Stacking two identical vhf yagi antennas

[cessna89811]

I have two identical antennacraft yagi vhf antennas pointing in opposite directions. I have them vertically stacked (spaced 3 feet), identical baluns, identical rg6 length, and splitter. I need to improve the reception of vhf channel 7. They are both facing in opposite directions with the one for channel 8 on the bottom. Channel 8 comes in clear and consistent. Also on my OTA system is my ClearStream 4 Ultra Long Range HDTV.

http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d8e03c6d9928aa2

[Jake V]

Please post your TV Fool Report so that people can understand what you are attempting

Here are some good instructions: http://forum.tvfool.com/showthread.php?t=14508

[rabbit73]

Thanks for the new TVFOOL report. I see you have a previous thread that might help us make an analysis.

Another UHF Antenna needed?
9-Oct-2013
http://forum.tvfool.com/showthread.php?t=13749

[rabbit73]

Is this what you have now?

C4 75° magn
264° magn \ H
CH 7 yagi UVSJ > preamp > coax > power inserter > TV
WCIQ \ / L
splitter
WGTV /
CH 8 yagi
78° magn

If it is, how does CH 7 do if you remove the splitter and connect the CH 7 yagi directly to the UVSJ?

Connecting two similar antennas, aimed in different directions, doesn't always work. The same signals from each antenna might interfere with each other if they are not in phase when they reach the combiner. Equal length lines are required for identical antennas aimed in the same direction. Equal length lines are irrelevant when they are not aimed in the same direction.

[cessna89811]

C4>preamp
\ H
CH 7 yagi UVSJ > dist amp > coax > TV
\ / L
splitter
/
CH 8 yagi

Here is my set up

Hopefully this "text" looks better... :)

[cessna89811]

trying to post my skematics

[cessna89811]

Thanks! I will go with your advice to connect the Channel 7 VHF antenna directly to the USVJ.

[rabbit73]

http://forum.tvfool.com/attachment.php?attachmentid=1353&stc=1&d=1437256910

Umm, your schematic looks a lot different than mine. Hold off on the changes until I've got it right.

First, I see that you have the 2 yagis connected to the input of the first LNA-200. How are you doing that? How can you insert two coax lines into one jack?

Second, why is there a splitter between the first LNA-200 and the UVSJ? A splitter is used to divide one coax line into two or combine two lines into one. A UVSJ is a UHF-VHF Separator-Joiner, used to combine a VHF antenna with a UHF antenna.

Third, where are the power inserters for the two LNA-200s?

[cessna89811]

Oops, I forgot to include the splitter in front of the preamp.

[cessna89811]

updated skematics :)

[cessna89811]

That is true about the first LNA-200 and the UVSJ. I did not know how to join the two VHF's with my UHF. Maybe I need tinlee to build a better joiner? I so love tinkering with my OTA. I love this old technology.

Thanks so much for your help.

[rabbit73]

http://forum.tvfool.com/attachment.php?attachmentid=1355&stc=1&d=1437259878

OK, that makes more sense with the splitter used as a combiner for the two yagis. That's what I was worried about. The two yagis might be interfering with each, that's why I wanted you to eliminate the CH 8 yagi for the test by connecting only the CH 7 yagi to the first LNA-200. I wanted you to do that to see if a custom AC7 combiner from TIn Lee would be worth the expense.

Now, before you make any changes to your system, please show me how you are getting power to the LNA-200s.

[cessna89811]

Power inserters are inbetween preamp and splitter.

[rabbit73]

Do I have it right now?

C4 > LNA-200 > Pwr Inserter
\ U
CH 7 yagi UVSJ > dist amp > coax > 4 TVs
\ / V
splitter > LNA-200 > Pwr Inserter
/
CH 8 yagi

If I have it right, disconnect the CH 8 yagi and connect the CH 7 yagi directly to the VHF LNA to see how CH7 does; it's your weakest signal.

What UVSJ are you using; what does it say on it?

What distribution amp are you using?

I don't see any advantage of using two LNA-200s. You could use just one to amplify UHF and VHF.

C4 >
\ U
CH 7 yagi UVSJ > LNA-200 > Power Inserter > dist amp > coax > 4 TVs
\ / V
splitter
/
CH 8 yagi

If CH 7 comes in OK without the CH 8 yagi connected, then the Tin Lee AC7 might work.

http://www.tinlee.com/Matv_filters.php?active=3
http://www.tinlee.com/MATV_headend.php?active=3#ANTENNASIGNALINJECTORS
http://www.tinlee.com/PDF/AC7-customer%20general%20hookup%20Info.pdf
http://www.tinlee.com/pricing.php?active=3

Call them and talk to one of their engineers and email your tvfool report to him.

http://www.tinlee.com/contactUs.php

C4 > LNA-200 > Pwr Inserter
\ U
CH 7 yagi UVSJ > dist amp > coax > 4 TVs
\ / V
AC7 CH.7 > LNA-200 > Pwr Inserter
/
CH 8 yagi

[cessna89811]

Using an antennas direct 8 way dist amp and the splitters are passive. A wingard brand.

Yes, you have my skematics right. :)

[rabbit73]

What exactly does the UVSJ say on it? A photo or link would help.

[cessna89811]

UVSJ is a pico Macon.

[cessna89811]

uvsj looks like this.

[cessna89811]

Going to try your skema with 1 preamp and Chan 8 disconnected from my OTA system.

So if Chan 7 works I might need to get tinlee to build ac7 injector?

Thanks so much for your help! I learned a lot about stacking VHF's in opposite directions that I don't need rg6's to be the same length... :) because maybe 7's sporadic signal is being cancelled out..

[rabbit73]

uvsj looks like this.That looks correct.

Before changing system to one preamp, try removing CH 8 yagi from your original two preamp system as proposed. Don't change more than one thing at the same time.

So if Chan 7 works I might need to get tinlee to build ac7 injector?Maybe so. I want to be as sure as possible your chances are good because an AC7 is expensive. Their engineer can help you decide.

WCIQ PBS on real channel 7 is much weaker than your strongest signals, and it is a poor quality 2Edge signal because of terrain interference, making it difficult to receive. It also has co-channel interference from WMUM also on channel 7, which is weak enough to probably not be a threat. It also has adjacent channel interference from CH 8.

[Tower Guy]

I'd try it another way. Connect the channel 7 yagi to the first LNA 200, then to the VHF input of a UVSJ but leave the UHF port empty. Combine the channel 8 yagi to the UHF antenna using a second UVSJ. Feed the output of the second UVSJ to the second LNA 200. Next combine the outputs of the First UVSJ and the second LNA 200 using a two way splitter. Finally, insert a 6 DB attenuator between the output of the 8/UHF LNA 200 and the input of the two way splitter.

With this setup your problem channel will be channel 8. There will be an optimum value of attenuation to balance 7&8 reception.