2nd May 2016, 8:49 pm | #381 |
Nonode
Join Date: Apr 2012
Location: Worcestershire, UK.
Posts: 2,052
|
Re: 405-Line VHF Aerials 2013 to the present day.
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
__________________
"What a depressingly stupid machine." [Marvin: HHGTTG] |
3rd May 2016, 3:41 pm | #382 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
|
Re: 405-Line VHF Aerials 2013 to the present day.
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. |
3rd May 2016, 5:16 pm | #383 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,536
|
Re: 405-Line VHF Aerials 2013 to the present day.
Aren't those band 3 aerials bayed, not stacked?
__________________
....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
4th May 2016, 1:07 pm | #384 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
|
Re: 405-Line VHF Aerials 2013 to the present day.
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. Last edited by SteveCG; 4th May 2016 at 1:10 pm. Reason: Added suggestion |
13th May 2016, 9:34 am | #385 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
|
Re: 405-Line VHF Aerials 2013 to the present day.
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 |
13th May 2016, 9:41 am | #386 |
Nonode
Join Date: Apr 2012
Location: Worcestershire, UK.
Posts: 2,052
|
Re: 405-Line VHF Aerials 2013 to the present day.
Oops ... yes, you're right, Chris!
__________________
"What a depressingly stupid machine." [Marvin: HHGTTG] |
13th May 2016, 11:17 am | #387 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
|
Re: 405-Line VHF Aerials 2013 to the present day.
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? |
26th May 2016, 4:38 pm | #388 |
Nonode
Join Date: Feb 2005
Location: Worcestershire, UK.
Posts: 2,534
|
Re: 405-Line VHF Aerials 2013 to the present day.
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
__________________
https://www.radiocraft.co.uk |
29th May 2016, 4:06 pm | #389 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
|
Re: 405-Line VHF Aerials 2013 to the present day.
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 |
29th May 2016, 6:05 pm | #390 |
Hexode
Join Date: Mar 2013
Location: Coventry, West Midlands, UK.
Posts: 280
|
Re: 405-Line VHF Aerials 2013 to the present day.
The Band I element spacing is correct for 75 Ohms but wouldn't the Band III aerial be closer to 300 Ohms?
__________________
Classic TV Show Theme Tunes |
31st May 2016, 10:43 am | #391 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
|
Re: 405-Line VHF Aerials 2013 to the present day.
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). |
17th Jul 2016, 12:59 pm | #392 |
Heptode
Join Date: Sep 2013
Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland.
Posts: 502
|
Re: 405-Line VHF Aerials 2013 to the present day.
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.
__________________
Dom Less snakes...more ladders! Last edited by sexton_mallard; 17th Jul 2016 at 12:59 pm. Reason: Correct typo. |
17th Jul 2016, 1:07 pm | #393 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
|
Re: 405-Line VHF Aerials 2013 to the present day.
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 |
17th Jul 2016, 1:16 pm | #394 |
Heptode
Join Date: Sep 2013
Location: Ellesmere, Shropshire, UK & Co. Cork, Ireland.
Posts: 502
|
Re: 405-Line VHF Aerials 2013 to the present day.
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.
__________________
Dom Less snakes...more ladders! |
17th Jul 2016, 2:13 pm | #395 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,433
|
Re: 405-Line VHF Aerials 2013 to the present day.
Hi Dom,
it was just a thought. Frank |
17th Jul 2016, 11:06 pm | #396 |
Octode
Join Date: Jan 2013
Location: Barnsley, South Yorkshire, UK.
Posts: 1,517
|
Re: 405-Line VHF Aerials 2013 to the present day.
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.
|
18th Jul 2016, 10:03 am | #397 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
|
Re: 405-Line VHF Aerials 2013 to the present day.
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.
|
18th Jul 2016, 11:16 am | #398 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
|
Re: 405-Line VHF Aerials 2013 to the present day.
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 |
18th Jul 2016, 11:40 am | #399 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
|
Re: 405-Line VHF Aerials 2013 to the present day.
Peter, re post no. 398,
... What an intriguing design! ... I wonder what its reception of "Chain Home" 30 Mc/s radar was like ? |
18th Jul 2016, 3:39 pm | #400 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
|
Re: 405-Line VHF Aerials 2013 to the present day.
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 Last edited by peter_scott; 18th Jul 2016 at 4:07 pm. |