Stack HD8200U with additional UHF antenna?

#1
Most of the channels I want to receive are UHF-these are also the "harder to get channels" for my location:

TV Fool

However, there are two other channels that I really would like to get as well on VHF (WPVI-6 PHL and WABC-7 NY)-these are also easier channels to get. If I were to go with an all band antenna like the HD8200U which has very good VHF performance, but lacks a bit in UHF, could I stack an additional UHF only antenna with it in order increase gain for pulling in the harder to receive UHF channels. Just a thought.
 

n2rj

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#2
You cannot stack dissimilar antennas. For stacking to work and produce gain, both input signals be identical in amplitude and phase. Stacking a separate UHF antenna would essentially be stacking a different antenna.

Why not get a VHF only antenna and then get two UHF antennas and stack them?
 
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Fringe Reception

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#3
Badfish,

WPVI is low-band VHF channel 6 and WABC is high-band VHF channel 7 so a HD8200U is a good choice. It could be combined using a UVSJ which will block UHF signals received by the HD8200U from entering your coaxial feedline. The UVSJ will allow you to connect a seperate UHF antenna to the same coax with minimal loss.

Both antennas do not need to share the same antenna mast and they probably should not. When antennas are located physically to close to each other, they tend to interact. At 599 mHz (channel 35) two antennas should be spaced no closer than 36" apart: the lower the frequency or channel, the greater the physical distance. It may or may not matter, but that's the recommendation "by the book".

I would not park a UHF antenna less than ten feet away from a low-band VHF monster antenna. Please refer to the same photo (below) I put on the post you made about antenna masts: the UHF antenna on top is located well above the high-band VHF antenna to avoid interaction. A HD8200U will be a significantly larger antenna than the lower mounted high-band VHF antenna in this photo.

Jim

 

dkreichen1968

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#4
Looking at the specs for the HD8200U I really don't think it will need help. It's gain specs for UHF are up close to the 91XG (16.7dBi = about 14.2 dBd) and then it has good VHF gain also. Of course, it is a monster... No doubt about that.
 

Fringe Reception

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#5
I was rethinking what I wrote and does anyone know if a UVSJ attenuates low-band VHF on the V-side? Then, I thought about using a HLSJ, but how much UHF attenuation is on the H-side? Hmmm.

Jim
 

n2rj

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#6
I wouldn't be too concerned about low VHF. WPVI channel 6 is about the only thing worth watching on low VHF and probably the only thing he'll receive anyway. It would be rather easy to receive from his location.

If I had to do this, I would get:

Fixed (below rotor):
Low VHF antenna fixed on Philly (Y5-2-6 from antennacraft)

On mast with rotor:
Winegard YA1713
2 x AD 91XG

HLSJ, UVSJ, 300 ohm ribbon feed, SD3700 coupler, rotor

I would wire the 91XGs with 300 ohm feed to the SD3700 and then run coax from that to the UVSJ's UHF side. The low band VHF antenna goes to the HLSJ's low side and the YA1713 goes to the high side, output goes to the VHF side of the UVSJ. That would then run to a preamp like the CM7777 or optionally a Kitztech or Research comms. If you are using the CM7777 you can omit the UVSJ and run the output of the HLSJ to the VHF side of the CM7777. The output of the SD3700 goes to the UHF side.

This might get a bit heavy and you'd have to break out the guy wire. But it would be a killer setup. And quite honestly I think it would give better results than the single VHF/UHF combo which is going to be heavy anyway.
 
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#7
I wouldn't be too concerned about low VHF. WPVI channel 6 is about the only thing worth watching on low VHF and probably the only thing he'll receive anyway. It would be rather easy to receive from his location.

If I had to do this, I would get:

Fixed (below rotor):
Low VHF antenna fixed on Philly (Y5-2-6 from antennacraft)

On mast with rotor:
Winegard YA1713
2 x AD 91XG

HLSJ, UVSJ, 300 ohm ribbon feed, SD3700 coupler, rotor

I would wire the 91XGs with 300 ohm feed to the SD3700 and then run coax from that to the UVSJ's UHF side. The low band VHF antenna goes to the HLSJ's low side and the YA1713 goes to the high side, output goes to the VHF side of the UVSJ. That would then run to a preamp like the CM7777 or optionally a Kitztech or Research comms. If you are using the CM7777 you can omit the UVSJ and run the output of the HLSJ to the VHF side of the CM7777. The output of the SD3700 goes to the UHF side.

This might get a bit heavy and you'd have to break out the guy wire. But it would be a killer setup. And quite honestly I think it would give better results than the single VHF/UHF combo which is going to be heavy anyway.
Sounds awesome-but I have LOTS of questions. First, how tall would the mast need to be total? I assume that there will need to be a fair amount of space between each antenna. I was planning on mounting the HD8200U 30' AGL which would mean a relatively short mast off of my roof. However, if I'm mounting four separate antennas I'm thinking that could mean a very high mast if starting at 30'. I'll need to think about this more in terms of total height, spacing, etc...before committing to it. I really appreciate the suggestion though! I'm guessing that you have a fair amount of land up there in Wantage. I have a little 1/4 acre lot down here in Hunterdon, otherwise I would seriously consider a tower like yours. This setup at 70' would probably do pretty well! One more thing-how much gain could I expect out of two 91XGs? Does it double, increase by 50%, etc...?
 
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#8
Sounds awesome-but I have LOTS of questions. First, how tall would the mast need to be total?
Quick question, do you have any type of surroundings that could possibly block your line of site? Do you know any additional information about your broadcast towers and the elevation that they're mounted at?
 

n2rj

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#10
Sounds awesome-but I have LOTS of questions. First, how tall would the mast need to be total? I assume that there will need to be a fair amount of space between each antenna. I was planning on mounting the HD8200U 30' AGL which would mean a relatively short mast off of my roof. However, if I'm mounting four separate antennas I'm thinking that could mean a very high mast if starting at 30'. I'll need to think about this more in terms of total height, spacing, etc...before committing to it. I really appreciate the suggestion though! I'm guessing that you have a fair amount of land up there in Wantage. I have a little 1/4 acre lot down here in Hunterdon, otherwise I would seriously consider a tower like yours. This setup at 70' would probably do pretty well! One more thing-how much gain could I expect out of two 91XGs? Does it double, increase by 50%, etc...?

For a vertical 2 stack with 91XGs the spacing does not have to be much, in fact you can probably even have them almost touching if you are really cramped for space. It is going to be a bit heavy though (13lbs) but so is the HD8200U (15.5lb). These are UHF antennas so they aren't going to interact unless the yagi portion is really close together.

The YA1713 is about 5lb so combined the high VHF and the UHF antennas aren't going to be much more than the single HD8200U.

Height? Oh, I dunno, about 10-12 feet? Up to you really. You would need to guy this setup though.

The low VHF antenna, you may be abe to get away with something smaller since WPVI is pretty strong (I get them up here on a high VHF antenna).

For a two stack you will gain 2.5dB which is slightly less than 2x the gain. By the way I didn't realize that the 91XG has a built in balun, so I am not sure you can use 300 ohm feed. Instead of the 300 ohm ribbon feed and SD3700 combiner, you can use two identical lengths of coax and an ordinary 75 ohm two way splitter to combine your antennas.

I think for what you are trying to achieve, you are going to have to resort to somewhat extreme measures to get reception out of NYC. I don't think any antenna setup is going to be small and/or light.

As for my setup? We have 6 acres up here, and I'm pretty much up on a hill. Makes things a bit easier.

 

Fringe Reception

Super Moderator, Chief Content Editor
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#11
Per what N2RJ wrote, a 3dB gain indicates a doubling of energy, so you can see a 2.5 dB gain could be VERY significant to you. There will be some minimal coaxial cable (and fitting) losses and antenna combination losses, but this is well worth trying.

Jim
 
#12
For a vertical 2 stack with 91XGs the spacing does not have to be much, in fact you can probably even have them almost touching if you are really cramped for space. It is going to be a bit heavy though (13lbs) but so is the HD8200U (15.5lb). These are UHF antennas so they aren't going to interact unless the yagi portion is really close together.

The YA1713 is about 5lb so combined the high VHF and the UHF antennas aren't going to be much more than the single HD8200U.

Height? Oh, I dunno, about 10-12 feet? Up to you really. You would need to guy this setup though.

The low VHF antenna, you may be abe to get away with something smaller since WPVI is pretty strong (I get them up here on a high VHF antenna).

For a two stack you will gain 2.5dB which is slightly less than 2x the gain. By the way I didn't realize that the 91XG has a built in balun, so I am not sure you can use 300 ohm feed. Instead of the 300 ohm ribbon feed and SD3700 combiner, you can use two identical lengths of coax and an ordinary 75 ohm two way splitter to combine your antennas.
OK-I put together this crude Google Sketchup drawing to represent how I see this coming together in my mind:



Note that I started this with a chimney mount in mind hence the representation in the drawing, but I'm reconsidering that at this point. The boxes represent the full dimensions of the antennas-ie: the 91XG is 93" long, 20" wide, and 22" high so I put two 93x20x22 boxes at the top of the mast basically sitting on top of each other. Twelve inches below that is the YA1713, and 12" below that (noting that there would be a rotor in between), is the fixed mount Y5-6-2. The dimensions on the side represent each antenna's distance from ground level. I'm less concerned about the distance from ground level right now than I am about necessary spacing of the antennas. Once I get that straight I'll know how high any theoretical tower would need to be because I can just add it to the distance above ground level for the lowest antenna. I'm toying with the idea of incorporating some kind of tower off of my shed in back of the house, but that would mean a 100+ foot coaxial run just from the top of the tower to the inside of the house, then probably another 75' once inside. Lots to consider, but I'm actually finding this interesting and fun.
 

n2rj

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#13
Yep, no doubt it is going to be a monster, both in wind load and weight.

You can try to mount the low vhf on another chimney mount to even things out.

But multiple, large, ugly antennas are what we have to deal with for the deep fringe.
 
#14
Yep, no doubt it is going to be a monster, both in wind load and weight.

You can try to mount the low vhf on another chimney mount to even things out.

But multiple, large, ugly antennas are what we have to deal with for the deep fringe.
Gotcha-how does that spacing between antennas look? Too much? Too little? Just right?
 

n2rj

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#18
Per what N2RJ wrote, a 3dB gain indicates a doubling of energy, so you can see a 2.5 dB gain could be VERY significant to you. There will be some minimal coaxial cable (and fitting) losses and antenna combination losses, but this is well worth trying.

Jim
Most of the losses will come from the combiner (splitter used in reverse) which has an insertion loss of 0.5dB The coax and fitting losses are negligible.
 
N

nascarken68@gmail.com

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#19
Stacking2xg91yahoo

So IF I STACK 2 XG91 THE SPACE BETWEEN THE TWO DOES NOT MATTER AND CAN I SODER BOTH FEED LIONS IN TO MY CM7777AMP THANKS KEN
 
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