405-Line VHF Aerials 2013 to the present day.

[Nymrod121]

Here are three venerable aerials seen earlier today in Bourton on the Water, Gloucestershire.
The vertically-polarised Band III Yagi stack is only missing half of one director ... not bad for a system that must be at least fifty years old.
Best wishes
Guy

[SteveCG]

The Band III double 6 aerial is a Belling & Lee - indeed a well made aerial that still passes the test of time. I'm not sure of the Band I 'H' - other than it is a 1/4 wave design and they were not the cheapest to buy.

In the background of the 4 element Band I aerial photo there looks to be part of a J-Beam skeleton slot Band III. Early J-Beam - another well made aerial - all nuts and bolts Al alloy so little corrosion; the only weakness was in the waterproofing of the junction box.

[Herald1360]

Aren't those band 3 aerials bayed, not stacked?

[SteveCG]

If by 'bayed' you mean side-by-side; and 'stacked' one above the other, then I would agree Herald1360.

In practice, doubles seemed to have been more intended to reduce side-lobes than necessarily increase forward gain.

P.S. looking at the 4 element Band I aerial in post no. 381 I suggest it was/is a channel B5, therefore looking to the BBC Wenvoe transmitter site.

[Focus Diode]

Revisiting Kings Cross earlier in the week, see post #32. Someone has since attached a satellite dish to the VHF mast. The other set with the folded BI elements is also still standing but on the verge of collapse.

I've seen many instances of UHF aerials attached to existing VHF poles but never a satellite dish until now!

Brian

[Nymrod121]

Originally Posted by Herald1360

Aren't those band 3 aerials bayed, not stacked?

Oops ... yes, you're right, Chris!

[SteveCG]

Re; post nos 32 and 385,

I've been puzzling over that Band III yagi. although it looks like an Antiference Trumatch product, I'm not so sure. There were other aerial makers who copied the Trumatch concept. The difference on the skyline comes down to close examinations of the element holders and the junction box. Antiference used a special round mounting (called rota-click ?) for the non-junction box elements and also special junction box fittings. The aerial in the picture does not, to me at anyrate, have the 'right' fittings for it to be an Antiference product. Perhaps Telerection?

[Panrock]

Spotted today atop a shop in Evesham High Street... a 3-element Channel 4 array for Sutton Coldfield, missing the top half of its dipole.

Steve

[Focus Diode]

Spotted this nice arrangement in Hexham earlier today, note the folded BI dipole.
The UHF aerial to the left is on the verge of collapse!

Brian

[ntscuser]

Originally Posted by Focus Diode

Spotted this nice arrangement in Hexham earlier today, note the folded BI dipole.

The Band I element spacing is correct for 75 Ohms but wouldn't the Band III aerial be closer to 300 Ohms?

[SteveCG]

Re posts no. 389 & 390

That Band I design seemed to perform well into 75 Ohm. As for the Band III design, well I've come across such aerials and they work - but I suspect the aerial impedance is more likely to be in the low one hundred than that of a 300 Ohm single folded dipole. Aerial design was/still is a bit of a black art (even with computer modelling).

[sexton_mallard]

Here is a tidy 405 line VHF specimen seen today in Ellesmere, Shropshire still pointing to (I think) Winter Hill along with most of its newer UHF companions.

[Nuvistor]

We're the UHF aerials pointing to Winter Hill or possibly The Wrekin transmitters? Well apart from the one being used for moon bounce.
If so that band 3 aerial could be ch 8 Lichfield.
Frank

[sexton_mallard]

The site photographed is on the 'wrong' side of a hill for the Wrekin whereas most of the town points to the Wrekin and possibly Sutton Coldfield as well as Winter Hill as far as I know.

[Nuvistor]

Hi Dom,
it was just a thought.
Frank

[Nicklyons2]

Originally Posted by sexton_mallard

Here is a tidy 405 line VHF specimen seen today in Ellesmere, Shropshire still pointing to (I think) Winter Hill along with most of its newer UHF companions.

Could well be a Belling-Lee specimen; it exhibits their tendency to not use a driven dipole for Band III and instead just use the proximity of the shorter Band III rods to 'loose couple' to the Band I dipole. This, in effect, made it a 'ready-made' version of the clip-on Band III wings which were affixed to existing Band I aerials on the arrival of ITV.

[Heatercathodeshort]

Originally Posted by ntscuser

The Band I element spacing is correct for 75 Ohms but wouldn't the Band III aerial be closer to 300 Ohms?

It is interesting to note that a number of early Band 3 receivers had provision for 300 ohm balanced feeder on Band 3 only. J.

[peter_scott]

I came across this interesting Yagi in an article about Spencer West who designed a low cost television for home construction in Television & Short-Wave World. He received good pictures in Beccles, Suffolk, 97 miles away from the Alexandra Palace transmitter in May 1938.

Peter

[SteveCG]

Peter, re post no. 398,

... What an intriguing design! ...

I wonder what its reception of "Chain Home" 30 Mc/s radar was like ?

[peter_scott]

Hi Steve,

There were certainly enough along the East Anglian coast hitting it from the side although the aerial would be pointing towards Weymouth where they were a bit thinner on the ground and rather far way but I guess there would be quite a bit of testing going on throughout 1939. I don't know the actual frequencies but there were apparently four in the range 20 to 55MHz.

The one at Great Baddow that still exists could potentially have caused interference.

Peter