out to this 8th character.

When using a repeater to make calls, the uplink repeater is always your local repeater and the port is always the appropriate band ID for your radio's operating band (conventionally A for 23cm, B for 70cm and C for 2m). All transmissions via the uplink repeater are heard on this port of the repeater by everyone.

To this point, things work similarly to an analogue repeater. However, like IRLP, D-Star allows you to gateway to a downlink repeater, or another port on the same repeaters (i.e. talk on 2m from your 23cm radio). Unlike IRLP, this is done conveniently in terms of call signs and entered directly into the radio, rather than messing around with DTMF tones and node numbers. You can use the following routing settings for different purposes (UR, RPT1, RPT2):

1. To route to a 2m port on a repeater "VE7FOO" from the 23cm port and talk to anyone:

2. To route to a 2m port on a repeater "VE7FOO" from the 23cm port and talk to VE7HAM:

3. To route to the 70cm port on a repeater "VE7BAR" from the VE7FOO 23 cm port, and talk to anyone:

Note that the / format call means "all at desination" (repeater/port), and the "G" port in RPT2 is the repeater's internet gateway port.

4. To route to a VA7HAM on whatever gateway/port he was last heard on the D-Star network:

Aside from these basic principles, I have read the following advice:

- You should always put the gateway into the RPT2 slot if you want DV Dongle users to be able participate. In other words RPT1 is always going to carry your call, and even if you don't need to route across repeaters/ports, putting the a gateway port into RPT2 allows internet connected stations to participate. This suggests that the forms:
... would always be preferable for talking to any station on another repeater or another port on this local repeater.

- You can leave the RPT1 slot empty on some radios, and when you key up the repeater, this field will be filled in automatically. Apparently the repeater is not 'opened' by this interaction. I shall try this on the ID-1. It's probably also a simple way to test that you're getting into the repeater.

Apparently V2 of the Icom repeater control software allows conferences, by using a conference name in the UR field.

All sounds like good fun. I just need to be able to make it into a repeater now to give it a go. Though I had registered with the VE7RAG repeater, it now looks like VA7ICM is going to be my home repeater, so I've requested registration there and hopefully this won't be long in coming (the VE7RAG registration was turned around in a day!).

No comments:

Post a Comment