Propagation by mode

…as opposed to by band.

If a band is usable at a certain time of day, it’s usable right? The mode of transmission shouldn’t affect it, notwithstanding that some modes are more efficient than others.

I’m in GW in the middle of a few days away activating, and obviously focusing on the Flavour band of 17m. I am observing the same pattern every day. Through the mornings, CW and SSB work well. Moving into the afternoon, it becomes much harder to make QSOs on legacy modes, and virtually impossible into the evening.

So in the second halves of days, I’ve been switching from CW to FT8 as my first choice activating mode. The interesting thing is that later in the day, when the CW and SSB portions of 17m fall silent, and no one comes back to a CQ call despite self-spots, the FT8 frequency is not only buzzing with signals from all corners of the globe (so to speak), but audibly loud too.

It’s as though hourly variations in propagation do not apply on 18.100MHz when they absolutely do below that and above it.

Similar I guess to the sudden upturns in propagation on major contest weekends!

1 Like

An educated guess: later in the afternoon the ionisation of ionosphere drops because the decrease of radiation from the sun.
With regard to influence from the sun, do not rely on SFI number but on X ray radiation from the sun.
Low A numbers are not good, upper A or B numbers are much better.
Do not forget the negative influence of a earth magnetic field disturbance.
I guess very strong Es will block F layer reflection?
Since you keep a good eye on the time, see if this effect you see shifts with seasons.
A good website for information on propagation:

for x ray radiation from the sun (GOES satellite measurements):
It is even possible to detect lower amount of qsos when the European OMs have their lunch.


First they took my Fuji Neopan 400, now they want my SSB and CW too…

1 Like

This morning I worked EA2BD for my first SSB contact of the 17m flavour, others that I looked for were inaudible. I even went as far as listening for some of the CW activations but no luck, the propagation force was not with me! Still, now I have proved to myself that it can be done, and I will carry on listening until the flavour is over. There was activity on sideband this afternoon but no SOTA, however there were some pretty strong signals from the computer jockeys!

Hi Brian, I could hear you working EA2BD, shortly before I worked him from Y-Golfa, GW/MW-061. You were rst 31 with me. I’ve had several inter - G contacts on the band in the last few days, which has surprised me.

On a much smaller sample than Tom’s, there did seem to be a change in “something” between Y-Golfa in the morning, and Stingwern atfer lunch. Same radio / power / antenna, and about one hour operating each time. And yes, lots of loud warbling on 18.100 in each case!

am 10 cw, 11 ssb
pm 12 cw, 1 ssb.

Hi Guys,
From my perspective as a chaser in California, CW signals are always easier to copy than SSB. It’s always easier to pick out a few characters or signal report on a real weak CW signal than on SSB. It just takes more signal to get that voice up out of the noise enough to copy. Time of day doesn’t seem to matter, except if propagation is better at some time of day, then both modes will improve. If you have some noise, the narrower passband used for CW reception will also cut down on the background noise. I use 250 Hz and sometimes 150 Hz filtering for CW.

73 and good hiking/chasing!
K6YK John in CA

1 Like

Yes, I could hear that you were there but not read anything from you.

I think the issue is social … It’s summer, vacation time operators in the afternoon are more absent. The FT8 does not allow robotic operation?

Gomes CT1HIX

I guess it’s possible the FT8 activity is largely automatic and can therefore continue without much operator intervention, while CW and SSB need a little more active operator presence? :smiling_imp: :japanese_ogre:

I’ve certainly seen traces of some interesting stations in the FT* scroll from places further afield than I’ve been able to hear on other modes, but then that’s at least partly why FT* is popular these days.

For me, time at the rig depends on the time-of-day, the weather, and what else is going on. I seldom turn a rig on in the morning until I’ve had at least one mug of coffee, so don’t expect me to be chasing SOTA much before 9am local. Then, if it’s not too hot or sunny I may go and do some garden work in the morning. The rig may get some attention early in the afternoon, particularly if it is too hot (or wet, or, at other times of year, cold) out in the garden. At this time of year early evening is prime garden time, so the rig won’t get much attention until the sun has set. At present that boils down to my doing most chasing between about 08:30 and 14:00 UTC, with the main peak around 09:00 and a second peak around 12:00.

The mode I work depends (a) on what mode is at present my favourite, (b) what modes are being spotted, and (c) which activators I can actually hear over the noise etc… Over the last few months that’s worked out at about 90% CW, 5% data and 5% phone.

So far this month I’ve heard chasers working a few 18MHz activators, but I’ve yet to hear an activator on 18MHz. Likely, much of that’s down to propagation at the times of day I’m at the rig. A few minutes ago, PROPquest | Graphs was showing me this:

Strange how it all works to me as I can’t hear a peep off Tom M1EYP yet I can hear ZL2JML Warren in New Zealand.

This remains true, so I guess I’m not picking up anything from the 18MHz “flavour”.

That often seems to be the way with the FT* modes. I’ve heard all sorts of interesting places while looking for SOTA datamode activators. I’ve even tried working some of the most interesting ones, but it seems there’s a significant difference between “hearing” and “being able to work” even on FT* modes…

…but I’m not bothered. My FT* activity, like my “flavours” participation, is mostly just another incidental by-line.

Propagation seems to be fickle. I don’t think the numbers mean much. There have been times I have work some good DX with the SFI at 68 and can’t hear anybody with an SFI of 73. Most of the time in the early morning I have trouble hearing any of the activators, then it will improve into the afternoon then drop off again later in the day. Then there are other days when the early activations are coming in very loud then later in the day they are weak or not copy-able. There are days when I am able to work several SSB activations and then can’t hear the CW ones (go figure that one). I have had activators come in very strong then an hour later another one from the same state or even the same summit on the same band is not copy-able. I have also seen times when 20 meters is poor in the morning then builds all day and is workable until 10pm local time. Also some times the skip is real short and sometimes it is long. So I guess my point is that there is many variables, some not understood or maybe not even discovered yet and some local like the activators antenna or antenna orientation. Trying to figure it out is near impossible with out a lot more data than we have. I have given up trying to figure it out, if someone is on I will tune in and if I can hear them great, if not I move on.
Jeff K6QCB

1 Like

Hi Jeff and all,

The propagation mechanism is as we know unaffected by mode. It is affected by where the sun is in the sky and how blotchy the face of the sun is.

The CW crowd probably pack it in around 11 am local when most of the bands go off for a siesta.

FT 8 never sleeps. Here 15, 17, 20 are OK mid to late morning picking up later in the afternoon. If you want to know where the band is open too, check what you can see on FT8.