Ionoscatter 2026

Ionoscatter ("ionospheric scatter") is forward scatter in the ionosphere. I often work stations on 2m from 800km out to about 1600km at around this time of year, but I reckon that ionoscatter has potential for use during much longer periods.

In the past ionoscatter was only thought useful for very high powered stations. Now with the benefit (?) of FT8 I find it useful at moderate power (200 to 400W) with an equally moderate antenna (9 elements) during June and July. With a more suitable data mode I suspect it would be useful for longer periods during the year.

Right, on now to this year's results so far:- 

144MHz Ionoscatter contacts at GM4FVM on 2 and 4 July 2026

Click to enlarge image etc. 

OK, so first issue:- this looks like the time of year and direction you might be working Sporadic E, so how can you be certain this is not Es?

Well, Ionoscatter (should we call it Is to distinguish it from Es?) is generally much weaker. Also, unlike Es it hangs around for ages and can last hours on an individual station. And thirdly it tends to occur only at this time of year (using FT8). So, in 2023 I heard it four times between 30 June and 12 July, in 2024 only once on 23 June, in 2025 not at all, and so far on two days in 2026, 2 and 4 July. Generally the times were between about 10:00 and about 13:00 but one as late as 14:39.

Left: a tropo signal (MM0CEZ), right ionoscatter (SM0LQB)

Ionoscater leaves a unique trace on the FT8 waterfall. It is often broken and patchy but stays at the same trength. Often you can see meteor scatter bursts which usually prevent the transmission from decoding. Using FT8 it can take a while to get the QSO finished. The key point is that although it is weak, the signal can been seen for long periods at fairly steady strength. The ultimate limit is FT8's ability to decode it because FT8 is not a very good mode for weak signal work.

Second issue. You may ask what is the point of looking for this form of propagation when it is weak and only usable for a short time of year. Well, it seems to me that if we were unleashed from the limitations of FT8 it would allow decodes over long distances for much longer periods of the year. 

The mode I would suggest which I fancy would work better would be Q65. Much work was done by G4CDN and others using JT65 and QRA, the modes which were available to them at the time (see  https://ei7gl.blogspot.com/search/label/Ionoscatter and please don't blame me if this link stops working - look it up instead). JT65 certainly works, but surely Q65 is much better suited to this type of work.

Ionoscatter is in fact working at the higher end of its frequency range at 144MHz. It is suggested that it works best at 35MHz and it should therefore be a good target for 50 and 70MHz experiments. And yet I rarely see European stations trying this. If I look at DXMaps I often see US and Canadian stations working to these sorts of distances using Q65, but I do not see that on this side of the Atlantic. Anyone interested? 

Some of you read my old blog, where I often lamented the use of FT8 on VHF/UHF when I feel sure that Q65 is far better suited to these frequencies. Well here I go again and I am not finished today. If you read the WSJT-X Users Guide you will see the uses Q65 can be put to. It even shows a Q65Ionoscatter image. I'll print it below here because I suspect that very few amateurs ever read the guide, but instead use WSJT-X without really knowing what they are doing....

So for now I will continue to look for Ionoscatter on 2m for a few weeks each summer, in the mornings. I know that it has far more potential, but if everybody insists on using FT8 then that is the only time I can use it.

Any Q65 skeds from stations in the 800km to 1600km range welcome. 

73 Jim

 

 Below: From WSJT:X users guide (link to QSJT-X site is in the side bar of this blog)

12.4. Q65

Q65 is designed for fast-fading signals: EME, tropospheric scatter, rain scatter, ionospheric scatter, trans-equatorial propagation (TEP), and the like. The following screen shot shows the Wide Graph and decoded text windows after processing a Q65-60A sequence received via EME on 6 meters, by W7GJ Transmissions are decoded from N0TB, N8JX, W1VD, and VE1JF, all by the EME path.

The Q65 decoder takes advantage of a priori (AP) information such as the encoded forms of one’s own callsign and the message word CQ. In normal usage, as a QSO progresses AP information increases to include the callsign of the station being worked and perhaps his/her 4-digit grid locator. The decoder takes advantage of whatever AP information is currently available.

Here’s a similar screen shot for a 6 m ionospheric scatter signal over the 1155 km path from K9AN to K1JT, using submode Q65-30A. The received signal was barely audible most of the time.