Reply by Dick Carroll; August 11, 20032003-08-11

Jerry Avins wrote:

> An > open-coil hot plate with a ceramic holder to support and contain the > nichrome element as filament*. Topped with galvanized window screening, > the zinc removed with muriatic acid so as not to noxiously sublime, > resting on the ceramic as (literally!) grid. Small glass beads -- around > 1/16" -- scattered on it to create a gap and hold the screening flat. > Atop that, a pie tin weighted with cooling water to serve as > (literally!) plate. With 700 volts on the plate, I got measurable > current on my 1000 ohm/volt meter. At -90 volts on the grid, the current > was too small to read. The gain was enough to sustain oscillation.
Now **that's** Homebrew!
Reply by John Moriarity August 10, 20032003-08-10
> > That bulb was probably an old coiled 'Edison' type . They were /are
known to
> > form a tuned circuit resonating in the old TV band 1 ( about 48 - 62
MHz)
> > acting as a TX when power is applied. > > > > Frank GM0CSZ / KN6WH > > Thank you thankyouthankyou! I've been called a crazy liar more than once > over that bulb. There was no channel 1 when that incident happened, but > I suppose that a small change of geometry could raise the frequency. The > explanation in QST had it that the frequency was swept over a fairly > large range as the voltage varied during a cycle.
I found such a bulb in the loft of the garage of a house we were renting in the mid-1950s. I had read an article about them somewhere, so I took it inside, screwed it into a lamp near the TV, and, voila, instant Channel 3 TVI (that was the main channel in Milwaukee, WI, then). I put it in a box in my shack, and didn't think about it for some time. I put up a tower and 20 meter beam. Before the coax was in the house, a neighbor sent his kid over to complain about TVI. I invited him to come over and see that the TV in my shack was not showing any interference, but he declined, and continued to complain over the next few months. While preparing to leave for two weeks vacation, I had a flash of inspiration. I put the bulb in a lamp, connected a timer to the lamp, and put it in a closet (so the light couldn't be seen in an otherwise dark house). The timer turned the bulb on during evening TV hours. I left it on for several days after our return. The neighbor never complained of TVI again. 73, John - K6QQ, glad for the statute of limitations.
Reply by Peter J. Kootsookos August 10, 20032003-08-10
Jerry Avins <jya@ieee.org> writes:

> > P.S. to Rick: That was before my time. >
Hey, Rick! Stop pickin' on the ol' guy!! ;-) Ciao, Peter K. -- Peter J. Kootsookos "Na, na na na na na na, na na na na" - 'Hey Jude', Lennon/McCartney
Reply by Rob Judd August 10, 20032003-08-10
Jerry Avins wrote:
> > Rob Judd wrote: > > > ... > > > Open-air triode?? Do tell, you have me fascinated... > > > > Rob > > I wrote of it before, so I'll be brief and hope I'm not boring. An > open-coil hot plate with a ceramic holder to support and contain the > nichrome element as filament*. Topped with galvanized window screening, > the zinc removed with muriatic acid so as not to noxiously sublime, > resting on the ceramic as (literally!) grid. Small glass beads -- around > 1/16" -- scattered on it to create a gap and hold the screening flat. > Atop that, a pie tin weighted with cooling water to serve as > (literally!) plate. With 700 volts on the plate, I got measurable > current on my 1000 ohm/volt meter. At -90 volts on the grid, the current > was too small to read. The gain was enough to sustain oscillation.
Tr&#2013265928;s bizarre! Rob
Reply by Jerry Avins August 10, 20032003-08-10
R J Carpenter wrote:
> > "Rob Judd" <judd@ob-wan.com> wrote in message > news:3F363E4E.F273DB5C@ob-wan.com... > > > Open-air triode?? Do tell, you have me fascinated... > > IIRC, field effect triodes {FETs} were made about the same time as the first > vacuum tubes, but they didn't work well enough, given materials technology > of the day.
I thought that FETs dated to the early 30s. De Forest's "audion" was invented in 1903 and made long-distance telephony practical by 1913. Jerry P.S. to Rick: That was before my time. -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Jerry Avins August 10, 20032003-08-10
Rob Judd wrote:
>
...
> Open-air triode?? Do tell, you have me fascinated... > > Rob
I wrote of it before, so I'll be brief and hope I'm not boring. An open-coil hot plate with a ceramic holder to support and contain the nichrome element as filament*. Topped with galvanized window screening, the zinc removed with muriatic acid so as not to noxiously sublime, resting on the ceramic as (literally!) grid. Small glass beads -- around 1/16" -- scattered on it to create a gap and hold the screening flat. Atop that, a pie tin weighted with cooling water to serve as (literally!) plate. With 700 volts on the plate, I got measurable current on my 1000 ohm/volt meter. At -90 volts on the grid, the current was too small to read. The gain was enough to sustain oscillation. Jerry ______________________________ * Driven through an isolation transformer with grounded center tap. -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by R J Carpenter August 10, 20032003-08-10
"Rob Judd" <judd@ob-wan.com> wrote in message
news:3F363E4E.F273DB5C@ob-wan.com...

> Open-air triode?? Do tell, you have me fascinated...
IIRC, field effect triodes {FETs} were made about the same time as the first vacuum tubes, but they didn't work well enough, given materials technology of the day.
Reply by Rob Judd August 10, 20032003-08-10
Jerry Avins wrote:
> > Eric Jacobsen wrote: > > > > On Fri, 08 Aug 2003 13:31:25 -0400, Jerry Avins <jya@ieee.org> wrote: > > > > > ... It has been one of my enduring regrets > > >that I didn't ask to keep the bulb. It was probably thrown out. > > > > > >Jerry > > > > I think that one may have been intended for an embassy somewhere... > > > About a year later, I read about such a bulb in QST. The author believed > that Edison-effect electrons excited a self broad-band resonance in the > doubly coiled filament, sustaining oscillation by a mechanism I forget, > but that seemed reasonable at the time. Incandescent lamps are filled > with low-pressure nitrogen to avoid damage from the Edison effect, and > interaction with the gas figured in his explanation. It was that > explanation that led me to build an open-air triode. I was surprised as > anyone when that worked, and I took it as a confirming instance for the > now-forgotten explanation.
Open-air triode?? Do tell, you have me fascinated... Rob
Reply by Jerry Avins August 9, 20032003-08-09
Frank Dinger wrote:
> > >>Without saying anything, I went over to the > > >stairway switch and turned it on and off a few times. "On" caused the > > >interference. When we swapped the bulb with one in a floor lamp, the > > >floor lamp caused the same interference. It has been one of my enduring > > >regrets that I didn't ask to keep the bulb. It was probably thrown out. > ================ > That bulb was probably an old coiled 'Edison' type . They were /are known to > form a tuned circuit resonating in the old TV band 1 ( about 48 - 62 MHz) > acting as a TX when power is applied. > > Frank GM0CSZ / KN6WH
Thank you thankyouthankyou! I've been called a crazy liar more than once over that bulb. There was no channel 1 when that incident happened, but I suppose that a small change of geometry could raise the frequency. The explanation in QST had it that the frequency was swept over a fairly large range as the voltage varied during a cycle. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Jerry Avins August 9, 20032003-08-09
Eric Jacobsen wrote:
> > On Fri, 08 Aug 2003 13:31:25 -0400, Jerry Avins <jya@ieee.org> wrote: > > > ... It has been one of my enduring regrets > >that I didn't ask to keep the bulb. It was probably thrown out. > > > >Jerry > > I think that one may have been intended for an embassy somewhere... >
About a year later, I read about such a bulb in QST. The author believed that Edison-effect electrons excited a self broad-band resonance in the doubly coiled filament, sustaining oscillation by a mechanism I forget, but that seemed reasonable at the time. Incandescent lamps are filled with low-pressure nitrogen to avoid damage from the Edison effect, and interaction with the gas figured in his explanation. It was that explanation that led me to build an open-air triode. I was surprised as anyone when that worked, and I took it as a confirming instance for the now-forgotten explanation. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;