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Old 20th Mar 2020, 12:10 am   #1
rambo1152
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Default 300 Ohm ribbon feeder.

Inspired by a comment arjoll made elsewhere about New Zealand practice I want to ask, was ribbon feeder ever used in the UK for domestic VHF TV or radio reception?

Apart from the indoor aerial that you draped around a picture-frame included with an imported hi-fi of course.

What about TV? I think in the early days, maybe pre-war, at least one manufacturer suggested using twin mains cable, but apart from that, were balanced aerial down-leads ever routinely used for TV as they were in North America?
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Old 20th Mar 2020, 12:22 am   #2
paulsherwin
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Default Re: 300 Ohm ribbon feeder.

I'm pretty sure all UK postwar TVs used Belling-Lee connectors and 75 ohm unbalanced downleads, but pretty much all valve era FM radios used balanced downleads of some description. The 300 ohm standard wasn't always used though - I've seen 180 and 200 ohms specified, and there were probably others.
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Old 20th Mar 2020, 12:34 am   #3
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Default Re: 300 Ohm ribbon feeder.

I have a couple of the Belling-Lee newssheets from the early 1950's ( pre-ITV) that were handed out at the annual radio shows, which illustrate not only the present co-ax plugs and feeder, but also both balanced unscreened and screened twin feeders, plus the 2 and 3 pin plugs used with them. The balanced feeders were more like twin mains flex, with closely-spaced bare conductors directly embedded in the sheath, quite unlike modern ribbon feeder. What is evidently the later one advised that the balanced feeders would only be available until stocks were exhausted. I posted scans here a few years ago. Typing this from my phone so can't repost them at present.

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Old 20th Mar 2020, 1:09 am   #4
Nuvistor
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Default Re: 300 Ohm ribbon feeder.

There was a mix of twin feeder and coax, depending of the set maker. The twin feeder was around 70-80ohms and some were screened.
Has Emeritus states more like twin mains flex.
Some information. Page 391
https://www.americanradiohistory.com...on-1952-02.pdf
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Old 20th Mar 2020, 2:09 pm   #5
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Default Re: 300 Ohm ribbon feeder.

Thanks for the link to the magazine. I see that, in the ad for Aerialite aerials on page 417, aerials could be supplied with either coax or twin feeder cables.

Lots of other OT gems, but the brief piece on page 419 of the imminent introduction of Bing Crosby's television tape recording is noteworthy.

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Old 20th Mar 2020, 4:19 pm   #6
m0cemdave
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Default Re: 300 Ohm ribbon feeder.

I used to have some attenuators for 300 ohm ribbon. I can't find them now, so presumably I disposed of them at a rally years ago. But as I remember they were brown plastic (Bakelite style), about 1-1/2" long and 1/2" square, and made by Belling Lee.
I always thought they were for TV sets.

The 75 ohm flat twin mentioned above is still available - I have used it to feed an HF fan dipole in my loft.
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Old 20th Mar 2020, 7:13 pm   #7
G6Tanuki
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Default Re: 300 Ohm ribbon feeder.

I don't remember ever seeing 300-ohm flat-twin in any TV application.

I *did* come across a sort-of-oval-cross-section 75-Ohm twin-feeder a couple of times - this was used in some very early [I'm guessing pre-1950?] Band-I TV installs. By the time I found it the rubber insulation had invariably gone brittle, and on outside runs had often disappeared altogether! Replacement with 'Low-Loss' 75-Ohm coax generally resulted in a much-improved signal and a happy customer.

Equally, I never experienced 'outdoor' runs of 300-Ohm flat-twin for Band-II antennas, though I gather that this was commonplace in the US.

[My favourite 'odd' antenna-feeder was the 1.5-inch-diameter dry-Nitrogen-pressurised stuff we used on some long-haul just-short-of-microwave applications. You don't need an electrician, you need a plumber!]
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Old 20th Mar 2020, 9:36 pm   #8
MotorBikeLes
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Default Re: 300 Ohm ribbon feeder.

I bought a NordMende 2245 colour TV in 1970. That had 300 ohm twin feeder for the aerial. Unsure of whether to alter the balun in the aerial itself (a Parabeam I think), I contacted BBC's technical people. I got a nice little reply which included a pencil sketch of a simple balun to fit directly into the TV's input, directly off the 75 ohm down lead.
That reply is still in my Antenna folder.
That was a hybrid set (big PD500 valve etc.), subsequent "official" UK models had a directly interchangeable input plate with two 75 ohm types (one VHF, one UHF).
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Old 20th Mar 2020, 9:48 pm   #9
G6Tanuki
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Default Re: 300 Ohm ribbon feeder.

The one place I *did* come across flat-twin feeder in a TV situation was on some of the Antex combined "X-for-Band-I-and-a-set-of-herringbone-elements-for-Band-III" antennas, which used a short length of twin-feeder to couple the X and the dipole of rthe herringbone.

As shown here: http://www.wrightsaerials.tv/aerialp...ient/012.shtml
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Old 20th Mar 2020, 9:49 pm   #10
Ed_Dinning
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Default Re: 300 Ohm ribbon feeder.

Hi Gents, our Radio Rentals 14" console set, bought in the late 50's and already fitted with a 4 channel selector (CH5 BBC and projected CH8 for ITV) for Pontop was supplied from and X aerial by 300 ohm feeder that terminated onto the screw and clamp co ax connector as found on Bush TV 22's

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Old 20th Mar 2020, 10:19 pm   #11
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Default Re: 300 Ohm ribbon feeder.

Leak & other FM tuners had 3 screw terminals where the outermost were shown as 300 ohm and one end to the centre terminal was shown as 75 ohm. The tuner had an impedance matching transformer fitted. You just connected the screen of your cable to the centre terminal and the core to the 75 ohm terminal. For 300 ohm use just connect to the outer terminals. It was made so either type of aerial could be connected n almost any part of the world without any special plug.
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Old 20th Mar 2020, 10:26 pm   #12
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Default Re: 300 Ohm ribbon feeder.

The Bush TV24C/TV33/TV36C and TV43 models have a 300ohm Band 3 aerial input. John.
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Old 22nd Mar 2020, 2:33 pm   #13
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Default Re: 300 Ohm ribbon feeder.

I remember my grandfathers home antenna was on a huge A frame tower in his back yard with a huge length of 300 ohm ribbon cable that looked like a plastic ladder running all the way from the top, under the house and up through the floor boards to a 2 pin plug.
I remember having to climb that tower and reconnect the cable and tape thejoin together after some cockatoos chewed through it in the middle of the cricket in the 80's
Stripped the wire with my teeth, twisted the ends together with my bare fingers and taped the joins.
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