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Discussion Starter · #1 ·
I am trying to stack two YA-1713s for more gain. I have them currently stacked vertically by 61 inches.


I am trying to receive WNBW Ch9.1 (real channel) from a tower that is 300meters 37 miles away running 4.7KW ERP. It is a challenge.


I had up one. The receiver said 40 with some fading on one YA-1713 at 20 ft. I added as second one above it and combined them with 2 identical leads of 5 feet to a Winegard CC 7870, then 7 feet of of line into a CM7777.


There is a 4221A into the UHF side of the CM7777 about 4 feet below them. It is feed into the amp with 5 feet of line (all the line is Belden Quad shield). I didn't match the length of the UHF side to the VHF as my experience with that amp it separates well.


Adding the second antenna didn't change much at all. I seem to have fewer drops, but that is hard to judge. I am still at 40 on the receiver.


Should I move them closer or farther apart? I am doing something futile? Maybe should I build a phasing harness instead of using the combiner?


I really felt I would see a little more signal on the meter, not exactly the same results.


Thanks in Advance!
 

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I come up with a capture area (based on channel 9 and 10dBi gain) of a little over 2 meters. If it was round, the capture radius would be 31.5 inches and stacking at 61 inches would be close to ideal. But the capture area of a yagi is elliptical; it's flattened vertically. So you may want to reduce the stack height.
 

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Quote:
Originally Posted by Piggie /forum/post/15589271


I have them currently stacked vertically by 61 inches. I am doing something futile?

61 inches is a bit far for channel 9, but that's not your real problem. They have an antenna null. The actual ERP in your direction is about 500 watts.


Try adding some artificial antenna height in tvfool and see if it helps.
 

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Discussion Starter · #4 ·

Quote:
Originally Posted by nybbler /forum/post/15590037


I come up with a capture area (based on channel 9 and 10dBi gain) of a little over 2 meters. If it was round, the capture radius would be 31.5 inches and stacking at 61 inches would be close to ideal. But the capture area of a yagi is elliptical; it's flattened vertically. So you may want to reduce the stack height.

I was thinking the same thing that closer might be better as if you get too far apart you get all sorts of strange grating lobes from what I have read.


According to http://www.hdtvprimer.com/ANTENNAS/w1713.html I am reading my H-Plane 3db beam width is about 50 degrees. I used two different stacking formulas and both came up 61 to 62 inches. And it said closer might be better with a larger front lobe with less gain, but smaller grating lobes in the H-Plane.


I would be happy to get a real 2db increase.


Here is something odd that happened. My beamwidth in the E-Plane got much tighter, which should not happen on paper. In other words, pointing it is now more critical. Another really strange effect is now CH6.0 from Orlando comes in off the back of the stack better than it did off a single yagi. That doesn't matter, just odd.


I also read not to go down to less than half the capture area, which should be around 36 inches (figuring a meter is 39 and change).


So I was going to try 48 to 50 inches in one big jump to see what happens. I am not sure if I should go closer together in 6 or 12 inches jumps. Any opinion?
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by Tower Guy /forum/post/15590665


61 inches is a bit far for channel 9, but that's not your real problem. They have an antenna null. The actual ERP in your direction is about 500 watts.


Try adding some artificial antenna height in tvfool and see if it helps.

TG, they are on a pushup pole. So with no wind I jammed them up higher to see what would happen. I had the top one at 35 and the bottom at 30 for an experiment. I didn't see any difference on the meter. So I lowered them back down so I didn't have to string guys, though I am pushing the limit right now on the pole. A single YA-1713 was doing just as well at 20 ft.


Another odd thing, there is a CH28.1 on the same tower. When my 4221A was jammed up within a foot of the YA-1713, the signal was 98. I put more separation on the 4221A to 3 to 4 feet and the signal went down to 90.


Antenna can be weird.


Also I talked to the chief over there and they were granted their CP for 4.9KW, but their transmit antenna still "protects" my direction. Which give me 860 watts in my direction. Still that is not much.


My other choice for NBC is WESH out of Orlando 83 miles away. But they are at 500m running 54KW. I can seem but they drop a lot.


One thing that has to help is when WFTV in Orlando turns off 9.0 in a month. The tiniest bit of kip even just seeing sync tips kills WNBW.


WNBW really needs more power. Even people 1/3 the distance in the same direction (Gainesville) the city its supposed to cover can't use indoor antennas of any kind and make them work.


One guy about 12 miles due west of the tower had a Y-5-7-13 up 30 ft and only gets 75 to 83 on his meter. Basically they were trying to get on the local cable.


Well once WFTV goes off if I can get a steady 40, at least that locks barely without pixels unless it drops below 32.


Stayed tuned. Any ideas are welcome.


PS: I emailed Winegard to see if they had an idea. And try calling them tomorrow. But probably pushing them closer is the best thing to try or go back to one antenna and sell the second one.
 

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I don't know how the antenna is constructed, but if you could attach the directors from the second antenna to the front of the first, that would increase gain.


The fact that pointing got more critical makes me wonder if the antennas are out of phase. The baluns should be identical and connected the same way.
 

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Discussion Starter · #7 ·
Quote:
Originally Posted by nybbler
I don't know how the antenna is constructed, but if you could attach the directors from the second antenna to the front of the first, that would increase gain.


The fact that pointing got more critical makes me wonder if the antennas are out of phase. The baluns should be identical and connected the same way.
http://www.hdtvprimer.com/ANTENNAS/w1713.html


Plus the Winegard attachment to view.


====


The balun in built in the antenna as it only has a 75 ohm unbalanced output. The balun can be reversed and I tried that with much worse results. The way it's built it's pretty obvious which way the balun is phased.


I am waiting for warmer weather and my sons to help me put them closer together.


the way it is built, you can take 3 directors from one antenna and add them to the other fairly simple. I have not measured to see if the distance is correct to do that as they are up in the air. But it appears the spacing would be very close. The stock antenna has 7 directors. D4 is right at the end of the main section, as is D7 at the end of the antenna. So spacing should work.


But adding 3 elements to a 7 director antenna probably won't add more than 1 to 1.5 db of gain, which one never knows until one tries might work better than 2 stacked. Antennas in the real world are not the same as on paper unless they are free space.


I promise to return here after every change in case it helps anyone else, in just the curious.

 

ya1713.pdf 49.4794921875k . file
 

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Discussion Starter · #8 ·

Quote:
Originally Posted by Tower Guy /forum/post/15590665


61 inches is a bit far for channel 9, but that's not your real problem. They have an antenna null. The actual ERP in your direction is about 500 watts.


Try adding some artificial antenna height in tvfool and see if it helps.

They raised their power and confirmed with their Chief Eng. But that still only give about 860 watts in my direction. Still it adds a little more than 2db for me, which is like stacking.


Do you have a suggestion in what increments I should reduce spacing? 6 inches at a time? 12 inches?
 

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Discussion Starter · #9 ·
Here is their answer:



The vertical spacing for your antennas should be at 42" which is 2/3 of a

wave length for channel 9. A full wave length would be 61'' but we stack at

2/3 wave length to obtain 3dB gain. It is possible that the bottom antenna

may be seeing a reflection off the metal roof. Try raising the stack 3-4

feet higher.


----


So I am going to try that as soon as one of the kids has a few hours off.


I will report back if anyone besides me is following what happens.
 

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Discussion Starter · #10 ·
An update. Not having signal test equipment leaves me at the mercy of propagation and local noise.


I have found out that it doesn't take much electrical noise to totally wipe out high band weak signals. I knew low band was horrible but I am starting to think high band is not much better.


I thought we were in a propagation lull, so I went up on the roof and reduced the spacing to 42 inches and had zero (started with zero at 61 inches that day). Then I went to 50 inches and still zero. Then I realized there was a lot of electrical interference by comparing on an analog channel. So I stopped, left them at 50 inches and since then in the cold, low humidity and wind, the noise has only left up a few times.


I either have to find that noise or wait for the humidity to go back up so it goes away to continue testing.


However seeing how little signal I have to play with it now looks like no matter how much antenna I put up short maybe stacking 8 single band 4 wavelength yagis, all with their own amps. Still the noise might overwhelm the signal.


Conclusion. We should have given away all the VHF channels and kept 52-69. VHF except in very strong fields is worthless and just gets the station on the local cable.


Sad.
 
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