For number of reasons it usually much easier to put a D-Star system up
on UHF rather than VHF. VHF is much more crowded in most places and many
locations have no open VHF pairs. Attrition may eventually open up some
pairs but many places have long waiting lists. Attempts to move D-Star to
the front of the list will prove fruitless as it should be. It will also
alienate those already on the waiting lists. So forget about VHF D-Star
repeaters for the immediate future unless you're in Montana or North Dakota.
( I can say that as I've lived both places.)
There are many more MHZ on 440 than two meters, therefore, many more
pairs. With 25 kHz between channels a D-Star repeater on an offset can be
placed closer to an analog system with out causing problems.
Another possibility is combining a D-Star system with an existing UHF
repeater's hardware. A frequency 300 to 500 kHz away from an exiting system
is easy to combine. I built up such a system here in eastern Illinois and it
works very well. The D-Star repeater shares the filters, feedline, and
antenna with an existing analog repeater and they play well together. Thanks
to ebay the combiner hardware set me back less than $300. YMMV on this,
though.
I would consider combining a VHF D-Star and analog system but the
requirements on VHF are much more stringent with only 600 kHz between
receive and transmit. The combining hardware is a lot more difficult to find
as well. Also, in Illinois D-Star systems are only to be assigned to 145
output frequencies so combining with an existing 146 or 147 system would
need at least another set of duplexers, a major expense.
If someone is going to be using D-Star they're going to have to buy a new
radio. All but a couple (IC-2200 and IC-V82) are dual band so they've
already got the hardware to use UHF. Therefore, I recommend very seriously
considering UHF first when planning your first D-Star system.
Al, K9SI
