The resistor details can be found in a thread from years ago, nothing special just a high temp beryllium resistor if I remember correctly....
Well, you are sort of correct... wires will collect radio energy. But you need to do the math...
The rub is that the energy is in the form of a wave, so the length of the wire has a great deal to do with what frequency it will efficiently convert from radio waves to electric currents. Typically this is a 1/4 wave length, since one end will have zero voltage and the other will have the peak voltage from the radio wave. The size of the antenna has nothing to do with how well it collects radio frequencies in general. Instead the size determines the frequency that the antenna will efficiently convert from TEM waves in space to TEM waves on a wire. The reason cell phone antennas are small is that cell phones operate at radio frequencies of about 2.4 GHz. The free space wavelength 2.4 GHz is 4.9 inches, so 1/4 wave is about 1.25 inches. Small enough to fit INSIDE the case. The old analog phones operated at about 900 MHz, which has a wavelength of about 13 inches. So those phones needed an antenna about 3 1/4 inches long, so they had a little pull out deal.
10 foot long speaker wires will efficiently collect energy at 24 MHz. The FCC licenses CB radios at that frequency (11 m) . So, that is not anywhere near as heavily used a spectral region as cell phones. Moreover, the harmonics you speak of require a nonlinear element to form. For example, the Taylor series expansion for a the exponential characteristic of a diode (a typical nonlinear element used to create harmonics) is:
So if the radio signal x is given by a generalized sinusoid: x=cos(wt)+jsin(wt), you will get all sorts of components at multiples of w. For example the X^2 term will produce cos^2(wt)+2jSin(wt)cos(wt)-sin^2(wt), which resolves to 1+2jsin(2wt), which is a second harmonic term, plus a DC offset. The higher order terms will produce 3rd, 4th, etc harmonics. Note too that the coefficients in the series are factorials, so the tiger order harmonics fall of very rapidly.
These harmonics may also inter modulate with each other causing higher and lower frequency (since the frequencies will add and subtract according to the sine and cosine sum and difference formulas from basic trig. For example a (2,1) intermodulation product have terms at at 3w and w, a (3,1) product will have tears at 2w and 5w, etc.
However, the reality is that the nonlinearity in a loudspeaker is hopefully near zero. and thus it will not produce much in the way of harmonics.
So, not only will the speaker cable only collect emissions from a little used frequency band, there is no nonlinear element to produce any audible sub-harmonics. In addition, to the extent that there are any such nonlinearities, they will be very minor (one would hope!!) so the already very small radio signals would produce harmonics that are much smaller than the audio signal.
A typical CB radio transmits at about 1 watt (30 dBm). If we assume that that is EIRP measured at 1 meter, then at 10 meters the power will be 20 dB down (10 mW) from that, and at 1000 meters (1 km) it will be an additional 30 dB down (10 uW). The reason we don't get cooked by our microwave oven is, aside from shielding, the signals fall of very rapidly with distance.
If we also assume less than 1% THD in the stereo system (very conservative, BTW) the harmonics would be 20 dB down from the base level of the signal, in this case about 10 uW. This means these harmonics, if they were coupled PERFECTLY (100% efficient antenna) into your system would be 70dB below the original transmitted power level, or 0.1 micro watt (uW)! Given that you may be listening at, say between .5 watts and 2 watts output at any given time, these harmonics, were they to exist at all, would be 20 log(.0000001/2), or -146 dB below the listening signal level.
I suspect there are many other sources of distortion that warrant your attention.
The ferrite beads can't hurt, but I'd be awfully surprised in they made any difference in harmonic distortion, and in fact they might introduce their own coloring through damping and frequency dependent saturation effects.
Scott
No, it doesn't. The RF is not directly affecting the audio signal, it is being mixed with the audio signal.
As an example of one way this can happen, let's say you have a microphone connected to an amplifier through a cable.
A nearby AM transmitter puts out a 1MHz signal amplitude modulated with audio of some guy talking about UFOs. That signal induces an RF voltage in the microphone cable (and pretty much any other wire in the system, the closer the wire is to the wavelength of the RF signal the more voltage will be induced).
Now, the cable is carrying the audio signal from the microphone AND the RF signal from the radio station. Somewhere inside the amplifier a non-linear junction (diode, transistor, bad solder joint) acts as an AM detector, recovering the modulating signal from the RF the same way an AM radio recovers the audio.
You now have the audio from the microphone and the audio of the guy talking about UFOs both being amplified and sent to the speaker.
Here are a few ways to mitigate this problem without enlisting the help of Werner Heisenberg, a snake oil salesman, or a psychic healer...
-Putting a ferrite on the cable will attenuate the RF signal before it gets into the amplifier.
-Shielding the cable will keep the signal out of the cable to begin with.
-Twisted pairs will pick up the RF signal in two conductors which are then connected 180 degrees out of phase so that any signal common to both conductors is canceled.
-Adding a capacitor across the input of the amplifier will shunt the RF signal to ground.
The ferrite bead adds a dissipative load a high frequencies (it enhances the inductance of the wire at the point the wire passes through it, and dissipates the signal). They put them on things like power cords (that little lump on the cable on some devices) to reduce any high frequency noise on the power lines.
The ferrite is saturated at lower frequencies and has little if any effect. You can see here that normal beads are effective in the 100 MHz range. For a CB radio bead (see my other post on this topic) you would need a HUGE bead..
Ferrite Beads Demystified | Analog Devices
Scott
not that any of this has any effect on the price of tea in china...
CB is 27mhz. The legal limit of power input to the final is 5 watts, so 3.5 watts out.
Now all those 200+ watt boosters, that's a different thing and those things have nasty outputs. Luckily CB is all but in the garbage can these days, at least in the USA
CB is 27mhz. The legal limit of power input to the final is 5 watts, so 3.5 watts out.
Now all those 200+ watt boosters, that's a different thing and those things have nasty outputs. Luckily CB is all but in the garbage can these days, at least in the USA
The question was does JB toss traces of these things in his goop to avoid out and out actionable fraud.
All claims of "near" room temperature superconductivity due to random traces of rare earths that have been used in superconducting experiments in the past are lies.
Anyone can buy samples of carbon nanotubes (for example) and mix them in epoxy and coat resistors and then sell them with any outlandish claims they want. Same goes for cryo treatment as long as they paid for the cryo treatment.
That particular mixture was available pre-mixed and was something like $10 a pound. Dirt cheap. The rest of the stuff like the ERS paper (or equivalent) probably costs more.
I did the cryo experiment on all sorts of items, no one could ever tell the difference.
I wasted literally 1000 liters of N2 on these tests. N2 is dirt cheap.
near superconductivity DOES NOT EXIST. Its either a superconductor at a particular temperature, or its not. For a 500mhz magnet operating at 150 amps circulating current, the drift in the field due to the resistance of the superconductor is about 5 hz per day. So to 9 places, the resistance is zero. A 25 ohm anything is not a near superconductor. And neither is .025 ohms.
I did the cryo experiment on all sorts of items, no one could ever tell the difference.
I wasted literally 1000 liters of N2 on these tests. N2 is dirt cheap.
near superconductivity DOES NOT EXIST. Its either a superconductor at a particular temperature, or its not. For a 500mhz magnet operating at 150 amps circulating current, the drift in the field due to the resistance of the superconductor is about 5 hz per day. So to 9 places, the resistance is zero. A 25 ohm anything is not a near superconductor. And neither is .025 ohms.
CMB sets the noise floor of electronic equipment. You can avoid adding additional noise through various heroics (cryogenically cooled amplifiers and such), but you cannot escape the CMB. On the up-side, it is very low level, and, for example on LPs it is about 120 dB below the maximum dynamic range of the LP. For FLAC audio files it is about 50 dB below, and thus barely perceptible. This is, however, why the largest audio DAC you can get is 32 bits. At 32 bits the quantization noise floor is -192 dB, so you have about 18 dB of digital volume control headroom before you start adding noise from the volume control.
Relative to your other statements on radios and AGC: a radio receives small level radio signals by running those signals through a nonlinear element (usually some form of diode). Most radios use a "mixer" which is a specialized diode circuit that allows the intentional mixing of a local signal (called a local oscillator, LO) with the radio signal of interest. The radio usually includes a bandpass filter on the front end to substantially attenuate about of band signals, and when mixed with the LO a pair of signals is produced. One of these signals, known as the intermediate frequency, IF) is then filtered with a very sharp filter, and amplified with a very high gain amplifier. This is where AGC is also used. All AGC does is assure that this amplifier doesn't saturate when the radio signal level is at its highest level, and that the gain is high enough to produce a useful output when the radio signal is at its lowest level.
Your speakers, of course, have none of this equipment, and so, per my other post, they make an incredibly poor radio receiver.
A last point: When electrical signals are laid on top of one another in a linear system, they have ZERO affect on each other. This is a property of linear systems known as superposition:
(Superposition principle - Wikipedia).
Basically the waves just pass through one another, and, in the absence of non-linearity, they will have no affect on each other. For this reason it is important to minimize any non-linearities in the signal handling components (mainly the amplifiers and such), and to shield any wires that the signal passes through PRIOR to any potential nonlinear elements (i.e shielded coax and twisted pairs on phono input lines). OTOH, speakers are passive and are unlikely to include any significant nonlinear elements, especially elements that would present nonlinearities at radio frequencies.
Scott
Last edited:
Thanks for the clarification. And, yes, it doesn't change the situation other than 3-4 dB..
Kevin Gilmore, I remember you. Weren't the guy who told us that there was Cerium in the Bybee and to keep it away from water? I actually tried your warning by taking apart a Bybee, putting it in a metal pan outside, with a fire extinguisher handy and added water. Guess what? Nothing happened and Jack was pissed off that I destroyed a Bybee. Trust but verify! '-)
Yes, it's called NONLINEARITY. If the amplifier can handle the RF signal linearly, either by passing it cleanly or by filtering it, there will not be interference. Lots of good amps do that fine. A non-ferrous wire is outstandingly linear and this effect will not occur in it. Things like tubes and transistors (and for that matter, ferrite) have narrow linear ranges which can cause the signals to interfere with each other when a signal gets larger in a band where they can't handle it. Or with themselves (that's called Harmonic Distortion).
edit: (Should have read ahead, I see others already answered this....)
Last edited:
Were you at Fermi or Argonne? (Or one of the universities in Chicago) That's a decent amount of analytical/metrology equipment to have at hand. Yeah, EM seems the wrong tool unless you were hoping to see crystal domains? XRD/XRF might have been better there, and definitely mass spec (as you did).
I'd be surprised if Cerium would have visibly reacted at trace levels, tbh. Was there a concern it was a higher concentration (which would have visibly degraded in air). But I'm really only an amateur material scientist when we get down to brass tacks. (Edit, sorry, didn't read your post correctly, feel free to ignore)
Anyhow, it's already clear that the Bybee claims are bunkum, and their electrical effect over audio and low-RF is, um, unremarkable. So not much left to flog here.
Last edited:
Thanks for these posts. I have read all of them and it has clarified things a bit.
Use a metal case and filter the lines in and out and almost no RFI gets in your circuit. Well known for at least a hundred years. Faraday cage.
Here's something interesting for the younguns who haven't seen it. A diode and 2 passives make a radio, no power supply needed.
Crystal radio - Wikipedia
One thing about putting ferrites onto speaker or power wires -- you should put the ferrite so it rings around both wires at the same time so the net high AC current passing through the ferrite hole is zero, and it won't modulate or distort with the audio waveform. RF won't travel differentially in the wires the same (much or most is common mode) so the ferrite can block that.
If you know the frequency of the RF getting into the system, try to place the ferrite clamp-ons so they are spaced about a quarter wave apart at that frequency, makes a much better trap.
If you know the frequency of the RF getting into the system, try to place the ferrite clamp-ons so they are spaced about a quarter wave apart at that frequency, makes a much better trap.
I didn't pay for the Bybees that I have so no expectation bias there....infact I don't like the signature that they impart.
Agreed it could be HF absorbtion/loading that then consequntly reduces lower order intermods, but I don't think that is the whole story, my filters also.
Dan.
- Status
- Not open for further replies.