All posts by Roy Barton
Below are all of Roy Barton's postings, with the most recent are at the bottom of the page.
Given what I wrote above, I can see it would not be a good idea to use a diplexer to combine signals from an H aerial with that from a V aerial. A switch would be the thing to use. (Nobody ever suggested that this would be a good thing to do.)
The more I think about it it seems that my H aerial may also pick up V signals as well. If that is the case I wonder what has happenned in the last few days to stop this happening. Perhaps the H and V signals have been made identical???
I could get paranoid over this !!!
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Roy Barton:
If as Jamie says the V and H signals are identical then they add up to a signal at 45 degress polarisation. Is that right?
If that is the case then I can't really see the point... unless it just a convenient way of getting a large signal that has V and H components.
Possibly a higher power from an transmitter antenna at 45 degrees migh be impractical.
I wonder what an omnidirectional H antenna looks like?
Probably the complexity of a omnidirectional aerial at 45 degrees makes it easier to have separate V and H ???
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To JB38. I too missed your posts when I replied to Jamie. Actually I did understand that you were being hypothetical in regard to combining signals. Your diplexing hypothesis triggered the thoughts I had on how H and V transmissions might interfere with each other if an aerial picked up both polarisations. With every post I get a better understanding.
We have just had another day of perfect reception on all channels. At this rate I won't have to dig out the satellite kit that purchased more than year ago and have not unpacked yet.
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Page 2
Sunday 24 February 2013 11:33AM
Wimborne
Thanks Briantist. That MIMO link explains all. I did not realise that the signals on H and V were different. I now understand, different signals on H and V keeps them separate. (Therefore effectively doubling the bandwidth.)
With the V & H co-frequency concept it is easy to see how you can can obtain 100% signal strength and 0% quality. (IE the two polarisations interfere perfectly with each other.)
I can see the problem, if the receiving aerial is not perfectly H or V then there is potential for the different signals operating on the same wavelength to interfere. Worse still any reflectors such as pylons might change the polarisation (?) and that would result in cross channel interference.
I am surprised that mixing H & V on the same transmitter works as well as it does on the fringes.
I wonder if the H & V divide explains why my BBC HD channel changed from 51 to 101 when I retuned? Before and after I got perfect signal quality and pictures on BBC HD (and all the other entertainment channels other than those on transmission channel 28) Is BBC HD on channel 51 in H and 101 in V ???
The subject gets clearer every post. (But there is still lots to mystify.