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1N4007 varactors
The common 1N4007 seem to work for HF but what is the max. frequency they
can be used as varactors? And how about zener diodes? JE |
1N4007 varactors
On Sat, 07 Jan 2006 17:26:23 -0500, JE wrote:
The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? I'd expect that all to depend on manufacturer (and, even, date code.) HNY es 73 Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK |
1N4007 varactors
JE wrote:
The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? JE I suspect any si diode will work to some extent as a varicap or zener. Not all diodes will be stable as zeners, the 1N506x series will probably work better as a zeners than the 1n400x series. BTW the 1n5061 will work as an 850v zener! Also the 1n4007 makes a good poor man's PIN diode for switching rf. |
1N4007 varactors
On Sat, 07 Jan 2006 17:26:23 -0500, JE wrote:
The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? I've used them at low VHF, the limiting factor there is minimum capacitance my be too high for some VHF uses. And how about zener diodes? As varicaps? Some are ok some very poor. You require a breakdown voltage well above the applied bias. Allison |
1N4007 varactors
Maybe 2N4401 will work, I built some simple 1 transistor FM transmitters
that modulate the base. If not, who sells dual varactors in small quantities? JE On Sat, 07 Jan 2006 17:26:23 -0500, JE wrote: The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? I've used them at low VHF, the limiting factor there is minimum capacitance my be too high for some VHF uses. And how about zener diodes? As varicaps? Some are ok some very poor. You require a breakdown voltage well above the applied bias. Allison |
1N4007 varactors
Why not just use a varactor... as a varactor... LOL
They are available in small quanities at www.mouser.com searchword "varactor"... Professor www.telstar-electronics.com |
1N4007 varactors
Since the 1N4007 isn't a dual, why do you require a dual varactor? I'd
expect diodes specifically made to be varactors would have less variation from part to part with respect to capacitance than would some other random diode. Have you tried Mouser (as Professor suggests) or DigiKey, or some of the surplus places like MPJA? I've heard that 1N4007s commonly make decent PIN diodes. If that's the case, if they really are made as a PIN structure, I would think they'd make lousy varactors. Wide-tuning-range varactors are commonly "hyper-abrupt" junctions, NOT PINs. Cheers, Tom |
1N4007 varactors
Maybe I'm confusing this with something else but I always thought 1N4007's
were 1000 V PIV, 1 A rectifiers. I believe "any" diode has varactor characteristics to some extent but if you need a varactor you'd be better off using one designed as a varactor. Dr. G. In article , JE wrote: The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? JE |
1N4007 varactors
Dr. Grok wrote:
Maybe I'm confusing this with something else but I always thought 1N4007's were 1000 V PIV, 1 A rectifiers. I believe "any" diode has varactor characteristics to some extent but if you need a varactor you'd be better off using one designed as a varactor. Dr. G. In article , JE wrote: The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? JE All diodes exhibit varactor and zener traits but not all are stable as such. All diodes when reverse biased exhibit a value of capacitance across them. In most cases it's usually quite small, less than 5 to 10pf. Increase the reverse bias and the capacitance goes down. At very high frequencies the capacitance change is enough to make a useful tuning diode. If you need a varactor to work at medium to high frequencies the tuning effect won't be very useful and you should use a true varactor diode. Such diodes have either larger areas, or thinner substrates to increase th capacitance. Any diode will work as a Zener, the zener voltage is where the reverse breakdown occurs. In a true Zener, the breakdown voltage is stable over a large range of current without the diode self destructing. Using a common diode as a zener requires limiting the reverse current to a small value, but if the current isn't large enough the zener voltage won't be stable. And yes the 1n4007 is a 1000 vpiv rectifier diode. It also makes a good rf switching diode thanks to it's PIN like structure. It's also quite cheap. |
1N4007 varactors
Ken Scharf wrote:
All diodes exhibit varactor and zener traits but not all are stable as such. All diodes when reverse biased exhibit a value of capacitance across them. In most cases it's usually quite small, less than 5 to 10pf. Increase the reverse bias and the capacitance goes down. At very high frequencies the capacitance change is enough to make a useful tuning diode. If you need a varactor to work at medium to high frequencies the tuning effect won't be very useful and you should use a true varactor diode. Such diodes have either larger areas, or thinner substrates to increase th capacitance. . . . Zener diodes have much more capacitance than this, with the amount of C being greater as the zener voltage gets lower. It's been a long time since I've looked at this, but as I recall you can get well over 100 pF from something like a 5 V zener. For the same reason, reverse biased E-B junctions can give quite a bit of C. Of course, the limited breakdown voltage limits your tuning range. Higher power zeners have higher C yet. I've used zeners for varicaps many times in HF rigs, to offset a VFO when switching bands, and for RIT. Haven't tried one as the main tuning capacitor, but I haven't tried a regular varicap, either. Diodes specified for varicap use have more predictable capacitance-vs-voltage characteristics, and you can get a variety of different characteristics. They might have lower noise, too, but I've never used one in an application where that was critical, so don't know if that's the case. But for a lot of one-off projects, zeners work fine as varicaps. As for using something else as zeners, emitter-base junctions work well. You don't get much variety, though -- most break down at around 5-6 volts. I've got a power supply I built over 30 years ago which uses a couple of series transistor E-B junctions as the voltage reference. It's still my main bench supply. Roy Lewallen, W7EL |
1N4007 varactors
It was just that they are dirt cheap and available.
I'll pony up for real ones. JE |
1N4007 varactors
On Mon, 09 Jan 2006 23:38:29 -0500, JE wrote:
It was just that they are dirt cheap and available. I'll pony up for real ones. JE I'd go with try it first. Also base collector junction of many transistors is fairly decent varactor. Low power transistors tend to be low capacitance and the amount of capacitance increases with device dies size (power level). Allison |
1N4007 varactors
Dr. G,
You are correct, but many circuits have used the 1N4000 series diodes as varactors with acceptable results. Any diode is a varactor (even transistor junctions), but those called varactors are just optimized for and measured/spec'ed as variable caps. If the cap value works in the circuit and losses/noise/whatever-else aren't a problem, then no problem. I chalk it up to: Some of us don't have the luxury of either well stocked basements or pocket books, or perhaps the willingness to run out to the local parts store (if you have one) and pick something out just to throw some neat little thingy together. Don't (some) zeners generate noise???...or is that only near the breakdown reigion? 73, Steve, K.9/D;C'I "Dr. Grok" wrote in message ... Maybe I'm confusing this with something else but I always thought 1N4007's were 1000 V PIV, 1 A rectifiers. I believe "any" diode has varactor characteristics to some extent but if you need a varactor you'd be better off using one designed as a varactor. Dr. G. In article , JE wrote: The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? JE |
1N4007 varactors
Steve Nosko wrote:
. . . Don't (some) zeners generate noise???...or is that only near the breakdown reigion? Some are very noisy. The noisiest I've seen have been ones in the 12 - 15 volt range when biased at considerably less than a mA. I've used one, followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to see filter responses with a spectrum analyzer. The noise is easily visible well up into the UHF region. But all zeners generate some noise, so you have to use appropriate filtering in sensitive applications. In my experience, though, band gap references can be even noisier than a typical zener. Roy Lewallen, W7EL |
Zener Noise (was: 1N4007 varactors)
Roy ...
I've been playing around (ahem, excuse me, heuristically engineering) with zener noise sources for a while using the same spectrum analyzer trick and as yet I haven't been able to make the noise as "flat" across the passband as I'd like. I've tried varying the bias, the voltage, and a few other tricks, but as yet, no joy. Can you shed some light on what you've found to make the noise power/voltage fairly level across the band? Jim Some are very noisy. The noisiest I've seen have been ones in the 12 - 15 volt range when biased at considerably less than a mA. I've used one, followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to see filter responses with a spectrum analyzer. The noise is easily visible well up into the UHF region. But all zeners generate some noise, so you have to use appropriate filtering in sensitive applications. In my experience, though, band gap references can be even noisier than a typical zener. Roy Lewallen, W7EL |
Zener Noise
RST Engineering wrote:
Roy ... I've been playing around (ahem, excuse me, heuristically engineering) with zener noise sources for a while using the same spectrum analyzer trick and as yet I haven't been able to make the noise as "flat" across the passband as I'd like. I've tried varying the bias, the voltage, and a few other tricks, but as yet, no joy. Can you shed some light on what you've found to make the noise power/voltage fairly level across the band? It's not particularly flat over the whole band, and I haven't attempted to make it be. My interest has been mostly in relatively narrow band filters, or the shape of a main filter rolloff. The noise is adequately flat over the bandwidths I've been interested in. It's been a while since I've fooled with it, but as I recall, the shape of the noise spectral distribution changed all over the map as I changed the diode bias. I imagine that it changes with temperature and with individual diodes, too. So any circuit used to flatten it would only work for a particular diode, current, and probably temperature. The bottom line is that it's probably a lousy way to try to generate a flat broadband noise spectrum. Roy Lewallen, W7EL |
Zener Noise (was: 1N4007 varactors)
RST Engineering wrote...
Roy ... I've been playing around (ahem, excuse me, heuristically engineering) with zener noise sources for a while using the same spectrum analyzer trick and as yet I haven't been able to make the noise as "flat" across the passband as I'd like. I've tried varying the bias, the voltage, and a few other tricks, but as yet, no joy. Can you shed some light on what you've found to make the noise power/voltage fairly level across the band? Good zener noise sources are carefully bred and tested, they do _not_ come naturally from garden-variety zener diodes. I suggest you go read the hundred or so messages in the famous zener oscillation thread a few years back here on s.e.d. In this you'll learn of my substantial investigations into the topic, some physics - and, very important, learn what a zener microplasma is. You'll see my ASCII waveform plots of actual bench measurements showing exactly what's going on. After all this you may decide to avoid using zener diodes for calibrated noise sources. Sorry about that! -- Thanks, - Win |
Zener Noise
RST Engineering wrote:
Roy ... I've been playing around (ahem, excuse me, heuristically engineering) with zener noise sources for a while using the same spectrum analyzer trick and as yet I haven't been able to make the noise as "flat" across the passband as I'd like. I've tried varying the bias, the voltage, and a few other tricks, but as yet, no joy. Can you shed some light on what you've found to make the noise power/voltage fairly level across the band? Jim Some are very noisy. The noisiest I've seen have been ones in the 12 - 15 volt range when biased at considerably less than a mA. I've used one, followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to see filter responses with a spectrum analyzer. The noise is easily visible well up into the UHF region. But all zeners generate some noise, so you have to use appropriate filtering in sensitive applications. In my experience, though, band gap references can be even noisier than a typical zener. Roy Lewallen, W7EL What I did for some project which needed equal amplitude uncorrelated noise,is amplify the zener noise with a wide band video opamp,with high pass and lowpass filtering. Used the low pass as input for a zero cross detector, delayed the zerocrossing 10 microseconds,and used that for clock to a circulating bit in a shift register. each parallel output of that register controlled a sample/hold opamp,sampling the highpass signal. Voila!! 8 audio frequency, non-correlated noise sources. The zerocrossing clock was made this way,to avoid detectable clock tones int the output.(2 to 20 microsec between crossings) the 10 microsecond delay was used to get a voltage at the sample and hold opamp which was not correlated to the zerocrossing. If you need only one signal ,leave out the shift register, and just use a 10 and a 1 microsec. oneshot for the s/h opamp clock. The application? A wind and engine noise generator for a car simulator. |
Zener Noise (was: 1N4007 varactors)
On Tue, 10 Jan 2006 14:30:01 -0800, "RST Engineering"
wrote: Roy ... I've been playing around (ahem, excuse me, heuristically engineering) with zener noise sources for a while using the same spectrum analyzer trick and as yet I haven't been able to make the noise as "flat" across the passband as I'd like. I've tried varying the bias, the voltage, and a few other tricks, but as yet, no joy. Can you shed some light on what you've found to make the noise power/voltage fairly level across the band? Jim Some are very noisy. The noisiest I've seen have been ones in the 12 - 15 volt range when biased at considerably less than a mA. I've used one, followed by a 50 ohm amplifier "pill" IC, as a broadband noise source to see filter responses with a spectrum analyzer. The noise is easily visible well up into the UHF region. But all zeners generate some noise, so you have to use appropriate filtering in sensitive applications. In my experience, though, band gap references can be even noisier than a typical zener. Roy Lewallen, W7EL These folks will sell you serious noise diodes... http://www.noisecom.com/NC/default.htm John |
1N4007 varactors
Zeners are also often used as noise sources, which might be a good reason NOT
to use them for the tuning, especially in a receiver. Dr. G. In article , Roy Lewallen wrote: Ken Scharf wrote: All diodes exhibit varactor and zener traits but not all are stable as such. All diodes when reverse biased exhibit a value of capacitance across them. In most cases it's usually quite small, less than 5 to 10pf. Increase the reverse bias and the capacitance goes down. At very high frequencies the capacitance change is enough to make a useful tuning diode. If you need a varactor to work at medium to high frequencies the tuning effect won't be very useful and you should use a true varactor diode. Such diodes have either larger areas, or thinner substrates to increase th capacitance. . . . Zener diodes have much more capacitance than this, with the amount of C being greater as the zener voltage gets lower. It's been a long time since I've looked at this, but as I recall you can get well over 100 pF from something like a 5 V zener. For the same reason, reverse biased E-B junctions can give quite a bit of C. Of course, the limited breakdown voltage limits your tuning range. Higher power zeners have higher C yet. I've used zeners for varicaps many times in HF rigs, to offset a VFO when switching bands, and for RIT. Haven't tried one as the main tuning capacitor, but I haven't tried a regular varicap, either. Diodes specified for varicap use have more predictable capacitance-vs-voltage characteristics, and you can get a variety of different characteristics. They might have lower noise, too, but I've never used one in an application where that was critical, so don't know if that's the case. But for a lot of one-off projects, zeners work fine as varicaps. As for using something else as zeners, emitter-base junctions work well. You don't get much variety, though -- most break down at around 5-6 volts. I've got a power supply I built over 30 years ago which uses a couple of series transistor E-B junctions as the voltage reference. It's still my main bench supply. Roy Lewallen, W7EL |
1N4007 varactors
Dr. Grok wrote:
Zeners are also often used as noise sources, which might be a good reason NOT to use them for the tuning, especially in a receiver. You mean that a zener diode biased at less than breakdown voltage generates more noise than a diode specified for varactor use biased at less than breakdown? I assume this noise would be in the form of time jitter of the capacitance, since the leakage current would be very small. Have you seen this in some specification, or is it from experience? Roy Lewallen, W7EL |
1N4007 varactors
|
Zener Noise (was: 1N4007 varactors)
...the famous zener oscillation thread a few years back
...my ASCII waveform plots of actual bench measurements showing exactly what's going on. Winfield Hill http://groups.google.com/group/sci.e...lation&f wc=1 |
1N4007 varactors
Steve Nosko wrote:
(snip) Don't (some) zeners generate noise???...or is that only near the breakdown reigion? I think that whether noisy or not, the noise generation mechanism kicks in, only when the zeners are reverse conducting via the zener breakdown process, so if you keep the voltage well below the zener knee, say, half of that, they are not particularly noisy compared to other diodes. So, yes, only near the breakdown region, especially just below the rated voltage (low reverse current). |
Zener Noise (was: 1N4007 varactors)
JeffM wrote...
...the famous zener oscillation thread a few years back ...my ASCII waveform plots of actual bench measurements showing exactly what's going on. Winfield Hill http://groups.google.com/group/sci.e...lation&f wc=1 That's one thread, perhaps the first in a series. That thread doesn't have the waveforms I was referring to (although there are some waveforms in posts 51 and 66). Tony, Bill, Roy and I, and some others here wasted masses of time on this subject over a period of a few months, eight and a half years ago. We took bench measurements, did calculations, found the scientific literature (it was a subject that occupied physicists in the late 50s, see posts 72-76), and we did plenty of speculation. -- Thanks, - Win |
1N4007 varactors
....impossible to tell! nobody ever characterized them for high
frequency use. the usual effects of the varactor are pernicious! they are crucial for low phase noise of the VCO using them. the only truly effective way to check is build one and measure the performance with a spectrum analyzer or a phase noise meter, both expensive items. my recommendation is to build one and try to listen to its signal on a receiver (stable one!), if the note is clean and not ragged it's OK. if not the VCO is too noisy for use. don't be afraid to check more than one diode in the same circuit. experience has shown that some units perform better than others. Saandy 4Z5KS JE wrote: The common 1N4007 seem to work for HF but what is the max. frequency they can be used as varactors? And how about zener diodes? JE |
Zener Noise (was: 1N4007 varactors)
Winfield Hill wrote...
JeffM wrote... Winfield Hill wrote... ...the famous zener oscillation thread a few years back ...my ASCII waveform plots of actual bench measurements showing exactly what's going on. http://groups.google.com/group/sci.e...lation&f wc=1 That's one thread, perhaps the first in a series. That thread doesn't have the waveforms I was referring to (although there are some waveforms in posts 51 and 66). Tony, Bill, Roy and I, and some others here wasted masses of time on this subject over a period of a few months, eight and a half years ago. We took bench measurements, did calculations, found the scientific literature (it was a subject that occupied physicists in the late 50s, see posts 72-76), and we did plenty of speculation. All of which led Roy McCammon to remark (post 90), "I'd have to say that it is the best thread this year." He said that Aug 5th, after 3 weeks of posts, and yet the followup threads in Aug and Sept on the same topic were just as long, and perhaps even more interesting. Ah, those were that days! -- Thanks, - Win |
1N4007 varactors
"John Popelish" bravely wrote to "All" (10 Jan 06 22:14:12)
--- on the heady topic of " 1N4007 varactors" JP From: John Popelish JP Xref: core-easynews rec.radio.amateur.homebrew:90859 JP Steve Nosko wrote: JP (snip) Don't (some) zeners generate noise???...or is that only near the breakdown reigion? JP I think that whether noisy or not, the noise generation mechanism JP kicks in, only when the zeners are reverse conducting via the zener JP breakdown process, so if you keep the voltage well below the zener JP knee, say, half of that, they are not particularly noisy compared to JP other diodes. So, yes, only near the breakdown region, especially JP just below the rated voltage (low reverse current). I never tested a zener when used as varactor but I think these have a much greater reverse saturation current (even far below breakdown threshold) and it is this that might cause comparatively more noise than a conventional diode with a tiny leakage current. Well, at least that is what the junction noise equations would seem to indicate. A*s*i*m*o*v |
1N4007 varactors
I never tested a zener when used as varactor but I think these have a
much greater reverse saturation current (even far below breakdown threshold) and it is this that might cause comparatively more noise than a conventional diode with a tiny leakage current. Well, at least that is what the junction noise equations would seem to indicate. ============================== Zener diodes are often used as wide band 'noise generators'for use in an impedance bridge used in conjunction with a receiver. Frank KN6WH / GM0CSZ |
Zener Noise (was: 1N4007 varactors)
OK, then. A zener makes a poor noise source according to what I'm reading.
Noise.com used to sell off-spec diodes by the onesies for we poor peons to play with, but for whatever reason that doesn't seem to be the case any more. Given that a zener (at whatever current) is a poor noise source, what is a good source of electronic broadband noise from low HF through high UHF -- say, 5 to 500 MHz.? (No smart remarks about spark gaps.) Jim "Winfield Hill" wrote in message ... We took bench measurements, did calculations, found the scientific literature (it was a subject that occupied physicists in the late 50s, see posts 72-76), and we did plenty of speculation. |
Zener Noise (was: 1N4007 varactors)
On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering"
wrote: OK, then. A zener makes a poor noise source according to what I'm reading. Noise.com used to sell off-spec diodes by the onesies for we poor peons to play with, but for whatever reason that doesn't seem to be the case any more. Given that a zener (at whatever current) is a poor noise source, what is a good source of electronic broadband noise from low HF through high UHF -- say, 5 to 500 MHz.? (No smart remarks about spark gaps.) Jim A hot resistor. How about a thermistor or a lamp filament that was 50 ohms at some high temperature. You could heat it with DC, sense its resistance/temp, and let it make noise, all in a single part. Old vintage noise figure meters used gas tubes. And I think there was a pencil tube that mounted in a waveguide and made shot noise. And, of course, the old photomultiplier trick. John |
Zener Noise (was: 1N4007 varactors)
I have seen a small "gain of wheat" type light bulb used as a noise
source... Feed it with DC through a choke and AC couple the noise out .... and you can vary it too!! Mark |
Zener Noise (was: 1N4007 varactors)
Immediately you say "choke" you have modified and peaked the bandwidth.
I'll buy that you can feed it with a resistor for broadband, but in my humble opinion the construction of a grain of wheat bulb won't get up into the UHF region with noise. Do you have any idea of the output level of this circuit? Jim "Mark" wrote in message oups.com... I have seen a small "gain of wheat" type light bulb used as a noise source... Feed it with DC through a choke and AC couple the noise out .... and you can vary it too!! Mark |
Zener Noise
John Larkin wrote:
On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering" wrote: A hot resistor. How about a thermistor or a lamp filament that was 50 ohms at some high temperature. You could heat it with DC, sense its resistance/temp, and let it make noise, all in a single part. Old vintage noise figure meters used gas tubes. And I think there was a pencil tube that mounted in a waveguide and made shot noise. And, of course, the old photomultiplier trick. I still like the flashlight/photodiode trick. You can get a really good calibration just from the dc, and can calibrate the frequency response with a spark plug. Cheers, Phil Hobbs |
Zener Noise
ORIGINAL MESSAGE:
"Phil Hobbs" wrote snip and can calibrate the frequency response with a spark plug. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I generally use a pipe wrench, but I'll try anything once. Bill, W6WRT |
Zener Noise (was: 1N4007 varactors)
"John Larkin" wrote in message
... Old vintage noise figure meters used gas tubes. And I think there was a pencil tube that mounted in a waveguide and made shot noise. I've got a gaussian noise generator, some SS in the power supply, tubes everywhere else, found it on the curb and apparently works. Uses a pair of 6D4 thyratrons in magnetic fields for the noise. Tim -- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |
Zener Noise (was: 1N4007 varactors)
On Wed, 11 Jan 2006 14:53:07 -0600, "Tim Williams"
wrote: "John Larkin" wrote in message .. . Old vintage noise figure meters used gas tubes. And I think there was a pencil tube that mounted in a waveguide and made shot noise. I've got a gaussian noise generator, some SS in the power supply, tubes everywhere else, found it on the curb and apparently works. Uses a pair of 6D4 thyratrons in magnetic fields for the noise. Tim GR? John |
Zener Noise
On Wed, 11 Jan 2006 14:10:32 -0500, Phil Hobbs
wrote: John Larkin wrote: On Wed, 11 Jan 2006 10:08:19 -0800, "RST Engineering" wrote: A hot resistor. How about a thermistor or a lamp filament that was 50 ohms at some high temperature. You could heat it with DC, sense its resistance/temp, and let it make noise, all in a single part. Old vintage noise figure meters used gas tubes. And I think there was a pencil tube that mounted in a waveguide and made shot noise. And, of course, the old photomultiplier trick. I still like the flashlight/photodiode trick. You can get a really good calibration just from the dc, and can calibrate the frequency response with a spark plug. Cheers, Phil Hobbs What's the light-flash waveform look like from a spark plug? What do you drive it with? Don't you have gobs of femtosecond lasers around your place? John |
Zener Noise (was: 1N4007 varactors)
Try this
http://www.noisecom.com/ "RST Engineering (jw)" wrote in message .. . Immediately you say "choke" you have modified and peaked the bandwidth. I'll buy that you can feed it with a resistor for broadband, but in my humble opinion the construction of a grain of wheat bulb won't get up into the UHF region with noise. Do you have any idea of the output level of this circuit? Jim "Mark" wrote in message oups.com... I have seen a small "gain of wheat" type light bulb used as a noise source... Feed it with DC through a choke and AC couple the noise out .... and you can vary it too!! Mark |
Zener Noise (was: 1N4007 varactors)
"John Larkin" wrote in message
... I've got a gaussian noise generator, ... GR? Come again? Tim -- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |
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