The reason to use DominoEx is only for FM DX communications. It is
slower than MT63, but much more sensitive, so you still get good copy
way below limiting and quieting. For that reason, on our local FM
digital net, we use DominoEx 8 and with horizontally polarized antennas,
include everyone in a range of 35 miles.
I suggest trying MT63-2000, and if some stations cannot copy, drop down
in speed to MT63-1000, and if necessary, drop down to MT63-500. Then if
you still have problems with some stations not copying, go to DominoEx 8.
If any station is below limiting, which is quite possible at 25 miles
using low verticals, MT63 may not work.
On UHF, where Doppler shift and Doppler spreading is a major problem
with SSB voice, we use Contestia 64-1000, which works very well on 200
miles paths.
73, Skip KH6TY
On 7/19/2010 7:58 PM, KB3FXI wrote:
Jon,
Here in WPA we've adopted MT63 2k long (64 bit) interleave as our
standard. The mode is very wide (2000hz) but fits very nicely inside
the typical FM transceiver and repeater audio passbands.
Here's some of the big advantages of MT63 2k long on FM:
-Massive amount of FEC (forward error correction) and interleaving
provides perfect copy, even under horrendous simplex conditions and
weak signals into repeaters (it even barrels through short drop-outs
and heavy noise with weak stations into our local UHF repeater)
-There's no need to have to tune on the waterfall as all MT63 submodes
in FLDIGI are fixed at a bottom waterfall frequency of 500hz (2k long
goes from 500 - 2500 on the waterfall)
-WPM rate is about 200wpm
-Works fine using only a hand mic on the computer speaker and the
computer mic somewhere in the vicinity of the received audio from the
transceiver
We run over UHF/VHF traditional voice repeaters and simplex
frequencies with great success on our net every week... even with
first time users.
Please give it a shot and let us know how you make out. Also, make
sure your ops do a proper sound card calibration. You only have to do
this once, unless you change your sound card or switch to a USB mic.
Here's a video I made on that subject of calibration using CheckSR.exe
and FLDIGI:
http://www.utipu.com/app/tip/id/9382/
-Dave, KB3FXI
www.wpaNBEMS.org
--- In digitalradio@yahoogroups.com
<mailto:digitalradio%40yahoogroups.com>, "JonP" <jpere...@...> wrote:
>
> I have the need to set up some reliable local digital communications
(say 10 mile radius from the base station) for data transfer, and to
do so in a short period of time.
>
> I would normally first think of VHF FM packet, but a lot of people
are running into troubles with things like Vista and Windows 7
(please, spare me the "Linux" or "Apple" and "D*Star" messages,
they're not realistic in this situation).
>
> I've seen some references to running DominoEX and MFSK-16 on VHF FM.
A number of my prospective operators are running digital modes such as
DominoEX, MFSK, etc. on their computers now (under XP, Vista, Win7)
without problems.
>
> Would one of those modes be realistic to run on 25 watt (or higher)
mobiles on 2 meter FM using vertically polarized antennas? I realize
that the vertical polarization would be an issue if we want to get out
of the local area, but right now the need is within a local area and
everyone would be running with a typical VHF vertical.
>
> If feasible, what sub-band would we use? I would assume the FM
simplex sub-bands. Is that correct?
>
> Anything else we should consider? Any special issues/problems? I
would think that we would not have to reduce power since these radios
are already running FM, but if not the case please correct me.
>
> Thanks.
>
> Jon
> KB1QBZ
>
