I will and thanks.
I think I have decided to build something I can buy boards for. I know there are several of those about. The store here has some, I saw a post where someone is building a Doug Self preamp that has boards available. Mr. Curl suggested I could buy boards from clone of one of his designs.
Do you have any thoughts of what you might buid if you didn't want to make boards and didn't want to point-to-point of breadboard either?
You at least try to provide some explanation.
Some others take it for granted.
I will ask. The BH curve nonlinearity and the permeability’s dependence on H field strength are phenomena known on x-former cores.
Assuming audio x-formers (input, coupling, output) have been used, studied and optimized for decades, where is the data quantifying the harmonic distortion generation due to these nonlinearities of ferromagnetic materials? (links, reference)
The shielding effect a metal provides on magnetic fields, is more or less achieved by the eddy currents generated within it.
Electrical conductivity and magnetic permeability play an equal importance on the eddy’s -counter -magnetic field strength.
Among different –ferrous and non ferrous- metals, electrical conductivity varies a hundred fold. Magnetic rel. permeability varies some ten thousand fold.
Therefore, for low freq. fields (50/60Hz and harmonics), substituting non ferrous for ferrous shields, one has to increase the shield thickness two to four orders of magnitude for to achieve equal shielding effects.
Rel. distance: By old ARRL handbooks, the distance of a metal shield from a HF coil had to be minimum 3 coil diameters for the Q of the coil to be affected by less than 10% (from memory).
Hey, maybe there's a 747 vertical stabilizer available out there on E bay. Maybe a group buy??
Still, some may take it seriously.
Free trading and unregistered procurement is illegal
(material controlled by the national AECs)Even thick primer paint hinters alpha. You are left to deal with the gamma.
Some 15 years ago the old balance weights had to be progressively replaced with tungstenium ones. The problem with depl. Ur. weights was with inter-granular corrosion.
Where attacked, depl. Ur. turned into thin, gray dust.
Once inhaled, alpha was eating you from inside.
George
Steel was way cheaper and stronger. And it was sometimes coated with Cadmium. Ooops. Another toxic metal that people managed to survive. It was interesting when it developed a whitish coating. The old JBL SA600 had cad-plated RCA connectors. When my father's developed loud hum, he was sure it was an electrolytic that had to "re-form", and would cycle the power, after which many times the hum was gone, or at least lower-level enough to be tolerable. When I inherited the piece I finally realized that the cycling just induced an oxide-penetrating transient that restored the RCA shell and/or tip connection.
Then is the danger for the population (users)
Sacrificial anodic coating turned into (toxic) sticky dusty oxide (Avoid "Scratch and smell").
George
It would be interesting, possibly horrifying, to be able to find out what happened to some of the people who worked soldering cad-plated chassis with lead-bearing solder for my father's companies over the years. He himself used to carry bits of Pb-Sn solder around in his pockets along with change and car keys.
Like I did.
I got used to when something is picked up as being more dangeropus than lots of other more dangerous things that means somebody wants to benefit from it. Like, asbestos had been declared most harmful in the building industry when the source of it left in Soviet Union mostly.
When I used to work at the bench a lot my geochemist grad student friend, who was doing a study about lead pollution due to tetraethyl lead in motor fuel, saw the smoke from the rosin core solder coming off of my iron. He asked me for a sample of the solder, which was Ersin Multicore.
He called me with some excitement. Mass spectrometry revealed that the isotopic constituency of the solder allowed its mines of origin to be identified as ones in Australia, unlike the lead added to gasoline. He wondered if I could spare a blood sample?
If I'd realized how much blood was involved I'd probably have declined, but went through with it. He returned with an analysis: I was well below the levels considered to be dangerous, but about 1/4 of the lead in my blood was indeed from the solder. The rest was just what was expected from living in Los Angeles, and not particularly close to a freeway
I was a little more careful to have the fumes vented away after that.
As Chris Knight (Val Kilmer) says in Real Genius: "In the immortal words of Socrates, 'I drank WHAT?' "
Mad hatters all.
It's paradoxical that the Winged Messenger should be associated with dementia.
The reason that Gold has such high value
is primordial memories of it's ingestion.
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Only those with no particular knowledge of chemistry and a willingness to believe quacks.
I would have to google for links, I do not have any available.You at least try to provide some explanation.
Some others take it for granted.
I will ask. The BH curve nonlinearity and the permeability’s dependence on H field strength are phenomena known on x-former cores.
Assuming audio x-formers (input, coupling, output) have been used, studied and optimized for decades, where is the data quantifying the harmonic distortion generation due to these nonlinearities of ferromagnetic materials? (links, reference)
However, that said..Amperes law states the magnetic field (B) around an electric current is proportional to that current. And Faraday's law states that the voltage generated in a loop of wire is proportional to the rate of change of (B) flowing through the loop.
Neither law invokes H, so if H is a non linear function, it does not directly impact either Ampere's law nor Faradays. So that's how I'd explain it, if I knew what I was talking about...
The non linearity of a BH curve will certainly impact the inductance of the system, and when you start to saturate, that inductance will drop. All these factors will come into play with the primary current, so the IR drop and varying impedance of the primary to its driver can cause all kinds of nasties..
BTW, I looked up hyperphysics to confirm what I've said w/r to Ampere and Faraday..really nice site, University of Georgia I believe..
For all conductive shields, you are correct. Materials with a relative permeability above 1 will start to direct the magnetic field along the metal bulk also. Unfortunately, as the field increases, the permeability will change, this is the distortion part.. Mu metal, while extremely high in relative permeability, saturates at very low levels. At half a tesla, it's useless. At half a gauss (earths magnetic field approx..) it's great, you can make a zerofield box really easy..
BTW, when a sheet of magnetic material is conducting time varying currents, as the frequency rises, the current density profile will change. At higher frequencies, the current will pinch to only part of the sheet, that path being the path which provides the lowest system reactance. If that path goes past sensitive input circuitry or ground reference wires going to the system star, oh well.
Unfortunately, in the days of vacuum tubes and high impedances, that was not so prominent. Once we went solid state and low impedances, this effect really raised it's ugly head.
Absolutely accurate.
Accurate as well in concept, I don't have the ARRL handbook. The Q in that application will depend on the combination of inductance and reistance of the coil. Using a standard Ls/Rs model, the Rs is the in phase loss of the system when driven sinusoidal. This measurement is also dependent on the losses caused by materials nearby which create eddy current losses. So for any inductor, proximity to a non ferrous metal will lower the system inductance, and raise the system losses. Modification of Q as it were.
jn
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