[pskmail] Alpha Testers for fast modes
- From: John Douyere <vk2eta@xxxxxxxxx>
- To: pskmail@xxxxxxxxxxxxx
- Date: Tue, 20 Mar 2012 18:03:10 +1100
Hello Pskmail operators,
I am ready to send, off list, a few copies of a special alpha Fldigi with
new modes for testing.
This first batch of new modes is targeted specifically at the fast FM
(normally VHF/UHF) links as they require a clean bandwidth of up to 2400Hz
and will suffer badly in the standard SSB passband. So please do not use
the wider ones on HF.
Also note that their baud rate is above the Amateur HF bands Baud limit in
the USA for all but two of the PSK modes.
Note that I am separately preparing a USA HF Amateur version with only
modes below 300Baud and one for HF outside of the USA with faster Baud
rates.
In this version, the top speed provides 3200 words per minute or 19200
characters per minute (using the Fldigi definition). In tests I got a 17124
characters text file to be downloaded in just under one minute in
compressed format, including repeats and ARQ overheads, so I think this
could be interesting.
Unfortunately as this point I have not been able to get my existing version
of the Windows cross-compile to work, so it is for Linux only until I get
this to work.
Instead of creating new mode designations I have simply re-mapped the
existing list of modes we use for Pskmail into a new set.
That has the advantage of making the tests simple by just using the
temporary Fldigi program on both sides without any change in Pskmail. All
features will be the same including the configurable mode list. The only
drawback is that the timeouts are still related to slower modes so will be
in some cases way too long (like 30 seconds for the PSK63 -> PSK1000R
mode). But the objective is to review the modes not the Pskmail performance
itself.
Of course these modes are usable with FLARQ of the NBEMS suite.
I expect to have about 5 to 6 new modes from the list below retained in the
final "FM implementation". They will then get their new designation and
RSIDs.
All these final modes will also be integrated in the Pskmail V2 (integrated
Java modems) and in the Android version of Pskmail (they already run on my
HTC Desire).
I have arranged these test modes in a similar order of robustness as the
ones they replace.
Here is the mapping:
Original mode New Temporary Mode
Speed Bandwidth (-3dB)
PSK63 1 Carrier PSK1000R
880WPM 1000Hz
PSK125 1 Carrier PSK1000
1600WPM 1000Hz
PSK250 6 Carriers PSK250
2400WPM 2000Hz
PSK500 2 Carriers PSK1000
3200WPM 2400Hz
PSK125R 2 Carriers PSK500
1600WPM 1200Hz
PSK250R 2 Carriers PSK1000R
1760WPM 2400Hz
PSK500R 14 Carriers PSK125
1540WPM 2400Hz
I have also re-mapped the MFSK and THOR modes the following way:
Original mode New Temporary Mode
Speed Bandwidth (-3dB)
MFSK16 MFSK64
240WPM 960Hz
MFSK32 MFSK128
480WPM 1920Hz
THOR8 THOR44-Double spaced
156WPM 1600Hz
THOR11 THOR44
156WPM 800Hz
THOR22 THOR88
312WPM 1600Hz
The MFSK64 mode is the same as the current one but that way we get to have
an RSID associated with it for our tests (the MFSK16 RSID).
The double spaced THOR44 is targeted mostly at NVIS conditions (4 dBs
better than the single spaced one) so I don't think it will provide a
benefit for FM paths.
The MFSK/THOR modes should be of most interest for poor FM links (where the
noise is high).
In some Pskmail tests I did over VHF, the THOR modes were virtually as
sensitive in FM as in SSB (I think Skip Teller - KH6TY - has an article in
QST about this).
Due to the required bandwidth I would suggest a waterfall audio centre
frequency of 1750 or 1800Hz for FM transmissions.
These preliminary modes specifications are published in the Pskmail wiki to
respect the regulation. See http://pskmail.wikispaces.com/newmodes
I have not made the source code available yet as it is preliminary but of
course it will be released under GPL in due course and I hope integrated in
the mainstream Fldigi.
Could you please feedback the following information which is of most
interest to me:
1. Any issue with the software itself.
2. CPU load of the different modes on your computer (approximate average
and peak value - use the "top" command in a terminal).
3. The modes that Pskmail mostly settle on, the ones it has problems with
and what were the conditions of the test (signal strength, quieting etc...).
4. More advanced: when frames are damaged, does it tend to be in
the beginning, the middle or at the end?
From my Pathsim tests and initial field trials I would bet on the following
set: PSK1000R, 2 x PSK1000R and 2 x PSK1000 as a useful mode list for FM
transmissions, plus a couple of FSK modes, but let's see what you find out
in the field.
To get a copy, email me off list at <my callsign> at gmail dot com
Have fun,
All the best,
73, John
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