# Multiple OTA antennas for HD?



## jrfuda (Jan 21, 2005)

_This is a duplicate post that I made at the AVSForum, but thought y'all may be able to offer some advice as well..._ 

I currently have my indoor antenna, a Terk HDTVa, aimed at 157 degrees, which gets most of my stations in zip code 78244. Here's a screencap of my antennaweb results:










I get all of the channels I want with these results:

4-1 WOAI-D: 100%
5-1 KENS-D: 98%
9-1 KLRN-D: 73%
12-1 KSAT-D: 85%
29-1 KABB-H: 81%
35-1 KRRT-H: 65%
2-1 KBEJ-D: Cannot Lock (may not be broadcasting yet)

The unlisted channels are channels I do not care to receive.

Anyway, my Dish VIP-622 does not work well with anything less than a 70% signal, so I can't really watch 35-1

So, I was thinking about springing for an outdoor antenna - just for 35 - and then realized it would be easier to than originally planned. See, when Dish came and upgraded my system last week, they consolidated the previously 2-cable feed into the house into a single cable using some splitter/combiners. So now I have a nice piece of RG6 running from the prime location for an antenna (pointing at channel 35) right to where my receiver is.. so all I'd have to do is mount, connect, and point the antenna.

I was looking at this antenna: http://www.radioshack.com/product/index.jsp?productId=2103088 It's a 40" 17-element UHF only antenna, and it's only $25. I can point it at 280 degrees and see how it works. If it's not strong enough I'll add a preamp.

Now, the big question, am I asking for trouble by having an amplified VHF/UHF antenna that's on about 12' of cable and pointed at 157 degrees and an unamplifed UHF antenna on about 40' of cable pointed at 280 degrees? I know HD won't "ghost" like analog, but if it's getting 2 identical signals a fraction of a second apart, will it be able to lock on to just one of them? My concern is with the stations I get really strong signals for... 4, 5, and 12. I seem to be able to get them no matter which way I point my indoor antenna, so it may be that the outdoor antenna will pick them up as well, even though it's not pointing towards them. Am I asking for truoble?

Of course, it's possible that the outdoor antenna, even pointed at 280 degrees, may be all I need and I can get rid of the indoor antenna all together (though I'll need a VHF antenna to get 9).

What do y'all think? Does anyone else have more than one antenna pointing in more than one direction?

I do not want to use a rotor, becuase - if I set up a timer on my VIP-622, it may not be pointing in the right direction when the timer fires. I need a solution that does not require any interaction on my part - with the antenna anyway.

Anyone tried one of those omnidirectional channel master disc antennas (CM 3000, I think)?


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## Jim5506 (Jun 7, 2004)

Because EVERY situation is different, you will only know if the omni will work if you buy one and try it. But be sure you buy from a dealer that will allow you to return it if it fails to perform.

I have one of those RS antennas, and I pick up my PBS station off the side, but it is <3 miles away. Expecting stable reception from quartering behind the antenna at 13-15 miles might be too much. Try it and see. Digital TV reception is an art, not a science. Experimentation is the only way to determine which combination is best for your situation.


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## Jim5506 (Jun 7, 2004)

Sorry for the multiple posts, my browser was goofy.


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## jrfuda (Jan 21, 2005)

I went back and forth between doing and not doing this, but even though logic said I should not have done this, and should just wait for HD Sat locals to be available, the tinkerer in me won and I had to start messing with stuff.

First I tried this: http://www.radioshack.com/product/index.jsp?productId=2062075 omnidirectional antenna. It dropped everything, except 29, into the low 70's, and could not get a lock on 35 at all. It had to go!

I ended up using one of these: http://www.radioshack.com/product/index.jsp?productId=2103088 pointed at 152 degrees and one of these: http://www.radioshack.com/product/index.jsp?productId=2103085 pointed at 280 degrees. I have them both connected to matching transformers, those transformers connected to a 3' length of RG6 each, connected to a splitter/combiner, then connected to the RatShack amp (I know it's not very good, but was on clearance for $29, so I gave it a try), then connected via 80' of RG6 to the indoor portion of the amp, and finally connected to the receiver.

It was a mixed bag... 4 and 5 got worse, 9, 12, and 29 got better, 35 got worse - however, this is the first time that I could get any signal at all on 32 without 29 getting bad multipath (before 29, though showing 81, was actually jumping all over the place and would lose lock duing actually viewing).

*BEFORE, WITH TERK HDTVa INDOOR ANTENNA:*
4-1 WOAI-D: 100% 
5-1 KENS-D: 98% 
9-1 KLRN-D: 73% 
12-1 KSAT-D: 85% 
29-1 KABB-H: 81% 
35-1 KRRT-H: 65%

*AFTER, WITH ANTENNA "ARRAY" MOUNTED IN ATTIC:*
4-1 WOAI-D: 84% degradation, picture good
5-1 KENS-D: 88% degradation, picture good
9-1 KLRN-D: 78% improvement, picture good
12-1 KSAT-D: 94% improvement, picture good
29-1 KABB-H: 98% improvement, picture good
35-1 KRRT-H: 59% degradation, picture bad

I think I can get some improvement by reducing the 80' of RG6 to about 15', and possibly negating any need for an amp. See, I trried to salvage an old run af RG6 that was leftover from a previous sat install. However, this had the RG6 being ran from the antenna's location (almost directly above the receiver) all the way to the back of the house, to the grounding block, then all the way back to the front of the house... an 80' trip counting the ups and downs.

However, I could use some existing "holes" in the wall/ceiling, with a total of only 15' or less between the receiver and antenna. I can also reduce the "leads" connecting the two antenna to the splitter/combiner to 12" each, since the 3' is overkill.

Also, since the receiver has a 3-prong, gounded plug, does the antenna "array" need to be grounded (it's in an attic, not outside), meaning I can get by with one less connection by skipping the grounding block.. The indoor antenna I was using, which was located only 5' away from where the "array" is now located, was not grounded.

I'm going to see what kind of results I get by shortening the leads. I may also have to play with the orientation of the antenna with the wife observing signal strengths, rather than the "up and down the ladder" routine I used this morning.

Other possible courses of action:

- get a better amplifier, like this one: http://www.antennasdirect.com/antenna_amplifier.html (3rd one down, PA-17 UHF/VHF Low Noise Pre Amplifier).
- try a second UHF only antenna, pointed at 280 degrees for 32 (another $25), will also need a 3-to-1 splitter combiner, or use twin-lead to mate the antenna together with a single matching transformer comming off this "mini array".


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## Richard King (Mar 25, 2002)

Jim5506 said:


> Sorry for the multiple posts, my browser was goofy.


Fixed.


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## Fifty Caliber (Jan 4, 2006)

I think reducing the length of your feedline would help. I deffinitely recomend grounding for any outside antenna. Also, in general, avoid using twin-lead.


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## jrfuda (Jan 21, 2005)

Thanks everyone, I've done a lot of reading over the past several days.

Right now I have it working pretty well WITHOUT using any bandpass filters/jointenna devices, however, I just barely have channel 32 (68%), and changes in atmospheric conditions will probably make it go away. I get another channel in the high-60%s that comes in perfectly clear, but for some reason, I get macro blocking for a few seconds every couple of minutes on 32, even though the signal remains at 68% +/- 2.

How did I do this, you ask? After reading about multiple antennas having to be in phase, and that the way a balun/matching transformer is connected can affect this, I simply reversed the connectors on one of my matching transformers and saw a gain of 10% signal accross the board.

However, there are a few things I'm going to do to get it working a little better.

First I'm going to replace the Radio Shack amplifier with a CM 7777 preamp.

Next, I'm going to use a CM 0585-2 jointenna tuned to let only channel 32 pass on one of my UHF antennas. I will use the jointenna to join my "all channels" UHF antenna with my "channel 32" UHF antenna. I will use my existing Radio Shack UHF antenna and a CM 4228 to do this, but I'm not yet sure which will be the "channel 32" antenna and which will be the "all UHF" antenna. The output of the jointenna will be connected to the UHF seperate input on the CM 7777.

Per conversation with Channel Master yesterday, when using the 7777 in seperate mode, the inputs are filtered to pass only their designated signal type, UHF or VHF.

Becuase of this, I can connect the combination VHF/UHF antenna to the VHF seperate input on the 7777, and the 7777 will only pass the VHF signal from it.

I've attached a diagram outlining my plan. I ordered the 7777 preamp and 0585-2 jointenna from Warren Electronics yesterday, and was told to expect them in two weeks due to it being a custom order.

I'm going to see if I can find a 4228 locally, since shipping on one from Warren Electronics is over $17. According to the message I got from Channel Master yesterday, Lowes sells CM products, so hopefully one of my local stores will have one.

Here's the diagram:


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## Jim5506 (Jun 7, 2004)

Your main problem with KRRT-DT is that it is a directional transmitter and you are slightly off the lobe of their transmission.


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## jrfuda (Jan 21, 2005)

Jim, I think you may be on to something. I went to the FCC's website and looked at info about KRRT. One of the items had a polar plot of the transmission... here it is:








Is that the directional shape you're referring too? Since the tower is 280 from me, that places me on a 100 degree back azimuth from the tower, which places me on 0.589 (I'm assuming % of signal strenght), wheras, if my house was located a little further south, even at the same distance, I would get a stronger signal, especially if I was in the 130-140 neighborhood.

Overlaying that image over a San Antonio map shows that the strongest part of the signal is pointing downtown.... What's funny, is I don't even think "down town" is the part of town with the greatest population density.

Other channels I looked at appeared to have a more omnidirectional transmittions, Is KRRT likely choosing this directional transmission in order to get more signal into San Antonio, or is it just the nature of the beast?


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## Jim5506 (Jun 7, 2004)

Stations use directional transmission to target populations and to avoid interference with other stations. In this case they are probablt targeting San Antonio from outside town.

Radio stations do it all the time. There is a 50,000 watt AM station only 150 miles west of me but I can't even begin to hear it because they broadcast directionally north and south to avoid interfering with another station on the same frequency that is about 200 miles east of me (I can't get it either because it also broadcasts N-S).

On the other hand there is a 50,000 watt station on Amarillo (about 120 miles) that is clear as a bell 24/7 because it broadcasts a normal pattern (circle).


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## jrfuda (Jan 21, 2005)

Thanks Jim, I Learn something new every day!


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## Chris Blount (Jun 22, 2001)

I live in the Ingram Mall area and I can barely pick up KRRT. They are puting out very little power so don't expect great things from them.


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## jrfuda (Jan 21, 2005)

Chris, not far from me at all - I'm off of FM78 between Converse and Kirby (near Woodlake Golf Course).

Last night I was getting a whole 73% and still saw macroblocking on KRRT - even with a strong signal I was getting a "bad" signal. Other stations come in fine in the 60's.


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## Fifty Caliber (Jan 4, 2006)

Any new news on this project?


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## jrfuda (Jan 21, 2005)

Fifty Caliber said:


> Any new news on this project?


It'll probably bee a good 10-15 days before I even get the jointenna, since it's special order. I'll post the results when I can


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