colly0410

H & X TV aerials.

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When I lived down the Meadows (60's) the rooftops were cluttered with H & X TV aerials, every house had one or the other unless they were posh & had Rediffusion cable TV. When I moved to Bestwood Village it was even more cluttered as there was no Rediffusion in the village. My cousin who came to visit from Canada was fascinated by them, I said "don't you have them over there?" He said "no, everyone in Ottowa has a V shaped rabbit ears antenna on top of the TV itself, no one has a roof antenna!" They must have had a strong TV signal over there..

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I doubt you could get a signal in Calgary on rabbit ears, it's vast, you'd need some kind of analogue/digital antenna or cable. I will check with my lad tonight to be sure.

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The H and X aerials were 405 lines and BBC only. When ITV came out, you had to get the 'toast-rack' bit added.

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They were indeed for the old 405 line system.

Although the old black and white TV I acquired for my bedroom in the 1960s used an old bit of wire strung up on the curtain rail. It helped to have line of sight to Waltham transmitter.

Not forgetting that while we used the PAL system for broadcasting, North America stuck with NTSC (Never Twice Same Colour), so may have needed a different style of aerial?

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I'm assuming Canada is similar to the US, but when I lived in Sacramento, we were serviced by several TV channels, all had their transmitting antennas at Walnut Grove, one 2000 foot tower, a couple of 1400ft towers and a 1000foot tower. Quite an impressive sight when going by them!! Pre digital, channel 3 ran 6Mw...No not a typo, 6Mw of power, their co-ax was several inches thick going up the tower to the vaults near the top.

Over here, towers tend to be high to reach viewers in a very large area, people also tend to have rotatable antennas, against fixed antennas, that allows to reach stations in different areas.

In the cities it would be possible to run off a "rabbits ears" on the TV, but would limit you to just local channels.

I never could figure out the old X antennas, as all VHF TV was vertically polarized.

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Them were the days standing behind the telly sorting out the vertical hold and the horizontel hold. no not with the missus the telly buttons, Teeeee Heeeee

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Had a buddy back then who told his wife if she went outside she would see the pictures going in the aerial. She was not even a blond but she went out and was out for some time before he called her back in. Said she couldn't see them.

(With apologies to any blond ladies here on the forum)

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I never could figure out the old X antennas, as all VHF TV was vertically polarized.

Been looking up H & X aerials: The H was a dipole with a slightly longer reflector at the back, the X was a sort of bent dipole with a slightly shorter director at the front. The shorter ITV ones usually had a folded dipole with a reflector at the back & several directors at the front.... When I lived in Chester-le-street in County Durham the VHF 405 aerials were horizontaly polarised, this was to try & cut down on co-channel interference from verticaly polarised transmitters. E.G. Lichfield transmitted ATV on channel 8 with vertical polarisation for the Midlands & Burnhope transmitted Tyne Tees on channel 8 with horisontal polarisation for the North East..

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When we moved in at Rise Park in 1972, our TV aerial was directed at Sutton Coldfield. we could never tune in to the Kimberley transmitter, if we tried we sometimes got a ghostly image that faded in and out. About three years ago I went on to the roof, aligned the aerial with the Kimberley mast (just a few degrees to the right) and rotated it 90 degrees so that the prongs were horizontal instead of vertical. I get a great signal, and I also still get a great signal from the West Midlands, as before, Work that out.

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Yup Chulla that's weird. Sutton is horizontaly polarised & Kimberley vertical. Bit of a black art are aerials as I found out when I was an army radio operator. When I rented an appartment in Miami Beach the TV had a V shaped rabbit ears aerial on the TV, it got channels 2,(PBS) 4,(NBC), 6,(CBS), 7,(FOX) & 10(ABC) almost perfect with just a bit of ghosting, also got 5 & 12 from West Palm Beach with a bit of snow, all the UHF channels were snowy. There is a site called '405 alive' all about the 405 line TV system, I found it very interesting but I'm a nerdy geek, or is that geeky nerd?

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Antennas aren't black art, they are a subject all to themselves, some of the most successful designs have been "stolen" from Ham designs, most popular is the Yagi, naked after a Japanese Ham, all modern multi element antennas were taken from his design, which acts like a torches reflector both as a receiving and transmitting antenna.

First thing I learned on antennas was to design and build a half wave dipole, from there designing almost any antenna becomes easy.

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The black art bit for me was when a sloping longish wire acted as a directional aerial when I was a squadie, I thought "hows it do that?" There was nothing on the Radio opps course about that! I now know it was acting as a sort of half rhombic against ground. When I read about the half rhombic against ground many years later I thought "ah ahh, I know how it worked!" The aerial that fascinates me is the frame & ferrite rod that use the magnetic part of the radio wave, I also think (but not too sure) that the slot aerial works on the same principle. I read that the BBC used to use a lot of slot aerials for the transmitters on the FM network. They've scraped them in the last few years & replaced them with crossed dipoles for mixed polarisation aerials..

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#10 and #11. That's right, Colly, regarding polarising of aerials - I got it wrong way round. I wonder if the Sutton transmitter is picked up by the Kimberley one, allowing the West Midlands signal to be seen by aerials tuned to Kimberley

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They say that cross polarising a UHF aerial would only reduce the pick up by only a few decibels (I've seen 5 or 6 mentioned) so if Sutton Coldfield comes in strong a few decibels less wouldn't affect the digital signal much.

When Sutton Coldfield was analogue it was know'n as a powerhouse transmitter as it transmitted at 1,000,000 watts (yes one million watts) at UHF. In comparison Kimberley transmitted at 2,000 watts & Waltham at 250,000 watts, Kimberley was a baby transmitter. Now they're digital Sutton Coldfield is 200,000 watts for standard definition & 89,000 watts for high def, Kimberley is 400 watts for SD & 100 watts for HD & Waltham is 50,000 & 25,000 watts for SD & 10,200, 5,000 & 1,400 watts for HD. The 1,400 watts is for Notts TV with a very directional aerial..

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UHF probably FM mode and Class C?? very inefficient so the 2 MW output would require somewhere in the region of 5MW input??? 3MW of losses, mainly in heat.

Most of the big TV stations here ran in excess of 2MW output, they strived for large audiences to bring in the big bucks in advertising.

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Them were the days standing behind the telly sorting out the vertical hold and the horizontel hold. no not with the missus the telly buttons, Teeeee Heeeee

When that didn't work anyone else bash the bottom of the telly to stabilise the horizontal or the side for vertical? It worked!!!!

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Watching the telly one day & the sound went off, Dad went up to it & belted it & the sound came back on. I think the poor thing was scared & didn't want another belt. :)

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Steve, many are changing over to solid state, using multiple amplifiers in cascade.

I've handled a few of the large external plate vacuum tubes, one was even heavy for two of us to lift, they have two lifting handles welded to them, bigger ones have eye bolts for cranes to haul them into place.

The ones I handled were on the way for rebuilding at Eimacs factory, the filaments were rated at 30 amps, I forget the voltage. RF Parts in California carry a large range of external plate tubes.

I've a box of 4CX250 tubes, some brand new others with still plenty of life in them, rated at 250 Watts each and require 4500-5000 volts on the plates. All ex mil and made by Eimac.

I've a HF amplifier with three 4CX250 tubes, it can dissipate nearly 2Kw very easily at Amateur ratings, ie none continuous duty, SSB only. They are in parallel, the power supply is a hernia maker!! I even have a spare plate transformer, spare filament transformer and spare choke, I got the lot for a "song" nearly 25 years back. The plate transformer weighs about 35lbs!!

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Loosely related to TV Antennas, in the mid 1960s I remember being at a friends house on Ilkeston Road, listening to Police transmisiions between stations on his TV. I later found out that he was dead opposite the police Transmitter at Clifford Court, Alfreton Road.

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Used to listen to police radio when they used FM band, usually somewhere around 100mhz.

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Antennas aren't black art, they are a subject all to themselves, some of the most successful designs have been "stolen" from Ham designs, most popular is the Yagi, naked after a Japanese Ham, all modern multi element antennas were taken from his design, which acts like a torches reflector both as a receiving and transmitting antenna.

Couldn't resist responding to this, John. Had visions of one of those Japanese sumo wrestlers after feasting on ham designing a multi element antenna and trying to get it up on the roof. LOL

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