John, even I figured it out in a short time --- this is a social medium type place. On other threads and forums, the moderator kicks your comments off if you dont stay on the subject. Not here... 'cause its basically a social outlet for designers and friends. Have a drink, my friend. It's OK.
THx-RNMarsh
Thanks George and kindhornman for the tips.
That just made me realize, I've been working brass for my antique clock repair stuff. duh.... I've some great experience working brass.
There's no reason not to use brass plates instead of copper...
jn
If you still want to source copper pick up some Tellurium Copper. That half a percent Te in the C14500 alloy makes a lot of difference while machining.
Dave
Thanks for the reply George.
The GR 1689M I have is nice old bench instrument with 0.02% basic accuracy. Even with an instrument of this caliber, re-calibration at each frequency point is required to get reasonably accurate and repeatable results since these measurements are at the bottom of its range. Noise and the limited resolution also matter down there.
Understood and agree. The 1689M in this case is connected to a fixture via 4 coax cables. Open and zero calibration is performed at the same place on the fixture where the test cable connects to eliminate these additional errors.
I was fishing a bit to see if there was some experience with proximity or other parasitic effects to a cable under test beyond the normal error sources. Attached are a pair of graphs showing the Ls and Cs per foot of an old ~9awg cable measured in free air vs. sitting on top of a wood and metal bench.
Dave
The GR 1689M I have is nice old bench instrument with 0.02% basic accuracy. Even with an instrument of this caliber, re-calibration at each frequency point is required to get reasonably accurate and repeatable results since these measurements are at the bottom of its range. Noise and the limited resolution also matter down there.
Understood and agree. The 1689M in this case is connected to a fixture via 4 coax cables. Open and zero calibration is performed at the same place on the fixture where the test cable connects to eliminate these additional errors.
I was fishing a bit to see if there was some experience with proximity or other parasitic effects to a cable under test beyond the normal error sources. Attached are a pair of graphs showing the Ls and Cs per foot of an old ~9awg cable measured in free air vs. sitting on top of a wood and metal bench.
Dave
Attachments
Would be interesting to test. The only commercial instrument I am aware of that could test this is an HP 4284A with a 42841A 20A bias generator (or two) added. I believe either the available fixture or the high current cable for the 42841A would have to modified to test cables. Just an educated guess as unfortunately I don't have such a beast available.
I'm not sure if the high current RCL "transformer" meters have a low enough Ls range work here...
Dave
A rise in inductance at the lower frequencies is certainly indicative of a metal benchtop with permeability to enhance the field.. So I would expect the metal to be magnetic. At the hf end, I would have expected a drop as the metal began to exclude the magfield.
If you repeat but use Ls/Rs, I suspect you'll see Rs increase at the upper frequencies. If you feel like doing it, that'd be great.
The capacitance is odd however, the proximity to the bench reduced it? Weird. Is it possible that whatever you used to hang the cable introduced capacitance?
jn
Gee John,
In the last decade of our repartee, you've never thanked me for anything.
Another decade or so of this treatment, and I may begin to think you don't like me.
jn
Now you're starting to use the right analogies for this high end audio business . . . Keep it going and you'll start to draw the right conclusions
I have a pair of 4284A's...mebbe if I stack em??
Seriously though, I'm making fixturing to wind some #10awg inductors for Ls/Rs testing, I'll also use a good CVR and my rmx1450 with some dummy series load to keep the amp stable.. I don't know if it'll be good enough for just a cable measure, I was gearing it towards an inductor of between .3 and .5 mH.
jn
Now you're starting to use the right analogies for this high end audio business . . . Keep it going and you'll start to draw the right conclusions
Don't tell me your wife stops at the Lancome counter...
There's always worse.
( http://i-cms.journaldesfemmes.com/i...re-nouvelle-ambassadrice-de-l-oreal-paris.jpg )
JN,
Your analysis on the bench materials is just about spot on. It is a wooden door top over a steel frame. There is a steel drawer set under the area where the cable was sitting for the test. Perhaps the distance on the HF end contributes to the lack of rise at the high end. The cable is the star quad alluded to earlier.
Easy to oblige as I recorded all of the data at the same time. I also have D and Q (fewer points with Q as I did it after the original measurements) if interested.
Dave
Attachments
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What about a tube phono stage with Jfets .....
You're about 40 years late.
Tube amplifiers for high-end audio by The David Berning Company
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