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Old 13-Mar-2014, 4:26 PM   #1
johnodon
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Join Date: Jan 2014
Posts: 41
Combining ANT751 and DB4 @ 90deg

http://www.tvfool.com/?option=com_wr...5b947ba1900476

So, I'll preface this by saying that I love my DIY projects. So much so that I am a glutton for punishment.

Anyway, I have an ANT751 that is picking up pretty much everything I need (UHF, Lo-VHF and Hi-VHF 30 miles away) in the direction it is pointed (122/123 true). I am very happy with the results.

However...

There are a few stations @ 36 true that I would also like to receive. So, I think I have 2 options....

1. I was going to build 2x 4-bay bowtie attenas (mclapp style) and point one at 122 and one at 36. I would also build a Hi/Lo VHF antenna (not sure if I can even build one of these) to also point at 122.

2. I would keep the ANT751 pointed where it is (122) to receive UHF/VHF and build 1x 4-bay bowtie attenas (mclapp style) and point it at 36.

Which is the better option?

if #1, can I combine the 2 UHF antennas using only a splitter in reverse and then combine the output of that with the VHF antenna using a combiner? Would this create too much loss?

If #2 is the better option, is there an issue using a combiner with a UHF/VHF antenna and another UHF antenna? Would this create some ghosting issues?

John

Last edited by johnodon; 27-Oct-2014 at 2:56 PM. Reason: update title
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Old 13-Mar-2014, 7:10 PM   #2
stvcmty
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The right way to use multiple antenna systems would be an A/B switch or separate tuners.

That being said, 122 Ė 36 = 86 which is almost 90. So you are pretty close to the situation where just combining two antennas with a splitter reversed is most likely to possibly work. If two antennas with deep nulls 90 degrees off axis are pointed perpendicularly and then combined, on paper, they should not be picking up signals that will interfere with each other. (The non-committal language is because this is an experiment at your own risk suggestion).

If there are only a few sub channels from 36 degrees you want and you donít mind SD picture, you could get a converter box for each sub channel you want from 36 degrees. Then you could modulate the analog output (red, white, yellow RCA) from each converter box to an unused UHF channel (remember most TVís have analog tuners that go to RF69) from 122 degrees.

If you want everything HD with a pretty interface, windows media center, tuners such as the HDHR, and Xbox 360ís would let you combine multiple antennas. WMC can use multiple tuners. Each tuner does not need to get the same signals. When setting up digital antenna signal strength, just tell WMC which tuners get which channels. Then WMC will put everything together in a nice guide. Put an xbox 360 at each TV, connect everything with network cable, and you will get a whole house DVR with the ability to use multiple antennas without any complicated filters.
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Old 13-Mar-2014, 7:34 PM   #3
teleview
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+=>
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Here some and not all build your own antenna web sites.

http://www.wtfda.org/mem/rhombictvants.pdf.

http://www.wtfda.org/mem/rhombic.pdf.

http://www.mapability.com/ei8ic/rhombic.php.

http://www.ccdxc.org/ant_calc.htm.

--------------------------------------------------------

http://www.antennacraft.net.

Has the already built , Y5-2-6 , VHF channels low band 2 thru 6 antenna.

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And it looks like , http://summitsource.com.

Has the , Winegard YA6260 , VHF channels low band 2 thru 6 antenna.

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Antennas of the 3 Tv channel bands.

VHF low band channels 2 thru 6.

VHF high band channels 7 thru 13.

UHF band channels 14 thru 51.

can be connected with separator / joiners.

HLSJ = VHF high band / low band , separator / joiner.

UVSJ = UHF band / VHF high and low band , separator / joiner.

----------------------------

Reversed splitters;

Basic splitters have direct wire connections on the inside the splitter , this allows signal strength bleed off from one antenna to another antenna.

To limit signal strength bleed off use.

Use capacitor coupled splitter.

Or use micro strip line coupled splitter.

-------------------------------------------------------------

Antenna selection can be done with a A/B switch and combinations of A/B switches.

http://www.mcmelectronics.com.

Model , 32-4425

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Or can use separate tuners connected to the separate antennas and to the Tv.

http://www.epvision.com

Last edited by teleview; 13-Mar-2014 at 9:53 PM. Reason: Clarify information and typos.
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Old 13-Mar-2014, 8:14 PM   #4
stvcmty
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Posts: 135
Quote:
Originally Posted by johnodon View Post
Would this create some ghosting issues?
Ghosting would be a problem with an analog signal. I think you are too far from Philly to get any of the LP analog stations. For digital the equivalent to ghosting is multipath, where you might see a reduction in signal quality from multipath.


Do you currently get WGAL on VHF 8? If not, 9 and 12 are far enough apart a Jointenna may let you merge a VHF antenna pointed at 36 degrees with an all band antenna (or the combined feed from VHF low, VHF high, and UHF antennas) pointed at 122 degrees. http://www.channelmasterstore.com/JO..._p/cm-0579.htm

Blonder Tongue made narrow band UHF yagis that in the range of your UHF signals from 36 degrees covered about 10 channels. 39 to 46 is less than 10 channels, which makes me think it would be possible to design a yagi that would get WFMZ and WLVT well while rejecting most other signals outside the range of channels 37 to 48. Then all you would need to do is trap RF42 from the 36 degree antenna, and RF 39 RF46 from the 122 degree antenna to combine UHF antennas with minimized multipath concerns. (A ľ wave open stub of coax would appear as a short at the frequency it was cut for, but look open further away from the frequency it was cut for, that could be a place to start for making a trap.)
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Old 13-Mar-2014, 8:39 PM   #5
randomguy
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Posts: 11
johnodon,

Please keep us updated with your results.

I'm not far from your area and have been seriously considering adding another antenna to see what else I can get.

I was able to pick up CBS from Harrisburg (roughly 70 miles away) but had to move the antenna to get all the Philly/Allentown stations.

I am very interested in what your results are.
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Old 13-Mar-2014, 10:47 PM   #6
dmfdmf
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Posts: 61
Quote:
Originally Posted by stvcmty View Post
That being said, 122 Ė 36 = 86 which is almost 90. So you are pretty close to the situation where just combining two antennas with a splitter reversed is most likely to possibly work. If two antennas with deep nulls 90 degrees off axis are pointed perpendicularly and then combined, on paper, they should not be picking up signals that will interfere with each other. (The non-committal language is because this is an experiment at your own risk suggestion).
I think this is the best strategy. The overall method is to re-aim your ANT751 to 126degT so that the null is at 36degT (the direction you want to add).

IF you can get good signals from 122degT while aimed at 126degT then you can add the second antenna. If moving the antenna offline loses you critical stations then you'd have to try a different approach or modify the ANT751 for better reception. The number one mod would be to make a twin-lead extension so the balun drops away from the boom as quickly as possible. More details here

http://forum.tvfool.com/showpost.php...1&postcount=48

I found that it really increased my signal strength across all channels.

I noticed that you are picking up RCH2, RCH4 and RCH6 from 122degT and aiming at 126degT might knock these stations out. However, the ANT751 is optimized for VHF-Hi with the two 16" elements at the rear of the antenna. These elements should be at least 33" per side to pickup RCH6 so you'd have to extend them pretty far optimize them for VHF-Lo but you probably don't need to go that far and try extending them 12" to buy you enough VHF-Lo gain (and so you don't lose RCH12) that everything works with the antenna aimed at 126defT. Unfortunately this might make FM interference a problem so check your FM Fool report and make sure you don't have any high power FM stations around.

So now that you have the ANT751 aimed at 126degT (so its null is at 36degT) and you have retained all the critical stations you want you can add in a second antenna. (You did say you were a DIY'er, right?)

I would install a DB4 type antenna aimed at 36degT. Hopefully you won't need an amp as that would make multipath worse but the signals should be strong enough from this direction. I would setup and test the second antenna independently of the ANT751 before combining and make sure you get RCH9, RCH39, RCH46 in a reliable signal and strength. If the DB4 does not have enough VHF-Hi gain to pickup RCH9 you could add VHF elements to this antenna as described here;

http://forum.tvfool.com/showpost.php...45&postcount=8

Once everything is tested you can then combine the antennas using a standard (low loss) two-way splitter. Connect the antennas, re-zero your tuner and then rescan for channels and see what you get. Test it without an amp but if you have one put it right after the antennas are combined at the splitter. Another thing you might do is rerun your TV Fool report and raise the elevation and see if that improves any of these signals, especially if your PATH column goes from 2Edge to 1Edge or 1Edge to LOS and the elevation is not too great consider a taller mast for one or both installations.

Caveat: This might not work.
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Old 27-Oct-2014, 2:55 PM   #7
johnodon
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Join Date: Jan 2014
Posts: 41
Hi guys.

I am revisiting this thread after sitting on it for quite some time and plan to move forward.

As far as the channels at 36degT, I really only care about 69.1, .2 and .3 (RCH46). I have not yet been back up in the attic but I plan to do that sometime this week. I'll point the ANT751 at 126degT and see what that does to my signals (particularly RCH2 and RCH6). If I am able to maintain a reasonable signal, I'll put in an order for a DB4 to point at 36degT and also a splitter/combiner.

Will this one satisfy my needs: http://www.amazon.com/CHANNEL-2512-P...4417918&sr=1-1

Here is an updated report for my location: http://www.tvfool.com/?option=com_wr...d243a1803bb42a

TIA!

John
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