Choke balun "Dirty Choke"

[drskeptical]

Hello
I have been looking into fixing up a half size G5RV aerial at my location.
Also I have been reading with a keen interest into building a "dirty choke" In my shed I had about 17 feet of RG8 MiniX coax, and some down pipe. I managed to get about 16 feet of cable round the pipe with about 6 inches either end to make of the connections.

See image here: www.amsnw.myzen.co.uk/IMG-20120202-00001.jpg

Then I thought it would be a good idea to test the choke too see what kind of results I obtain before I go out and fit it. Hmm this is where I am now totally confused!!

I have connected the OUTER or the braid of the coax to the measuring pin and the inner to the "earth" side.
As I understand it, it is the inductance of the outer braid I am interested in rather than the centre conductor. I also have read that for the choke to be of any use I need about 1000 ohms reactance, more the better. As you can see from the scan result here;

www.amsnw.myzen.co.uk/choke%20balun%20outer%20test.PNG

Luckily my choke remains inductive across the HF band. As I am only using a half size G5RV then 40mts is my lowest band but looking at the Xs and series inductance I would have thought I would get higher results. Bye the way I have also terminated the far end of the choke into a 50 ohm resistor.
I also thought that I would get away with about 16ft cable as I am only going down to 40mts rather than 80.

Any advice / discussion would be appreciated
Kindest regards

Andy. M5ALA

[Bob]

Hi Andy,
To measure the inductance of the choke, hook it up like a regular coil. One end of the braid goes to ground the other end of the braid goes to the center of the RF connector. You can use gator clips and calibrate the clip leads by putting the short, open, resistor loads at the end of the leads.
Be sure the choke is well separated from any metal objects while measuring it.

--73/Bob

[drskeptical]

Feb 8, 2012 22:26:25 GMT -5 Bob said:

Hi Andy,
To measure the inductance of the choke, hook it up like a regular coil. One end of the braid goes to ground the other end of the braid goes to the center of the RF connector. You can use gator clips and calibrate the clip leads by putting the short, open, resistor loads at the end of the leads.
Be sure the choke is well separated from any metal objects while measuring it.

--73/Bob

Hi Bob
Thank you for reply.
Will do more experimenting this week end. Work has sadly got in the way for the moment.
I realise that normally I would connect the centre core to signal and braid to ground under normal conditions, I just got confused when reading that it is the braid that acts as the choke the centre conductor and inside of the braid are not effected.

Regards
Andy