[VHFcontesting] Ionosphere Scatter

N1BUG paul at n1bug.com
Mon Oct 24 10:30:17 EDT 2016


Hi Sean,

I am no expert by any means but I can share an anecdote or two.

I became interested in ionoscatter at 144 MHz after talking to 
SM2CEW and other Europeans about it. For a period of time in the 
early 1990s I ran daily or almost daily skeds with big stations in 
the midwest. I was running 1500 watts and 20 to 21 dB antenna gain. 
My antenna was an EME array, quite low and blocked by trees so I may 
have suffered some there. This was all using CW. Most skeds were at 
noon or close to it. Earlier or later signals were not as good.

I could work KB8RQ at 836 miles almost every day. Actually I don't 
recall any days we tried and failed. Some days it was a struggle, 
other days signals were very solid 539. A couple of times we 
switched to SSB and were able to communicate. KB8RQ was running 1500 
watts to an array with gain somewhere in the 26-30 dB range!

On the better days I could work stations with 20 dB gain at similar 
distances. On the very best days I could just barely eke out a QSO 
(callsigns, signal report, RRR) with K0IFL at something over 1200 
miles (I have forgotten the exact distance, though 1220 miles seems 
to keep floating around my brain as I think about this). K0IFL had 
20 to 21 dB antenna gain.

Perhaps you can roughly extrapolate what is possible on digital 
modes from this. I have no idea.

I must say it was fun being able to work 800+ miles every day on 2 
meters! If I ever get that much power and antenna gain again, I 
would like to continue to play with this fascinating propagation mode.

73,
Paul N1BUG



On 10/24/2016 10:02 AM, Sean Waite wrote:
> Hi everybody,
>
> I see that WSJT has an "ISCAT" mode for ionosphere scatter. I can't find
> much about how to operate in this mode, or even much about ionosphere
> scatter in general.
>
> I gather that it's a daytime mode, best at noon and loves it when the K
> index is high. I also see things about how the military used to do it with
> 40kW transmitters through 20dB gain antennas. I'm a few dB short of that on
> most bands.
>
> OZ1RH has an article on qsl.net (qsl.net/qz1rh/ionoscatter_lecture_2002.htm)
> where he has a little info on it, but not much about what mode he was using
> and given the age I doubt he's using any of the JT modes. He suggests 1kW
> with a 12dBd antenna may be possible on 6m, but I'm hoping with the ISCAT
> mode a lesser station could do it, and maybe even 2m.
>
> I can't find much about whether the antenna requires elevation.
>
>  He does suggest that it has a sweet spot of around 1000-1800km, which I
> think puts it beyond the reach of meteor scatter. Is this a mode that is
> ever used in the contests? Does anyone have any additional information
> about it?
>
> Thanks and 73,
> Sean Waite, WA1TE


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