Paolo:
The HP4260 is a 1 KHz bridge (I have one as well, along with a GR1650 1
KHz bridge) and the first inductor on Page 53 is wound on Type 43
material. The relative permeability of 43 is not constant with frequency.
The choke, on the other hand, is probably wound on material with a
relatively constant relative permeability versus frequency. The powdered
iron cores (type -2 and -3 material, for example) also have relatively
constant permeability. I've measured coils wound on Type 2 material, for
example, at 1 KHz with my GR bridge and at 7.9 MHz with an HP4342A
Q-meter and found little difference in inductance.
You can see the curves for Type 43 material at FairRite's home page.
http://www.fair-rite.com/. The catalog has a page for each material type
with detailed electrical specifications.
I am a bit puzzled, however, in that 43 material specs show relative
permeability = 850 at the lowest frequency in the graph, 100 KHz and
that it is flat between 100 KHz and 1 MHz, at which point it starts to
drop. If I have some extra time today, I'll wind up a few turns on an
Type 43 core and measure it at several frequencies, including 1 KHz.
Jack K8ZOA
paolo gramigna wrote:
Hi all,
I'm arrived at page 53 of the manual, and I'm making my first toroid. I
followed the instructions, and then out of curiosity I tried to measure the
inductance, using my old HP 4260A. I know that I'm not supposed to match the
indicated inductance, and that I should stick to the published turns count;
in fact I was just willing to give a try to the HP 4260A, the least used
instrument in my lab.
Well, it ended up indicating a value of 160 uH, not 18 uH as supposed. So I
tried to measure the value on another bridge I had there by chance, and
ended up with a very similar value.
So I tried the HP 4260A on the solenoidal RFC (the green bodied) and I found
values very similar to what I expected.
I know that i'm doing something wrong, but I cannot understand what's my
mistake....
Cheers,
IK4YNG Paolo
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
