Nate,
My thoughts on putting 2 D* repeaters in one analog UHF channel (I don't
like the word channel in Ham Radio, but guess I need to get over it) is
since 25 kHz spacing and D* occuping 6+ kHz then say taking 444.250 ch,
putting one D* at
444.24375
and one at
444.25625
(the D* rigs will tune these).
They would put them 18.75 kHz away from the +/-25kHz of the adjactent
repeaters. It would be squeeze, but not much more than say on 2 m at 20
kHz spacing and better than the 15 kHz spacing. And since D* is only 6
kHz (+/-3kHz) it should work. UHF is good start with the 25 kHz
spacing.
Sure each repeater needs to be studied. Would not put these at same
site and would have to know about other repeaters in same area. Wide
area coverage another issue, but since we now put repeaters close on 2m
with 20 kHz spacing and 16F3 mod it should work.
When one goes from 16 kHz wide signal to 6 kHz wide it opens up a lot.
This is the thinking of FCC with the 12.5 and 6.25 narrow banding (I
know you know this, hi).
The rigs are the problem as with commercial. Commercial are better
positioned for they need to change radios every 5 or less years anyway.
Since the users are not the owners they use the rigs to open beer cans,
crack nuts, beat their kids, etc. So changing is not as difficult.
Hams keep everything forever even if it don't work...well I do.
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 7:49 PM, Nate Duehr wrote:
Ron Wright wrote:
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.
You're starting to "think like" the folks who are trying to come up with
good ideas, now you've got it!
However... you forgot the next step...
Next you have to think about the original adjacent channel analog
systems on either side.
It's a "matrix". Now mess around with the locations of all three.
Trying to do a "raw" matrix analysis gets complex, real fast.
Might be necessary to seperate distance wise as we do for 2m 15 kHz
adjacent repeaters. Here it is 35 miles.
We have to go a LOT further here, based on Height Above Average Terrain
(HAAT).
On VHF we have some systems that will EASILY hear a mobile user out past
80 miles.
(And this is why each area has their own coordination bodies...
tailoring the situation to the local conditions, is key.)
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.
Needs more bench testing and real-world experiences with digital
"against" digital and digital "against" analog. I suspect we'll see
more good work out of people who've already published.
(Utah's coordination group, and Mark N5RFX have both done some very nice
published work for D-STAR systems specifically, and I've talked to a
number of radio folks who DID similar or useful work to test such things
on their systems, but never had time or energy to publish.)
Nate WY0X
