is it the termination of the trap? measuring with the leads is probably a lot lower impedence than in the antenna, and the grid dip technique doesn't load the trap much at all. I think.
Making the trap and exposing the second part of the shield , you can compress it, when the shield fattens you can insert a small screwdriver or forceps or pick on the side of the shield close to the jacket and inserting this tool about a 1cm or so, then start separating the mesh of the screens revealing the underneath polypropylene central tubing/wire and loop it out making a neat shield and central tube/wire separation
I had the same confusion, when tried directly connect trap coil to S11 NanoVNA. Frequency is lower, I think due to cable's and Nanovna's parasitic capacitance. Measuring with loop is better. Same result also if you connect coil as S21 to Nanovna.
Making a physical connection to the trap you add capacitance and lower the frequency. A loop only couples the magnetic field . No connection no extra capacitance.
is it the termination of the trap? measuring with the leads is probably a lot lower impedence than in the antenna, and the grid dip technique doesn't load the trap much at all. I think.
Making the trap and exposing the second part of the shield , you can compress it, when the shield fattens you can insert a small screwdriver or forceps or pick on the side of the shield close to the jacket and inserting this tool about a 1cm or so, then start separating the mesh of the screens revealing the underneath polypropylene central tubing/wire and loop it out making a neat shield and central tube/wire separation
I had the same confusion, when tried directly connect trap coil to S11 NanoVNA. Frequency is lower, I think due to cable's and Nanovna's parasitic capacitance.
Measuring with loop is better. Same result also if you connect coil as S21 to Nanovna.
Not sure but shouldn't the trap be connected between s11 and s21 with their grounds connected together?
Hello Rick, 1.5" is inside or outside diameter? and which type of RG58 did you use?
1.5" is the outside diameter. Velocity factor of coax changes drastically, the first trap will be trial and error.
Making a physical connection to the trap you add capacitance and lower the frequency. A loop only couples the magnetic field . No connection no extra capacitance.