[RTTY] RTTY Digest, Vol 135, Issue 33

[Michael Adams]

Joe W4TV wrote:
> On 3/19/2014 9:35 AM, Michael Adams wrote:
>  > It doesn't take much of a message for a narrow sub-300bps signal to  >
> become painfully slow, and potentially problematic if conditions  > aren't the
> best.
> 
> If conditions aren't good enough for 300 symbols per second, they will certainly
> not be any better for faster signals.  

In real-world practice, your mileage can vary significantly depending on the modes involved.

For example, in MARS, I've seen where one of the STANAG waveforms that's being adopted works best if you choose a speed that is not too slow, and not too fast.  Too fast, and it will be unintelligible to the receiving stations;  too slow, and you risk losing part of an over due to QSB removing the signal sync.

In an ARQ situation, you want to keep the overs reasonably short, so that you don't waste too many transmissions where fading or a static crash prevented correct reception.  Negotiating a speed that is fast enough to be efficient, but not so fast as to be uncopyable, will make better use of limited bandwidth.

> through an eye of the needle.  300 baud is enough for *amateur* purposes at HF
> - if there is a requirement for faster communications, take it to commercial
> internet either maritime service or satellite based service.

I would be careful about wielding arguments relying on "need" or "availability of other services" around.

In this day and age, what is the "need" for amateur radio in general?   If communications via amateur radio are supposed to be limited to incidental communications not possible by other services...well, what does that really mean in a world where the internet is available on a 24/7/365 basis by satellite at most latitudes?

Perhaps we should kick all the ragchewers and nets off the bands, shut down the NTS, and dismantle the amateur side of winlink, because such communications are possible (and are more effective and efficient) by commercial means today.   Perhaps the only transmissions permitted on the amateur bands should be the occasional test transmissions, if need/availability are the key criteria.

(Just let me make DXCC Honor Roll, and give me a bit more time to reliably get my CW speed above 35wpm before the purge begins, please!)

Heck, given the availability of good HF-simulating software now, perhaps even on-air experimentation is no longer "needed"; perhaps it's time to start non-renewing our tickets because there's no "need".

I agree that slow, narrow signals are quite adequate for the ragchews and keyboard-to-keyboard communications that are one of the highlights of amateur radio.   A lot of the broadband stuff isn't needed on a routine basis in amateur radio; the modes I use in MARS I mostly wouldn't normally consider using (at least not at the same signal-widths, or not on HF) on a routine basis because it's wasteful of our limited bandwidth.

We should be reminding ourselves that, not only should we be using the minimum power required to effect a desired communication to minimize QRM, we should also be using the minimum bandwidth required, also in the name of reducing QRM.

However, one of the raisons d'être for amateur radio is to provide a place for hobbyists to experiment -- to research, play, and learn in a sandbox without there necessarily being a need...or perhaps with an eye towards taking any knowledge gained and putting it to use in other, more conventional services.

The NBEMS crowd have done some pretty impressive things with narrowband transmissions; several of the mode-variants now found in fldigi, for example, aren't permissible on HF from the US today because of the 300 baud restrictions.    And, if I had the time and skills to do so, I think it would be an intriguing challenge to try to improve upon what the Germans have done with Pactor 3/4...preferably in an open-sourced manner.

Such fast/broad transmissions aren't needed for routine ham communications...but there is still plenty of opportunity for experimentation, provided (of course) that such experimentation is done in a responsible manner which doesn't excessively disrupt other users of the bands.

It's the need to not excessively disrupt other users of the bands that the League seems to have forgotten in their petition.

-- 
Michael / N1EN