By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

Ofcom trace interference to a lightbulb

All Topics | Latest Posts

Search for:  in Thread Title in  
Robin Colbourne25/09/2020 10:35:13
avatar
697 forum posts
17 photos

I can just imagine the next generation of 'Wild Weasel' radar-jamming aircraft, festooned with old lightbulbs and an ancient TV set on each underwing pylon...

Simon Chaddock25/09/2020 10:46:12
avatar
5794 forum posts
3063 photos

Most discharge lamps not only emit light in the visible spectrum but also in the non visible ultra violet range. To make use of this the inside of the glass is coated with materials that absorb the UV and emit visible light hence the term fluorescent lamp. This process has some 'persistence' so it will continue to glow dimly for a short while after the light is switched off.

The quality of the light a fluorescent lamp produces can be changed by using different types of coatings hence warm, cool and daylight types.

ron evans25/09/2020 10:46:44
avatar
465 forum posts
28 photos

J D 8, The bulbs were 3x low energy candle type.

Ron

ron evans25/09/2020 10:55:50
avatar
465 forum posts
28 photos

Simon, this occurred in the morning, before the lights had been switched on that day, so would any residual have lasted from the previous evening.

Ron

Geoff S25/09/2020 13:09:32
3827 forum posts
49 photos
Posted by J D 8 on 25/09/2020 09:54:01:

What sort of bulbs were they? If you hold a fluorescent tube under a high power cable it will glow.

When I was still at school (1953 ish) I went on a visit to the Rugby Long wave transmitter facilty with a local radio club. There was a large hall-like room where the feeds to the aerial arrays left the buildings and I was amazed to see how fluorescent tubes lit when suspended form bits of string. Very useful for maintenance I suppose.

Of course it was all thermionic valves and the big transmitter power output ones had removable glass covers so that elements that failed could be repaired, the covers replaced and the valve evacuated.

All very impressive to a 13 year old and quite impressive to an 80 year old, too

Geoff

J D 825/09/2020 13:45:18
avatar
1620 forum posts
87 photos

Sounds like the transmitter visit was fun Geoff. We had for many years in a rented part of a shed on the farm a Ship to Shore radio repeater. There was a distinct smell from the valve radio.

A friend who is a radio ham has a Spark generator radio, like the sort on the Titanic . He found it at the local dump in very good condition complete in its lovely wooden case's! Say's he would like to fire it up but dare not as he thinks it would drown out most signals for miles around. Cheers John.

Kevin Wilson25/09/2020 17:49:11
avatar
403 forum posts
13 photos
Posted by Geoff S on 24/09/2020 14:56:36:
(snip)....... I think eventually houses will be wired with a 12 dc circuit for lighting with a central ac to dc regulator/rectifier and much simpler (and probably cheaper) LED bulbs with greatly extended life.

Geoff

Geoff, I work at a UK satellite TV broadcaster and wiring the buildings for DC was under passing consideration a few years back. One of my buildings is a large broadband hub and we have many DC systems at 50volt, a data centre standard evolved from GPO so I am told. Typical loading of a DC system is around 1000Amps. And that is the rub with LV DC. Low volts = big currents = big cables.
China and India are leading the way with MV DC transmission lines (yes, 1million volts) now possible by high efficiency HV semiconductor converters. hopefully they are built to a higher standard than the SMPS in domestic LED lamps.

Peter Christy25/09/2020 19:39:29
1905 forum posts

Many decades ago, I worked at the Holme Moss TV transmitter, just outside Huddersfield. This was a 405-line VHF transmitter (Geoff will know what I'm talking about!). I was told that it was the original Alexander Palace transmitter, famous for bending the German navigation beams during the war, while it was still at AP.

It looked like something out of H.G.Wells! Lots of brass, ebony and ivory, a "dynamotor" (3-phase electric motor turning a generator) to produce the current for the filaments in the valves, and a 3-phase mercury vapour rectifier, nicknamed "The Mekon" (again, older readers will get the reference!).

The actual circuitry was pretty basic, but the scale of it was enormous! Old hands used to measure the SWR by sliding their hands along the co-ax feeders (looked like sewage pipes!) feeling for "hot spots". Quite often, a day or two later, their hands would be peeling from RF burns!

I was on duty in the control room one day when the transmitter suddenly shut down! I hit the big red "Alarm" button to summon everyone to the front and started powering up the standby transmitter. Unbeknownst to me, someone was in the modulator section of the standby transmitter (a room the size of a small garden shed!) and was quite surprised when relays started pulling in all around him! Luckily it was all heavily interlocked, so he was in no danger, but it sure made him jump!

In the control room, circuit diagrams were pulled from their pigeon holes - a bit like legislation in the Houses of Parliament - and the various parchment scrolls studied.

"I reckon its R34", pronounced one of the senior engineers, "Have we got one in stores?". Receiving an answer in the affirmative, said engineer vanished into the transmitter hall, and into the bowels of the transmitter itself. Much banging and cursing later, he reappeared with a 3 ft long charred carbon rod. This had been "R34"!

"Told you so!", was all he said!

--

Pete

Geoff S25/09/2020 20:05:51
3827 forum posts
49 photos
Posted by Kevin Wilson on 25/09/2020 17:49:11:
Posted by Geoff S on 24/09/2020 14:56:36:
(snip)....... I think eventually houses will be wired with a 12 dc circuit for lighting with a central ac to dc regulator/rectifier and much simpler (and probably cheaper) LED bulbs with greatly extended life.

Geoff

Geoff, I work at a UK satellite TV broadcaster and wiring the buildings for DC was under passing consideration a few years back. One of my buildings is a large broadband hub and we have many DC systems at 50volt, a data centre standard evolved from GPO so I am told. Typical loading of a DC system is around 1000Amps. And that is the rub with LV DC. Low volts = big currents = big cables.
China and India are leading the way with MV DC transmission lines (yes, 1million volts) now possible by high efficiency HV semiconductor converters. hopefully they are built to a higher standard than the SMPS in domestic LED lamps.

Of course that's true if you need real power for heating etc (one reason I think our 240v mains supply is superior to the US 110v - though we had a 110 v supply at work which was rarely used). However I would think the current involved in LED lighting would be quite modest and any extra copper conductor cost would be offset by the lower energy requirements of pure LED lighting (as opposed to the current LED bulbs which need 240v ac to a low voltage dc converter in each one with the potential for EMI). In your case the energy requiremnts may well justify high voltage/low current supplies but that probably wouldn't be the case in a domestic setting.

I admit I haven't done either the maths or any research but it seems worth consideration. Vehicle lighting is also becoming more LED based. When I edited a national cycle club magazine (Tandem Club Journal) back in the late 80s I was given some LED rear lights to review (red LEDs being really the only ones generally available then) and they were brilliant both literally and figuratively. The main advantage was their reliability and low weight. The so-called Never Ready cycle lamps were notorious for intertmittent operation LED cycle lighting is now so good that motorists complain about their being too bright whereas back in the 80s the complaint was of cyclists having no lights at all.

Geoff

Chris Walby25/09/2020 22:18:11
avatar
1350 forum posts
338 photos

So was the lamp at fault.... or more likely what was passing through it?

Was it just acting as an aerial? There are plenty of candidates that produce higher frequencies than 50Hz or any of the harmonics associated with that fundamental frequency or switch mode power supplies operating at higher switching frequencies where their harmonic frequency aligns with the equipment effected operating frequency?

All Topics | Latest Posts

Please login to post a reply.

Support Our Partners
Sussex Model Centre
CML
Slec
electricwingman 2017
Sarik
Advertise With Us
Latest "For Sale" Ads
NEW POLL - has the pandemic altered your event safety perceptions?
Q: Has the covid pandemic deterred you from attending shows and events in 2021?

 No, I'll be attending just as many as I usually do
 No, but I'll choose my event with greater care
 Yes, I'll attend fewer events going forward
 Yes, I wont attend any where previously I have

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E!