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 Merging antenna signals. 
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Post Merging antenna signals.
TV related rather than ham.

I have two TV transmitters presenting reasonably strong signals at the chimney pot. They are roughly 90 degrees apart in direction. One has multiplexes spread right over the spectrum carrying all sorts of channels. The other has just 3 multiplex with a limited range of channels. The channels used do not clash. The local one uses 23,26,30 the remote one 32,54,35,36,48

If I point an antenna at both how do I go about mixing the two signals into one 75ohm feeder down to the tv. ?

I guess it must be possible to wind a transformer on a ferrite core that represents 75ohm in all directions but don't know where to start.


Mon Dec 18, 2023 3:39 pm
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
G8WBO wrote:
TV related rather than ham.

I have two TV transmitters presenting reasonably strong signals at the chimney pot. They are roughly 90 degrees apart in direction. One has multiplexes spread right over the spectrum carrying all sorts of channels. The other has just 3 multiplex with a limited range of channels. The channels used do not clash. The local one uses 23,26,30 the remote one 32,54,35,36,48

If I point an antenna at both how do I go about mixing the two signals into one 75ohm feeder down to the tv. ?

I guess it must be possible to wind a transformer on a ferrite core that represents 75ohm in all directions but don't know where to start.

You could simply combine with one of these.
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How successful any combining will be depends on the relationship of the signals from the different stations when combined.
If it happens to be particularly strong, and out of phase you'll have issues.

Alternatively, if both are strong signals you could try an antenna, with wide beam width, pointing between the two.
Again, multipath might be an issue.

I'd go with the cheap combiner, I've used them loads of times and, usually, it's worked.

Cheers

Tony

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Mon Dec 18, 2023 6:38 pm
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
Point one antenna at the weakest .. you may well find the other one is there anyway, TV antennae are not ultra directional.

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Paul


Tue Dec 19, 2023 4:56 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
G0TSG wrote:
Point one antenna at the weakest .. you may well find the other one is there anyway, TV antennae are not ultra directional.

With a 90deg difference in location I suspect beam width would be an issue, with all but the smallest of antennas.
Even a bow tie, with reflector, is only 60deg beam width and has very little gain.
Then there's the issue of multipath.

The best solution is a rotator!

Cheers

Tony

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Tue Dec 19, 2023 10:11 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
I was going to suggest UHF combiner, either passive or active - plenty of choices but they all seem to be for mixing satellite and UHF or VHF, not UHF / UHF, unless you pays your money:
https://www.globalprofessional.co.uk/uh ... -169-p.asp

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Tue Dec 19, 2023 11:15 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
gw8asd wrote:
G0TSG wrote:
Point one antenna at the weakest .. you may well find the other one is there anyway, TV antennae are not ultra directional.

With a 90deg difference in location I suspect beam width would be an issue, with all but the smallest of antennas.
Even a bow tie, with reflector, is only 60deg beam width and has very little gain.
Then there's the issue of multipath.

The best solution is a rotator!

Cheers

Tony

Or maybe the omnidirectional antennas used on camper vans?

Just search for "Omnimax".

73, Mark...


Tue Dec 19, 2023 6:50 pm
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
gw8asd wrote:
With a 90deg difference in location I suspect beam width would be an issue, with all but the smallest of antennas.
Even a bow tie, with reflector, is only 60deg beam width and has very little gain.
Then there's the issue of multipath.

The best solution is a rotator!

Cheers

Tony


Or two antennas via a switch maybe?

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Tue Dec 19, 2023 6:54 pm
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
You can do it with a splitter/ combiner, these work either way round https://www.blake-uk.com/2way-external-masthead-splittercombiner-with-5g-and-tetra-filtration-1-input-2-output.html make sure the coax is the same length from antenna to splitter.

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Sun Dec 24, 2023 7:05 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
g7pan wrote:
You can do it with a splitter/ combiner, these work either way round https://www.blake-uk.com/2way-external-masthead-splittercombiner-with-5g-and-tetra-filtration-1-input-2-output.html make sure the coax is the same length from antenna to splitter.

Why would you need to make the coax the same length?

Cheers

Tony

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Sun Dec 24, 2023 11:15 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
gw8asd wrote:
g7pan wrote:
You can do it with a splitter/ combiner, these work either way round https://www.blake-uk.com/2way-external-masthead-splittercombiner-with-5g-and-tetra-filtration-1-input-2-output.html make sure the coax is the same length from antenna to splitter.

Why would you need to make the coax the same length?

Cheers

Tony

I assume he was thinking along the lines of co phasing, but its not really a case of true antenna co phasing in one direction, so odd lengths would most likely work just as good or bad depending on how it works out. ;)
As it happens I have two TV antennas coupled together to a common down feed here but pointed at 90 degrees to each other, as here we have a choice of the Wrekin transmitter multiplex, or Sutton Coldfield, both reasonable signals, as Sutton being the furthest runs more power than the more local Wrekin one, but some channels multiplexed on one are not available on Freeview from the other one, and vice versa.
It's only a difference of a couple of channels or three, but for the price of another cheap chuck up TV antenna you may as well get all the free channels you can! :)
I just used a simple passive TV antenna splitter, as signals from both are more than adequate.
It works for me, and I have not experienced any co-phasing problems.

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Sun Dec 24, 2023 11:25 am
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 Merging antenna signals. 
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Post Re: Merging antenna signals.
G0BHD wrote:
gw8asd wrote:
g7pan wrote:
You can do it with a splitter/ combiner, these work either way round https://www.blake-uk.com/2way-external-masthead-splittercombiner-with-5g-and-tetra-filtration-1-input-2-output.html make sure the coax is the same length from antenna to splitter.

Why would you need to make the coax the same length?

Cheers

Tony

I assume he was thinking along the lines of co phasing, but its not really a case of true antenna co phasing in one direction, so odd lengths would most likely work just as good or bad depending on how it works out. ;)
As it happens I have two TV antennas coupled together to a common down feed here but pointed at 90 degrees to each other, as here we have a choice of the Wrekin transmitter multiplex, or Sutton Coldfield, both reasonable signals, as Sutton being the furthest runs more power than the more local Wrekin one, but some channels multiplexed on one are not available on Freeview from the other one, and vice versa.
I just used a simple passive TV antenna splitter, as signals from both are more than adequate.
It works for me.

I could see the reason, if the antennas were stacked or bayed, but not when looking at different paths.
As you say, whatever the length of feeder, when antennas are pointing to different sources, it's a matter of luck and experimentation as to the actual outcome. :)
It's a long time since I've used terrestrial TV, far too prone to being clobbered by my transmissions. :lol:
When I did I used a rotator as there are four transmitters, if I wanted the full options including the Welsh ones.

Cheers

Tony

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Sun Dec 24, 2023 11:35 am
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