where could one finds these modes
MATTHEW A. GREGORY
KC2PUA
----- Original Message ----
From: Rick W. <[EMAIL PROTECTED]>
To: digitalradio@yahoogroups.com
Sent: Sunday, August 3, 2008 11:46:11 AM
Subject: Re: [digitalradio] Has anyone looked into FPGA-based digital modes?
Hi Paul,
Sounds like you might be getting caught up with some of your other work
and can devote some time again to digital modes:) For those who are not
aware, it was Paul's paper on ARQ concepts that lead to development of
several current uses of ham radio ARQ modes.
Some comments and questions:
1. Years ago we had the outboard programmables but they never really
were all that popular. I know of only one ham in our area (multi-county
rural area) who had one. Can the paradigm be revived? I don't think it
can for the average HF digital ham since they do not seem to have that
much interest in ARQ modes. Most are quite happy to only use PSK31 and
no other mode. When it doesn't work, they don't tend to switch to MFSK16
or Olivia. They just go and do something else.
2. Is it really true that computers (using a sound card) can not switch
fast enough? When I toggle the PTT on my sound card modes, I can barely
tell there is any delay in switching the rig. While I would not want to
key CW that way, it seems plenty fast enough for reasonable switching
speeds needed for an ARQ digital mode. Since we would not necessarily
need to exactly duplicate Pactor modes, couldn't there just be a few
extra milliseconds of padding to take care of differences in any delays
depending upon the computer?
Based on the timing for Pactor 2 and 3, do you still find that the
average computer can not handle the window for the ARQ ACK/NAK response?
3. The SCAMP mode, developed by the Winlink 2000 group, proved
conclusively that you don't even need such close timing anyway since you
could do the decoding in the background (pipelining) during the time
that the next packet was being sent. SCAMP worked fabulously well with
good signals. If other slower protocols were used (but still keeping the
1000 wpm speed) it would work with much more difficult conditions.
4. Other than a few of us who have significant interest in public
service/emergency communications and the need for absolute accuracy in
messaging, there seems to be nearly no interest:(
I wish it was not this way, but consider that the FAE400 mode, which is
very sensitive, can work under fairly difficult conditions that would
make PSK31 impossible, and has ARQ built in, is almost never used after
a modest interest in testing it last year.
5. Therefore, it seems important to insure that there is a purpose for
the development of a new ARQ mode to meet some unmet need. I might
suggest that possible interest in having the capability to handle public
service messaging, with total accuracy, and under conditions that may
make CW difficult, and yet provide the access to automated e-mail that
can also handle time shifting store and hold for later retrieval.
As an example, there are probably a few of us who used to be active with
CW/phone traffic handling a few decades ago, but who did not want to be
forced to adhere to a specific schedule during non emergency times.
Packet BBS systems had some of the paradigm but for decentralized
systems did not work well on HF since the mode requires very good
signals and throughput was often marginal to nil.
A decentralized ad hoc, robust, low cost system that gave us a choice of
routing e-mail or holding it for a "local" ham could be a new paradigm
that enough radio amateurs might move toward. There is no other system
that can do this now and nothing on the horizon.
I would personally be interested in hosting such a system. Any other
hams feel the same way? Or do you think such an approach would languish?
73,
Rick, KV9U
Paul L Schmidt, K9PS wrote:
>
> Speed and resolution are, of course, relative :) While those chips
> are capable of crunching on half the HF spectrum at once, I was thinking
> initially of just audio (for which the on-board converters would be
> fine) - kind of a super-TNC, with capabilities (speed/bandwidth) similar
> to Pactor-III with no patents, open-source software, and significantly
> lower hardware costs.
>
> Sound card modes, of course, have gained popularity due to their
> flexibility and low cost - but can't handle the tight timing needed for
> pactor-type modes.
>
> It just seemed to me that something like a commercially- available low-cost
> FPGA board might be able to get the best of both worlds.
>
> Yeah, I'm suggesting a minor paradigm shift. Scary.
>
> 73,
>
> Paul / K9PS
>
