3.4GHz big dish test.

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G4EWJ
Posts: 945
Joined: Wed Feb 17, 2010 10:11 am

3.4GHz big dish test.

Post by G4EWJ » Sat Nov 24, 2018 10:14 pm

To determine the unknown qualities of the 2.4m Es'hail-2 dish at G3NWR, we arranged with G4CBW to compare our satellite reception against his 3.0m dish on C-band (3.7GHz). As Tony has a linear feed, the only satellite we could both see was at 46E.

By coincidence, the azimuths to 46E and G4CBW are the same, so we decided to try a direct contact on 3.4GHz. On paper, the path is terrible. The path loss is 19dB worse than the path to the satellite, but it works on 23cm SR4000 with 15W. In the end, it worked very well and G4CBW was received on various combinations up to SR4000, APSK32 and 20W.

Brian
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9cm-1.jpg
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Last edited by G4EWJ on Wed Dec 12, 2018 3:48 pm, edited 1 time in total.

G4EWJ
Posts: 945
Joined: Wed Feb 17, 2010 10:11 am

Re: 3.4GHz big dish test.

Post by G4EWJ » Sat Nov 24, 2018 10:17 pm

The path is just to the right of the flagpole, between Bidston Lighthouse and Bidston Observatory, some 60m higher.
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9cm-2.jpg
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G4EWJ
Posts: 945
Joined: Wed Feb 17, 2010 10:11 am

Re: 3.4GHz big dish test.

Post by G4EWJ » Sat Nov 24, 2018 10:18 pm

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9cm-3.jpg
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g0mjw
Posts: 1482
Joined: Sat Sep 20, 2014 9:15 am

Re: 3.4GHz big dish test.

Post by g0mjw » Sat Nov 24, 2018 10:34 pm

G4EWJ wrote:
Sat Nov 24, 2018 10:14 pm
To determine the unknown qualities of the 2.4m Es'Hail-2 dish at G3NWR, we arranged with G4CBW to compare our satellite reception against his 3.0m dish on C-band (3.7GHz). As Tony has a linear feed, the only satellite we could both see was at 46E.

By coincidence, the azimuths to 46E and G4CBW are the same, so we decided to try a direct contact on 3.4GHz. On paper, the path is terrible. The path loss is 19dB worse than the path to the satellite, but it works on 23cm SR4000 with 15W. In the end, it worked very well and G4CBW was received on various combinations up to SR4000, APSK32 and 20W.

Brian
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9cm-1.jpg
Consistent at least. It is a single knife edge diffraction path, with 200 dB loss. But 15W and a lot of antenna gain makes up for it.
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G4EWJ
Posts: 945
Joined: Wed Feb 17, 2010 10:11 am

Re: 3.4GHz big dish test.

Post by G4EWJ » Sun Nov 25, 2018 12:24 pm

Doesn't that count as 2 knife-edge diffractions? The left-most of the central peaks is much more pronounced on yours. I assume that's down to different database granularities.

I didn't realise that G4CBW was using a 1.0m dish for terrestrial, so we had about 10dB less gain than I originally thought. Even so, it's equivalent to 20 megawatts betwen 2 diploes.

Brian

g0mjw
Posts: 1482
Joined: Sat Sep 20, 2014 9:15 am

Re: 3.4GHz big dish test.

Post by g0mjw » Sun Nov 25, 2018 12:51 pm

You are right - I didn't spot the one nearest the TX.

M0DTS
Posts: 467
Joined: Sun Feb 24, 2008 9:03 pm

Re: 3.4GHz big dish test.

Post by M0DTS » Sun Nov 25, 2018 4:06 pm

Big dishes really work well for regular tropo paths.
If you try working any big european station on the higher bands they all use a dish.

I use my 3m dish at ground level for most 23cm QSO's now, it out performs the yagi's on the mast 25ft higher even in directons where there are low down obstructions to the dish!

Good to hear success :-)
Very hard to tweak dish feeds on tropo signals but you will get it close enough.

Rob

Tony G4CBW
Posts: 12
Joined: Sat Dec 31, 2016 12:16 pm

Re: 3.4GHz big dish test.

Post by Tony G4CBW » Sun Nov 25, 2018 8:44 pm

Nothing nicer than a big dish apart from an even bigger one. Attached picture is of my current mini dish farm. 3 metre mesh dish on the left, currently playing on C band with G3NWR tests. The white offset is 1.5 metres and is currently on Badr, receiving most signals at around 13 / 14 dB MER. The mast is at approximately 10 metre AGL, carrying the tropo system which comprise of a 1 metre offset dish, 3cm taking prime spot with 9cm offset by 5 degrees, this being what I used to work G3NWR. We may try the 3 metre dish next time. Above the 1 metre dish is the H/B 5 el for 146.5MHz. This will be coming down soon to be replaced with 25el 70cm DATV. There is also an 80cm dish hidden amongst the others for domestic sat tv.

Happy DXing

73 Tony G4CBW
Attachments
G4CBW's Mini dish farm
G4CBW's Mini dish farm
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Tony G4CBW
Posts: 12
Joined: Sat Dec 31, 2016 12:16 pm

Re: 3.4GHz big dish test.

Post by Tony G4CBW » Sun Nov 25, 2018 8:46 pm

Sorry, it was the correct way around on my pc!

G4EWJ
Posts: 945
Joined: Wed Feb 17, 2010 10:11 am

Re: 3.4GHz big dish test.

Post by G4EWJ » Sun Nov 25, 2018 9:55 pm

Rob,

The original idea was for the dish to be fixed for Es'hail-2, but it's food for thought to do other things - maybe even moonbounce.

Brian
Last edited by G4EWJ on Wed Dec 12, 2018 3:48 pm, edited 1 time in total.

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