handle = muscle around, like what Goliath would have done
complain = tick ... tick .. tick .. tic-a-tic-a-tic .. PHUT ... *POOF*
I've got a Boonton "megacycle meter" here. Not nearly as precise for Q measurements as your setup but it sure has that 40's look. This kind, except mine has original coils except for one:
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Except you have that 0.1 ohm directly across the sig gen. I have noted the series 50 ohm output resistor in some HP signal generators with a nice brown patina to them. I see how that happens.:-) Mike
Our old mil-version Wayne Kerr seems happy. I'm assuming it's a genuine 50 ohm source, so shouldn't mind driving any impedance load.
Some of the older tube-type HP and GR generators could source watts of RF, so maybe they could fry their output networks. The Wayne Kerr is only good for +12 dBm or something wimpy like that. Limp-wrist Brits!
I get the most signal across my 0.1 ohm by connecting directly to the generator. I suppose I could use a step-down transformer, but that's another chore.
John
I was surprised when I found my HP 651B Signal Generator had a very low output impedance amplifier with a series 50 ohm resistor to set the output impedance. Although maybe I didn't have enough experience to be surprised, maybe I just learned something. :-) MikeK
Our old mil-version Wayne Kerr seems happy. I'm assuming it's a genuine 50 ohm source, so shouldn't mind driving any impedance load.
Some of the older tube-type HP and GR generators could source watts of RF, so maybe they could fry their output networks. The Wayne Kerr is only good for +12 dBm or something wimpy like that. Limp-wrist Brits!
I get the most signal across my 0.1 ohm by connecting directly to the generator. I suppose I could use a step-down transformer, but that's another chore.
John
n
uH.
Ooopps, yes, nanohenries. X(L) of about 63 ohms @ 50MHz. I had microhenries on the brain somehow...thanks.
-- Cheers, James Arthur
an
0uH=3DThe web calculator gives 0.200uH =3D=3D 200nH -- it's right, the slip was mine.
-- Cheers, James Arthur
Nice white LED on the front panel.
John
It's actually red, and an Edison electric lamp, not to be lit with match :-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
pF
e Q
re
tI thought Litz wire was only good at reducing eddy currents at freqs below a couple Mhz. Past that, the distributed capacitance just shorts out the strands so they become the same a solid conductor. Most AM radio antenna loopsticks use Litz in the range of 500KHz to 1.6Mhz, which seems to be ideal.
-Bill
The capacitance would have to be pretty big for its admittance to be comparable to solid copper!
Making metal things smaller to prevent eddy currents is how powdered iron cores work too.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net
he
33 pFure Q
core
ect
e .t- Hide quoted text -
Oh good, I meant to ask you about that statement.
"IIUC Litz wire is all about reducing eddy current loss in the windings. The skin effect verbiage is all nonsense."
Are you talking about eddy currents going around a whole turn, or just currents moving within the diameter of one wire? It doesn't seem like Litz wire would help with the first, and the last looks like a really small effect.
I thought Litz wire was about the skin effect and making more 'area' for the current to flow in. But I'm happy to be corrected.
George H.
I'm laying out a 4-layer test board with the 50 MHz triggereble oscillator, and I'll try some solid and Litz wound inductors. My ultimate measurement criterion will be jitter of clock edges versus edge number, which should be indicative of Q.
I'm also including a rather nasty photodiode signal processing chain. I may plead for advice on that one.
John
. . What I wouldn't give for a good solid state version of the Boonton
250B Rx Meter... {;-(Jim
We work mostly in time domain. I guess that makes me the inverse Fourier transform of an RF engineer.
John
We use Litz wire for R.F. transformers for a 100KHz 250kWatt oscillator.
THe transformer is inside a SF6 vessel. The xformers are Pie in design and wound with flat braided litz wire. This type of wire does 2 things, it reduces eddy currents to a minimum due each wire being wrapped and because of the braided cross hatch pattern, skinning is almost non existent which is very important to reduce stray build. The overall structure creates a nice heavy low R conductor at 100Khz.
P.S. even though SF6 is an insulating gas, it is also is a dialectic and if the structure isn't properly fitted in side the vessel, it does actually cause a conductive path under AC. So using Litz in this area is very important. The majority of the voltage in the vessel is DC at the final end, and this gas does well as a insulator and makes up for the dialectic needed for the chorona rings. 2 Million volts is a lot to deal with..
Jamie.
Hide quoted text -
We went through this earlier this year in this very boutique. The skin effect argument relies on the conductor being isolated, i.e. it feels only its own magnetic field, so the current can reconfigure itself to reduce the field energy. Litz wire is braided, so that every strand spends part of its time in the middle of the conductor and part at the edges. It turns out, though, that from a skin effect point of view you're better off with cylindrical wire--at least then you have part of the wire giving a straight shot at low impedance, whereas by interleaving you make every part essentially as bad as the core of the wire. I gave a somewhat more detailed version of this argument back in February--search on the subject "Litz wire".
When you add the effects of the other turns of the coil, and especially the effect of the core, you can write down pretty accurately what the field is going to be, and it's far from zero even well inside the wire--there's no way for the current to reconfigure itself to get rid of the field from all the other turns. That makes the skin depth derivation completely inapplicable to toroids. (Type-I superconductors are different, but there the eddy currents don't cause loss.)
So Litz wire helps a lot with eddy currents, because the available area for the current loops is smaller. Tape winding does more or less the same thing by minimizing the perpendicular component of B at the conductor's surface.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net
The
o 33 pF
asure Q
de
gr core
ffect
re
ine
gs.
s.net-Hide quoted text -
t- Hide quoted text -
Thanks Phil, I must have missed (forgot?) the previous discussion.
George H.
om
r. The
two 33 pF
measure Q
le 68.
made
ing
or core
effect
wire
mine
ings.
srts
al.net-Hidequoted text -
tem
in
in
fnet-Hide quoted text -
I found the old thread. And I do remember.
If I understand your arguement correctly there should be no difference if one used braided and unbraided multi-strand wire. Since both will 'break up' the eddy currents. And perhaps the unbraided would even be better? The current carrying strands on the outside of the bundle are not forced into the central region of the bundle.
George H.
Big conductors inside toroids can be awful. My induction heater's output transformer dissipates an awful lot of power, and it's only two turns (of
3/8" copper tubing) through a toroid. I wish I knew how much, all I know is it acts like a work coil inside the chassis. Any metal nearby gets HOT!Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.