On Wed, Apr 9, 2025 at 09:15 AM, va3rr wrote:
There is some small interaction between the two windings on a binocular core which ultimately limits the directivity of the coupler, but it is not at all an issue for the QMX.
I believe that the largest contribution to imperfect directivity is capacitive coupling between the thru and coupled windings, causing VSWR readings to increase at higher frequencies despite having a good termination.
On my list is to find a small-enough miniature coaxial cable and replace the plain wire thru winding with an electrostatically-shielded one.? This should flatten out the VSWR readings be eliminating the capacitive leakage.? IIRC this has been done and reported on this forum.
73, Don N2VGU
Donald S Brant Jr