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Crazy Monkey
11-20-2015, 10:26 AM
I modified my rooftop setup last night. I removed the high-VHF antenna and replaced it with an XG91. So now I have a vertically stacked XG91 setup with a 5’-0” spacing from center to center of antennas. It works well. I already notice improvement in signal strengths. There hasn’t been any tropo here, but I can see that my weaker locals are now stronger. WYFX-LD 19 is a good example. That signal is 50 miles away with 15 kW. With just one antenna, it was below the decode threshold… now it’s watchable, with a 50% SNR bar on the Zenith converter box.

WOUC 35/44 also improved. That’s the farthest signal I can receive 24/7 at 69 miles. With one antenna, it was just barely above the decode threshold with a 45% SNR. Now with two antennas, it’s at 60-65% SNR.

I’ll be interested to see how this new setup performs during tropo. The horizontal beam width is no different. With a vertical stack, the vertical beam width is reduced. The disadvantage is that I cannot null out signals from different azimuths using a vertical stack. But one advantage is that the vertical stack helps null out my local WDLI, which is only 1 mile away. WDLI is coming from 11 degrees above the horizontal, so a vertical stack creates a null at about that spot.

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indysteve
11-20-2015, 03:36 PM
Great job, Andrew. Keep us posted on your reception. I've had various horizontal stacks but I've never tried a vertical stack. I'll keep this in mind.

Crazy Monkey
11-20-2015, 04:45 PM
The vertical stack was the easiest for me to do without buying a lot of extra hardware. All I had to do was take off the VHF antenna and replace it with another XG91. It was that easy. I would prefer a horizontal stack, but at least the vertical stack is better than one single XG91. I get the benefit of the added 2.5 dB gain, but I don’t get the benefit of the sharp nulls a horizontal stack would have, which would help during strong tropo with too much co-channel interference. Antenna aim isn’t as crucial with the vertical stack. I could be off by a few degrees, and it wouldn’t matter as much. It’s definitely doing its job.

When I first set up this vertical stack, I made a mistake… I accidentally didn’t realize I had a couple extra feet of cable coming from one antenna. That’s a no-no. The cable lengths from each antenna need to be exactly the same. It clearly was making the signals worse than a single XG91, but once I realized my mistake, I corrected it.

Before...
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After...
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mikegmach1
11-20-2015, 07:00 PM
Great job, Andrew! I hope the vertical stack does help null that local blow torch. It is fun to make a significant change and get results. Look forward too future reports.

gregb
11-21-2015, 12:36 AM
You could do a vertical with some horizontal directivity like this;

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/001_zpshdpyhgwv.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/001_zpshdpyhgwv.jpg.html)

Or,you could get carried away with directivity like this;

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/001_zpsornbkck2.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/001_zpsornbkck2.jpg.html)

Or,get the count down and have room for the VHF. Reduces the directivity down to a more usable level;

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/004_zpshuvbooww.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/004_zpshuvbooww.jpg.html)

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/006_zpsmembtuku.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/006_zpsmembtuku.jpg.html)

I like playin around with stacks.The bigger they are, the more scatter you get.

mikegmach1
11-21-2015, 07:37 AM
Very impressive, Greg! Can you share some reception reports? It would be interesting to see how well that stack works.

Crazy Monkey
11-21-2015, 10:02 AM
Greg, I don't think it's big enough. Perhaps you should go with 16 XG91s instead, or 32. ;) I suppose that really does a good job picking up the really weak tropo and nulling out any co-channel interference.

indysteve
11-21-2015, 03:21 PM
Greg, great to see you back in business again with a big stack and thanks for posting. Over the years I believe you've tested about every combination of stacking that's possible. You introduced me to Yagi stacking around 12 years ago.

I've attached a pic of the Televes stack you had up in 2004.

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gregb
11-22-2015, 11:02 AM
Very impressive, Greg! Can you share some reception reports? It would be interesting to see how well that stack works.

Here's what I've observed so far. The more metal in the air,the more signal gathering ability,regardless of the configuration. Most effective with outlying markets in the 100-150 mile range under normal conditions in late afternoon when things are mostly deadband. I only had one good opening while doing a test between two vertical rows of three stacked horizontally with a two antenna horizontal mounted 5 ft above that. It was the opening to the east about a month ago which included several Pittsburgh stations. In every case the 2-stack decoded slightly behind the bigger stack but grabbed every one,including KDKA on 25 which has been a 15 yr wait for that one. So,from what I've seen the big stacks are better for weak scatter but,when real DX comes in anything might work.

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/002_zpsjyxpecp4.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/002_zpsjyxpecp4.jpg.html)

mikegmach1
11-22-2015, 08:28 PM
Very interesting, Greg. I agree that when Tropo is good you don't need the best antenna. However, I have gotten a few logs that were very weak during a good Tropo event that required all of my big dish. Most recently I logged KRIV 26 Houston at 890 miles. So, that monster array is worth it if you want the very hard to get DX.

Crazy Monkey
11-22-2015, 09:12 PM
In my observations, I've noticed that the vertically stacked XG91s are providing that extra gain that is needed to pick up the weaker signals. The LDs for example may be making it out far because of the high transmitter height, but they're weak. WYFX-LD 19 is a good example here... I'm 50 miles from the transmitter which is 759' HAAT, but with 15 kW, it's pretty weak. These LDs have a hard time penetrating trees, terrain, and other obstructions, so having that extra gain may be all that's required to get a decodeable signal. Since upgrading my setup, I've seen improvement on the lower power LDs... WYFX, WIVM, and W16DO.

A couple weeks ago, there was some good tropo here that was the best I've seen over the past year. I was able to receive almost all the logs I had ever received in just a single night. But there were still several that escaped, just barely below the decode threshold. Having a stacked setup at that time would have helped.

NN2E
11-23-2015, 12:25 PM
I'd like to know how y'all are combining the stacked antennas.

I've been in search of a low loss, 4 port, broadband, combiner for years but haven't found anything suitable.

I can think of a few ways of combining antennas but none of them are really the correct way to do it.

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

Crazy Monkey
11-23-2015, 12:56 PM
Ed, for a dual-stacked setup, I just use a regular splitter to combine the signals. If someone knows a better way, then I'd like to hear it. But from what I understand, the loss is as much as 0.5 dB, so it's not bad. If it was perfect, having two antennas would deliver a gain of 3 dB, but instead, I'm seeing 2.5, perhaps even 2.7 dB.

The stacked setup is working great. There was a bit of enhancement this morning, and I was seeing stronger signals than I usually see. Even WNPB 33/24 @ 135 miles was coming in nicely, and that's usually a hard one to lock onto.

I'm hoping to see the stacked setup decode some of those annoying sub-decodes that seem to slip away.

gregb
11-23-2015, 09:07 PM
I'd like to know how y'all are combining the stacked antennas.

I've been in search of a low loss, 4 port, broadband, combiner for years but haven't found anything suitable.

I can think of a few ways of combining antennas but none of them are really the correct way to do it.

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

Easy.Give ole Dave a call and tell him what you want;

http://www.hamtv.com/oal.html#split

Here's a pic of the two 4-ways I use combined together with a 2-way T splitter and two gold plated RS female couplers;

http://i498.photobucket.com/albums/rr342/locknut-1/Antennas-Dxing/005_zpsbkay2tdh.jpg (http://s498.photobucket.com/user/locknut-1/media/Antennas-Dxing/005_zpsbkay2tdh.jpg.html)

NN2E
11-24-2015, 05:44 PM
Thanks Greg...

I'll look into it.

I would think using the 2M or 70CM (can't really tell the scale from the picture) power dividers would tend to make the antenna system frequency specific and not broadband.

This might be a good time for K6STI to chime in...

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

gregb
11-24-2015, 11:12 PM
Thanks Greg...

I'll look into it.

I would think using the 2M or 70CM (can't really tell the scale from the picture) power dividers would tend to make the antenna system frequency specific and not broadband.

This might be a good time for K6STI to chime in...

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

That's why I told you to call and tell him what you want.He'll custom build to suit.The one's pictured are for UHF 470-850 Mhz and F connectors.They work just as good as the Lindsay combiner I sold Mike Glass.

NN2E
11-25-2015, 09:10 AM
I'd like to do some SWR analysis on that device... A 380 Mc (470 Mc to 850 Mc) operational bandwidth seems a bit optimistic for that type of power divider.

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

mikegmach1
11-25-2015, 03:16 PM
I like big dishes because you don't have those problems, Just how to put that monster in the air!

gregb
11-25-2015, 09:09 PM
I'd like to do some SWR analysis on that device... A 380 Mc (470 Mc to 850 Mc) operational bandwidth seems a bit optimistic for that type of power divider.

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

I'm not into the technical aspects,only the end use and they seem to work ok. I really wish there were some weak analog stations still on the air to compare the different setups.

gregb
11-25-2015, 09:16 PM
I like big dishes because you don't have those problems, Just how to put that monster in the air!

Yes,and keep it there during an ice/snow storm.That's why I prefer the stacks.

mikegmach1
11-26-2015, 06:20 AM
So true, which is why you, I, and many others have crank up towers! However, we don't always get advanced notice on bad weather...

billmalona
11-26-2015, 10:47 AM
All those arrays are awesome! Very impressive setups. Happy Thanksgiving.

mikegmach1
11-28-2015, 09:39 PM
I'd like to do some SWR analysis on that device... A 380 Mc (470 Mc to 850 Mc) operational bandwidth seems a bit optimistic for that type of power divider.

73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds

I gave Dave Clingerman at the Olde Antenna Shop in Colorado a call and asked him about the combiner he makes for UHF TV antennas. He says they are broadband and will cover the UHF TV band with very little loss. He said he uses a cone shape instead of a bar inside the unit to give it a broader band width. I don't fully understand how it works, but what he makes for Greg is not a traditional power divider.

larrykenney
11-30-2015, 10:35 PM
Greg... your stacks are amazing! Thanks for sharing your photos.

I have a stacked XG91 and 10 element VHF yagi - Y-10-7-13, along with a few other antennas on my roof, but nothing compared to what you've got in the air. Those interested in seeing photos of my antennas can check out this page my website: http://www.larrykenney.com/tvantennas.html