UHF/Satellite antenna?

[123tim]

Here's a question that I'm certain that knowledgeable people will laugh at. It's sort of hypothetical, and probably stupid, but the more that I think about it, the more I feel that I just have to ask.

I got to thinking in this angle after reading statements about repairing C - Band BUD's. These statements started me thinking that antenna precision might not be all that critical in C - band (relatively speaking of course.).

A long time ago, I was active in terrestrial TV DXing. I still have remnants of this hobby laying around, including a five or six ( I forget exactly which ) foot Channel Master parabolic UHF antenna.

My question is this...Could this antenna be covered with mesh screen and used for satellite reception? If (in theory) it would work, would the focal length be the same as it was for UHF?

Even though I know that the answer will be NO! I'd love to hear that it might work for on a strong C-band transponder. Even better still would be that it might work for KU. (I'm almost certain that won't work for this.)

I'm the type of guy who will go out immediately and try something if he hears that it can't be done, so I guess that I'll be trying this no matter what the answer might be.... Unless the answer is "maybe"

Well, Thanks! You can stop laughing now.
I'd love to hear any thoughts on this.

5 feet = 1.52 meters.

 

[7720driver]

I'm not familiar with UHF parabolic antennas, Tim. What do they look like? Could you post a pic here of your 5 or 6 footer?

 

[techpuppy]

What an interesting idea! Someone can correct me if I'm wrong but I think it's going to come down to the beam angle of the antenna. It might be a little too broad for satellite, but perhaps not. The focal point should be the same as your driven elements and it might take some tweaking. If the mesh you add is fine enough I think I'd go for the KU signals first. It wouldn't surprise me if you didn't do quite well with them. The only problem I can think of is if the beam angle is too wide you might have some interference from adjacent satellites if you're aiming near one of the DBS satellites. To sum up my rambling: I'd try it. If nothing else you'll get your neighbors wondering what you are up to.

 

[ken2400]

The Arrl antena book may be a good book to check out?
http://search.ebay.com/arrl-antenna-book_W0QQfkrZ1QQfromZR8

 

[brandon]

Here is an interesting site
http://www.uhf-satcom.com

You can probably make a customized antenna for UHF satellite reception. Most of the UHF SatCom downlinks are in the 243-263 MHz range. Unfortunately most traffic is encrypted but occasionally you can catch some clear stuff.

Sometimes strong enough to hear with a regular discone scanner antenna, I've been able to do it when living in an apartment and using an antenna in the attic.

 

[123tim]

Well, I got up in the garage and measured my antenna. It has a diameter of seven feet! It's been a couple of years since I've looked it, and I thought that six feet might be an exaggeration. I guess that I was wrong. I'm really encouraged by the comments received. Thank you.

I'll answer them in the order received:

7720driver
This is a link to a picture of the type of antenna that I have:
http://www.kyes.com/antenna/pointing/pointuhfparabolic.jpg

If I had one like this I think that I'd be ready to start experimenting!:
http://idealantenas.com.br/parabolicavazadauhf.jpg

One of the problems that I think that I might run into is the fact that there isn't any reinforcing rim on my antenna (like the one shown in the second picture).
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TechPuppy:
I think that I'm going to use fine aluminum screen...I'll try KU first.
The neighbors are always wondering what I'm up to!
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Ken,
Thanks for the link. I'll probably be getting that book!
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Brandon,
Checked out your link and downloaded some of the audio files. I'm definitely going to check this out further. Thank you.
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[mdovell]

Here is an interesting site
http://www.uhf-satcom.com

You can probably make a customized antenna for UHF satellite reception. Most of the UHF SatCom downlinks are in the 243-263 MHz range. Unfortunately most traffic is encrypted but occasionally you can catch some clear stuff.

Sometimes strong enough to hear with a regular discone scanner antenna, I've been able to do it when living in an apartment and using an antenna in the attic.

It's pretty interesting when you think about it that we're just scratching the surface of what is in the air. After hdtv goes mainstream I think the only other way to go might be with 3d...

 

[7720driver]

Yeah, Tim...that's what I imagined a parabolic UHF antenna would look like. It looks a little too flimsy to use as a frame for attaching mesh. It could be done, though. The key would be finding a mesh-like material that is strong enough to stand up to brisk wind, yet malleable enough to be fashioned into a parabolic curve.

 

[Tron]

123Tim, I'd bet that parabolic UHF antenna would be exceptional for receiving distant OTA DTV!

We have nearly a dozen DTV stations here in New Orleans, but it would be nice to be able to pick up Baton Rouge (about 80 miles away) and Gulfport/Biloxi, Mississippi (about 80 miles away and mostly over water from New Orleans)...

 

[123tim]

OK, So I took the time to dig out, and partially assemble my old UFH antenna. The way it stands now (if things work out the way I hope) I'll have a warped 7 foot BUD when I'm finished. Some of the elements are slightly out of true. I hope to make this better by finding the focal point and using a piece of string to bring the elements closer to where they belong. I also noticed that the LNB will be looking directly down the antenna arm. I don't know much about this, but I think that I might need a button hook design of some kind.

Tonight, in the name of Science, I plan to fabricate a complex Duct-Tape LNB bracket, and try to use an old circular LNB and my "Outdoor NASA alignment tool" (An old DTV receiver ) to try to see if I can get any signal strength on a DTV bird. This will be without any screen modification. I think that the reflector element spacing (as it stands now) wont work at all for this frequency, but I'm really interested in seeing what it might do. If this wont work, I'll dig out my nine dollar satellite pwr. meter and see what comes of that.

Anyone want to hazard a guess on my chances of making this work?
Any guesses on the amount of power I might find (not find) tonight?

At least I'll be ready for OTA DTV, Tron

Edit- Oops, I forgot to rotate my picture!

 

[Tek465m]

The W1GHZ Online Microwave Antenna Book. Try this book for ideas.
I think it can be done. But I'm sure you'll run into the problem of doing 30db of work for 3db of gain.

The antenna might be perfectly engineered for UHF frequencies, although you might find it completely out of whack in the microwave band.

Browsing through Chapter 4 it seems that as long as the dish is reasonably parabolic, the critical step will be finding the focus. It will be interesting to see what you discover.

Good Luck.

 

[123tim]

I just got back from working with the dish. So far I have nothing. I'm not really surprised....I will admit that I had hoped to get at least get a bar or two on the level indicator. I'm having the misfortune of misplacing my power meter.

Thanks for the excellent link Tek465m. I've only had time to skim chapter four. I think you're right about the focus. I've been moving it up and down, but it's hard when you don't even know if you're focused on a satellite. I guess that I'll have to invest the time in screening it somehow. Sure do wish that I could find that power meter!

Thanks again.

P.S. Was it Tron or Katrinasucks that said that they found a metal plate antenna?
If you're reading this, chapter three of the link that Tek465m posted, is about this.

 

[Tron]

I found a planar microwave antenna. It's square in shape, about the size of a Winegard Square Shooter. These were used to receive the terrestrial microwave signal for Bellsouth Americast, which is now defunct, but I'm not sure whether they can be used for anything else (like maybe microwave links from news trucks, you'd have to be directly in their line-of-sight though)...

 

[Larry1]

You should try to receive OTA Hi-Def signals as others have pointed out. That type of antenna would provide a lot of gain and be very diectional. OTA HDTV signals can provide great picture quality as they do not have to compress their signals as much as satellite and usually provide 1 main and 2 sub channels for each station. That type of UHF antenna is very hard to find, but is the best for distant UHF reception.

 

[Change]

Also check out the Radio Laboratory Handbook, might be some good stuff in there: http://wireless.ictp.trieste.it/handbook/index.html

 

[123tim]

Just writing to inform anyone who might be interested, that I'm shelving this particular project.

The antenna did show some promise, being able to get a small (very small) power reading without any modification. However it didn't show the initial results that I had hoped for. Second, it became obvious that the tilt needed would be a killer next winter. The amount of snow that it would hold would be a real problem. Something as flimsy as this would certainly need to be offset.

Finding a Primestar dish today during cleanup day in our town was the final deciding factor.

I'd like to thank everyone for their comments and help.

 

[voomvoom]

I would be more interested in you to continue with this project and send the Primestar my way. I'll take good care of it for you.

Al

 

[Tron]

I would be more interested in you to continue with this project and send the Primestar my way. I'll take good care of it for you.

Al

...And if you don't want that UHF antenna, I'll take good care of IT for you.

 

[123tim]

I would be more interested in you to continue with this project and send the Primestar my way. I'll take good care of it for you.

Al

Al and Tron,

Thanks! I'll be getting those out to you today.