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In Reply to: Re: The outer conductance posted by Dan Banquer on April 2, 2007 at 11:36:31:
In order for this network to work at all at these frequencies for measurement the "resistor" would have to be a 50 ohm load over a huge band. Secondly, when does the AC line represent a 50 ohm load?
You might wish to take some time and think about the above.
d.b.
Follow Ups:
And I think that no one would spend the money on network analyzers that only analyzed networks that presented conjugate matches to the analyzer!The analyzer will be happy to tell you what's happening on networks that aren't 50 ohms. Just ground one end and look at S11 and you'll know what the impedance really is. If you have access to an analyzer buy lunch for one of the guys that use it a lot and I bet they'll be glad to help. If you don't, what do you have? There are a lot of ways to measure these things, and I've probably done most of them, but the network analyzers are cool and fast.
With respect to the inductance at 100kc, I'm looking at your data. Did you happen to notice what the Q was doing at the various frequencies? Also I'm not clear what the column with ohms as a unit is. Is it the impedance of the DUT or the resistive component of the impedance?
You're probably right about stray capacitance rearing it's ugly head, you'll likely find a self-resonant frequency, but the Q may be low depending upon the shunt resistance. Watch the phase.
You might consider doing a careful sweep by hand using your function generator and scope noting amplitude and phase as you go. If there is any question about the Zo of the Fn generator or it's ability to drive low Z loads consider using a build-out resistor to give you exactly a 100ohm source.
On behalf of myself and likely many other interested folks, thanks for looking into this.
Rick
O.K. Rick, Let's take a close look at some microwave theory here.
If you take that analyzer and connect a length of romex or line cord, and terminate into 50 ohms, your insertion loss and return loss will be all over the map. Why? because romex is not a 50 ohm line. The insertion loss alone will negate any conducted power along the line. Now instead of a nice clean 50 ohm termination use a variable termination of anywhere from 1 ohm to 10K ohms and think of the insertion and retrun loss under those conditions.
Now think of a power resistor claiming that it will absorb microwave energy and placing somewhere on the AC line. If you manage to place the resistor in exactly the right place it might reduce some RF, but in reality this will be purely by chance because we don't know exactly where the 1/4 wave will be. Move the "resistor" 1/4 of an inch and you will get a different response.
Now take that analyzer and connect something like a tripplite isobar, line cords and all with a varable termination. The isobar standard filters with real chokes, and MOV's will prove far losssier that the "power resistor". To it's benefit it will give some decent surge suppression, and low frequency RF attenuation where you really need it.
If microwave is an issue for household/consumer lines it will a radiated issue, not a conducted issue. Shielding will help, decent grounding practices will help, But if you think about any real power at microwave frequencies it should not be legal or allowed near any consumer or residence.
Now, for those of you who have their audio systems next to radar transmitters....................................
Hope this helps;
d.b.
Hi Dan,The reflected impedance is not quite ALL over the map. I presume the map in question is a Smith chart in which case it will be running around in a circle at the VSWR radius.
I don't think anyone claimed that the power resistor would absorb microwave energy, but I did speculate that it might provide a low impedance for the audio, or AC and that it's inductance would force higher frequency currents to flow more in the outer resistive layer which should stay resistive into the GHz region. As you pointed out, stray capacity in the resistor may limit it's ultimate attenuation.
As far as location goes, it probably doesn't matter as much as you'd suppose. To the traveling wave it's a loss, to the standing waves it varies, but except for the comb of frequencies where it's right at a current node it will help, especially since the reflected energy will pass through it over and over.
Microwaves are an issue for all of us nowadays, of course on the plus side it's convenient being able to hear our cell phones ring through the stereo... They may start radiated but usually end up getting picked up by the wires.
So, back to the issue at hand, I think we are looking for mechanisms that could account for the Bybee filters helping without invoking magic. Magic of course meaning things I don't understand...
I think we need to go back to the initial premise:
If it sounds like a duck, walks like a duck, and looks like a duck, is it a duck?
Not in High End Audio: it's the quantum visualization of a duck.
d.b.
OK Dan,Are you saying that girls WON'T be hopelessly attracted to guys with Bybee purifiers in their systems? You can trust advertising, we have laws...
It well may be floobydust and that further study would reveal nothing. Tis your call, you're doing all the work. I guess my electrons will just have to get along as best they can, smashing into each other and falling into holes like drunken sailors.
Regards, Rick
PS: I'm married to a birder. Just because something looks, sounds and walks like a duck no longer makes it a duck. Nowadays it's DNA has to declare it a duck. Thought you'd like to know...
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