Using a satellite dish to make a HD parabolic antenna? Worth it?

ken2400

Thread Starter
SatelliteGuys Pro
Sep 4, 2004
1,255
109
Central NY State
I have a number of 18" dishs setting around and was wondering if it was worth trying to convert one or more into a UHF HD antenna?

Should I look for a 30+" instead?
Should I just use a large corner UHF antenna?

Also I have a large UHF/VHF antenna. What would cutting off the VHF do for the signal?

Thanks
 

Jim5506

SatelliteGuys Master
Pub Member / Supporter
Lifetime Supporter
Oct 19, 2004
7,101
1,731
Lubbock, Texas
Just place the active element at the focus of the parabola.

It might be best to use a Dish500 since its focus is along a line from each lnb to the other - would focus signal on the driven element better.

It is probably not worth the effort since better antennas are not very expensive.
 

nsaspook

SatelliteGuys Pro
Nov 15, 2003
356
1
Fairview, Oregon
I have a number of 18" dishs setting around and was wondering if it was worth trying to convert one or more into a UHF HD antenna?

Should I look for a 30+" instead?
Should I just use a large corner UHF antenna?

Also I have a large UHF/VHF antenna. What would cutting off the VHF do for the signal?

Thanks
This is the size for a UHF dish reflector with good gain SPS-40.

400-450 mhz band.
sps-40_drawing

Stick with a normal TV antenna.
 
  • Like
Reactions: 907TECH

Nevyn

Member
Mar 13, 2008
7
1
Come on now, how cool would it be to have one or two of those behemoths up on the roof spinning round? :p
 
  • Like
Reactions: glen4cindy

ciwsguy

SatelliteGuys Family
Dec 27, 2007
110
1
Come on now, how cool would it be to have one or two of those behemoths up on the roof spinning round? :p
:D:D Well, those who know how crummy the SPS-40 video was would know better than to waste the money building a structure to support it. But it would be a VERY GOOD WAY to thumb your nose at those neighbors who complain about "no antennas" and cite those archaic, illegal HOA rules. It might be worth the hassle, don't you think?:D
 
  • Haha
Reactions: glen4cindy

dodge

SatelliteGuys Pro
Aug 1, 2004
1,197
0
Plano, Illinois, United States
:D:D Well, those who know how crummy the SPS-40 video was would know better than to waste the money building a structure to support it. But it would be a VERY GOOD WAY to thumb your nose at those neighbors who complain about "no antennas" and cite those archaic, illegal HOA rules. It might be worth the hassle, don't you think?:D
Just put up a winegard hd8200p, that will really piss the neighbors off that antenna is 17' long.
 

NightHawk

SatelliteGuys Pro
Jan 20, 2005
506
0
I have a number of 18" dishs setting around and was wondering if it was worth trying to convert one or more into a UHF HD antenna?

Should I look for a 30+" instead?
Should I just use a large corner UHF antenna?
18 inches is far too small for an effective UHF antenna. Probably less than 3 dB effective gain at 500 MHz. At 30 inches your still only around 10 dBi and below that of a good log periodic.
 

ciwsguy

SatelliteGuys Family
Dec 27, 2007
110
1
Just put up a winegard hd8200p, that will really piss the neighbors off that antenna is 17' long.
Dodge, you apparently don't know how big the SPS-40 antenna is. It dwarfs the HD8200p. SPS40 would definitely PO the neighbors much more. But it would also exceed the 1meter dish limit size.:D
 

David Taber

Member
Jan 21, 2018
8
5
Santa Rosa, California
Hookay, old thread...but I have a response.

Situation: 70-120 miles away from some very big signals (1 MW), but almost nothing less than 30 miles away. Everything is UHF except VHF 7 and 11.

Goal: Grab every signal I can; currently at about 75 virtual channels (but up to 100 are possible)

Baseline: Stacked AntennaCraft Yagis with WG7870 combiner CM7777 preamp. Due to wife's objections, these are at about 15' AGL (although we're near at the top of a hill, the signal has to pass through some treetops).

Hypothesis: Hotter antenna (think CM4251) would do the trick. But...why not go even bigger with the parabolic reflector? Acquired 10' C-band satellite dish, repurposed to TV with bow-tie element.

Photos, measurements, and lessons learned: when it stops raining.
 

David Taber

Member
Jan 21, 2018
8
5
Santa Rosa, California
In the mean time, to think about:
  • Satellite dish is rugged, will last forever
  • But it's way over 100 lbs and unwieldy. You will not get this on your roof without an amazing forklift, helicopter, etc.
  • Required pole is 3" steel; due to weight and wind-load, you're going to need minimum of 5 ft deep 18" cylinder of concrete. Minimum of 250 lbs there.
  • Even if you've got strong friends and ladders, the center of the antenna is unlikely to be more than 8 ft off the ground
  • Antenna output highly correlated to height above ground. Most sources indicate at least 20 ft is best (and they can prove it)
  • So...you're fighting lower signal with higher gain from the antenna (unless you're getting the signal as a tropospheric bounce)
 

David Taber

Member
Jan 21, 2018
8
5
Santa Rosa, California
So, the first thing you have to realize is that the 10' C-band antennas are pretty solid, heavy and with a fair degree of wind resistance. As the reflecting surface is typically expanded metal with 2 mm perforations, this thing is going to present quite a wind load. Even after removing all the C-band electronics and unnecessary aiming motor, the parabolic and its mounting structure is probably 150 lbs...so this thing is not going up on any mast I know about.

(images of antenna can't be posted here, the content filter doesn't like them. you can find them at saleslogistix dot com slash IMG1.jpg, and IMG2.jpg, and IMG3.jpg)

What it does get mounted on is 3" galvanized steel, and for obvious reasons that pipe needs to be at least 5' out of the ground. In my case, I went for 7 feet out of the ground...but that means 5' in the ground, surrounded by at least 300 lbs of concrete. Unless you have a really big augur, it's hard to do much more than that. Luckily, the ground drops off significantly from where the pole is, so it's effectively maybe 12' AGL.

Once the dish is mounted, configuring the antenna element is pretty straightforward. I live in an area with almost no signals in any direction, so I don't need a reflector behind the antenna element: it's just a matter of making the element (bow-tie) the right size and in the focus of the dish.

According to theory, the bow-tie is of infinite size...and I'd like to get down to to channel 7 so the wavelength is almost 2 meters. But the focus of the dish is probably less than a meter across, so there's not going to be any advantage to an bow-tie even that big. My first pass is with bow-tie wires 16" long. (I will experiment with solid bow tie and other variations in a week or so.) Through experimentation and measurement, I find the best distance for the bow-tie element and we're off to the races.

My main signal challenges are about 100 miles away, and my baseline for comparison metrics is a pair of yagis, with the bottom one about 12' AGL actual...but due to drop off of ground level effectively 17' AGL. According to the models, I shouldn't be getting much of anything...but with the stacked yagis and a nice preamp most of the time I get about 75 virtual channels (from about 20 transmitters). The new dish with a preamp gets nearly all the channels the same way, and the first pass of spectrum analysis (using the Nuts about Nets USB-based system on a PC) shows nearly identical signal strength. The dish is more directional than the Yagis (no surprise) but not as super-directional as I was worried about.

So now: how do I make the bow-tie outperform the Yagis? They are signficantly farther off the ground, which gives them a big gain advantage (I'm guessing 6 dB)...but the "collecting surface" of the dish should give the bow-tie even more than that.

The answers come next time I have time to mess with it.
 
  • Like
Reactions: FTA4PA

FTA4PA

Satellite Guys Family
Lifetime Supporter
Nov 13, 2013
4,499
2,373
Central Pennsylvania
So, the first thing you have to realize is that the 10' C-band antennas are pretty solid, heavy and with a fair degree of wind resistance. As the reflecting surface is typically expanded metal with 2 mm perforations, this thing is going to present quite a wind load. Even after removing all the C-band electronics and unnecessary aiming motor, the parabolic and its mounting structure is probably 150 lbs...so this thing is not going up on any mast I know about.

(images of antenna can't be posted here, the content filter doesn't like them. you can find them at saleslogistix dot com slash IMG1.jpg, and IMG2.jpg, and IMG3.jpg)

What it does get mounted on is 3" galvanized steel, and for obvious reasons that pipe needs to be at least 5' out of the ground. In my case, I went for 7 feet out of the ground...but that means 5' in the ground, surrounded by at least 300 lbs of concrete. Unless you have a really big augur, it's hard to do much more than that. Luckily, the ground drops off significantly from where the pole is, so it's effectively maybe 12' AGL.

Once the dish is mounted, configuring the antenna element is pretty straightforward. I live in an area with almost no signals in any direction, so I don't need a reflector behind the antenna element: it's just a matter of making the element (bow-tie) the right size and in the focus of the dish.

According to theory, the bow-tie is of infinite size...and I'd like to get down to to channel 7 so the wavelength is almost 2 meters. But the focus of the dish is probably less than a meter across, so there's not going to be any advantage to an bow-tie even that big. My first pass is with bow-tie wires 16" long. (I will experiment with solid bow tie and other variations in a week or so.) Through experimentation and measurement, I find the best distance for the bow-tie element and we're off to the races.

My main signal challenges are about 100 miles away, and my baseline for comparison metrics is a pair of yagis, with the bottom one about 12' AGL actual...but due to drop off of ground level effectively 17' AGL. According to the models, I shouldn't be getting much of anything...but with the stacked yagis and a nice preamp most of the time I get about 75 virtual channels (from about 20 transmitters). The new dish with a preamp gets nearly all the channels the same way, and the first pass of spectrum analysis (using the Nuts about Nets USB-based system on a PC) shows nearly identical signal strength. The dish is more directional than the Yagis (no surprise) but not as super-directional as I was worried about.

So now: how do I make the bow-tie outperform the Yagis? They are signficantly farther off the ground, which gives them a big gain advantage (I'm guessing 6 dB)...but the "collecting surface" of the dish should give the bow-tie even more than that.

The answers come next time I have time to mess with it.
Interesting experiment, looking forward to the (hopefully positive) results. :)
P.S. I believe the site won't let you post images or links until you have 10 posts (spam safeguard). I think mods can lift that limit for you if you ask.
 

kittyhas1000legs

That's a lot of claws!
Pub Member / Supporter
Aug 8, 2012
1,609
1,226
Western Slope, CO
I tried a UHF bow tie combined with a 1M fiberglass dish. It did well enough as a directional antenna (got Springfield MA channels nicely in New Britain, CT) and got rid of enough noise from the PC/TV/consoles/modem/wifi mess. Here's the thread (though not as old as this one).

Interference on RF 22

Shoot, now i feel like trying this again with the Slimline I have collecting dust...
 
  • Like
Reactions: danristheman

k.r.

SatelliteGuys Pro
Mar 4, 2013
256
217
Floyd knobs indiana
Channel master 4251
Look them up for your idea...
attachment.jpg



Notice the 2 bay with reflector at the top antenna with a kinda parabolic reflector ..with out the reflector on the bowtie you would be getting the signal with like a multipath interferance and just totally ruin it..ive thought of playing round with my 8 ft solid to see if/what gain i get..
 
  • Like
Reactions: danristheman

navychop

Member of the Month - July 2014!
Pub Member / Supporter
Lifetime Supporter
Jul 20, 2005
50,350
15,211
Northern VA
What a shame Channel Master has dropped all their larger antennas. I can’t even buy another like what’s on my roof.

I’m tempted to buy a used 4251 for our RV.
 

Users Who Are Viewing This Thread (Total: 0, Members: 0, Guests: 0)

Latest posts

Top