Have not done the math, but for 25 kHz spacing as on UHF what about
putting 2
D* repeaters one + 6.25 and one -6.25 kHz from a standard channel.
Might be necessary to seperate distance wise as we do for 2m 15 kHz
adjacent repeaters. Here it is 35 miles.
The D* rigs can do this and might be enough seperation. However, I do
not know the D* rcvr selective spec. They might use the same IF filters
that is used for the analog.
73, ron, n9ee/r
Ron Wright, N9EE
727-376-6575
MICRO COMPUTER CONCEPTS
Owner 146.64 repeater Tampa Bay, FL
No tone, all are welcome.
On Fri, May 16, 2008 at 5:38 PM, Bill Powell wrote:
--- In Repeater-Builder@ yahoogroups. com
<mailto:[email protected]> , Ron Wright <[EMAIL PROTECTED]>
wrote:
For D* there is the one issue of less bandwidth. D* occupies about 6
kHz, about 1/3rd that of analog allowing for putting 2 D* in same
space as 1 analog.
This little tidbit of "information" , courtesy of ICOM's badly
misleading charts, needs to be laid to rest once and for all.
Although the bandwidth occupied by D-Star and other digital modes is
1/2 (or less) than that of wide band FM operation it DOES NOT mean
that one can "automagically" get 2 for 1 by going digital.
However, allocating a full FM channel to a D-Star or other narrow band
repeater is a complete waste of bandwidth. Something needs to be
done. . .
First: It's not necessarily simple to change repeater frequencies.
We are channelized in our repeater operation. In some places 2M
channels are allocated in 15 kHz and 20 kHz (I hope there are no 25
kHz) channels. D-Star repeaters can operate on ONLY either 5 or 6.25
kHz channels. Do the math: If you can't divide the "new" channel by
6.25 or 5 it can't be used for D-Star. The same for many other
synthesized radios.
Second: We have and live by band plans.
As a coordinator I would never consider putting both an digital and
analog repeater on the same channel with overlapping 19 dBu contours.
Tis best to not mix the lions and lambs. I'm not even sure about
sharing a channel between D-Star and P25 digital. Any volunteers?
Third: What do we really want to do?
If bandwidth reuse and maximizing channels is the ONLY intent, Narrow
Band FM works just fine too. In this case, 12.5 kHz channels make the
most sense for everybody.
If it's just a case of finding a way to weasel "new" channels for new
D-Star toys, get thee to the back of the line; we have a waiting list.
Fourth: The taxi is already occupied.
There are many, many existing systems and users on the current
channels. How does one convince them that it is their best interest
to move off "THEIR" channel to make room? In MANY cases, existing
repeaters are crystal controlled and not easily moved even "only a
couple of kHz".
In summary: No matter how we do it, gaining / splitting channels is
by no means simple - especially when the human element is added to the
mix.
But, we have to do "something" sooner or later.
JMNSHO,
Bill - WB1GOT
<mailto:[email protected]>
