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H X & K aerials.

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Re: H X & K aerials.

Post by Katie Bush » Wed Sep 07, 2016 7:22 pm

Refugee wrote:That one looks more the part.
It looks like one that would sell well in places with the TV stations at opposite ends of town.


It never seemed to matter.. There were dozens of those in our area, once upon a time, aimed at Holme Moss and Emley Moor - from here, that was virtually a dead straight line through both transmitters.. The little band iii elements have negligible affect on the band i signal.

The whole array was set out in a dead straight line in every case.

Given the nature of "co-site" transmitters, I'd think it extremely unlikely that you'd be "piggy in the middle" with a transmitter at either end.. It does raise the question though, was the 'X' component reversible on the off chance that might happen? As just could be the case if for some reason you preferred to watch BBC (North) from Holme Moss and Granada TV from Winter Hill, and you just happened to live in between.

 
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Re: H X & K aerials.

Post by nuvistor » Wed Sep 07, 2016 7:33 pm

The X part would pivot through 270 degrees, not a complete match for every situation but very many.
Frank

 
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Re: H X & K aerials.

Post by Refugee » Wed Sep 07, 2016 7:39 pm

Surely the X would work from two directions and the band III would only work for one direction.
With the transmitters on the same site the band III would be in front of the X.
The ability to swing the X more than 180 degrees would be to avoid conflicts with the mast and chimney stack.

 
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Re: H X & K aerials.

Post by Niall » Wed Sep 07, 2016 7:44 pm

In the unlikely event of needing the last bit of gain in the opposite directions it would be easy enough to swap the X elements around.

 
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Re: H X & K aerials.

Post by Katie Bush » Wed Sep 07, 2016 7:58 pm

Remember though, only one upper, an one lower, element on the 'X' are connected to the co-ax, the forward pair being the dipole, and the rear pair being merely a passive reflector, not connected to anything, in which case the reflector would (in theory) obscure the band i signal from reaching the dipole, which is why I wondered about being able to physically reverse the 'X' however, logically, that wouldn't work, would it? Since the band iii signals still need the band i elements to conduct the band iii signal to the co-ax.. Reversing the 'X' would put the band i reflector in between the band iii array and the band i dipole, thus obscuring the band iii signals.... :ccb

 
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Re: H X & K aerials.

Post by Niall » Wed Sep 07, 2016 8:26 pm

I had forgotten that only the band 1 element is connected, but it still works at B3 if you swap the elements round as it's still the elements next to the B3 section which are connected. You just convert the B1 section from reflector + driven to driven + director.
Now that I think about it the right way to do it would be to leave the driven element as is and trim down the reflector to be a director.

 
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Re: H X & K aerials.

Post by nuvistor » Wed Sep 07, 2016 9:55 pm

Refugee wrote:Surely the X would work from two directions and the band III would only work for one direction.
With the transmitters on the same site the band III would be in front of the X.
The ability to swing the X more than 180 degrees would be to avoid conflicts with the mast and chimney stack.

If the stations were at 90 degrees to each other, point the band 3 aerial at that transmitter and move the X to 90 or 270 depending the direction of the Band 1 transmitter. The forward lobe on the X aerial would be quite broad. Conflicts with mast or chimney just meant using a different type of mounting mast. That's how I remember it, but it is 50 odd years ago.

Has for elements affecting each other perhaps they did but they gave good performance.
Frank

 
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Re: H X & K aerials.

Post by colly0410 » Fri Sep 09, 2016 12:09 am

Katie Bush wrote: Since the band iii signals still need the band i elements to conduct the band iii signal to the co-ax.. Reversing the 'X' would put the band i reflector in between the band iii array and the band i dipole, thus obscuring the band iii signals.... :ccb


I've got a bit lost here. I presumed this aerial worked on (from left to right) band 1 = dipole + director & the band 3 part = reflector + dipole + 3 directors. Or band 1 = reflector + dipole & the band 3 part = reflector + dipole + 3 directors. If only the band 1 dipole is connected to the co-ax how does the band 3 part work? Some kind of coupling with that last band 3 end bent element?

 
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Re: H X & K aerials.

Post by nuvistor » Fri Sep 09, 2016 8:37 am

The coax was definitely connected to the band 3 dipole, I cannot remember how the X was connected to that connecting box, I think it was a cable down the boom from the X to the box but cannot be definite about it. it was out of sight. I presume they had designed some form of diplexing arrangement. There was only one downlead.
We installed a lot of these around Bolton and Wigan, Winter Hill band 3 was approx north and Holme Moss Band 1 was approx east. so the X was approx at 90 degrees to the band 3, depending just which location we were at. If the X was not generally pointing towards Holme Moss it could mess the picture up so they had some directivity.

Frank

 
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Re: H X & K aerials.

Post by colly0410 » Fri Sep 09, 2016 12:20 pm

Remember seeing some of these X + 5's on the side of the road waiting for the scrap man, wish I'd had a look at how they were connected, too late now init? In the Nottingham/East Derbyshire area Sutton Coldfield & Litchfield were in the same direction so all band 1 & 3 aerials pointed the same way. In the Mansfield area it seemed to be an equal mix of Sutton/Litchfield & Holme Moss/Emley Moor. When UHF fired up Mansfield was (& still is) a 4 way mix of Emley Moor, Belmont, Waltham & Sutton. When I lived at Kirkby near Mansfield I was on Sutton, (as were most neighbours) next door on Emley Moor, across the road on Waltham (with a very high pole) & down the road on Belmont, we all got different local news of course...

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