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Old 23-Nov-2011, 6:45 PM   #1
Jammer
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Behind a hill in southern Minnesota

Hi Folks.

Trying to get OTA reception at my new house. I'm only 45 miles from the cluster of transmitters north of Minneapolis but am shaded by Manitou Hill, a local topographical feature three miles north.

http://www.tvfool.com/?option=com_wr...ec128c97bb4e6b

There's a college on top of Manitou Hill with buildings as high as 17 stories which means that there isn't really much of a clean edge for diffraction so the signal levels are probably worse than the simulation shows. Height won't help me because even if I believe the simulation, I need 80 feet agl to get LOS and again in reality the buildings and trees on Manitou Hill will increase that.

With rabbit ears and a UHF loop I can get my tuner to lock on to 11 and 29 but there are dropouts. It won't lock on reliably to any other channels even if I add them manually although at times and in certain rooms I can pick up 9 and 23.1 (rf channel 3). This leads me to conclude that the signal levels are actually worse than the signal analysis shows, because it seems to me that any of the channels that are 20 dB over noise ought to come in ok.

I'm planning on putting a 91XG and a YA1713 on the roof and feed them into a CM7777 amp on the mast. The PBS affiliate on channels 17 and 23 is going to be the hardest to get and I'm hoping that the 91XG will pull that in. The 91XG should outperform anything currently on the market on those channels and won't be as bulky as a combined VHF/UHF antenna.

I figure that the YA1713 is the obvious choice to get the two VHF channels (9 and 11), since there's no low band VHF in my area.

The main question I have is the amount of vertical separation I need to have between the two antennas so they won't interfere with each other.

Also would welcome any other advice or comments.

Have considered putting up a tower on the hill 1/2 mile east of my house and running coax, signal is LOS and 20 dB better there, probably not worth doing though for the obvious reasons.
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Old 23-Nov-2011, 9:07 PM   #2
phone man
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If you're pickup up two of those stations, even with drop outs, with rabbit ears and a UHF loop, I'l bet a decent roof mounted antenna will work just fine. Have you considered a single antenna solution such as the 4228HD? It's rated for high VHF as well as UHF which would cover all your stations including ch 9. My signal strength and distance to towers is very similar to yours and I'm dealing with 2 edge reception and a ragged horizon as well.
With the 4228HD and CPA-19 preamp I have no problems getting channels 40 to 65 miles away.
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Old 23-Nov-2011, 9:24 PM   #3
No static at all
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Your antenna & preamp choice sounds good to me, but I would personally use the Antennacraft Y10-7-13 instead of the YA-1713.

The standard vertical separation recommendation is 3.5 to 4 feet, but I have never had a problem with much less when space is tight. (about 1 foot boom to boom)
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Old 24-Nov-2011, 5:58 AM   #4
Jammer
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Phone man, thanks for the reassurance. I did consider the 4228HD but was concerned about build quality and reflective losses due to the feedline coupling design, based on the negative reviews at hdtvprimer.com. Also, the 91XG has 2 dB more gain on my most critical channel. 2 dB doesn't sound like much but experience leads me to conclude that you never want to give up gain if you can help it.

No static, thanks, elevation shouldn't matter much and I have 10' of mast to work with so I should be able to achieve the customary 4'. My choice of the YA1713 was not based on any strong preference -- do you have specific concerns about this antenna or just an overall preference for Antennacraft?

Jammer
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Old 24-Nov-2011, 6:15 AM   #5
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I would opt for the Yagi antennas. I expect that they will do better in the multipath environment you're describing.

As far as vertical separation is concerned, be willing to experiment with moving either or both antennas up or down the mast in small steps. The UHF signals may be prone to 'hot' and 'cold' spots within a few inches of each other. The placement of the VHF antenna may have some influence on the phenomena. Ken Nist at http://www.hdtvprimer.com/ discusses this in some detail.
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If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

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Old 24-Nov-2011, 5:11 PM   #6
Electron
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91xg

The 91XG can be adjusted with the front of the antenna pointed up at the top of the hill and buildings for better reception of the defracted signals. Other antennas can be pointed up by bending the mast.
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Old 30-Nov-2011, 10:56 PM   #7
Jammer
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Well everything showed up yesterday and after numerous trips up to the peak of the roof everything's put together. I have to put some sealant on some of the F connectors, which I forgot -- but at least I remembered the one I can't reach. My wife is acrophobic and I ended up doing this without any help.

You can see Manitou Hill in the background of one of the photos, just slightly to the left of the line of houses.

Reception is better than I expected with both VHF stations being very strong and the "must have" UHF stations also being very strong. The lowest s/n of the "must haves" is 19.2 according to the calculator. In addition I am now receiving KPXM digital reliably (2.7 calculator s/n) as well as analog station K43HB (1.1 calculator s/n). Two weaker analog stations are providing noisy but still viewable signals, WUMN (-16.8 in the calculator) and K14KH (-27.8 in the calculator).

I haven't used tripod mounts before. I've always used a mast foot and guy wires. But I opted for a tripod this time after reading up on best practices and also because the roof is fairly steep and lacks much usable ridgeline for placement of guy anchors. I have the tripod feet bolted to the roof deck with 2" fender washers and locknuts on the attic side. I'm not entirely sure whether that's overkill or insufficient or just right, and would invite any suggestions. It's a 10' mast.
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Old 30-Nov-2011, 11:12 PM   #8
phone man
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I envisioned a much more cluttered horizon. Glad to hear the XG91 is working out. Your stations are about the same strength and distance as mine. How fussy was the XG91 about aiming and finding the best reception position? Did changing the height by a few inches affect the signal very much.
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Old 30-Nov-2011, 11:25 PM   #9
Jammer
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Phone man,

I tried the XG in two places.

First I had the whole setup on the ground just to confirm that I had all the pieces and that everything worked. No point waiting until it's all up in the air to find out that a piece of coax or whatever is bad.

The signal analysis showed somewhat stronger signals at 10' than at rooftop height (40'). Any RF simulation will have its limits and I was skeptical of this particularly given the row of buildings to the north and also the difficult-to-model effects of Manitou Hill.

I don't have any useful way to measure signal strength but judging by the differences in what stations I can receive clearly I believe there was an overall 10 dB improvement in signal with the move to the roof.

I was satisfied with what the XG was doing in its first location and so I didn't experiment with tilt, height, or azimuth adjustments. It has a very slight uptilt, 5 degrees at most, which probably doesn't do anything since the the front lobe is larger than that.
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Old 1-Dec-2011, 1:21 AM   #10
phone man
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OK, I thought you might have had a second pair of eyes on the TV's signal strength meter while you aimed it on the roof. You must have nailed it the first time or had a pretty good idea which way was north!
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Old 1-Dec-2011, 1:33 AM   #11
Electron
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Reception

The way you discribed it , I had visions of living right under the hill , looking almost straight up at some very tall buildings on top of the hill. Very nice pictures , the tress and hill are far away , other then the hill with buildings , a clean view of the transmitters. Sounds like good job of bolting the tripod down. Better to have the tripod bolted down better. As opposed to not enough. Your location has many digital channels and digital sub channels and analog channels to receive.

Last edited by Electron; 2-Dec-2011 at 3:15 AM.
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Old 24-Oct-2019, 5:14 PM   #12
Jammer
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An update.

About one year ago severe storms passed through the area including several small tornados. There were several spruce trees uprooted and blown over in the neighborhood. My antenna mast bent at the top of the tripod until the antennas were in contact with the roof. I had a local antenna contractor replace the mast. I don't think he tightened the setscrews quite enough because the antennas later spun the mast in a relatively minor blow.

The corner reflector on the UHF antenna was damaged and the contractor discarded it. There was also part of the first director broken off.

I am finding that I have more than adequate gain on VHF, and am relocating the VHF antenna to the attic to reduce wind load. I am going to move the UHF antenna down a few feet for the same reason.

Overall the antenna has performed well and we've had television for under $1 a month.
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Old 27-Oct-2019, 11:52 PM   #13
phone man
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That was a fun thread to revisit. Sorry about the storm damage to your antenna. Since 2011 our channel count has more than doubled with all the sub channels and a couple new independent stations. Knock on wood, everything I installed in 2011 is still working well.
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