Waiting for family, working the bands

Another round of waiting for teenagers to return from some crazy activities somewhere led to a brief opportunity to work 17m from the shore this afternoon.  Weather continues to be amazingly warm and sunny for the time of year, but with a moderate easterly wind that brought out the windsurfers.

I wondered if I could get JTDX to work on the Raspberry Pi 4B, so downloaded it using the mobile wi-fi.  Whilst the version listed for Linux wouldn't work, the version for the Pi 3 did.  

One thing to note if you download JTDX for the Pi is that, once installed, you must reboot to see the program listed under 'Sound and Video'.

 JTDX, up and running on the Pi 4 in the car.

From then on, it was easy going!  No more WSJT-X, which is far less capable than JTDX.  

Very happy to be the only station being heard on 17m WSPR by VU3KAZ (1W out), despite the simplicity of my /P station.  Of course, with the seawater, the effective signal is known to 'grow' to something between 10 and 25W typically. 

Just a shame K2IL started sending FT4 for quite a while, straight on top of ongoing WSPR transmissions.  In fairness, after sending him a polite e-mail, he moved a good distance down in frequency within a minute or two.

Sun, wind and kite surfers (and a weirdo doing something with a big antenna!)

I managed 19 FT8 QSOs using 6-8W, spanning the western US to Brazil and Indonesia.  Again, very pleasing results with such low power.

6-8W FT8 coverage at 18MHz from the beach.

Latest on JTDX RC144_5

 
After 39 of my own WSPR recordings at 14MHz were analysed yesterday, it's now possible to say that the latest JTDX update, which is not generally available at the moment, has a 2.7% better decode rate than WSJT-X 2.1.2.

[UPDATE 1: after an overnight listening session on 40m, the 2.7% improvement fell to just 0.5% with a much larger (1049) sample of decodes.  WSJT-X managed to decode 1044 of these.

UPDATE 2: a roughly 18 hour listening session at 14MHz resulted in 728 decodes, 717 of which were decoded by WSJT-X, yielding a 1.5% advantage to JTDX.] 

I had a look at which signals WSJT-X was failing to decode.  It's all a bit odd, because there were two signals of -25 and -26dB, and one of +3dB.  None of the signals were very close to other traces, so I can't figure out what WSJT-X is doing.  The difference appears from time to time, regardless of how strong propagation is at that moment.

UPDATE: -30 and -31dB signals are being decoded regularly by JTDX now.  It is also getting down to -34dB so far, which is as low as the alternative WSJT-X goes:

2019-11-29 13:20

LA7EPA

14.097191

-34

0

JP99of

5

JTDX vs. WSJT-X

For a long time, I've been wondering whether JTDX has fallen behind WSJT-X in its sensitivity to WSPR signals.

For some reason, I never simply saved a set of receive runs and worked out the numbers.

So, this morning, that's exactly what I set out to do.

Reception was carried out at 14MHz using a Yaesu FT-450, in a stable operating temperature, having run continuously over the past 36 hours.  Recordings of the time slots were made, and then played back for decoding 'offline' by each software.

Number of 2-minute time slots: 21 (42 minutes total data gathering)

Time of recordings, including gaps between switchovers/other activities: 07:18UT - 08:20UT.

Recordings made using JTDX v2.0.2-rc139 (Release Candidate) as the receiving software:

JTDX decodes: 97
WSJT-X decodes: 105

Recordings made using WSJT-X General Release 2.1.0 as the receiving software:

JTDX decodes: 104
WSJT-X decodes: 117

Combined spots for all runs:

JTDX total spots: 201
WSJT-X total spots: 222

Only in one time slot (07:38UT) out of 21 did JTDX decode (one spot) more than WSJT-X.

A check was made that 'live' decodes were no different to decodes from saved recordings.  There were no such differences.

So, the firm conclusion is that WSJT-X is 10.4% better than JTDX, at least in their current forms, accepting that both softwares are in continuous development, and that the JTDX version used is a RC, not a General Release version.  Importantly, JTDX developers have tended to focus on FT8-based HF DXing aspects of their software over the past months, whereas WSJT-X WSPR performance has been improved - clearly rather successfully.

It's likely that, at different times of the day, notably into the later evening at present, when most signals are weak at 14MHz, WSJT-X will prove to outperform JTDX by a wider, possibly much wider margin.  More on that as data is gathered...

WSJT-X vs. JTDX - a quick test.

Yesterday, I reported on the SDRPlay RSP1a appearing to be a very good receiver, at least as good as my FT-450 transceiver.

That result, which got me to number 5 in the DX listening challenge, was using the latest version of WSJT-X, which is meant to have 'improved' WSPR sensitivity.

At just after midnight on 20/12/2018, I changed to using JTDX for WSPR reception over another 24 hours.  So that I could tell the difference, I used plain MW1CFN as the call, rather than the MW1CFN/SDR used the previous day.

Was one software better than the other?


Well, I came in at number 6 with JTDX, four spots away from being number 5.  Realistically, one can say this is an inconclusive result, especially as it only covers two full 24 hour periods.  Those stations in the top 10 can move around a lot from day to day, mainly according to geomagnetic conditions.

Overall, the two softwares seem to be very similar.  For general antenna performance checking, use of one over the other might be of no real consequence.  For more critical work, the new WSJT-X may be preferable.

The weekend is now here, together with it's massive uptick in QRM.  Therfore,  SDR operations are given over to VLF reception, down at around 5kHz, with a new multi-turn wire loop (about 215m total wire!) that even got my daughter excited and busy winding last night!  The flexibility of SDRs is really amazing, and opens up yet another lifetime of radio interest!