3.4GHz big dish test.

[G4EWJ]

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 (121.38 KiB) Viewed 5270 times

[G4EWJ]

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 (224.17 KiB) Viewed 5268 times

[G4EWJ]

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9cm-3.jpg (173.79 KiB) Viewed 5269 times

[g0mjw]

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.

[G4EWJ]

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]

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

[M0DTS]

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]

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

[Tony G4CBW]

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

[G4EWJ]

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