Weak 405 transmitter power at the end - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Heatercathodeshort · 26th Mar 2007, 7:42 pm

I have a copy of that IBA closedown film on Betamax. Its very good. It was broadcast a second time on channel 4 due to demand from engineers. I NEVER saw any notices of the closedown of 405 and did not receive a single phone call about 'loss of picture'.
I did have a guy bring a little Thorn 12" 980 portable in for repair that he had bought at a bootsale......He left it with me...I still have it...
When the BBC closed down for the night showing the old Baird receiver, the transmissions continued the following morning for a few hours. No further announcements were made.

Panrock · 26th Mar 2007, 8:00 pm

Quote:

Originally Posted by Heatercathodeshort

When the BBC closed down for the night showing the old Baird receiver, the transmissions continued the following morning for a few hours. No further announcements were made.

Thanks. That's an interesting historical postscript I had no idea about! I wonder why this was done but I guess an answer would be off-topic.

Steve

standing wave · 27th Mar 2007, 1:36 pm

I don't remember Crystal Palace coming back on the following morning but I think Holme Moss continued to mid afternoon. If remember correctly Croydon was on the air until the end of TV am. Does anyone have the exact times when the BBC / IBA transmitters closed?.
Terry.

mickjjo · 27th Mar 2007, 1:55 pm

Hi Terry, There is a good list here:-

http://www.bvws.org.uk/405alive/info/tx_list.html

Regards, Mick.

DoctorWho · 27th Mar 2007, 3:26 pm

We stayed with 405 right until the closedown in 1985, we lived about 50 miles from London and we received the Crystal Palace signals perfectly well, I well remember watching the last transmission and the picture was clear and stable. Channel 1 was certainly giving first class service at that time.

We also used to receive Anglia, but I can't remember now which channel that was on, again picture quality was very good up until the end.

It wasn't until after the shut down that we actually had a 625-line set, interestingly not only our household but also my grandparents and both of my great-grandmothers were also still on 405 only, no one had seen the need to upgrade to a 625-line set.

If the power was reduced we certainly never noticed it. What would have been the point of doing so anyway, after all, the transmitter and converter would still have been switched on.

It was mentioned above that there were not many 405 only and dual standard sets around still working. Interestingly I was at secondary school when 405 was switched off, and I found lots of sets at that time which had been put in to skips, I also visited the local TV rental shop and they were piling the sets up for dumping. I took a lot of these sets home (mostly dual standard) and they were all either in perfect working order or else only needed very minor attention. A friend also gave mer her dual standard set as she could not get channel 4 on it, the problem turned out to be that it was one of those tuners which needed the plate turning over for the appropriate button so that it could tune across UHF.

I tried being a bit adventurous and also placed adverts in the paper asking for 405 line sets, and I obtained a variety of sets either for free or very cheaply, the ones which stick in my mind most are a Pye B16T, a Philips 385U and a Pye B18T and a Pye D18T. At that time I had no way of supplying a 405-line signal to them, but the Pye B16T, the Pye B18T and the Philips 385U all powered up and gave a perfect raster, so there must have been quite a few sets still in good working order when 405 was switched off. If only I had been able to keep the sets I rescued back then!

Panrock · 27th Mar 2007, 4:14 pm

If you look at the service area maps of AP (17Kw) and CP (200Kw) you'll see they're remarkably similar in coverage. There's an argument that weak transmitter power didn't really matter that much.

The ultimate extent of the service area seemed to be more determined by geography and antenna throw-height. 'Power' as such only made reception in the fringe areas more proof from interference.

Steve

Focus Diode · 27th Mar 2007, 4:21 pm

Didn't Anglia TV switch off a good year before the rest of the 405-line network?

Speaking of ERP Pontop Pike ch5 gave remarkably good coverage despite being only 17KW ERP!

Cheers,
Brian

Ray Cooper · 27th Mar 2007, 8:04 pm

Panrock:

Quote:

...If you look at the service area maps of AP (17Kw) and CP (200Kw) you'll see they're remarkably similar in coverage...

Point at tissue, Mr. Chairman... the ERP of AP was 35kW, not 17kW. This 17kW figure is a hang-over from pre-war practice of quoting transmitter powers rather than ERPs: in point of fact, MF/LF station powers are still quoted as TX power rather than ERP to this day.

A couple of points: the original London Television site was North-London preferred rather than South-London: they'd worked out that a North London site coincides better with the 'centre-of-gravity' of the desired population coverage than does a South London site. Part of the reason for the much higher ERP of CP was to match the existing coverage pattern from AP as well as possible.

Also, the two sets of maps given are not necessarily strictly comparable. The pre-war map is nice insofar as it gives actual field-strengths expected, whereas the later EID maps don't quote field strengths: only likely areas of satisfactory reception. These later figures would likely be quite a bit higher than the old AP figures since they'd probably contain a degree of protection against co-channel and continental interference, which was no problem for the old AP setup.

Interesting from the later map, though: the coverage areas of the Swingate and Oxford stations, both having quite low ERPs.

Heatercathodeshort · 27th Mar 2007, 8:19 pm

This is so frustrating! I took pictures from the screen of my 900 HMV on the morning of closedown. It shows Lyn Faulds Wood on the Breakfast TV programme.
I did send some to the BBC for archive but Have around five in a stiff envelope but can I find them....?
I went down to the shop to serve a customer, and when I came back the transmission had vanished for ever! When I do find them I will post! The transmission quality was first class, typical of the BBC in the 80's.
Regards John.

evingar · 27th Mar 2007, 9:09 pm

Quote:

I did have a guy bring a little Thorn 12" 980 portable in for repair that he had bought at a bootsale.....

I was asked to repair my cousin's set that she used in her bedroom (a portable 405 Line only DER set ISTR). I had to break the bad news to her it would never work again

I used it for spare parts !

On the subject of people using 405-line sets at close down, one of my mums friends certainly was, they were forced to buy another set !

System A · 27th Mar 2007, 9:56 pm

Hi all
I, too, was asked to look at my aunt's friend's tv. It was the 2nd January 1985. It was a 17" Stella, which she told me that was bought secondhand in 1964 ( the year of BBC2). It worked until 1981 when she showed me a bill for £10 for a replacement PL81 valve. It worked then up until 1985, when I had to inform her that her set was now obsolete. She was very upset as it was like losing an old friend !
I got her a nice 24" Philips single standard, which made her happy! I still have the set in my collection but sadly the lopt failed a couple of years ago.
Regards GP.

mickjjo · 27th Mar 2007, 10:28 pm

I watched the last year or so of BBC1 405 lines from C.P. on my Bush TV22, bought in Margate for £18 in 1983, Always had a good signal with a 4 foot bit of wire stuck in the aerial socket right until the transmissions ended. It was a sad day when the screen went blank. I've just found this old cartoon I cut from the Sunday Mirror, November 4th 1984 :-

http://i15.photobucket.com/albums/a3...kjjo/405tv.jpg

I'm glad I kept that now.........

.

Regards, Mick.

26th Mar 2007, 7:42 pm	#21
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Weak 405 transmitter power at the end I have a copy of that IBA closedown film on Betamax. Its very good. It was broadcast a second time on channel 4 due to demand from engineers. I NEVER saw any notices of the closedown of 405 and did not receive a single phone call about 'loss of picture'. I did have a guy bring a little Thorn 12" 980 portable in for repair that he had bought at a bootsale......He left it with me...I still have it... When the BBC closed down for the night showing the old Baird receiver, the transmissions continued the following morning for a few hours. No further announcements were made.

27th Mar 2007, 1:36 pm	#23
standing wave Pentode Join Date: Sep 2006 Location: Tipperary, Ireland Posts: 121	Re: Weak 405 transmitter power at the end I don't remember Crystal Palace coming back on the following morning but I think Holme Moss continued to mid afternoon. If remember correctly Croydon was on the air until the end of TV am. Does anyone have the exact times when the BBC / IBA transmitters closed?. Terry.

27th Mar 2007, 1:55 pm	#24
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Weak 405 transmitter power at the end Hi Terry, There is a good list here:- http://www.bvws.org.uk/405alive/info/tx_list.html Regards, Mick.

27th Mar 2007, 3:26 pm	#25
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: Weak 405 transmitter power at the end We stayed with 405 right until the closedown in 1985, we lived about 50 miles from London and we received the Crystal Palace signals perfectly well, I well remember watching the last transmission and the picture was clear and stable. Channel 1 was certainly giving first class service at that time. We also used to receive Anglia, but I can't remember now which channel that was on, again picture quality was very good up until the end. It wasn't until after the shut down that we actually had a 625-line set, interestingly not only our household but also my grandparents and both of my great-grandmothers were also still on 405 only, no one had seen the need to upgrade to a 625-line set. If the power was reduced we certainly never noticed it. What would have been the point of doing so anyway, after all, the transmitter and converter would still have been switched on. It was mentioned above that there were not many 405 only and dual standard sets around still working. Interestingly I was at secondary school when 405 was switched off, and I found lots of sets at that time which had been put in to skips, I also visited the local TV rental shop and they were piling the sets up for dumping. I took a lot of these sets home (mostly dual standard) and they were all either in perfect working order or else only needed very minor attention. A friend also gave mer her dual standard set as she could not get channel 4 on it, the problem turned out to be that it was one of those tuners which needed the plate turning over for the appropriate button so that it could tune across UHF. I tried being a bit adventurous and also placed adverts in the paper asking for 405 line sets, and I obtained a variety of sets either for free or very cheaply, the ones which stick in my mind most are a Pye B16T, a Philips 385U and a Pye B18T and a Pye D18T. At that time I had no way of supplying a 405-line signal to them, but the Pye B16T, the Pye B18T and the Philips 385U all powered up and gave a perfect raster, so there must have been quite a few sets still in good working order when 405 was switched off. If only I had been able to keep the sets I rescued back then!

27th Mar 2007, 4:14 pm	#26
Panrock Nonode Join Date: Feb 2005 Location: Worcestershire, UK. Posts: 2,533	Re: Weak 405 transmitter power at the end If you look at the service area maps of AP (17Kw) and CP (200Kw) you'll see they're remarkably similar in coverage. There's an argument that weak transmitter power didn't really matter that much. The ultimate extent of the service area seemed to be more determined by geography and antenna throw-height. 'Power' as such only made reception in the fringe areas more proof from interference. Steve __________________ https://www.radiocraft.co.uk

27th Mar 2007, 4:21 pm	#27
Focus Diode Octode Join Date: Jan 2006 Location: Borough of Gateshead, UK. Posts: 1,420	Re: Weak 405 transmitter power at the end Didn't Anglia TV switch off a good year before the rest of the 405-line network? Speaking of ERP Pontop Pike ch5 gave remarkably good coverage despite being only 17KW ERP! Cheers, Brian

27th Mar 2007, 8:19 pm	#29
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Weak 405 transmitter power at the end This is so frustrating! I took pictures from the screen of my 900 HMV on the morning of closedown. It shows Lyn Faulds Wood on the Breakfast TV programme. I did send some to the BBC for archive but Have around five in a stiff envelope but can I find them....? I went down to the shop to serve a customer, and when I came back the transmission had vanished for ever! When I do find them I will post! The transmission quality was first class, typical of the BBC in the 80's. Regards John.

27th Mar 2007, 9:56 pm	#31
System A Pentode Join Date: Feb 2006 Location: County Durham, UK. Posts: 234	Re: Weak 405 transmitter power at the end Hi all I, too, was asked to look at my aunt's friend's tv. It was the 2nd January 1985. It was a 17" Stella, which she told me that was bought secondhand in 1964 ( the year of BBC2). It worked until 1981 when she showed me a bill for £10 for a replacement PL81 valve. It worked then up until 1985, when I had to inform her that her set was now obsolete. She was very upset as it was like losing an old friend ! I got her a nice 24" Philips single standard, which made her happy! I still have the set in my collection but sadly the lopt failed a couple of years ago. Regards GP. Last edited by Mike Phelan; 27th Dec 2007 at 2:55 pm. Reason: S&P

27th Mar 2007, 10:28 pm	#32
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Weak 405 transmitter power at the end I watched the last year or so of BBC1 405 lines from C.P. on my Bush TV22, bought in Margate for £18 in 1983, Always had a good signal with a 4 foot bit of wire stuck in the aerial socket right until the transmissions ended. It was a sad day when the screen went blank. I've just found this old cartoon I cut from the Sunday Mirror, November 4th 1984 :- http://i15.photobucket.com/albums/a3...kjjo/405tv.jpg I'm glad I kept that now......... . Regards, Mick.