Weak signal modes

This has been said here many times, but weak signal modes like WSPR and JT65 are ideal running  "in the background" modes for bands that seem dead but that may not be. At the moment and for the coming years 10m is in this category for many months of the year.

If it is SSB contacts you are after, then move down a few bands. If, like me, you are interested in "pushing the boundaries" then I recommend JT65 or WSPR is left running in the background on 10m. Both modes are ideal for beaconing and there are usually plenty of monitors. On JT65 I send "B callsign locator" when busy or not looking for 2-way QSOs and this then shows up on PSKreporter if I am copied. On WSPR the standard format is used. Both modes only need low power. JT65 seems to get more results than WSPR,even though not quite as good theoretically. The 1 minute TX period may also help.

No, I am convinced that 10m is "open" far more often than was previously thought. It is just we have not had such effective weak signal modes in the past. As we go down cycle 24 and into cycle 25 modes like JT65 and WSPR will really "come good" on 10m.

Join those of us out to prove the experts wrong!

UPDATE 1704z:  In the last week alone 19 countries have been spotted here on 10m JT65. Sunspot count is low or very low and South America as been copied most days, as have stations in Europe. There is still life on 10m for those prepared to look, even with very simple gear and antennas.

UPDATE 1836z: Best DX on 10m JT65 RX is LU3VCC (12470km).  So far this evening, 4 South American stations spotted here as well as Canary Is and several Europeans.

New versions K1JT weak signal digital modes

Bob, G3WKW, has passed on this information from Joe Taylor K1JT:

"Date: Fri, 07 Aug 2015 16:28:19 -0400

Several people have asked for an update on development of the "Fast modes" in WSJT and WSJT-X.  So here's a brief summary.

First, a review of some relevant terms and motivations.  It's convenient to think of the various WSJT protocols ("modes") in two groups:

*Slow modes* -- JT4, JT9, JT65, and WSPR.  These modes are designed for communication with extremely weak signals -- often too weak to be heard. Target propagation modes include EME and long-distance troposcatter on HF-and-up bands, and QRP Dxing on the LF, MF, and HF  bands.  Relevant signal amplitudes are approximately constant over a minute and more, aside from so-called "libration fading" for EME. Transmit/receive sequences are 1 minute for JT4, JT9, and JT65, and 2 minutes for WSPR.

*Fast modes* -- JTMS, FSK441, ISCAT, and JT6M -- and now also *FSK315* (implemented in WSJT) and *JT9E* through *JT9H* (implemented in WSJT-X. These modes are made for communication with rapidly varying signals:for example, meteor scatter, ionospheric scatter, airplane scatter, and scatter off the International Space Station.  The decoders are designed take advantage of short enhancements of signal strength.  T/R sequences are 30 seconds (or sometimes even shorter).

Bill, ND0B, has implemented a trial version of FSK315 in WSJT.  Think of this mode as FSK441 slowed down to 315 baud; the bandwidth is therefore narrow enough to make the mode legal in the "CW and data" portion of the 10 meter band.  Bill and a few others have been experimenting with FSK315 and also ISCAT-A on 10 meters, under dead-band conditions, using meteors and ionospheric scatter propagation.

I have implemented experimental submodes of the JT9 protocol in the program branch WSJT-X v1.6.1.  As with JT4 and JT65, letters following the "JT9" designator indicate increased spacings between the FSK tones. Traditional JT9 (now also called JT9A) has tone spacing 1.736 Hz, so the signals used at HF and below have total bandwidth 9*1.736 = 15.6 Hz.  The widest of the new submodes, JT9H, has tone spacing 200 Hz and therefore bandwidth 9*200 = 1800 Hz.

When used with the standard 1-minute periods, the wide JT9 submodes should be useful for the same purposes as the wide JT4 submodes: microwave EME, for example, where libration fading can cause Doppler spreading of 100 Hz or more.  Used in this way, all JT9 submodes are "slow" modes; they use 1-minute T/R periods and keying rate 1.736 baud, and they send the full 85-symbol message protocol in 85/1.736 = 48.96s.

Optionally, the wide JT9 submodes can now also use "fast" keying rates equal to their tone spacing.  "Fast JT9H", for example, uses keying rate 200 baud, so the full message protocol is transmitted in 85/200 = 0.425s.  The message is sent repeatedly for the full Tx period, in the same way as done for the other fast modes.

The fast JT9 submodes should be very effective for meteors and ionoscatter propagation, especially on the 6 meter band.  Sensitivity should be similar to ISCAT, or perhaps slightly better.  Because JT9 includes strong forward error correction, decoding results are like those for all the slow modes: you should see messages exactly as they were transmitted, or nothing at all.

Tests of the fast JT9 submodes are currently under way, with excellent results.

   -- 73, Joe, K1JT"

A couple of 20m JT9 QSOs in the log already

QSO with UA4PPQ on 20m JT9-1 today

Well that was pretty easy: I loaded the latest software, listened a bit, then called CQ in JT9-1 and managed a couple of QSOs within 15 minutes (it takes about 6 minutes per QSO). Reports also received from the USA, Canada and Siberia, so everything working well.

The mode certainly seems to be very useful on HF and takes up very little bandwidth - the scale on the screenshot above is in Hz above 14.078MHz, which is the USB dial frequency.

Using 2.5W to the end fed Par 10/20/40 antenna, but reports suggest much lower power would be fine too. Now QSYed to 28.078 MHz USB dial JT9-1 and calling CQ.

Low cost weak signal work from VLF to light

Well, I do get about a bit - in the spectrum that is!

1. At the moment I am running a test transmission on 8.977188kHz (precisely) to G3WCD who is trying to detect my VLF beacon in a 22uHz (yes micro-Hertz) bandwidth over several days. Chris is 32km away.
2. I am running WSPR on 28MHz with 200mW and, for the second day running, my QRP signals have reached Australia.
3. In 2 weeks time (when the grandchildren have gone home) I will be resuming my over-the-horizon QRSS tests on 481THz (red light) using my high power beacon and more sensitive detector. The signal is too weak to see by eye, yet the sensitive kit can detect it.

All three of these have one thing in common: the circuitry to do them all is very very simple and the kit cost just a few pounds to build.

Over-the-horizon 481THz optical signal from G4HJW last winter

In each case though the processing power of a PC is used to help extract weak signals from deep in the noise. Luckily the software in each case is absolutely free: Spectran and Spectrum Lab for VLF and optical frequency detection and WSPR software for the WSPR tests.

Presentation on CW and other weak signal modes

Andy Talbot G4JNT has put an interesting presentation about weak signal modes onto his website. He gave this talk at a recent Microwave Round Table. See http://g4jnt.com/MartleSham.htm. It is exploring how we can push the boundaries further when working with very weak signals.