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Old 6th Jun 2018, 6:05 pm   #1
Heatercathodeshort
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Default Interesting UHF aerials.

It is now 54 years since UHF aerials began to appear on rooftops. I thought I would kick the thread off with a picture of this 'Bow Tie' on the roof of a shop premises at Tooting Broadway.

As far as I can remember it was erected exclusively for rental customers by DER. [Domestic Electric Rentals, not DERWENT] They must be rare these days.
John.
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Old 6th Jun 2018, 6:11 pm   #2
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Default Re: Interesting UHF aerials.

I remember Radio Rentals using them in areas of high signal-strength (within about 15 miles of a transmitter). They were certainly used in Wolverhampton/Birmingham [line-of-sight to Sutton Coldfield].

Often they still used the thin foam-dielectric coax typically used with Band-I/III antennas, rather than the thick 'Low-Loss' semi-air-spaced coax we're more familiar with in traditional UHF installs.
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Old 6th Jun 2018, 7:16 pm   #3
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Default Re: Interesting UHF aerials.

Your eyes aren't deceiving you, that is a pair of log-periodics mounted just a few inches apart on a bungalow in Wellington Gardens in Coventry! The second log has been added some considerable time after the first, presumably to serve a second room? Or perhaps the signal from the original wasn't strong enough to pick up the interim muxes from Sutton Coldfield and some cowboy thought a bigger log would work better but couldn't be bothered to remove the original?
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Old 8th Jun 2018, 2:27 pm   #4
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Default Re: Interesting UHF aerials.

I remember seeing just such an aerial when visiting London in the mid 60s - its shape stuck in my mind. Fast forward 30 odd years and I came across one in Grange-Over-Sands (on the Cumbrian coast) a group C oriented to the Winter Hill transmitter about 50 air miles away.

I do know that G-O-S received high field strength signals from Winter Hill on both Band III VHF (CH B9 & B12) as well as UHF (CH 62 back then); so given the poor sensitivity of the early valve tuners especially at the top of the UHF band, the field strength really must have been remarkable!
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Old 8th Jun 2018, 3:14 pm   #5
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Default Re: Interesting UHF aerials.

The UHF aerial in G.O.S could have been receiving from the Lancaster transmitter, same direction as WH and designed to cover Lancaster, Morecambe and the South Lakes.
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Old 9th Jun 2018, 10:43 am   #6
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Default Re: Interesting UHF aerials.

Frank, I understand your point, but no, I saw it very close up and it was oriented in the Winter Hill direction and its physical dimensions were those of a group C. If I remember correctly the Lancaster relay came along in the 1970s - but yes it was quite strong enough for use in G.O.S. Hence the Lancaster relay would not have been there when this early type of aerial was being installed.
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Old 9th Jun 2018, 11:27 am   #7
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Default Re: Interesting UHF aerials.

It’s interesting how UHF signal strength can vary. The local weak signal area near where I worked was Parbold Lancashire, quite close to WH but behind a large hill. Yet one house managed with an 11 element standard aerial whereas houses either side had various large arrays.
Parbold had it’s own small UHF repeater which relieved the problem, that must have come on line in the 70’s, presume it is still there for Freeview.
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Old 11th Jun 2018, 7:19 pm   #8
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Default Re: Interesting UHF aerials.

We have had Bow Ties but how about an Egg Whisk?
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Old 11th Jun 2018, 7:22 pm   #9
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Default Re: Interesting UHF aerials.

See a few of those around, I have no idea how well they work, that particular one is a bit tired.
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Old 11th Jun 2018, 7:53 pm   #10
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Default Re: Interesting UHF aerials.

Standard failure mode for Televes aerials. Special care needs to be taken with the reflector fixing, which is just an M4 screw with wing nut. Most installers just nip them up finger tight so it doesn't take much for them to come loose and the reflector drops off.
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Old 12th Jun 2018, 9:58 am   #11
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Default Re: Interesting UHF aerials.

Horsham has never been a good reception area even back in the 405 days.
It was shown on field strength maps as a fringe area and many rooftops sported channel 3 & 11 aerials from the Isle of Wight transmitters.
Many UHF installations have pre amps fixed to the masts.

Our 'local' is Midhurst for Southern TV with reception from Crystal Palace possible with a well sited aerial. There is also a severe problem with foliage attenuation a problem that also affects mobile phone coverage.

These aerials are in Station Road Warnham. John.
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Old 12th Jun 2018, 11:11 am   #12
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Default Re: Interesting UHF aerials.

I was only about 6 at the time but I vaguely remember having a bow-tie type when living near Maidstone. The TV was rented from DER and the additional aerial would have coincided with an upgrade to a dual-standard set.

Looking back, it seems quite impressive that such a simple aerial gave good reception from Crystal Palace
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Old 12th Jun 2018, 11:20 am   #13
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Default Re: Interesting UHF aerials.

Lots for those interested in aerial photography here

http://www.wrightsaerials.tv/aerialp...hy/index.shtml
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Old 12th Jun 2018, 11:28 am   #14
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Default Re: Interesting UHF aerials.

Quote:
Originally Posted by Dai Corner View Post
I was only about 6 at the time but I vaguely remember having a bow-tie type when living near Maidstone. The TV was rented from DER and the additional aerial would have coincided with an upgrade to a dual-standard set.

Looking back, it seems quite impressive that such a simple aerial gave good reception from Crystal Palace
The beauty of the bow tie array is in its performance in areas of reflections. It has a good gain and up to 180 degree beamwidth. There is also multipath cancellation due to the phasing of the driven elements. Surprising that they fell out of fashion, for digital I would have thought that they could be a lifesaver.
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Old 12th Jun 2018, 11:55 am   #15
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Default Re: Interesting UHF aerials.

More metal = more profit?

I'm a fan of minimalist design and would much rather have a bow tie on my house than some of the monstrosities you see around.
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Old 12th Jun 2018, 12:46 pm   #16
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Default Re: Interesting UHF aerials.

The bow tie is quite expensive to make in comparison and doesn't help when you need gain and directivity.
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Old 12th Jun 2018, 1:07 pm   #17
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Default Re: Interesting UHF aerials.

If it is interesting aerials from an early era that performed well, then the 1967 vintage J. Beam, 18 element, Parabeam is the one that gets my vote. I've come across Group B examples and Group C examples but never a Group A one in the flesh, since where I live now did not have any Group A transmitters at the time these aerials were made. The later models with their thinner Reflector and Slot dipole elements are just not quite the same...
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Old 12th Jun 2018, 1:37 pm   #18
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Default Re: Interesting UHF aerials.

Another vote for the Parabeam, excellent aerial.
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Old 30th Jun 2018, 11:49 am   #19
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Default Re: Interesting UHF aerials.

This group c/d aerial probably dates back to 1969 and is on the chimney of the cottage that I use to live in back in the mid 1970ís. Itís pointing at the Mendip TV mast which is 12 miles away and clear LOS.
I think itís an old J Beam design but stand to be corrected.
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Old 30th Jun 2018, 11:55 am   #20
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Default Re: Interesting UHF aerials.

Looks like a J Beam Parabeam.
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