How do you merge two antennas to one signal. - AVS Forum
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post #1 of 19 Old 04-28-2007, 02:12 PM - Thread Starter
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I have two HD antennas that I would like to combine to one. I live between Milwaukee and Chicago. So one antenna is pointing south, one north. I tried combining them with a Winegard CC-787- coupler but I only get one antenna not both. Both antennas have a pre-amp. Any one with who you can combine two antennas to one.
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post #2 of 19 Old 04-28-2007, 03:11 PM
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Might I suggest that you post in the antenna forum,

Combining antennas can be tricky; two antennas, 180 out is probably not a good idea.

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post #3 of 19 Old 04-28-2007, 03:13 PM - Thread Starter
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Thanks!
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post #4 of 19 Old 05-02-2007, 07:01 PM
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Nope, not a good idea at all. Radio waves are a lot like waves in water. If you have two waves heading for each other, but one wave is out of phase with the other wave (the trough of one wave matches up with peak of the other wave) they will actually cancel each other out; same thing happens with radio waves especially if the antennas are 180 degrees in seperation. The only reason you are getting one antenna is most likely signal strength but the signal is probably degraded with the other antenna hooked up. While not elegant the best thing to do is either get a rotary antenna, run 2 cables into an A/B switch or get an omni directional antenna.
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post #5 of 19 Old 01-16-2008, 07:50 AM
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I've found that it can work without using Jointennas if you have a few factors in your favor:

1. You're more or less equidistant from each set of towers, or, no closer than 20 miles from any of them. This keeps from getting multipath issues off the "back" of one antenna from the stations that the other antenna is aimed at. If you're at least that far away, you generally have too weak a signal on the back, if you use a highly directional antenna, to have much effect.
2. Use very directional antennas - see above
3. None of the stations are "barely" able to be picked up - since you'll have about a 3db signal loss with the combiner
4. There are no trees or obstructions between the antenna and the towers on either side - this lowers risk of multipath.
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post #6 of 19 Old 01-16-2008, 11:53 AM
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Quote:
Originally Posted by akron05 View Post

I've found that it can work without using Jointennas if you have a few factors in your favor:

1. You're more or less equidistant from each set of towers, or, no closer than 20 miles from any of them. This keeps from getting multipath issues off the "back" of one antenna from the stations that the other antenna is aimed at. If you're at least that far away, you generally have too weak a signal on the back, if you use a highly directional antenna, to have much effect.
2. Use very directional antennas - see above
3. None of the stations are "barely" able to be picked up - since you'll have about a 3db signal loss with the combiner
4. There are no trees or obstructions between the antenna and the towers on either side - this lowers risk of multipath.

So, in other words, get the rotator or an A/B antenna switch?

Just because there is a knob doesn't mean you should turn it.
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post #7 of 19 Old 01-16-2008, 01:24 PM
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mrjim-

All the above posts have good pointers. In general combining antennas is difficult because of interaction between them, especially if not aimed in the same direction and spaced correctly.

In your case there's one more thing to look out for. You said both antennas have preamps, but only one seemed to work when combined. I assume each has its own power supply/inserter at the indoor end of the two antenna lead-ins, and that you are trying to combine the signals downstream or from the output side of the two power supplys. If you try to combine the two downleads upstream, i.e. between the power unit and the mast-mounted preamp, one or the other might not get power if the splitter/combiner doesn't pass DC or low voltage AC up the leads to both preamps.

In theory you might be able to power both preamps from one supply if it has enough current available and if they are the same type/model. It would be easier and more practical to connect the combiner after the power units, or use a single preamp after a combiner mounted near the antenna and a single lead-in.

Mike
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post #8 of 19 Old 01-26-2008, 10:17 AM
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For this to work properly you need notch filters on each antenna. The one pointing south need a filter to block the channels from the north and vise versa.

This will eliminate any multi-path and phase cancellation issues from signal that will be picked up on the back of the antennas.

Back in the day people used to make a tuned stub to do this. I can't remember the formula right off the top of my head, but it was when everyone used 300 ohm twin lead anyway.

All said and done you might be better off just getting a rotor or running two runs and using a A/B switch.

A 'phile and his money are soon parted...
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post #9 of 19 Old 01-26-2008, 11:58 AM
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Notch filter! I remember that. Basic RC circuit. Used it to tune out closer/more powerful stations in order to tune in farther away TV station that was carrying the football game that was blacked out in my area. That was 35 years ago but still useful in places where the nearest station is 60-100 miles away.
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post #10 of 19 Old 02-11-2009, 06:01 PM
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I found that using a remote control A/B switch from Radio Shack was the best solution for me. I would like to use a combiner, but it sounds to complicated.
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post #11 of 19 Old 11-22-2013, 01:45 PM
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Now that I have some empirical experience on this subject, I joined your forum just so I can share what I learned over the past week  -  I did a fair amount of research on the subject of the best way to combine two HDTV antennas into one feed so all the channels would show up on all 4 of my TV's and my TiVO

 

I never did find much help  -  Lots of naysayers who claimed it was next to impossible to do.  Just as I was about to try the splitter/combiner up on the roof (which guarantees you lose half of the strength of each signal) I did a little research on the 4 way amplified splitter I've been using in my basement for the last 6 or 8 years

 

It is a Channel Vision CVT-2/4 PIA and I can highly recommend it to anyone who needs a good distribution amp/amplified splitter.  It has served me well for a long time.  Anyway, I knew it had a TV antenna input which I used for years with my incoming cable signal and now that I've 'cut the cable' I've had one antenna connected there for the past several months.  This amplifier also has a 'modulated input' which I believe was intended for use to combine the signal from a dish to your antenna signal for distribution to all 4 sets.  I did some research on this 'modulated input' and found it is compatible with all UHF frequencies  -  Anything above 450 mhz.  As a test, I removed my antenna from the antenna input and put it on the modulated input and then checked all my signal strengths using the meter built into my TiVO  -  No differences

 

So, I installed my new antenna, ran a second cable from it to the basement and hooked up both antennas  -  Works perfect!

 

In my case, I have a 4 bay antenna pointed nearly due east to get several stations which are 60 to 75 miles away.  It has always worked pretty well.  My local group of stations came in pretty well too, but since their antennas are located nearly due north from me, I was receiving those stations off the corner of the antenna, so occasionally they would break up, even though their signal strength on my TiVO is always higher than the far away stations my antenna is pointed toward

 

I bought a smaller 2 bay antenna and mounted it about 6 feet lower on the pole, pointed it 90 degrees to the north of the 'main' antenna and then hooked everything up.  My local stations used to have signal strengths in the 80 to 90 range on my TiVO strength meter and with the new antenna, those are all in the low to upper 90's now  -  Two stations now peg the meter at 100

 

If you use this technique, remember that the modulated input on the Channel Vision amp is only compatible with UHF frequencies (though it did appear to work OK for me on channel 13 in a test) so if you need the VHF frequencies on one antenna but not the other, use the normal antenna input for that antenna and put the other on the modulated input

 

Hope this helps someone else on down the line

 

Don

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post #12 of 19 Old 01-05-2014, 01:58 PM
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I will probably post in the Detroit HDTV antenna thread in detail, but I'm in a situation where I have two antennas, am not more than 25 miles away from the strong stations I want to receive, and need to combine two antennas. A remote A/B switch is useless since two TVs are used simultaneously, as is running separate wires from each antenna to each TV (this house is a rental and wiring to the family room is pretty much set in stone).

I have one of those Winegard combiners, and I also tried a direct connection between the two antennas, putting the balun between two equal length 300 ohm leads. Both worked about equally mediocre, and I dropped a couple of stations. I have a channel in Canada almost due south, and the Detroit-area stations in Southfield are just about to the west, so the two antennas are at almost a 90 degree angle to each other.

Given any interference between the two, would it help to separate the antennas? I get a strong and very usable signal on the Canadian channel if connected on its own, and likewise for the other. I can put the antennas at opposite ends of the house if that would help. But before I go to that much trouble, I thought I'd ask here. The Canada antenna, in fact, works well at between 9 and 10 ft. off the ground--I could tuck it around a corner, out of sight of the other.

-= N =-
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post #13 of 19 Old 01-06-2014, 10:18 AM
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Figure out the frequencies you need from the South-facing antenna - you might be able to find a band-pass filter (inverted notch filter) or build one with a low-pass / high-pass filter too get it to work.

Are you using a highly directional antenna for the South-facing one? That might help, too.

And no, separating the antennas won't help. That 50' difference won't alter reception coming from 20+ miles away...

Definitely a good question for the Detroit HDTV reception thread, though!

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post #14 of 19 Old 01-06-2014, 12:47 PM
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Quote:
Originally Posted by jautor View Post

Figure out the frequencies you need from the South-facing antenna - you might be able to find a band-pass filter (inverted notch filter) or build one with a low-pass / high-pass filter too get it to work.

I did a lot more reading late last night. (I mean, what else is there to do after a foot of snow is dumped on your neighborhood? biggrin.gif ) I figure I'll share that here, especially since it is generic and can apply to any broadcast area. I may work through these and check in to the Detroit HDTV thread once I figure out what is working.

The true problem in my situation is likely multipath cancellations. I am at a height disadvantage with the primary antenna, preventing me from getting a handful of lesser locals, but I'll be able to take care of that once the weather gets above freezing. It still pulls in most locals we're interested in, however.

First, what you describe turns out to be available in a former product made by Channel Master: a JoinTenna. What it does is offer a notch filter for the primary antenna (all channels, minus one), and a very narrow bandpass filter for the secondary antenna (no channels, except for one). While that is for the most part acceptable, I do lose the ability to get a crummy local station off of the backside of the secondary antenna which is almost in the opposite direction of the Canadian station. (Crummy? Their picture quality is lousy, as in VHS vs. BluRay lousy, and they stretch all 4:3 format broadcasts to 16:9.) And the Canadian channel also has a secondary transmitter on the same broadcast tower for a 2nd channel. Anyway, I primarily want the one Canadian channel, so this solution would work.

Here's the JoinTenna: http://www.channelmasterstore.com/JOIN_TENNA_CM_0579_p/cm-0579.htm?CartID=1 (Although $12+ shipping for a $3.99 part is sort of disheartening. I might see if my local electronics store carries the brand and might order it in with a stock order.)

This company in Canada offers an even more interesting solution: they build filters and distribution devices to custom specifications. http://www.tinlee.com/index.php

If I had the know-how, I could build a series of three notch filters myself (Channels 9, 32, 38) and the corresponding bandpass filters (Ch. 2-7, 11-30, 34-36, 40-up). I'm currently looking into how it's done, as I have easy access to components locally. I could just make my own JoinTenna equivalent, in other words.

Interesting side note about notch filters: you can easily make one for other antenna applications (such as remote control airplanes and video cameras) by using a "T" connector and fabricating a small "stub" of coaxial to attach to one side of the "T". The length of that stub corresponds to a calculation based on the frequency you are notching out. Fascinating stuff for DIY-ers! http://www.rcgroups.com/forums/showthread.php?t=1758166

Second, I found out that separating the antennas does make a difference. There is a formula out there wherein, if you are mounting two antennas together on a vertical mast, you want to separate the antennas by the half wavelength of the lowest frequency you'll be receiving. The example they used in their formula was Channel 2, the lowest frequency, which puts the antennas at more than 8 ft. apart on a vertical mast. If orienting two antennas horizontally, you want them at least one full wavelength apart. With that in mind, I can easily put my south-facing antenna on the eastern side of the house, and keep the primary antenna on the western side, which gets them more than 25 ft. apart. http://www.tvantenna.com/support/tutorials/combining.html

I plan to battle this beast until 1) I get what I want or 2) it kills me. biggrin.gif

-= N =-
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post #15 of 19 Old 01-06-2014, 01:33 PM
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And while poking around Channel Master's site a moment ago, I find this:

http://www.channelmasterstore.com/SMARTenna_HD_Antenna_p/cm-3000hd.htm?Click=32510

They claim up to a 50 mile range if mounted outdoors.

Thing is, I have never trusted nor had good luck with omnidirectional antennas. It seems like it would pull in most channels OK, but not pull in any one channel great. But if I take the chance and try a chimney mount with this one, it could possibly work. I also remember omni antennas having a limited range, nothing near what a good directional antenna can pull in.

-= N =-
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post #16 of 19 Old 01-07-2014, 05:54 AM
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Quote:
Originally Posted by Wildcat445 View Post

And while poking around Channel Master's site a moment ago, I find this:

http://www.channelmasterstore.com/SMARTenna_HD_Antenna_p/cm-3000hd.htm?Click=32510

They claim up to a 50 mile range if mounted outdoors.

Thing is, I have never trusted nor had good luck with omnidirectional antennas. It seems like it would pull in most channels OK, but not pull in any one channel great. But if I take the chance and try a chimney mount with this one, it could possibly work. I also remember omni antennas having a limited range, nothing near what a good directional antenna can pull in.

You might want to search for reviews--most omni-directional antennas are crap! But I don't know this antenna specifically. Also, digital TV is different--either you have enough signal for a lock or you get nothing. Completely different from the old days of analog where you got various levels of 'snow' in the picture.

BTW, you may be able to use just one antenna. My two sources, (Toronto and Buffalo) are at 80+ degrees to each other. Antennas often have a leaf-shaped pattern of stronger/weaker reception. A little futzing with the aiming may get you acceptable reception on all the channels you're interested in.

http://www.hdtvprimer.com/ANTENNAS/cm4228.html

Craig
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post #17 of 19 Old 01-07-2014, 06:14 PM
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Quote:
Originally Posted by Pvr4Craig View Post

You might want to search for reviews--most omni-directional antennas are crap! But I don't know this antenna specifically. Also, digital TV is different--either you have enough signal for a lock or you get nothing. Completely different from the old days of analog where you got various levels of 'snow' in the picture.

BTW, you may be able to use just one antenna. My two sources, (Toronto and Buffalo) are at 80+ degrees to each other. Antennas often have a leaf-shaped pattern of stronger/weaker reception. A little futzing with the aiming may get you acceptable reception on all the channels you're interested in.

http://www.hdtvprimer.com/ANTENNAS/cm4228.html

Craig

I had no luck with one antenna--the Canadian channel was particularly stubborn.

Agreed that many omni antennas are crap--they're fine if all the signals are strong and local. But if anyone could pull off a good omni DTV antenna, Channel Master could. The reviews I've seen were mostly positive. Seeing that all stations are 25 miles or less, and I can get decent height, I will be willing to try it. If so, I'll have two nice antennas for sale... wink.gif

-= N =-
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post #18 of 19 Old 01-08-2014, 06:27 AM
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Quote:
Originally Posted by Wildcat445 View Post

But if anyone could pull off a good omni DTV antenna, Channel Master could.

+1!

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post #19 of 19 Old 03-13-2014, 08:56 AM
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I am in Livonia. I just plugged in the Winegard Flatwave FL6550a. I have it sitting on the floor of my family room leaning against the doorwall; pointing SE. I picked up 35 channels, including 9 and 32 from Canada, and all the regular Detroit channels. 

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