Serious UHF Antenna for Deep Fringe

[Nick]

In my search for the ultimate UHF antenna, I ran across this monster from Lindsay Antenna (http://www.lindsayelec.com/com_rec.html), a division of Lindsay Electronics out of Ontario.

http://www.lindsayelec.com/images/1szz.jpg
Super Zig Zag Series UHF Antennas
Models: 61SZZ, 2SZZ, DSZZ, & 4SZZ

Boasting gain of up to +23 dB, the UHF stacked array is intended primarily for commercial head-end use, but could employed by consumers to solve deep-fringe receptions problems for OTA HD applications.

These frequency-tuned antennae can cost as much as the price of an HDTV set itself, and thus are only for the most dedicated and well-heeled, but 'signal-deficient' videophile.

[Richard King]

Will your landlord allow you, the resident dedicated, well-heeled signal deficient videophile, to install one? :D

[Nick]

Thankfully, no, thus preventing me from taking a trip to temptation island and saving me dinero grande. :)

[Mike123abc]

My problem with large UHF antennas is at night you suffer from channel overload. My area has too many repeaters and close markets that every direction yields different channels.

Of course that one does not look like it will rotate...

[dlsnyder]

The list price is $1990 Canadian. Isn't that only about five bucks US?

[RJS1111111]

Originally posted by Mike123abc
My problem with large UHF antennas is at night you suffer from channel overload. My area has too many repeaters and close markets that every direction yields different channels.

Of course that one does not look like it will rotate...

That thing is so directional, it can probably pick out each source.

Sure, it's on a mast, so you can rotate it, right? Just get the biggest rotor motor made, and keep the slew rate down, so
the top end can keep up without twisting off.

I'd get one, if I could afford it, unless it's tuned for just one
or a small number of channels, instead of the whole band.

:lol:

[Nick]

These models are cut for a specific channel and are highly directional. Any antenna that can mount on a vertical pole can be rotated.

[raj2001]

The list price is $1990 Canadian.

I can build an array of stacked yagi's that will do the trick for way less than that.

[AntAltMike]

Originally posted by Nick
These models are cut for a specific channel and are highly directional.

The model that is shown in the posted picture, 1SZZ, isn't very directional in the horizontal plane, which is the plane in which most of the ghosting reflections occur. It has a horizontal beamwidth of 43 degrees, which is less directional than even bottom-of-the-line yagis.

The strengths of that particular antenna are gain (19dB), front-to-back ratio (26dB), narrow vertical beamwidth (9 degrees) and reduced wind resistance compared to parabolic antennas with comparable specs.

There are very few consumers who would benefit from such an antenna. I have never dealt with vertical reflections, but I guess they would come off a lake, or maybe off the Bonneville salt flat.

Model 2SZZ, which seems to be two 1SZZs, stacked horizontally, has a gain of 21dB but its horizontal beamwidth of 22 degrees is only a tiny bit better than a Channelmaster 4228 8-bay bowtie. The big difference is that the 4228 only has a gain of about 10 or so dB.

The exceptional performer in this series is the 4SZZ, which is four of these behemoths stacked horizontally. It has a beamwidth of just 11dB, which could be very useful in a hostile reception environment, like if someone is trying to receive a UHF signal from maybe 80 miles away, across a lake, with an inconveniently located building providing a multipath reflection. At $3,785 ($2,000 real money?) it would be a bargain to some but an absolute waste for most situations.


Originally posted by raj2001
I can build an array of stacked yagi's that will do the trick for way less than ($1,990 Canadian).

I don't think that I could build a comparable quality Yagi stack that would yield all of those performance benefits at a favorable price. The materials for an 8 antenna vertical stack of Blonder-Tongue Yagis would cost about the same, would be a lot more work to assemble and tune, and it would have inferior wind drag.


Originally posted by Mike123abc

My problem with large UHF antennas is at night you suffer from channel overload. My area has too many repeaters and close markets that every direction yields different channels.

If you are pushing a UHF preamp right up to its input limit during the day, then it might creep over its input threshold at night, but someone using an antenna like this one would put a bandpass filter on the downlead before preamplifying, if preamplifying was even needed.

[DarrellP]

Check out this (http://coyotecreekranch.com/DTV/) solution.

[dlsnyder]

And people wonder why so few DTV tuners have been sold. I suspect not many people would bother with such an elaborate setup to watch TV. Not that those living in a city grade or grade A area would have to resort to this. Alot of people think they would though and that is why cable continues to be so popular.

I think that antenna solution is much cooler than cable though! :cool:

[Nick]

dlsnyder said... "I think that antenna solution is much cooler than cable though!"

:D :D :D

Never thought I'd ever anyone say THAT, but only a techie would understand. I bet there are a lot of people that don't even know that free TV is available OTA. :rolleyes:

[akron05]

And people wonder why so few DTV tuners have been sold. I suspect not many people would bother with such an elaborate setup to watch TV. Not that those living in a city grade or grade A area would have to resort to this. Alot of people think they would though and that is why cable continues to be so popular.

I think that antenna solution is much cooler than cable though! :cool:

Unless you're like me and want to watch out-of-market stations from Youngstown, Pittsburgh, and Wheeling-Steubenville.

[midwest_dxer]

I can build an array of stacked yagi's that will do the trick for way less than that.

Yep,way less than that,and good for the whole band.Here's a pic of a vertical quad I did last summer just for kicks.It worked very good,but no room for anything else on the tower.Somewhere around 18-22db gain from the bottom to the top of the band.Cost around $240 for all four antennas.

http://community-2.webtv.net/GregBarker/ANTENNAPICS/index.html

[Michael P]

Unless you're like me and want to watch out-of-market stations from Youngstown, Pittsburgh, and Wheeling-Steubenville.Well cable will never give you Youngstown, Pittsburgh or Steubenville unless you move to Columbiana County (due south in the Youngstown DMA) where they have significantly viewed status of some stations form Cleveland and Pittsburgh. With an antenna Wheeling/Steubenville would come in OTA.

[BornToFish]

I've considered ganging 4)4228's together, and have a 32-Bay monster. I've seen some info on the internet concerning this, but I think it can be done better. I'm hearing the 4228 suffers from insufficient connection factors between the Bays of the antenna. If one can improve the efficiency there, and connect them together in the same efficient manner. It would be a real performer! The problem has been guys trying to hook them together via baluns, and splitters, therefore introducing loss. I'm thinking about using either heavy twinlead, or copper wire, or aluminum wire. If you improve the efficiency of the bay connections, and cross connect the antennas together, without baluns, and splitters. Also connect all the screen units together as one, with no gaps. This will improve the VHF high capabilities of the antenna. All that's left is building the cubical mast support, and installing a small/medium duty amateur radio rotator. Of course a good low-noise amp would be a good addition, and RG-11 would be the cream on the pie!:D

[Jeff McClellan]

Plastic ties will join the 2 screens in a more efficient manor. You can drill out the connectors and use copper wire to join them between antennas.

[BornToFish]

Yeah, I have a single 4228 now, and I did that when I installed it. I didn't know about the loss on VHF(Hi), if the wind got to blowing. I'm glad I'm a prefectionist, it benefited me this time. I haven't tried the improvement on the bay connections yet, but that sounds like a good idea.:sure:

[Bill Stratton]

How do I match two uhf xg91 antennas stacked vertically? Each is rated at 75 ohms and when I connect them together I will end up with 37.5 ohms. I know of no matching transformers that would work. I understand I need to seperate them by about 24 inches.. right or wrong.
Bill S.

[Scott in FL]

You can accomplish this for a single frequency with 106 ohm coax cut to 1/4 wavelength. This will transform the impedance to 150 ohms. When you parallel these together you'll get 75 ohms. The problem is your limited to one channel, and finding 106 ohm low loss coax could be tricky.

This article recommends you combine the two antennas via a combiner, but they do have loss:

http://www.hdtvprimer.com/ANTENNAS/16bay.html

[Tower Guy]

How do I match two uhf xg91 antennas stacked vertically? Each is rated at 75 ohms and when I connect them together I will end up with 37.5 ohms. I know of no matching transformers that would work. I understand I need to seperate them by about 24 inches.. right or wrong.
Bill S.

A splitter used as a combiner would have about .5 db loss.

You can transform 37.5 ohms to 75 ohms by using a 1/4 wavelength of 50 ohm coax. (Use BNC connectors instead of type F.)

[n3ntj]

Ahhhh. Time to get out your Smith Charts..brings back memories of my electrical engineering courses back in college.

[Scott in FL]

Ahhhh. Time to get out your Smith Charts..brings back memories of my electrical engineering courses back in college.

I had to scratch my head and think about it for awhile. I thought, wait... I know this... And then still missed the better solution using 50 ohm coax.

Thanks Tower Guy.

[Bill Stratton]

I want to stack identical xg91 antennas vertically. If I remove the existing balums on each antenna I am told that the impedance of each antenna will be 300 ohms. Therefore I can connect them together and come up with 150 ohms. Now, all I need is a device that can convert them either to 300 ohms or 75 ohms.

If by removing the balums of each antenna the impedance of the antennas will not be 300 ohms each then I need an antenna combiner the will connect two 75 ohm antennas and end up also with 75 ohms. My problem again becomes where can I get a combiner that connects two 75 ohm antennas together and end up with 75 ohms.

Can anybody out there help me. I need advice...

Bill Stratton

[Scott in FL]

Bill,
I assume you're not going after only one channel, so a broadband combiner is the way to go. I also assume you're doing all this to increase your gain, not receive channels from different directions.

I would not remove the baluns. They add a little bit of loss, but in my opinion the convenience of working with 75 ohm coax is worth it. If you want to squeeze every last 0.1 dB out of your antenna system, Winegard still makes a combiner that takes two 300 ohm inputs, combines them, and outputs 75 ohm to coax. But it's not cheap (the SD3700 at Winegarddirect costs about $30 with shipping), and you have to find some good quality 300 ohm twin lead and stand-off insulators.

Keep your baluns at the antenna terminals. Make sure the antennas are about 1/2 wavelength apart for your lowest channel, use identical lengths and types of good quality coax, and combine them with a good quality 75 ohm combiner. Winegard has the CC7870, but you can spend less for a good combiner.

If you have everything identical -- antennas, coax, lengths -- you'll pick up about 2.5 dB if the antennas are pointed in the same direction. By the way, if you want to go after different channels in different directions, you'll lose about 3.5 dB in each direction.

[Bill Stratton]

Thanks a million. I'll go with you. But, I looked up the formulas an I figured one wavelength at 470 GHz is .025 plus inches. So I guess I am still in the dark about wavelenghts. How long is 1/2 wavelength and 1 wavelength. How do you figure it?
Bill

[Sam Spastic]

Thanks a million. I'll go with you. But, I looked up the formulas an I figured one wavelength at 470 GHz is .025 plus inches. So I guess I am still in the dark about wavelenghts. How long is 1/2 wavelength and 1 wavelength. How do you figure it?
Bill

Maybe try at 470 MHz. Just multiply your answer by 1000 assuming you did everything else right.

[Scott in FL]

How long is 1/2 wavelength and 1 wavelength. How do you figure it?
Bill

The wavelength is equal to the speed of light divided by the frequency.
Speed of light = 300,000,000 meters per second
Frequency = 470,000,000 Hz
One wavelength = 0.638 meters = 25.12 inches.
1/2 wavelength = 12.56 inches at 470 MHz

Another formula is 984/Freq in MHz = wavelenght in feet

Or use this calculator: http://www.csgnetwork.com/freqwavelengthcalc.html

This is OK for open air, like antenna spacing. In your case you just want the two antennas to be 1/2 wavelength apart at the lowest operating frequency so they don't interact. These formulas are fine.

If you want to calculate a 1/4 wavelength of coax you must multiply by the velocity factor (the foam dielectric in RG-6 slows the waves down). Or if you want to calculate the length of a 1/2 wave dipole you must account for end effects.

[Bill Stratton]

Thanks again to Sam and Scot. I can't figure out why I was using 470 GHz instead of MHz. I guess in my old age I am going fast...

Anyway, I figure I will have to space the two XG91's apart by 2 feet 1 1/8 inches. Please correct me if I am still wrong. Now, my next problem will be placing the VHF antenna. I don't have any math to figure it but I believe it must be at least 5 feet below the two yagis. Below the VHF antenna I will place my TB-105 support bearing and below that I will place my Roter. On top of all will be my 3 pole 30 foot mast. All of which will be on top of my house. Any way the three antennas plus the support bearing will be on at 10 foot mask (if they will fit). If you can give me more data or corrections I really would appreciate it. As you can see I am weak on wave propagation.

[peano]

So if my lowest channel is UHF 14, what is the best spacing?

[Bill Stratton]

Another quick question; When I move the bottom xg91 antenna up or/and down how can I tell if the reception is getting better or worst. I will assume that the signal only increases or decreases a small amount. If I were working with analog I would just measure it using a scope but with digital I don't know.

[Scott in FL]

Bill,
You can always use the signal strength meter on your converter box or tv. But the vertical spacing between the two UHF antennas shouldn't affect the signal strength. You want them far enough apart so they don't interact, but not so far apart that your coupling coax gets too long. Both antennas also must be in phase, so you want them in the same general area. Keep them about 1/2 wavelength apart at the lowest frequency and you'll be fine.

Place the VHF antenna as far below the two UHF antennas as possible.

[Tower Guy]

Another quick question; When I move the bottom xg91 antenna up or/and down how can I tell if the reception is getting better or worst. I will assume that the signal only increases or decreases a small amount.

It will be very hard to try to optimize signal strength vs antenna spacing. I'd use your 2' 1 1/8" and not play with it.

[Jim5506]

Not only is manually moving the antennas difficult to optimize signal strength, but your presence there moving one of the antennas also slightly distorts the waveforms in the area, i.e. you are part of the antenna complex when you are in the vicinity.

Play with an indoor antenna, try touching it and placing your hands, etc. near it. You can see the signal come and go as you alter the field by the mere position of your body.

[Bill Stratton]

Back again with question about mounting the two xg91 stacked vertically.
When I install the Winegard CC-7870 coupler that will couple the two antennas together where will I put it? I plan on placing it between the two xg91's on the mast half way between the two antennas. Of course I will make sure the coax for both antennas are the same length. Please correct me if I am wrong or there is a better way. I have NO experience with digital or very little experience with antennas as you can see.
Bill

[Scott in FL]

Bill,
That's correct. Keep the two coax lengths exactly equal and as short as possible. Halfway in between would be the best place.