Ok, and sorry you ran with my mistake, I calculated Q with 100Mhz instead of the correct 50Mhz. So 33/ 80 = 0.4125. Then 0.4125 x 1.4 = 0.5775 ohms. Sure would be nice to have equipment to measure such things.
Mikek
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
The equipment at Semco was a bridge type of meter that could do C or L. You first zero everything, including the peak pot..
Put the DUT on the jig, and then turn the main dial back the res again, and the turn the main POT to bring the peak back to the null point.
The main pot was just that, a potentiometer, that would give you the Q of the coil, because a correction had be made from the original zero point. As for the frequency offset, that would thus report L or C, what ever you were measuring. I've done the poor mans trick. You need the signal generator and a high Z RF millvolt meter. In your case, a 24Pf cap with the 105nh coil. Sweep the generator and do the math at the skirts of the bw window.
Not trouble, maybe wasted copper, the Q is better the bigger the wire, because the larger circumference provides more copper even if most of the current is in the outer 0.001" in depth. My opinion, until I get better info.
Mikek
Ya, I've done the poor man's trick many times, but at lower frequencies. I guess in one of my stupid moments I disposed of a high frequency generator. I guess I thought I would never need it.
Easy to remember just remember you need the number 2, and three terms, permeability, conductivity, and frequency
In the MKS system skin depth is the square root of the whole quantity of 2 over the quantity of permeability times conductivity times frequency sd = sqrt(2/(p*c*w), easier to visualize this equation then remember it. p, permeability is in absolute value, like free space is 4 pi 10-7 c, conductivity is in S/m, copper is 58 MS/m, or 58e6 [58 x 10-6] w, is 'frequency' but in radians per second, or 2*pi*f [f is frequency in Hz] sd, skindepth in meters
there is, HP's Network Analyzer, select the complexity of the model you want and it will give you all the values for a best fit.
just inductor inductor plus resistance inductor plus resistance, cap, and parallel resistor
On Monday, December 2, 2013 5:51:22 PM UTC-5, amdx wrote: ...Q often will start to decrease in a 240uh coil near 1.5Mhz, and it is not near SRF.
Mirek, FYI - SI Units based on a person's name are always capitalized. So, MHz (not Mhz), uH (not uh), etc...
Don't mean to derail your thread. At least you're consistent. :)
Only when abbreviated. The full names, hertz, henrys, etc., are not.
Shame on you.
I have two HP 1Ghz generators and a old 1 Ghz service monitor at home base.. The service monitor has a duplexer alignment facilitie on it, I bet I could use that to perform that same task.
Jamie
Yes, that is the one but something tells me mine was in feet/inches :) Jamie
If the aspect ratio and everything is good. A coil too tight (pitch near wire diameter) has lower Q because the field can't circulate around each wire, or equivalently, the wires induce eddy currents in each other, causing more loss than the tight winding increases inductance. Typically pitch is double the wire diameter for best results. And solenoid diameter is some times the wire diameter, for similar reasons.
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
My experience with AM broadcast band coils, says, 1 wire spacing between turns provides a good Q. Better than close spaced. Mikek
Heinrich Hertz is probably pissed at me. Mikek :-)
Yes, but due to all the conversion terms, it's very difficult to remember! ;)
The 'silly' chart on my wall says skin depth of copper at 1 MHz is a bit less than 100 um. 100 MHz will be a bit less than 10um.
There must be a table on the web George H.
Interesting chart, mine says 66 um, and 6.6um for excellent copper [58MS/m conductivity] and 80um at 1MHz for PCB copper-like stuff. [40MS/m conductivity]
Doesn't matter a lot, because skin depth is based upon a planar wave hitting infintiely large planar material perpendicularly to its surface. Don't get a lot of that around here. ;)
That seems about right... for me a factor of two can be "a bit". (I like to let 2*pi = 10)
100um looks to be closer to 300 kHz, (it's not a very good chart.) so ~sqrt(3) off...George H.
10?! now THAT is rounding off.
"...not a very good chart."! is accurate, more like 440kHz to yield 100um
If you have octave [free MatLab clone] I can send you the function given frequency, [conductivity, and [permeability]] brackets mean optional entries, in *.m text script form. Or, the function that returns frequency given skin depth, etc.
It's set up to accept an array of frequencies too.
Apparently you did not see that you should multiply R by sqrt(2). And I'm not going to waste time finding the posts for you that have your answer.
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