Wanted ~3m PF dish South UK

uhf-satcom.com

uhf-satcom.com

Regular Member
My Satellite Setup
UHF to Ka coverage; 1.1M Ku/Ka 60E-50W , 1.5M S/Ku-Band 26E, 2.85M full az/el UHF/S/C/X/Ku/KA.
My Location
Wimborne, Dorset, UK
Hi Chaps, our EME group is looking for a 3m + PF dish for EME activities to 24GHz. We have already the mount, tracking mechanism and feeds etc, just need a more accurate dish surface. The existing 3.7m isnt good at 24GHz at all.

Let me know what you have!

KR, Paul M0EYT.
uhf-satcom.com
 
I wish you lived in my neck of the woods as you could have my 3 meter "C" and "Ku" band dish.

What is wrong with your 3.7 meter dish's surface?
 
I still have that broadcast quality reflector here though 24 GHz would be a stretch. It may be an original Antesky or a good clone . not cassegrain.

You were part of the thread regarding the groundstand


I assembled it some years ago for an exhibition, then dismantled and in storage ever since, west London.
 
The existing dish which is in use to 10GHz is a 4 petal terrestrial uwave link antenna that originally was on the BT tower in London. When it was decom'd in the 80's one of our club members harvested it and transported it back to Oxford then down to Wimborne.

The problem with the antenna is the surface accuracy, it was designed for c-band p-t-p links, its performance on 10GHz is OK but probably not optimal.

The club are looking for a better quality reflector to try some 24GHz eme experiments. We have transport available and can move big stuff.

Channel Hopper: I'll forward the link to the guys to see if that antenna might work. Can you remind me of the diameter?

KR, Paul.
 
uhf-satcom.com said:
The existing dish which is in use to 10GHz is a 4 petal terrestrial uwave link antenna that originally was on the BT tower in London. When it was decom'd in the 80's one of our club members harvested it and transported it back to Oxford then down to Wimborne.

The problem with the antenna is the surface accuracy, it was designed for c-band p-t-p links, its performance on 10GHz is OK but probably not optimal.

The club are looking for a better quality reflector to try some 24GHz eme experiments. We have transport available and can move big stuff.

Channel Hopper: I'll forward the link to the guys to see if that antenna might work. Can you remind me of the diameter?

KR, Paul.
Click to expand...
It's a 3m sectional (12 petals I think), so the longest dimension would be just under 1.6m centre to rim.

There might be a picture of it assembled on here, though the site was attacked by an idiot a decade ago, many images were lost.
 
uhf-satcom.com said:
The existing dish which is in use to 10GHz is a 4 petal terrestrial uwave link antenna that originally was on the BT tower in London. When it was decom'd in the 80's one of our club members harvested it and transported it back to Oxford then down to Wimborne.

The problem with the antenna is the surface accuracy, it was designed for c-band p-t-p links, its performance on 10GHz is OK but probably not optimal.

The club are looking for a better quality reflector to try some 24GHz eme experiments. We have transport available and can move big stuff.

Channel Hopper: I'll forward the link to the guys to see if that antenna might work. Can you remind me of the diameter?

KR, Paul.
Click to expand...
Is the surface of that dish mesh or solid?

If it's a mesh type dish can you put a #2 wood pencil through the mesh of not? If you can then the mesh is too big to work so good for that frequency.

I have (over many years ago) used aluminum window screen to re-surface the mesh on a 3 meter type "C" band dish, this improved the "Ku" band reception quite a bit, I used a hot glue gun to hold the new screen in place, the screen was cut to fit as close to the curve of the dish as possible.
 
Paul,

I still have a single piece Precision Antennas spun aluminium prime focus dish. It is one of the pair I removed from the S4C site on the day we all had a day out to dismantle the auction purchases. It comes with the original Precision feed support arms.

I am not sure how good those 2.8m dishes we collected from Cardiff would be for 24GHz, the highest band I have used on on has been Ku?
 
A dish that was originally setup for 11 t0 12 GHz should work at 24 GHz, 24 GHz divided by 2 should equal 12 GHz as a half wave reflector. (There or about)
 
Terryl said:
A dish that was originally setup for 11 t0 12 GHz should work at 24 GHz, 24 GHz divided by 2 should equal 12 GHz as a half wave reflector. (There or about)
Click to expand...
I would be interested in the theory behind that one.

A cassegrain dish (solid with associated feedhorn) is better adapted to functioning at higher frequencies, but the o/p is definitely not having the IRTE I am working on).
 
Terryl said:
A dish that was originally setup for 11 t0 12 GHz should work at 24 GHz, 24 GHz divided by 2 should equal 12 GHz as a half wave reflector. (There or about)
Click to expand...
This explanation is correct. A dish acts as a mirror. It becomes less effective at low frequencies because the ratio dish size / wavelength determines how much signal reaches the LNB. For higher frequencies dish geometry accuracy becomes important, which is why some C-band dishes do not work well on Ku (e.g., those with meshes). Again what is important is "accuracy in millimeter" divided by the wavelength. The wavelength gets smaller at higher frequencies, so the effect of inaccuracy also grows with frequency.
 
deeptho said:
This explanation is correct. A dish acts as a mirror. It becomes less effective at low frequencies because the ratio dish size / wavelength determines how much signal reaches the LNB. For higher frequencies dish geometry accuracy becomes important, which is why some C-band dishes do not work well on Ku (e.g., those with meshes). Again what is important is "accuracy in millimeter" divided by the wavelength. The wavelength gets smaller at higher frequencies, so the effect of inaccuracy also grows with frequency.
Click to expand...
Yes, but a dish 'designed' for 10 GHz ....
 
This is the dish in question;
1790590844173.webp
It was originally on the post office tower in london, running on a much lower frequency. The parabola is "OK" for use up to 10GHz, it was used for 2GHz links. There is an interesting history document on the EME activity at FRARS, using this dish, at https://www.frars.co.uk/wp-content/uploads/2023/10/FRARS_EME_12-1.pdf

KR, Paul.
 
Four piece ?

I recall seeing a number of panels from a similar sized dish on the back of a scrap lorry near Heathrow years ago. Unfortunately they had already been cut apart rather than unbolted, or I may have asked for a price.
 
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