On Wed, Feb 10, 2021 at 11:05 AM, David Eckhardt wrote:
* I have actually tried one vs. both wires in parallel with the VNA in
measuring CM attenuation.. There is a very minor difference. The largest
practical effect is to reduce resistance (not so much the ¡ÀjX portion). *
* Considering each wire of the bifilar pair contributes equal
inductance by itself, so the total connected in parallel will be half that
of each wire alone. This ignores mutual coupling. A 3 dB difference in
30 dB of total *
* attenuation, to me, is of little concern. The total
inductance of two inductors in parallel can be calculated from L(total) =
[L(1) X L(2)] / [L(1) + L(2)], just like resistors in parallel.*
Second question, what is the procedure for coax chokes? I *think* what I
have seen and understand is that you connect the *braid* only on CH0 and
CH1 (Port 1 and Port 2). This is the path that the CM would take. Is this
correct for coax chokes?
*You are correct. Connect the braid from one end to CH0 and the other end
to CH1. *
I have the NanoVNA and love it. Building and measuring CMCs is my next
adventure. Thanks to you and the group for a wonderful resource.
*Anything to encourage learning the NANOs and building your own
"whatevers". Experience is the best teacher!*
*Dave - W?LEV*
Dave, thank you again for the thoughtful reply.
And, thanks to the group for the additional insight.
Adam - N0KTB
