On Thu, 6 Jul 2017 15:21:48 -0400, Phil Hobbs
wrote:
On 07/06/2017 01:00 PM, Jeff Liebermann wrote:
On Thu, 6 Jul 2017 09:51:44 -0400, Phil Hobbs
wrote:
No, it's a coupled plasma/surface effect. It's really cool. It
peaks down around a few tenths of a millitorr, but it's still
appreciable at higher pressures.
According to Wikipedia:
https://en.wikipedia.org/wiki/Incandescent_light_bulb the gas
pressure in a common light bulb is about 70 kPa or 525 torr. That's
quite a bit higher than a few tenths of a millitorr.
The light bulb thing was discovered by somebody turning on an
incandescent lamp and wiping out his reception.
I don't quite believe it. In the early daze of light bulb research,
it was wrongly assumed that a better vacuum produced a better light
bulb. So, early light bulbs had a fairly high vacuum, which might
explain the RF interference,
How exactly, if not Barkhausen? Hot wires don't produce a lot of RF IME.
All that I know is that someone allegedly turned on a light bulb which
produced enough RF to wipe out their radio reception. My point was
that until 1916, when Irving Langmuir invented the gas filled light
bulb at GE, light bulbs were made with a sufficiently high vacuum to
produce Barkhausen noises. The light would also need a tungsten
filament, which was introduced in 1908. So, if the bulb really did
produce noise, it would have to have been manufactured between 1908
and 1916. The Barkhausen effect was discovered in 1919, so the person
flipping the light switch would have needed a pre-1916 light bulb, in
order to call the noise Barkhausen Effect by running the test after
1919.
Meanwhile the radio receivers of that era were crude at best
consisting of coheres, magnetic detectors, cat whiskers, liquid
diodes, and early triodes. Regular entertainment broadcasting didn't
begin until 1922. Therefore, whatever was being broadcast between
1908 and 1916 would probable have been amateur radio or military
signals. The receive technology lurched forward rapidly, but I
suspect there was nothing worth listening to until the 1930's by which
time all the light bulbs would probably have been gas filled.
If not Barkhousen noise, the light switch could have caused an arc
somewhere in the light circuit. It could have turned on something
else in the circuit, such as a carbon arc lamp, which generates enough
RF noise to clobber even the most deaf receivers of the day.
I'm also having problems believing that the weak paramagnetism of
tungsten, can generate enough RF to be heard on the presumably AM LF
(low frequency) receiver of the day. Also, I don't see why a high
vacuum is required since there are several YouTube videos
demonstrating the effect at 1 atm.
https://www.youtube.com/watch?v=H7nJi5episc
https://www.youtube.com/watch?v=YLycGnOCqLc
So, do I wrap some wire around an incandescent light bulb and feed it
to my spectrum analyzer? Or, is this a waste of time with modern gas
filled light bulbs?
except that radio hadn't really become
common at the time. Eventually, someone figure out that it was the
water in the glass that was killing the filaments. Once the water
was baked out of the glass, subsequent light bulbs had a much lower
vacuum.
If you read my original post, I pointed out that it was only the old
fashioned evacuated bulbs that showed the effect, not the modern argon ones.
I read that, which is why I'm questioning the timing. At the time
when there were radio receivers sensitive enough to hear Barkhousen
Effect noises, the light bulbs were all gas filled. Well, I guess the
person flipping the switch might have been using an antique light
bulb:
http://www.centennialbulb.org
I don't know if the pressure in the transient suppressor is low
enough for Barkhausen--if not, it's probably the neon bulb
oscillation as others have said.
I don't think that the ceramic gas discharge tubes have a vacuum.
More like they are under pressure in order to lower the conduction
current. However, I'm guessing and don't have time to look it up
right now.
You don't want to reduce the conduction current in a gas suppressor
tube, though, do you? My guess is that they'd be a torr or two, to get
lower breakover voltage, which is on the high side for Barkhausen, for sure.
I wish I could xray the ceramic GDT and measure the spark gap spacing.
My guess(tm) is that it's fairly wide at perhaps 1 mm, something
similar to a common NE-2 neon lamp. I wouldn't need to have a hard
vacuum in order to get a lower breakdown voltage when neon breaks down
so easily. So, if I don't need a vacuum, and want plenty of ionized
neon atoms to provide conduction, I would pressurize the tube with as
much neon gas as I could cram into the package.
Cheers
Phil Hobbs
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
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Skype: JeffLiebermann AE6KS 831-336-2558