[pskmail] The hardware modem idea (sri, long rant)

  • From: Per Crusefalk <per@xxxxxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Mon, 30 Apr 2012 12:41:09 +0200

Hi all,

A hardware modem has been proposed by some here and so I started
thinking about why we would want that. Using an external modem is of
course the way we have connected computers to external communications
for as long as I can remember but is that still the best way to go about
it? 

The term hardware modem makes me think about a solid, dependable old
tone encoder/decoder like a bell 103 modem. A very simple modem that did
not have a cpu and very rarely caused any trouble. Todays modems are not
like that, they are small computers. For instance the P4 Dragon was
mentioned and it sports a Quad core DSP from Freescale weighing in at
6400 MIPS. That's a PC you can connect to your PC. As the cost is 1400
euros its not a cheap pc either.

But, I tried to see both sides of this and so I wrote two columns on a
piece of paper. What are the benefits of using an external modem and
what negative effects can I see?

Positive effects:
* System testing can be done more effectively when we better define the
hardware that will be used, less surprises with unknown stuff.

* If we create a custom modem we could have that do stuff without the
pc, like position beacon transmission with a timer.

* Some very capable modems allow very good transmission speeds.

* PC requirements can be lowered as the processing is external

* Radio interfacing standardized so that levels, rfi is possibly better
controlled

* The concept is known and easy to understand for beginners

Negative effects:
* There are no "hardware modems" that can handle the modes and the
adaptive use of them we have today.

* If we use a pactor modem then we will rely upon a proprietary modem
that breaks many of the benefits we have now:
- The android client becomes useless. Today we can work using only a
radio and a phone/tablet. Using a phone, a pactor modem and a radio is
not an improvement.
- Very good narrow, robust modes for QRP stations gone.
- Cost. 1400 euros can be better spent on other things.
- Cost is also a huge barrier to entry for new users.
- We become yet another system that relies on pactor. Other projects 
have done that for a long time so we will be many, many years behind
their features.
- I like open source and in the long run I think its likely that the
remaining hardware modem firms will join the likes of AEA, Timewave,
Kantronics e.t.c. and either completely disappear or stay around but
slowly wither and become obsolete. Its hard to compete with free,
especially if the free alternative is better.

* Creating a custom modem that better supports our modes and needs is a
big project in itself and will have an impact on project progress.
- Support organization needed, production of these beasts??

* Likely an extra hurdle slowing down waveform progress

* An extra modem, power supply and cables takes a lot of extra space in
my backpack.


Summary:

Why use an external modem when you still need to connect the PC to do
anything with it? Why not let the PC to do the processing as it's
already up and running? The cost is huge. It takes up extra space on my
boat and requires power. Custom things like position beacon with timer
can be handled just as well by the android client. The concept of using
an external modem is tied to the old model of desktop computing. It does
not translate very well to the modern world where a phone, a bluetooth
interface and an FT-817 in the backpack can be all you need.

At the moment we are having stability issues with our current choice of
modem software (fldigi). It crashes once a day for me. Moving to a
pactor modem will remove many of the benefits this system has today but
a custom made modem could handle "our" modes. Moving to a custom made
hardware modem that supports the modes we require is a process of
developing a software that can use a dsp to decode and encode the
waveforms we need. That is just what we already do with fldigi so the
challenges are the same. We would need to get that custom modem very
stable (which is exactly what we need with fldigi now).
One idea could be to open a socket on the android client and use a phone
or a tablet as your hardware modem... 

Conclusion:

The negative effects of using an external modem far outweigh the
positive.

Sorry about the long rant here but this has been proposed several times
so I needed to think and say a few words about this.

73 de Per, sm0rwo

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