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If I get you correctly, that is the "skin" current that gets radiated from
the antenna as pure RF ? If so, that remaining common mode current is
reflected back at the source and then "recombine" at the connector to be
read as "raised noise" or reflected power ? Can I see it this way ?

RF energy that is intended to be radiated from the antenna all reduces as
fields inside the coax. Fields between:

1) The inner surface of the outer shield, and

2) The outer surface of the center conductor.

The internal fields carry the RF power.

What is referred to as the common mode current travels on the outside
surface of the outer shield.

If I'm still correct, then the 2-3 turns around the ferrite will "trap"
this third wire current and give me a more accurate reading ?

A few turns through the toroid will not "trap" RF energy on the outer
surface of the shield, but it will prevent energy from the antenna inducing
current on the outer surface of the shield. As such, your coax will become
isolated from the assembly. Of course, there will be no effect on fields
internal to the coax. There will be a small amount of "trapping" due to
losses in the ferrite. Some ferrites are designed specifically for loss.

In the last test I did, I had wrapped one ferrite at each end of the cable
for 2 turns. When I put my hands on coax, I could see that I got almost no
" hand touching" effect on the VNA. Well, I want to thank you for this
advice because it really helped me.

Your result is just what we were striving for. There is little or no
interaction between the assembly/antenna and the outer surface of the
shield. Excellent!

Now, here are the inductors and capacitors I bought.

Wurth Electronics 0603 RF inductor designer's ket


RF and microwave 0603 capacitor kit


Excellent!

As for all the previous test I made in the last few days, each and every
time I tried to add a matching inductor and/or capacitor, it did not
helped. My measurement got to the other side of the spectrum. This leads me
to think that as exactly as you pointed out, my measurement accuracy is
distorted.

With a few turns through your toroids at each end of the coax, the impact
of the matching network may become more observable and not disturbed by
grabbing the coax.

I'll make some other testing with my smaller ferrite with 3 turns instead
of 2 as close as I can to the insertion point and get back to you with some
results.

I don't know much I can thank you enough for all the time you take helping
me out. It is truly appreciated.

Just glad to help and apply what I've learned over some 60+ years to help
others.

Dave - W?LEV


On Sun, Mar 16, 2025 at 6:17?PM Nico via groups.io <nicolassimard=
[email protected]> wrote:

@Roger And @Dave,

If I get you correctly, that is the "skin" current that gets radiated from
the antenna as pure RF ? If so, that remaining common mode current is
reflected back at the source and then "recombine" at the connector to be
read as "raised noise" or reflected power ? Can I see it this way ?

If I'm still correct, then the 2-3 turns around the ferrite will "trap"
this third wire current and give me a more accurate reading ?

In the last test I did, I had wrapped one ferrite at each end of the cable
for 2 turns. When I put my hands on coax, I could see that I got almost no
" hand touching" effect on the VNA. Well, I want to thank you for this
advice because it really helped me.

Now, here are the inductors and capacitors I bought.

Wurth Electronics 0603 RF inductor designer's ket



RF and microwave 0603 capacitor kit



As for all the previous test I made in the last few days, each and every
time I tried to add a matching inductor and/or capacitor, it did not
helped. My measurement got to the other side of the spectrum. This leads me
to think that as exactly as you pointed out, my measurement accuracy is
distorted.

I'll make some other testing with my smaller ferrite with 3 turns instead
of 2 as close as I can to the insertion point and get back to you with some
results.

I don't know much I can thank you enough for all the time you take helping
me out. It is truly appreciated.

Nic

--

*Dave - W?LEV*


--
Dave - W?LEV