开云体育

QUOTE: In such a case, the measurements will be distorted by the
transformation introduced by the CRC's twin-lead line.

These CMCs are not made of just "twin lead line". They are intelligently
chosen conductors, ideally insulated with Teflon, and properly wound in
bifilar manner on an appropriate toroidal core.

Opinions don't count in this game of antennas and transmission lines! Real
properly measured data using the correct instruments and techniques are
what's important. In other words, "show me the data" !!!

Measure Z at the antenna. Any, and I do emphasize "any" reactance at that
point when coupled to a good 50-ohm XMSN line will alter the impedance at
the shack end of that line!!! The effect of a short length of transmission
line embodied in the CMC will do typically less than any reactive component
at the antenna. So, again, show me the data before offering "opinions".
Please.....

I'm only attempting to keep this thread on a technical basis and not based
on opinion. Science and engineering rely on hard theory and data to back
up the theories. Antenna and transmission lines rely on hard science and
data, not opinion.

Dave - W ?LEV

On Wed, May 14, 2025 at 9:36?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi Miro
I believe you asked the right question here.
In my opinion, not having the correct characteristic impedance (Zc) for
the CRC that matches the Coax/Antenna system slightly alters the impedance
seen by the coax from the antenna and also the propor resonnance frequency
, CRC become a part of resonnance frequency . It also affects the impedance
measurements taken at that point, especially if the NanoVNA is calibrated
right at the point just below the antenna. In such a case, the measurements
will be distorted by the transformation introduced by the CRC's twin-lead
line.

For example, consider a CRC with a Zc of 140 Ohms used with a 50 Ohm
coaxial system: the impedance measured with or without the CRC will be
different, and correcting the antenna accordingly becomes much more
difficult. On the other hand, if the CRC has a characteristic impedance
equal to that of the Coax/Antenna system, the measured impedance will be
the same before or after the CRC. This would greatly simplify both the
calculations and the practical adjustments needed to optimize the antenna
system.

73's Nizar

--

*Dave - W?LEV*


--
Dave - W?LEV