Input / Output impedance = 2.000 Ohms
Measuring setup:
Transformer impedance ratio = 2.000 / 50 Ohms = 40
I started with 2 turns / 13 turns but the impedance of the transformer was too low (see my blog "how many turns are needed").
So, next try was with 3 turns / 19 turns. This was very good at first sight.
Measuring results:
SWR rose with decreasing frequency so for 455KHZ it was already nearly 1.7
I decided to take 3 cores to get better low frequency behavior (see my blog "transformers for receiving antennas").
SWR @ 455 KHz is now 1.01
Insertion Loss measurement:
@455KHz only 0.21 dB which is negligible.
The results:
SWR
Insertion Loss
Specification ==> Maesured value
IL < 7dB ==> 4,9 dB
6 dB BW +/- 1.1 - 1.3 KHz ==> - 1 KHz + 1.3 KHz
Max. BW total < 4.5 KHz ==> 2.3 KHz
@ - 1.75 KHz suppression = 72 dB
@ - 1.95 KHz suppression = 65 dB