Author Topic: New Member and An Interesting Story (Read 11082 times)

gutfinski · « **on:** January 10, 2003, 02:41:00 pm »

Hello,

I just joined this Forum and I have an interesting story about how I first became interested in early light bulbs. Back in the 1950's when I was a young boy in western Massachusetts, I used to assist my father in his part time work of installing and repairing the new fad of televisions. He had a customer who complained that every evening about the same time his TV viewing was disturbed by interference which ruined both the picture and sound on his set. After several trips to the home we learned that the interference began every evening when the man's wife went out to the barn to feed the chickens. What we discovered in the barn attached to the house was an original "GEM" lamp with exhaust tip. Every time the lamp was turned on the TV went bonkers on the only channel which at the time was channel 4 out of Boston. Apparently, current flowing through the filament caused RF interference which was picked up by the VHF TV receiver. I assume this was caused by the alternating current flowing through the particles of metallized carbon in the bulb's filament. The customer said that the bulb in question had been used in the barn since before the World War I! My father put in a new bulb and saved that old "GEM" bulb and I still have it today as the first in my collection!

Max · « **Reply #1 on:** January 13, 2003, 03:30:00 am »

Hello Gutfinski,

Welcome to this forum and thanks for your interesting story.
concerning the electromagnetic interferences I don't think that the mechanism was the electric current through the metallized carbon particules. I would rather think of a transient electric discharge in the lamp due to a improper vacuum, or some tiny sparks on the lamp socket due to a corroded surface or bad electrical contacts...
Have you tried to re-light the lamp near a TV antenna to see if you can still get this phenomenon?

Max

Ray Ladegast · « **Reply #2 on:** January 13, 2003, 09:02:00 pm »

Hi Gutfinski
Welcome, I also have a exhaust tip tungsten filament bulb that caused interference on our family TV. The bulb was in our porch light,so every time we had visitors at night it was goodby TV. My Dad thought it was a bad connection and cleaned the contact, no improvement. After many protest from us every time the light was on Dad changed the bulb. He gave me the old one. I still have it along with other early tungsten bulbs. As soon as I have time I'm going to try it to see if it still interfers with the TV when lit.

James · « **Reply #3 on:** January 14, 2003, 10:35:00 am »

Hi Gutfinski and welcome!

I first came across this phenomenon while working for GE Lighting when we were producing carbon filament and drawn wire tungsten cage lamps about 5 years ago. It intrigued me that the chief of the labs specifically instructed us that we must not print the "CE" mark on these lamps, a symbol which would normally be printed on every other lamp to state is suitability for use in all commercial and domestic environments on the mains electricity supply.

The reason, he said, is because both these kinds of lamps have a tendency to generate strong radio frequency emissions because the vacuum is good, but not perfect enough to ensure that the remaining gas inside the lamp cannot be ionised around the hot filament. It doesn't happen with every lamp, but just a proportion of them which happen to have a particular level of vacuum. Sure enough we did find that a significant number of the carbon lamps we made that year would destroy the picture on a television when illuminated in the vicinity. Eventually, we managed to nearly eliminate the problem by using a special new getter mixture and pumping process which dramatically lowered the vacuum in the lamps. Modern carbon lamps from Philips have an exceptionally rigorous pumping process and I have never come across this effect with their products. The tungsten cage lamps made by Victory Lighting UK are of a design particularly likely to generate such radiation though because of their filament geometry, and nearly every lamp will produce the interference effect.

I understand that the problem does not occur in any coiled-filament vacuum lamps though. Presumably because the filament is essentially linear and there is no possibility for current leakage between parallel sections of filament through the "vacuum" space, so if any ionisation did take place the discharge current would be insignificantly low.

Thanks for bringing up this interesting topic!

James

Ross · « **Reply #4 on:** January 16, 2003, 02:07:00 pm »

Fascinating ! I really had never considered that a non-discharge lamp could cause this type of problem.

Ralph · « **Reply #5 on:** July 28, 2003, 12:02:00 am »

I remember reading about that interference
problem with the "cage" filament in an old
QST (Ham Radio) magazine. The magazine
described the sections of the bulb filament
acting as cathode, grid, anode, inductor,
and other elements of an electronic
oscillator. I will post again if I can find
that magazine issue.

James · « **Reply #6 on:** August 04, 2003, 12:12:00 pm »

Hi Ralph,

If you do come across that issue please do let us know, I'd be fascinated to learn a bit more about it! Last month I was over at the Philips incandescent factory in Holland where this subject came up in discussion again. It appears that the modern squirrel cage lamps might become prohibited for sale in Europe because of this problem, so we'd perhaps stand a better chance of redesigning the lamp to avoid it if we could first understand a little more about the causes.

Best regards,

James.

Tim · « **Reply #7 on:** August 04, 2003, 12:47:00 pm »

quote:
Originally posted by Ralph:
I will post again if I can find
that magazine issue.

Anyone here a member of the ARRL? I think they maintain an online searchable database of everything that every appeared in QST magazine. You must be a paid member of the ARRL to access it though. I most likely have this issue in my paper archives and I would post it if anyone can come up with the year of this issue.

------------------
Tim
Kilokat's Antique Light Bulb Site
Mountain Dew Collectibles, Volume I

Ralph · « **Reply #8 on:** August 04, 2003, 10:36:00 pm »

Good idea Tim!

Just did an ARRL search and found reference to "light bulb QRM" in FEB,1931 QST magazine, also found "K6USL hears K6ODY on light bulb" in May,1959 QST magazine. I threw most of my old magazines out, but will be contacting the ARRL to get reprints of those two articles and will let you know what I receive.

Best Regards to All

Ralph

Ralph · « **Reply #9 on:** August 11, 2003, 10:22:00 pm »

James
Just received the articles from the ARRL
--- no luck. One article described noise emitted by bulb failure and the other article described the use of a bulb as a transmitter tuning indicator.

Some of the things I remember from the article I read a long time ago about the cage filament bulb acting as a radio transmitter were;
1. A certain section of the filament acted as a cathode.
2. Another section of filament acted as a grid.
3. Part of the mount acted as the anode.
4. The better the vacuum in the bulb, the better it radiated radio frequency energy.
5. Stray inductance and capacitance between the bulb elements formed a tuned circuit to determine the operating frequency.

What you might want to do is attend a radio fair (hamfest), share a cup of tea (coffee) with an older ham operator, have him explain valve (vacuum tube) theory to you and let him see my comments.

Hope I have been of some help and I will be reading the forums often.

Best Regards!

Ralph

Mónico González · « **Reply #10 on:** August 12, 2003, 03:22:00 am »

I've recently have purchased a couple of new straight tungsten filament cage lamps, made as replicas or reproductions from those originals. These lamps that are actually under production, are quite detailed and finely made by a prestigious German brand (please, I prefer to ommit the name, sorry).
These amazing bulbs are pear shaped, stem exausted, not tipped, all of them comes with genuine brass/vitrite E27 caps and are 230V/60W rated. Really a very nice lamp!.
But some months ago, some days after I did read these Forum posts, I was testing one of
such lamps, and I did notice that when I turned on the bulb, it can be hear a strong 50Hz "hum" on VHF/FM band, at a radio receiver, around 100MHz.
The noise dissapeared when I switched off the bulb, and re-appeared when I lit on it.
The radiated RF appears to be not only amplitude, but frequency modulated too by mains AC frequency.
In fact, due to transversal vibration of filament, the stray capacities are varying at the same AC frequency, so, the LC constant of whole resonant system are also mains frequency dependant, giving as a result a frequency modulation emission.
The output frequency are entirely dependant upon filament?s lenght, number of "V" sections on it, distance between those sections, diameter vs. lenght of cage, working temperature, voltage across both sides of the filament... a very complicated amount of equations.
Fortunately, the strenght of radiated RF decreases rapidly with distance; the farther are the receiver from the bulb, the lower are the interference effects. Altough the RF interference can be carried and radiated by the power line itself, travelling beyond the room and being capable to interfering with another radio or TV sets outside the lamp location.
in any case, please be careful when use these kind of bulbs.

P.D. In Spain, such lamps are not prohibited by EC rules at the moment, perhaps due to the fact that have not been found serious RF interference phenomena vinculated to ordinary household use, so, they are sold and are becoming some popular as classic decorative bulbs to fit old styled fixtures.

[This message has been edited by M?nico Gonz?lez (edited August 12, 2003).]