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> Antenna Vs Fluoro Tube, just curious
Jimthecopierwrench
Posted: August 31, 2011 12:28 pm
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Couple of general questions, but I may be asking them wrong.

RF energy can exite a fluoro or discharge lamp, and there used to be mobile antennas with (neon?) elements that would (as advertized) 'flash' in sync with the modulation.

I assume these flashy antennas sucked at actually being antennas, Yes?

How (or is) frequency dependent on the light output? Does the tube (gas) mixture or tube dimension play a greater roll? That is, is it purely an atomic thing which would imply that (power equal) certain frequencies will produce more light, or does the ionized gas become an 'element' whos physical dimension as (part of) a radiator will exhibit Q - that is with equal power and frequency, tubes of different length will have different outputs?

What does a fluoro tube look like to a feedline? Or is this question simply laugable.

How much did the smaller 'glow sticks' - like the small NE-2 on the end of the 1/4 wave verticals - actually affect the antenna trim?

Slightly different - was there ever an application that used a low pressure tube with an external RF field? For example some sort of RF gated high power glass 'SCR'.

Could this method not be used for relaible cold environment (lighting) tube starting?

Edit - Although not what i had in mind, a Xenon flash comes to mind. Wonder if it'd be audible on AM broadcast? If I remember Ican check that out tonight quite easily as coincidentally enough I have a cheap 'party strobe' and clock radio less than 5 feet from each other - would just have to turn them on.

Gnaw, not thinking of any application or doing anything - just the curious child



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tekwiz
Posted: August 31, 2011 06:25 pm
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Most of the antennae of which you speak were CB antennae, & the NE2 on the end is too small to signifigantly affect tuning, especially considering that the CB band is exactly that...a band.
Hell, with a big enough amp, the bulb isn't even necessary. whistling.gif
As for discharge lamps being used as antennae, it might work(poorly) for transmitting, with enough power, but for receiving it wouldn't work, simply because there's no ionized conductive path when the lamp isn't energised.
The actual ionization isn't frequency dependant, AFAIK. The frequency dependance is mainly in coupling power to the ionized material.
I don't know if any RF triggered tubes are made, but there are purely RF excited lasers & lamps made.
Some CO2 lasers are RF excited, & so are sulphur lamps. Sulphur lamps are very efficient microwave excited lamps, where enough light for an entire large building comes from a quartz globe about the size of a golf ball. These use nuker frequencies, at ~1.4-3.5kW excitation. The light comes from a few milligrams of sulphur in the quartz globe.
They produce an incredible amount of wide spectrum light.
The Air & Space Museum in Washington has it's main spaces entirely lit from a single sulphur lamp setup, with 2 globes & an advanced light pipe installation.
http://en.wikipedia.org/wiki/Sulfur_lamp

I'd love to build a smaller setup that runs from a single nuker magnetron. thumbsup.gif


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GPG
Posted: September 01, 2011 12:19 am
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QUOTE
I don't know if any RF triggered tubes are made,
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CWB
Posted: September 01, 2011 03:05 am
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QUOTE (GPG @ August 31, 2011 06:19 pm)
QUOTE
I don't know if any RF triggered tubes are made,

beat me to it .


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GPG
Posted: September 01, 2011 03:33 am
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Used to maintain Blueport-ACT shipping in the South Pacific as well as domestic vessels.
Some other small lines would put up with a problem if they were going to load at Timaru, our base.
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ChipUser
Posted: September 02, 2011 07:34 pm
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@ Tekwiz,

QUOTE
As for discharge lamps being used as antennae, it might work(poorly) for transmitting, with enough power, but for receiving it wouldn't work, simply because there's no ionized conductive path when the lamp isn't energised.


In our company, they have a lab where new technology is demonstrated by the developers. I have seen a product demo for a plasma antenna. It was connected to an FM radio. When turned off, the radio produced some static. When turned on, you could get very good reception of FM stations. This technology is developed for stealth use. The developers are haleakala-research. Their website seems to have vanished. I found some references:


The product shown here is similar to what I saw
http://www.aps.org/meetings/unit/dpp/vpr20...ad/anderson.pdf

http://www.afsbirsttr.com/Publications/Doc...la-AF05-041.pdf
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GPG
Posted: September 02, 2011 11:37 pm
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Added the http:// ,but the second comes up corrupted or not a PDF.
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CWB
Posted: September 03, 2011 12:03 pm
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hmmm ...
somehow i don't think they would work so well in conjunction with an AM detector .

the theory should be easy enough to prove out by connecting a 4' fluorescent lamp to a bcb fm receiver (with good hv isolation of course) and use some sort of rf field or a "fire it up" ballast system .
i am betting the rf excitation would work best .

i wonder if a dc operational current would work better than ac .


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ChipUser
Posted: September 03, 2011 02:53 pm
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@ GPG,

QUOTE
Added the http:// ,but the second comes up corrupted or not a PDF.


When I use the search term "haleakala-research" in MSIE, it is the second hit to show up.
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GPG
Posted: September 03, 2011 05:09 pm
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Ta, link fixed.
To all, use "copy link location" and paste into post to avoid this kind of editing.
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tekwiz
Posted: September 03, 2011 08:02 pm
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QUOTE (ChipUser @ September 02, 2011 10:34 am)
@ Tekwiz,

QUOTE
As for discharge lamps being used as antennae, it might work(poorly) for transmitting, with enough power, but for receiving it wouldn't work, simply because there's no ionized conductive path when the lamp isn't energised.


In our company, they have a lab where new technology is demonstrated by the developers. I have seen a product demo for a plasma antenna. It was connected to an FM radio. When turned off, the radio produced some static. When turned on, you could get very good reception of FM stations. This technology is developed for stealth use. The developers are haleakala-research. Their website seems to have vanished. I found some references:


The product shown here is similar to what I saw
http://www.aps.org/meetings/unit/dpp/vpr20...ad/anderson.pdf

http://www.afsbirsttr.com/Publications/Doc...la-AF05-041.pdf

Now that's an interesting twist, thanks for posting it. I'll bet neon sign tubes would be ideal.


@CWB: It wouldn't surprise me if some DC bias was required, depending on how fast the plasma reverts. I can see that AC would allow a few more "special effects", however.


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For to you, kings & armies are things mighty & enduring.
To him, mere toys of the moment, to be overturned at the flick of a finger.

Fortuna favet fortibus.
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Sch3mat1c
Posted: September 04, 2011 04:28 pm
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Deionization time is in the ms for typical neon, xenon, mercury, etc. plasmas. Light gasses like hydrogen and helium have shorter times, and hydrogen thyratrons have fast switching times on the order of nanoseconds. So for most purposes you can get away with anything faster than lowfer in assuming the entire tube is conducting.

You will end up with distortion, even at fairly high frequencies (>10MHz?), which will be troublesome for IMD and interference (3rd and 5th harmonic most importantly).

Tim


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