[resent after my ISP reported mail server bounced it ...]
Hi, Joe...
So far, I haven't personally used WSJT above 6M because I do all of my upper
band operating while roving or mountain topping, and I've preferred to travel
light (using CW when SSB doesn't cut it), but that's about to change. Others
have solved these problems by operating from home or by using laptops with
ultra high contrast displays and built in GPS (as found in police patrol cars
and firetrucks). Some ops don't have CW, so even FT8 is a big jump in
sensitivity for them.
There are about half a dozen ops in 6 land who have been on WSJT at 10 GHz and
based on the response at a recent Microwave Update session on digital modes and
activity in recent contests, that number is due to rise. A common comment is
the desire for shorter overs and for six digit qrids.
The early adopters that I spoke with came from the EME and meteor scatter/weak
signal terrestrial communities and mostly had tried JT65C, with some attempts
at QRA64 (unsatisfying) and ISCAT (satisfying). Others were beginning to try
FT8.
For tropo scatter at 10 GHz, they found that there is a watery sound (rapid QSB
under 1 sec period) combined with a medium slow fading. There is some
spreading, but it's not too bad (except during higher winds and rains catter
periods). The medium slow fading period is short enough that 30 second overs
and retries on dropouts make it tedious to complete a QSO, so the shorter
periods of FT8 appear to be a good trade for the slight reduction in
sensitivity and the narrower tone spacing. They reported that a fast mode like
ISCAT can work better than JT65, even though the sensitivity is much less; they
want to catch the QSB peaks and get the QSO done. Of course, this is even more
true for aircraft scatter (another popular mode for DX), as you know from
extending ISCAT for Rex Moncur.
I can't comment on MSK144... the short overs are appealing, but I don't know
anyone who's tried it yet for aircraft or tropo scatter. I'm not sure how well
the OQPSK modulation will do on a microwave tropo scatter channel, as opposed
to the FSK modes. Other fast modes (upper JT9 modes?) might be worth a try, too
(especially during rain or wind scatter, where the wider tone spacing might
help), but aren't slated to support the larger payload at this time.
The upcoming revision is a great opportunity to find out how just how well FT8
and MSK144's short overs will work. Most microwave activity (other than DX
record attempts and occasional local activity) is during the contests; longer
exchanges and sending six digit grids by an extra pair of free form messages
are inhibitors that can easily be removed. Why not add this to our toolbox?
73, Mike
PS: In reviewing the MSK144 writeup, I noticed the mention of the call sign
hashing, which I'm guessing is also used in the DXpedition mode compound reply
(reported with the < > notation). If it can work, reusing this method to
shorten the contest exchange is probably better that the shorthand suffix
method that I suggested. Implementor's choice.
----- Original Message -----
From: "Joe Taylor" <[email protected]>
To: "WSJT software development" <[email protected]>
Sent: Saturday, August 4, 2018 5:38:46 AM
Subject: Re: [wsjt-devel] NA UHF/SHF Contests
Hi Mike,
On 7/27/2018 8:15 PM, Mike Lavelle K6ML wrote:
> Hi, Joe and team...
>
> I think the ver. 2 FT8/MSK supporting six digit grids is a great idea.
>
> Now that you're willing to encode six-digit subgrids and have a bit more
> payload,
> I'd like to request support of six-digit subgrids for the NA UHF and
> microwave contests. ...
Thanks for your message suggesting possible FT8/MSK144 features that
could be interesting for NA UHF and microwave contests.
We're quite aware of the required exchanges in these contests... but it
seems to me that the capabilities of FT8 and MSK144 are not well matched
to the needs for these bands. Are you aware of any significant use of
FT8 or MSK144 on 222 MHz and higher? I am not. In the past I have used
JT65 on 222 and 432 MHz to gather a few hard-to-work multipliers in VHF
contests. In those cases (troposcatter, very weak signals) JT65 is
probably a better mode than FT8. (Six-digit grids can always be
exchanged, where needed, in free-text messages.)
Are you really suggesting the use of FT8 at 10+ GHz? Have you tried it?
-- 73, Joe, K1JT
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