For me it was interesting enough that it was a SMPS giving 10uv of noise in 10v output, as the engineer said.He didn't say anything about the bandwidth...most probably it must be about a very reasonable bandwidth working with deflecting an x-ray laser...
CG etc.
Thanks. I don't really expect a microphone to emit much at all. I want to see if it picks up energy and demodulates it or even if the noise level increases. From acoustics we would us an echoic chamber to create a uniform noise field.
So my first pass will be a 6 dB pad into a loop inside the box. I can measure a with a small bit of accuracy RF levels inside the box. It should be easy to modulate the test signal and see if anything nasty comes out of the DUT.
Bill I actually have some circulators around that should handle the power! So I suspect I will use an attenuator into an SWR bridge into the circulator first to get a feel for safety. I only have one amplifier. (Need to look may have a few more. A minor problem with a shop size that I express in acres.)
Thanks. I don't really expect a microphone to emit much at all. I want to see if it picks up energy and demodulates it or even if the noise level increases. From acoustics we would us an echoic chamber to create a uniform noise field.
So my first pass will be a 6 dB pad into a loop inside the box. I can measure a with a small bit of accuracy RF levels inside the box. It should be easy to modulate the test signal and see if anything nasty comes out of the DUT.
Bill I actually have some circulators around that should handle the power! So I suspect I will use an attenuator into an SWR bridge into the circulator first to get a feel for safety. I only have one amplifier. (Need to look may have a few more. A minor problem with a shop size that I express in acres.)
25 years at LLNL. Q clearance. Plenty of test equipment available. Often serial number one. 1 billion dollars a year budget will get you anything you need. Back when a billion was a lot of money. The budget was being cut - political purposes... redirecting priorities. So, thats when I left. Future possibilities for growth are limited with budget cuts. No big new science programs coming. Bailed out. But the people where great. Pure research. When the money is flowing, there is no better place to work than a national laboratory.
-RNM
🙂
I'll update the docs when I have some time.
(apologies to all that I lead astray on that one)
Your stuff is great, a lot of time to invest just to help educate others. On the comment on Barrie Gilbert, the article was sort of a teaser (I think) that was supposed to lead into a lot more on his real passion which was current mode circuits. Not necessarily what we are talking about here but Log-amps and VGA's, and other translinear circuits.
I dont know how anyone can make ac line filters without test equipment. It isnt CAD-able unless you know the Z's and freqs of interest to be removed/atten.
I think a lot of negative issues could be reduced if cable design and shield grounds where done differently. but also power grounding between and within equipment.
A typical coax cable is grounded as shown in Fig A and C with little effectiveness. [see 17735]
Here we have a power filter which isnt grounded properly also.... with and without ground.
View attachment Fltr gnd and ungnd.pdf
Here is a cheap Panamax and their better model (I have dozens of brands and models tested):
View attachment Panamax 500 and 1000.pdf
and one of my early first attempts (patented) ac line filter designs:
View attachment Z filter.pdf
THx-RNMarsh
I think a lot of negative issues could be reduced if cable design and shield grounds where done differently. but also power grounding between and within equipment.
A typical coax cable is grounded as shown in Fig A and C with little effectiveness. [see 17735]
Here we have a power filter which isnt grounded properly also.... with and without ground.
View attachment Fltr gnd and ungnd.pdf
Here is a cheap Panamax and their better model (I have dozens of brands and models tested):
View attachment Panamax 500 and 1000.pdf
and one of my early first attempts (patented) ac line filter designs:
View attachment Z filter.pdf
THx-RNMarsh
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RNM,
It is very easy to make power line filters without any test equipment. I can only assume you mean ones that actually work!🙂
My Monday project is to make a pair of broadband antennas, pretty much the inverse project. The design is in theory simple, a tapped antenna to essentially be a series of tuned and filtered antennas. A pair is needed to tune by reciprocity. As I don't think there are accurate models of the antenna's core material, simulation is of limited use. Test and cut is actually pretty simple as once one section works, it is just scaling to ballpark the rest. Then comes the tweaking.
For real fun one day I will build an antenna tuned by varicaps! The DSP tracker should be interesting.
It is very easy to make power line filters without any test equipment. I can only assume you mean ones that actually work!🙂
My Monday project is to make a pair of broadband antennas, pretty much the inverse project. The design is in theory simple, a tapped antenna to essentially be a series of tuned and filtered antennas. A pair is needed to tune by reciprocity. As I don't think there are accurate models of the antenna's core material, simulation is of limited use. Test and cut is actually pretty simple as once one section works, it is just scaling to ballpark the rest. Then comes the tweaking.
For real fun one day I will build an antenna tuned by varicaps! The DSP tracker should be interesting.
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I think this is what you want to fabricate: GTEM cell - Wikipedia not just a box. How big is your amp? Up to what frequency? If you can get to 2.4 GHz you can also use it as a microwave oven. . .
And if your time has any value this make a lot of sense: FCC TEM Cell Transverse Electromagentic Cell DC to 1600 MHz | eBay
While I find the inputs about optimum toplogies pertinent, I feel that they are incomplete without 'stage count' added in. Now, to me is how many devices are in series with the input-output signal, tubes, fets, bipolars used as a gain stage count 1, followers, differential, or cascodes of any kind count 1/2. All else being equal, lowest stage count should be better. This keeps some designers from 'piling on' added devices like Darlingtons, extra followers, etc everywhere as they add to 'stage count'. Check it out with your circuits.
Save yourself some trouble- buy a 2G GSM cellular module or eval board and an antenna. Put it in debug mode and blast the DUT with 33 dBm in the GSM low band. If your DUT doesn’t sing or stop working then congratulations. GSM is 217 Hz TDM.
Thanks Demian,
I found a nice diy guide!
https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/5632/research.pdf?sequence=3
Will actually be faster to build this in my shop than to order one! Really!! My guess is under an hour.
I suspect I will be able to build the chamber, antennas and turn it on Monday. Will post a picture.
Thanks again,
ES
I found a nice diy guide!
https://mospace.umsystem.edu/xmlui/bitstream/handle/10355/5632/research.pdf?sequence=3
Will actually be faster to build this in my shop than to order one! Really!! My guess is under an hour.
I suspect I will be able to build the chamber, antennas and turn it on Monday. Will post a picture.
Thanks again,
ES
There is no better place for creativity and discoveries than when people who create do not depend from people that paid them ;-)
An other law of the good old west: "Simple is beautiful."
Relative to 'stage count' current feedback amps can be better than voltage feedback amps, just because they remove the differential input. However, it also shows where jfets can be better, because they are intrinsically high Z, compared to bipolars, and their quietest noise operation is higher current, rather than a relatively low operating current.
Often, more practical compromises must be added, like extra followers, and cascodes, but consider the tradeoff.
The folded cascode is dependent on a 'current source', either active or resistive to make it work. It is not a load resistor as such. IF you can make a quiet current without too much noise gain or distortion, it is best, because it greatly improves the POWER SUPPLY REJECTION. If you do use a resistor, then a very quiet power supply is absolutely necessary for phono, not so much for line. Charles Hansen also knew this tradeoff when we made our designs, but we thought the folded cascode better than the typical added second stage. Sometimes, it is better to compromise, depending on the tradeoffs, like buildability, (by non-experts), power supply rejection improvement, etc. This is how I designed the A-I phono stage (non-cascode and second stage with gain)
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I think that the best phono preamps ever made with silicon are actually voltage feedback, but it's a matter of opinion.
I highly doubt that there was a single design in the diyaudio world better than Kenwood l-02a (made by Kensonic for Kenwood-the Accuphase engineers in fact).The whole amp is a gem actually and few other amps were ever built better and smarter.
I highly doubt that there was a single design in the diyaudio world better than Kenwood l-02a (made by Kensonic for Kenwood-the Accuphase engineers in fact).The whole amp is a gem actually and few other amps were ever built better and smarter.
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