Multiple OTA antennas for HDTV?

[jrfuda]

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)?

 

[roashru]

jrfuda, yes it is possible to create an antenna setup like that.

(1) vhf/uhf combo antenna for KPXL-DT, KRRT-DT, KBEJ-DT
channel master gold medal or crossfire series
winegard platinum series
terk tv36 or tv38

(2) uhf yagi antenna for KVDA-DT, KWEX-DT, KSAT-DT, WOAI-DT, KHCE-DT, KABB-DT, KLRN-DT, KENS-DT

to connect the antennas together you can use 300 ohm ultra low loss wire or 75 ohm rg6 cable the correct balun transformers are needed to match everything together. i recommend contacting an amatuer radio operator in your area and ask them if they can help you even if you have to pay them to help you setup everything. most people here in this forum do not follow ohms law!

 

[jrfuda]

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".

 

[roashru]

jrfuda, no, uhf reflectors do not need to be grounded as long as the sunlight static electricty is not a problem. from your description you want to connect everything together using rg6 coax the balun transformers and combiners needed cannot be purchased at radio shack.

 

[ghia]

Unless I missed something here you are try to combine two antenna into one coax cable without using a bandpass filter / channel trap. You are essentially attempting to inject the one channel (35.1 @ 280 degrees) into the rest on your indoor ant. Have a look here
http://www.channelmaster.com/Pages/TVS/Passives.htm
and here
http://www.tvantenna.com/support/tutorials/combining.html
I would also recomend the hdtv primer page concerning antenna basics here http://www.hdtvprimer.com/ANTENNAS/basics.html

Hope this helps.

 

[jrfuda]

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:

 

[roashru]

jrfuda, that antenna setup i'snt showing any good grounding block at the farthest point up the pole of coax. also when you use the wrong antenna to coax transformer with a coax "splitter" without correct antenna to coax transformers for the multiple antennas and ferrite core combiners ohms law was changed. its o.k. as long as your hdtv receivers a.g.c. (automatic gain control) can handle it.

 

[jrfuda]

Guys, I received my channel 32 jointenna and CM 7777 preamp yesterday and installed them this morning. Here are my new results:

4-1 WOAI-D (UHF 58): 100%, clear
5-1 KENS-D (UHF 55): 100%, clear
9-1 KLRN-D (VHF 8): 75%, occasional macro blocking (every few minutes)
12-1 KSAT-D (UHF 48): 98%, clear
23-1 KHCE (UHF 16): 64%, mild macro blocking (every 1-3 seconds)
29-1 KABB-H (UHF 30): 98%, clear
35-1 KRRT-H (UHF 32): 74%, mild macro blocking (every 10-20 seconds)
41-1 KWEX (UHF 39): 100%, clear
60-1 KHCE (UHF 38): 100%, clear

So, joining antenna using the correct methods work much better than just using splitter/combiners. I'm still using the old antennas. I know this is probably not a completely sound idea, but I put two matching transformers on the VHF/UHF combi antenna (pointed in KRRT's direction, 280 degrees) and ran one line to the jointenna's 32 input and the other to the 7777's VHF input. I ran another line from the UHF-only antenna (pointed a 154 degrees) to the jointenna's "all channels" input, and then ran the jointenna's output to the 7777's UHF input.

I also put a 0-20db variable attenuator between the preamp power injector and my receiver. I found I got an increase in ALL signal strengths by placing this attenuator a little more than half way to its highest setting. I tried the attenuator at various others locations and it killed reception on one or more channels, so I guess the 7777 was putting out a wee but too much for my receiver, and the attenuator is padding it down just right.

roashru, I was told by many folks that a grounding block is not necessary because the antenna are in the attic, also, all of the various "splitting/combining" devices (the jointenna and the CM 7777 preamp) are specificaly designed for these purposes and I'm sure they perform impedence matching so that the signal that finally arrives at the receiver is correct.

So, the ch-32 jointenna works as advertised and does not appear to hurt channel 30 at all. Maybe they have improved on the design and adjacent channel attenuation is no longer an issue (or less of an issue).

My next step is to change the channel 32 antenna (UHF/VHF combi) out for a CM 4228. That's probably be a few weeks away, though. I had some on backorder with Warren Electronics, and decided to wait, as there's a chance we may have to move out of this house in the next 2 months rather than 1-2 years from now. My landlord's daughter and son-in-law, who is also in the military, is being stationed in San Antonio and wants to live in the house. Our lease is up in July, so we may be moving then. We called the old guy earlier this week and he was very receptive to our request, so maybe he'll convince his son-in-law to look for alternate accommodations. We'll see....

 

[roashru]

jrfuda, grounding coaxial cable is not for lightning its for signal. for best results all coaxial cable should be grounded at both ends with no splices then if outside waterproof seal.

 

[Rick0725]

" grounding coaxial cable is not for lightning its for signal. for best results all coaxial cable should be grounded at both ends with no splices then if outside waterproof seal."

This statement is not correct.

The grounding of the mast and transmission line is required practice in an antenna installation. The grounding is intended to dissipate static charge to lessen the possibility of lightning strike. The antenna is usually the highest point on the structure and is most prone to attack. Signal should be the least of your worries.

The cm 7777 is too much amp for towers 16 miles away. You are going to attenuate too much signal at the higher frequencies turning the attenuator to more than 50%.

Suggestion...When you order your cm4228 consider an amp with less gain to amplify the signal from the closer towers. The winegard hdp 269 is better suited at those distances. The AP 8700 will also be too much. And use your cm7777 to amplify the signal for the towers at the greater distance with the cm4228. This would require a slight mod to your layout. Then you you can eliminate the attenuators and improve performance.

High 5 for the thought that went into your system plan by the way.

 

[roashru]

Rick0725, my grounding comment was only about adding a rf ground for better reception. a safety ground is not really needed for an attic antenna setup like jrfuda did.

 

[jrfuda]

...High 5 for the thought that went into your system plan by the way.

Thanks for the feedback. All my plans/expirements are on hold until I find out if I'm staying in this house or moving in June/July. The only good thing about the move is that I'll be about 5 miles closer to my distance station and 5 miles further from my near stations.... However, I'll be living in military housing and may not be able to put up an outdoor or attic antenna at all... Everyone I know that has Dish with on-post housing has their dish(es) in the yard on a tripod.