On Tue, 28 Jan 2014 21:05:07 -0600, amdx wrote:
Nope, almost zero ohms, shorting one end and measuring center to shield
on the other end at 3.58MHz.
To reiterate, measuring this 12ft of RG58/u with 42 half cores of 3B7
(material) (size 3019) slide over the coax, shows an impedance of about
3,350 ohms with an inductive phase angle of 22.5*.
You previously said "I have measured the R at 3.85MHz, It is 3,350
ohms." Now, you change it to impedance. Please make up your mind.
However, I screwed up in my previous message. I forgot that you're
working with coax cable, where the center wire is shielded from the
effects of the inductors by the outside shield. So, you'll see the
equivalent of what you would get with a single wire going through all
the cores.
Got an Al value for a single core? I can't find a data sheet on the
new and useless Ferroxcube web pile. Here's roughly how I would do it
if I had the Al of your cores.
L(mH) = Al * N^2 * n / 10^6
N = number of turns, which in this case is 1.
n = number of cores, which in this case is 42.
Xl = 2 * Pi * f * L
Xl = 6.28 * 3.85*10^6 * L(mH)/10^3
The DC resistance is so small that it can be neglected.
You obtained a 22.5 degree phase angle which might be the capacitance
of the coax cable. I don't really know where it came from. That
angle would normally come from a resistance in the loop, but the coax
is nearly zero ohms. If there were any resistance, the phase angle
would be:
phase-angle = arctan(Xl/R)
If it is the cazapitance:
For RG-59/u 16.2 pf per foot for 12 ft would be 203 pf.
Xc = 1 / (2 * Pi * f * C)
Xc = 1 / (6.28 * 3.85*10^6 * 200*10-12)
Xc = 207 ohms
The vector sum of the reactances should give you the impedance.
Now, all you have to do is either supply a measured inductance or find
the Al of your cores.
Are you sure it's 3.85MHz and not the more common 3.58MHz? I smell a
transposition of numbers here.
The whole system is touchy, putting your hand on the coax changes the
current shown on the scope, also reorienting the coax will change the
current.
That's mostly because of the broken cores causing Al to change as they
move. More duct tape.
What are your thoughts, Jeff specifically and anyone else.
My thoughts are that I'm going to throw up. However, it's not your
questions or academic exercises. It's the junk food I excavated from
the back of the office fridge. Time to recycle everything.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558