[ADXA] UKSMG Proposal

[Crownhaven]

This was received from the UK Six Meter Group.  Some of you might be 
members.  I highly recommend joining.  In any case, here it what is up 
their sleeve.  Just FYI.......

Steve, QQ

Some interesting thoughts from G4IDR?

73

Chris

G4IFX

cid:338141019 at 14042014-1FF4

/www.uksmg.org/<http://www.uksmg.org/>//

*From:*WSJTX at groups.io [mailto:WSJTX at groups.io] *On Behalf Of *David Redman
*Sent:* 25 May 2020 12:29
*To:* WSJTX at groups.io
*Subject:* [WSJTX] FT8 on 6m SpE

Listening to the recent 6m Sporadic E openings ( SpE ) with some 
possible F2 mixed in there then it is apparent to me that the 2.5 / 3kHz 
window is somewhat impracticable when we have widespread sporadic E 
openings particularly in busy Europe.

Following on from the recent comments of others I agree that stations 
need to spread out

In one opening I was copying FT8 signals down to -24 but the strongest 
was +42 (  a local station 30 miles away ) BUT SpE European ‘local’ 
stations from southern Spain and Italy were +38. This is not uncommon 
given how SpE works and comparing FT8 signals with the strength of some 
SpE contacts on SSB and CW.

So we have a range of signals of some >66dB WITHIN the audio passband. 
No matter how good your rigs filter is ( SDR or analogue ) it’s not 
going to help ,  we are asking a lot to decode every signal in this 
2.5kHz passband down to the decode limits of FT8  ( can you switch your 
agc off ( does your noise floor change on the waterfall as the AGC comes 
into effect on strong signals )  , do you peak the wanted signal , notch 
the strong , narrow your passband assuming you know where the real weak 
DX station is in the passband etc etc )

Paraphrasing from W9KNI et al ,  if the station your working is stronger 
than -18 your not working the real DX

If on 6m SSB you have a 150kHz segment and 2.5kHz signals then that’s 
potentially 60 stations without overlaps.

Turning this to FT8 with a 50Hz bandwidth in 2.5KHz that 50 stations , 
ok similar without overlaps

However I do note that at busy times the FT8 QSO throughput rate is very 
low AND many stations are calling CQ for 10 minutes or more without a reply.

*_A Proposal_*

So how about spreading out into say 5 segments 2.5kHz wide ( In this 
suggestion I am using 2.5kHz rather than 3Khz or 4kHz as it seems to be 
the most used ). My suggestion of 5 segments is a compromise of 
spreading out v time to decode all segments

WSJT-X has rig control, most stations use it , so how about adding a 
little search automation to the WSJT-X program on FT8 and it searches 
these segments 50.5080 , 50.3105 , 50.3130 . 50.3155 and 50.3180MHz

It could be user selectable to search *1^st * ( even ) sequence ( 0 to 
15 and 30 to 45 , *2^nd * or *both* periods ( 0 to 30 secs ) before 
moving on automatically to the next segment and doing the same. Decoded 
signals are then indicated by the segment or grouped by segment.

Once a stations signal you want to contact is decoded and you double 
click on it then WSJT-x would place your TX in that segment and on that 
frequency so that we don’t have split QSO’s spread over the entire 12.5kHz.

This way QSO’s are spread out , you can use your receiver filters to 
better effect and I am convinced that the FT8 QSO throughput would go up 
despite it taking 5 times longer to scan all segments AND you would 
contact more weaker stations.

This proposal still keeps regional SpE contacts away from 50.323MHZ the 
Intercontinental DX calling frequency and rightly so.

Just trying to help 50.313MHz might not be the right frequency area for 
such a proposal  , others can decide and it you don’t like my suggestion 
fine , make an alternative or carry on as you are.

Frankly after making some FT8 SpE QSO’s , I went lower in the 6m band 
and had a few SSB SpE and even more weak signal CW QSO’s , much more fun 
with further distance QSO's and easier on the ears despite my tinnitus.

I think at least 80% of theFT8 QSO’s today could have been made on SSB 
and 95% on CW , so by spreading out we might be able to ‘hear’ the weak 
-24dB FT8 signals ( which we would not be able to work on CW ) far more 
often.

Currently I don’t think we are consistently reaching the full potential 
of the weak signal capability of FT8 especially given the enhanced 
decode capability of WSJT-X-rc1 ( now rc2 ).

I use -24dB as the lowest signal decoded , maybe it’s lower but you get 
my point

This concept could be applied to other bands BUT PLEASE keep this FT8 
mode away from the existing EME CW and JT65 / QRA64 sub-bands.

Of course if MAP65 had FT8 capability it would serve the same effect but 
not everybody has that external I/Q SDR into MAP65 capability. MAP65 is 
a very useful program and I believe that there are some possible 
enhancements to its JT65 capability already trialled but not implements 
so it’s due for an upgrade anyway. Again MAP65 could decode a 12.5kz 
bandwidth each cycle but with up to 5 times the processor power needed 
?? this might be a limitation compared to the above segmented approach ) 
and with an improved rig control interface could then move your rig to 
the required TX frequency.

Notice I use segments not channels and QSO’s / signals not Traffic……. 
some of you will understand my point.

Dave

G4IDR

VHF up DX contacts rule ok ( EME , F2 , SpE , Tropo etc )

p.s. I write very little code so don’t ask me to do it , I am not a 
radio or electrical engineer but a decent mechanical engineer who enjoys 
the technical aspect of amateur radio including construction and trying 
for weak signal QSO’s and have done so for some 45 years.

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