Re: Enough is enough


David Hilton-Jones
 

Many thanks Neil.

 

A lot of info and I’ll look at the links you mention.

 

Not sure I’ll try following planes with the slew drives!

David

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Neil Smith G4DBN
Sent: 20 July 2022 09:50
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Enough is enough

 

I've had some RS contacts with Clive from up here in East Yorkshire, also seen him on aircraft scatter and tropo, so it's certainly a feasible path so long as there isn't a load of absorptive wetness over the Staffordshire Moorlands. KBQ is detectable here about 50% of the time at 342 km, and usually by AS even if there's no RS or tropo, subject to absorption being low enough.

 

The scatter map at https://www.egloff.eu/rsmap/rsmap.php is sometimes useful as it shows bearings for both ends of a contact to a particular scp.  I was looking into a feature request for the paid-for service from Weatherquest to add in a lot more facilities for rainscatter, like tagging and tracking scps and setting alarms, but other priorities came up.  WQ has 5 minute radar updates.  Problem as ever with radio folks is that paying for a service it often a step too far!

 

The Midwest folks use their meteo service to look for storm heights as well as location.  not much use in the UK as we rarely have "proper" RS like within continental Europe. I sometimes get decent RS from storms over the ON/PA coast deep into Germany, but they are right at the distance limit.  Storms over the North Sea very rarely produce any returns.

 

With RS there are two main models of the scatter mechanisms depending on the distribution of drop sizes.  Mie scattering has a lot of forward gain but needs drops to be a significant fraction of a wavelength. They are both the same physical effect, but as the drops get larger, there are phase shifts and other effects that modify the pattern. Most scatter at 10 GHz other than from large hail in thunderclouds is Rayleigh scattering, which is described well by Mike G0MJW at http://www.mike-willis.com/Tutorial/rainscatter.htm

 

I can't remember the maths but there is a dependency on scatter angle of the polarisation. I was thinking about retrofitting rotatable polarisation to my terrestrial setup just to see if there is any benefit for side-scatter. If you want full-on techie details, there's a good paper at https://www.jstage.jst.go.jp/article/pjab/86/6/86_6_539/_pdf/-char/en

 

Don't forget that backscatter works as well, I've had a few contacts from storms over the French coast back into the southern UK.

 

If your slewing drives are fast enough, you should be able to track planes and try off-axis aircraft scatter by pulling the ADS-B location data and using that to drive the az-el.  I do it using my terrestrial setup from planes on the glide path into Doncaster and East Midlands, but I only use it with omni beacons and the WebSDRs as I don't know anyone else who is daft enough to have the right setup to play.

 

Pointing your EME dish at nearby thunderstorms at 20 degree elevation might produce some interesting results. You are behind my tree belt so there's almost zero hope of a direct contact, but it should be a doddle using off-axis plane or rain scatter.

 

Neil G4DBN

 

 

On 20/07/2022 09:03, David Hilton-Jones via groups.io wrote:

GM Clive

 

I’m relatively new to 3cm. I have a 1.8m dish and 20 watts for EME. For tropo a 60cm dish and 3 watts.

 

I have been on EME for about 9 months and worked 30 initials. The dish is offset, and I’m limited to elevation above ~20 degrees, so no use for tropo/RS/etc.

 

But on tropo I have much less experience and am very keen to experiment and learn more! In particular, I’d like to try rain scatter.

 

I can normally copy the Taunton beacon. Yesterday there was a band of rain between us. There was marked signal enhancement, with a lot of spreading.

 

I’d be very keen to try with you when we have some precipitation between us – and I’m sure you have more experience than I do, so very open to suggestions.

 

What I used yesterday, to see the rain between me and Taunton, was:

 

https://www.metoffice.gov.uk/public/weather/observation/rainfall-radar#?map=Rainfall&fcTime=1658263800&zoom=5&lon=-4.00&lat=55.01

 

but if there are any better facilities then please let me know.

 

 

Join UKMicrowaves@groups.io to automatically receive all group messages.