Hi,

I have a matching circuit that matches 50 Ohms to 4500 Ohms in parallel
with 2.5pF at 45MHz.

The coil was measured at 147nH with a Q of 50 at 45 MHz.

The circuit is a C-Tap typology with following values.

Tap input to ground = 784pF
Tap to hot side of coil = 92pF
Par inductor = 147nH

My design calculations predict Loaded Q = 26 and BW = 1.7 MHz.

I used a 50p trimmer in par with 68pF cap for top of tap to fine tune.

A 4k7 resistor and 2p2 cap were placed across the output to simulate the
correct load.

The test results show BW = 1.7 MHz and Loaded Q = 24.7 (agree with
calculated values).

When installed on the IF front end, the expected sensitivity is achieved
when tuned. This would indicate most of the signal must be getting
through or sensitivity would be effected due to mismatch.

All seems to look ok but when I attach the MJF-269 Analyzer I get
impedance of 280 angle 35 degrees (240 -j 179) for the impedance, I get
SWR = 6.1 , return loss of 2.8dB and match efficiency of 48%.

I cannot understand why there is such a discrepency between the design
values and tested results (using sig gen, spectrum analyzer and power
meter) compared to the MJF-269.

Is there something I am doing wrong here or is it a mis-interpretation
of displayed values ?

Thanks for any help.