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Combining the signal from two antennas |
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#1 |
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Forum Member
Join Date: Nov 2004
Posts: 40
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Combining the signal from two antennas
Is it possible to combine the signal from two antennas using a diplexer. One aerial is pointing north and the other south and one aerial is vertically polarised and the other horizontally polarised.
If a diplexer can be used is there a special one available for aerials. Most show sat as one input and antenna as the other input. Thanks |
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#2 |
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Forum Member
Join Date: May 2005
Location: Redditch Worcs
Posts: 17,288
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Depending on which uhf channels the two transmitters use then you may be able to use a uhf/uhf diplexer.
http://www.aerialsandtv.com/ampsands...html#diplexers |
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#3 |
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Join Date: Apr 2006
Location: North Derbyshire
Posts: 41,779
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It's really only practical if the two transmitters use widely spaced channels (say one group A and one group C/D), and you can buy specifically designed 'diplexers' to combine two such aerials.
However, the easiest solution is to use a simple aerial switch, to switch between the two aerials as needed. I had a switch between Sutton Coldfield and Emley Moor aerials for years, although in practice I almost never used the Sutton aerial. However - with analogue having shut down now, it might be worth trying joining them with a simple splitter/combiner and see how it works. The basic drawback with analogue was ghosting, which DTT is supposedly immune to. |
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#4 |
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Join Date: Dec 2009
Location: West Lancs.
Posts: 90
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Years back I had two aerials fitted on my chimney and the fitters used something they called a 'combiner'. I suppose this was some type of diplexer.
I'm situated not too far fro Liverpool ang get my signal from Winter Hill, now digital of course. A couple of weeks ago I thought I'd try out getting something from the Moel y Parc transmitter in North Wales. I manged to get S4CHD, Clirlun, along with Welsh versions of other channels. It's disappeared now, I suppose it's closed down. |
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#5 |
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Join Date: Jan 2010
Posts: 127
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I built a diplexer many years ago to combine the output from an A group aerial pointing at Ridge Hill and a CD group aerial pointing at Mendip. On the A input was a low pass filter which attenuated frequencies above 650MHZ and the CD input a high pass filter attenuated signals below 650MHZ. If you just combine the two aerials you will get very unpredictable results with some channels missing as the signals from the two aerials cancelling each other out at some frequencies.
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#6 |
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Join Date: Dec 2007
Posts: 955
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If the aerials are pointing in opposite directions and are opposing polarities, there will not be much signal going into both aerials.
Therefore, a frequency-discriminating combiner is not necessary. A simple combiner would do. Thanks my opinion, anyway. Do you plan to combiner the signals on the roof or indoors? |
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#7 |
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Join Date: Oct 2007
Posts: 5,007
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Quote:
If the aerials are pointing in opposite directions and are opposing polarities, there will not be much signal going into both aerials.
Therefore, a frequency-discriminating combiner is not necessary. A simple combiner would do. Thanks my opinion, anyway. Do you plan to combiner the signals on the roof or indoors? Also simple combiners lose about 4db whereas a good duplexer will only lose 1dB. |
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#8 |
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Join Date: Dec 2007
Posts: 955
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OK. Thanks for correcting me.
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#9 |
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Forum Member
Join Date: May 2005
Location: Redditch Worcs
Posts: 17,288
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If the Op posts which two transmitters are involved then there is a lot more chance someone can post actual facts rather than mere speculation.
Future 3G services might even make a current solution inpractical in the first place. If the vertical polarised source is a relay off the main transmitter (which seems likely), what advantage is there in getting the same channels twice ? Should the OP ever get a Freeview-pvr it will be totally pointless (most hate channels from more than 1 transmitter) |
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#10 |
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Inactive Member
Join Date: Aug 2012
Location: Guisborough, North Yorkshire
Posts: 2,878
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Quote:
Your opinion is not necessarily right. If one signal is local and the other distant the stronger signal will still quite strong on the other aerial.
Also simple combiners lose about 4db whereas a good duplexer will only lose 1dB. It is annoying, but I can live with it, I just have to delete the duplicate channels manually. |
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#11 |
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Join Date: Oct 2009
Posts: 117
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Quote:
Originally Posted by Winston_1
Your opinion is not necessarily right. If one signal is local and the other distant the stronger signal will still quite strong on the other aerial.
Also simple combiners lose about 4db whereas a good duplexer will only lose 1dB. You're right that you will lose a few more dB in a combiner, but you probably won't notice the extra loss if the signal levels are reasonable. You may not have any choice depending on the frequencies involved. |
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#12 |
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Join Date: Oct 2009
Posts: 117
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Quote:
Originally Posted by grahamlthompson
If the vertical polarised source is a relay off the main transmitter (which seems likely), what advantage is there in getting the same channels twice ? Should the OP ever get a Freeview-pvr it will be totally pointless (most hate channels from more than 1 transmitter)
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#13 |
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Join Date: Mar 2010
Posts: 4,815
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One Panasonic Freeview HD+ HDD/DVDR , the XW380, doesn't hate multilple signals , and doesn't store duplicates of anything but BBC One, itv1, itv1+1 and the two Rabbits in my experience.
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#14 |
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Join Date: May 2005
Location: Redditch Worcs
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Quote:
One Panasonic Freeview HD+ HDD/DVDR , the XW380, doesn't hate multilple signals , and doesn't store duplicates of anything but BBC One, itv1, itv1+1 and the two Rabbits in my experience.
It's pvrs that have problems( with the accurate record signals, well Humax ones do ) What duplicates you get is down to where you are. |
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#15 |
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Join Date: Mar 2000
Posts: 6,110
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I know some of this thread started ages ago but hope you can help.
I was told that if I put a splitter so that two aerials going into one receiver one for Winter Hill the other for Moel Y Parc - would cancel each other out. However, the two transmitters use different frequencies so if I got a second aerial pointing to Moel Y Parc, could I put that feed into one side of the splitter and the Winter Hill aerial into the other and get both sets of muxes at the same time? Currently I get Winter Hill (but not COM7 or 8), and Moel Y Parc PSB1 and PSB2 off the back of the Winter Hill aerial. Occasionally I get SDN from Moel Y Parc but rarely. Your help is much appreciated. Thanks |
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#16 |
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Join Date: Apr 2006
Location: North Derbyshire
Posts: 41,779
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Quote:
I know some of this thread started ages ago but hope you can help.
I was told that if I put a splitter so that two aerials going into one receiver one for Winter Hill the other for Moel Y Parc - would cancel each other out. However, the two transmitters use different frequencies so if I got a second aerial pointing to Moel Y Parc, could I put that feed into one side of the splitter and the Winter Hill aerial into the other and get both sets of muxes at the same time? Assuming the two are FAR apart in frequencies, then you can get frequency dependent splitters for this exact purpose, usually ordered for the specific frequencies you want. Easiest solution is to get an aerial switch, and switch to whichever aerial you're using at the current time. |
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#17 |
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Forum Member
Join Date: May 2005
Location: Redditch Worcs
Posts: 17,288
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Quote:
I know some of this thread started ages ago but hope you can help.
I was told that if I put a splitter so that two aerials going into one receiver one for Winter Hill the other for Moel Y Parc - would cancel each other out. However, the two transmitters use different frequencies so if I got a second aerial pointing to Moel Y Parc, could I put that feed into one side of the splitter and the Winter Hill aerial into the other and get both sets of muxes at the same time? Currently I get Winter Hill (but not COM7 or 8), and Moel Y Parc PSB1 and PSB2 off the back of the Winter Hill aerial. Occasionally I get SDN from Moel Y Parc but rarely. Your help is much appreciated. Thanks Worth a try using a splitter as a combiner. Note do not attempt to autotune. Add each mux you want manually. |
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#18 |
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Join Date: Mar 2000
Posts: 6,110
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Quote:
The best way to do this is using a diplexer with a band filter on each input, This though requires a obvious channel you can split the UHF band at. Sadly the above transmitters use interleaved channels.
Worth a try using a splitter as a combiner. Note do not attempt to autotune. Add each mux you want manually. When I get my aerial sorted I will give it a try. |
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#19 |
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Join Date: Feb 2003
Location: Easternmost England
Posts: 1,120
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Winter Hill uses
31 37 49 50 54- 55 56 58 and 59 Moel-y-Parc uses 32 34 39+ 42 45 48- 51- and 52+ Therefore a filtered combiner cannot work to provide all of the frequencies from both transmitters at the same time. A simple combiner will give unpredictable results due to the pickup of the 'wrong' transmitter from the rear... but might be worth a punt. Only the multiplex frequencies marked in bold carry different regional programmes (AFAIK). Taylor Bros do filtered channelised combiner levellers and other (notch) filters that might allow the three from M-y-P to be combined with all from WRH with some ingenuity and expense. Of course in the next couple of years that will all be a waste of effort as the 700MHz clearance will force a complete frequency reshuffle into the 21 to 48 band for both transmitters. |
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#20 |
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Forum Member
Join Date: Oct 2007
Posts: 5,007
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What one really needs is some form of coaxial relay like a diseqc switch, but no TVs have such a facility. Many years ago in the analogue days I used a coaxial relay to combine two aerials, CP and Hannington. I fitted a micro switch to the mechanical tuner such that one button operated it and sent 24 volts up the coax to operate the relay.
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#21 |
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Forum Member
Join Date: Jul 2010
Posts: 24,096
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PA metal inductive (NOT plastic resistive) tv aerial splitter, used in reverse as combiner, will ''add'' 2 aerials together, but as said, there's all sorts of possible problems, especially in trying to use freeview muxes from different transmitters. And special filters can be damn expensive. Easiest thing, i should think, is 2 separate aerials feeding 2 independent freeview pvrs. If u can put up, or afford to have put up, 2 separate tv aerials, then the cost of a second freeview pvr isn't significantly much more ........
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#22 |
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Join Date: Jul 2010
Posts: 24,096
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Depends how much cross linkage there is between 2 yagi aerials, different polarisation and location and pointing direction all help reduce this ........
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#23 |
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Join Date: Jul 2003
Location: Somewhere
Posts: 365
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I use Taylor unit in the loft to combine various antennas and a couple of DVB-T modulators. They are the best option. A few hundred pounds and it will work. I did the combiner route and things just weren't stable.
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#24 |
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Forum Member
Join Date: May 2008
Posts: 759
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I have 2 loft aerials pointing at 2 main transmitters. I purchased a 3 way junction for about £4 in Asda and connected leads from the 2 aerials and then sent the one cable down to the TV. Absolutely no problems except that from the more distant transmitter, picture was freezing on HD channels. I then swapped the co-axe cable for satellite cable and all is well.
So, no paying for men to go up to the chimney, aerials protected from the weather, 2 regions and no paying out for expensive equipment or people to come to my house! The more distant regions’ channels load in the low 800’s. |
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#25 |
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Forum Member
Join Date: May 2005
Location: Redditch Worcs
Posts: 17,288
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Quote:
I have 2 loft aerials pointing at 2 main transmitters. I purchased a 3 way junction for about £4 in Asda and connected leads from the 2 aerials and then sent the one cable down to the TV. Absolutely no problems except that from the more distant transmitter, picture was freezing on HD channels. I then swapped the co-axe cable for satellite cable and all is well.
So, no paying for men to go up to the chimney, aerials protected from the weather, 2 regions and no paying out for expensive equipment or people to come to my house! The more distant regions’ channels load in the low 800’s. http://aerialsandtv.com/ampsandsplit...FromTwoAerials Note Freeview+ pvrs often will not work properly with 2 transmitters tuned. The duplicate MUX play havoc with the broadcasters CRID codes, You would need a pvr for each transmitter and manually tune both. |
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