Tarmo Tammaru wrote:> > Dave, > > Thanks for the info. In my case, the source seems to be a bank of 4 > transformers on a pole about 300 feet away. Weirdest thing I had was S9 > white noise from about 40 to 55 MHz with about 50% amplitude modulation at > around 50 KHz. Turned out to be a 60 amp cartridge fuse in my fuse box about > to go bad. I think the 50 KHz was a mechanical resonance in the fuse. >... There are lots of weird noise sources. As a kid in the 40s, I was part of a family visit to an old farm west of Bethlehem Pa., in what was definitely "fringe area" TV reception. The man of the house was telling my father about the strong zig-zag pattern that sometimes showed up on the screen, blanking out the video and often lousing up vertical synch. He wanted to know if the FCC would track down the interference; he thought it was a ham about half a mile away. Just then, the interference started, and right after, his son came downstairs to join us. A little while later, his daughter went upstairs, and the interference cleared when she got to the top. 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. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Automatic RF noise cancellation and audio noise measurement
Started by ●August 5, 2003
Reply by ●August 8, 20032003-08-08
Reply by ●August 8, 20032003-08-08
Tam- never had much luck with one got (also 6 meter op), but , also, BEWARE if into weak signal stuff - has 6 dB LOSS on recieve (DC bands, who cared, background noise worse than that, but at VHF ???) If you want one, make you good deal! Jim NN7K Tam wrote:> Randy, > > Thanks for your response. The obvious thing you would like to do is tohave> the software be smart enough to distinguish between signal and noise. But > then the hardware becomes moot, and you have invented a better DSP noise > reduction circuit. > > BTW, I am considering getting an ANC4 to get rid of power line noise on 6 > meters. Fortunately, the noise is coming from the North, a very seldomused> beam heading. > > Tam/WB2TT > >
Reply by ●August 9, 20032003-08-09
On Fri, 08 Aug 2003 13:31:25 -0400, Jerry Avins <jya@ieee.org> wrote:>Tarmo Tammaru wrote: >> >> Dave, >> >> Thanks for the info. In my case, the source seems to be a bank of 4 >> transformers on a pole about 300 feet away. Weirdest thing I had was S9 >> white noise from about 40 to 55 MHz with about 50% amplitude modulation at >> around 50 KHz. Turned out to be a 60 amp cartridge fuse in my fuse box about >> to go bad. I think the 50 KHz was a mechanical resonance in the fuse. >> > ... > >There are lots of weird noise sources. As a kid in the 40s, I was part >of a family visit to an old farm west of Bethlehem Pa., in what was >definitely "fringe area" TV reception. The man of the house was telling >my father about the strong zig-zag pattern that sometimes showed up on >the screen, blanking out the video and often lousing up vertical synch. >He wanted to know if the FCC would track down the interference; he >thought it was a ham about half a mile away. Just then, the interference >started, and right after, his son came downstairs to join us. A little >while later, his daughter went upstairs, and the interference cleared >when she got to the top. 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. > >JerryI think that one may have been intended for an embassy somewhere... Eric Jacobsen Minister of Algorithms, Intel Corp. My opinions may not be Intel's opinions. http://www.ericjacobsen.org
Reply by ●August 9, 20032003-08-09
>>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
Reply by ●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. �����������������������������������������������������������������������
Reply by ●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 / KN6WHThank 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. �����������������������������������������������������������������������
Reply by ●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 ●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 ●August 10, 20032003-08-10
Rob Judd wrote:>...> Open-air triode?? Do tell, you have me fascinated... > > RobI 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. �����������������������������������������������������������������������
Reply by ●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. �����������������������������������������������������������������������
