During the process of re-engineering an SB-101 transceiver a series of measurements was conducted on both the Pi tank and miniature adjustable inductors used on each band in a number of SB-Line units and the results presented below.

With respect to the adjustable inductors, ‘Core in’ is the maximum inductance position and ‘Core out’ is with the outer end of the core level with the top of the former.

All measurements were taken on a Marconi TF-1245A Q-Meter with a Racal 9916 frequency counter and with each coil supported in free air and away from nearby metal.

The underscore in the part number should be read as a hyphen  i.e. 40_529 = 40-529.

The capacitance columns are those values required to resonate each inductor at the specified frequency for the respective core positions. Readers can calculate resonant frequencies with other capacity values as required.

All of these coils are wound on formers made of a relatively thin material with an outer diameter of 9/32 (0.28) inch, an adjustable dust iron core and a chassis mounting clip. Considerable care is required in moving the cores as they break very easily - the plastic hexagonal trimming tool must be a good fit in the core and not loose. Single winding coils have a pair of connection tags and those coils with an additional link winding have three connection tags.

Since the rebuilt SB-101 will cover top band and the WARC bands additional coil and crystal data will be provided in due course.

Shorting out the unused sections of the inductor as was done in the SB-101 PA circuit resulted in a reduction of about 5% in measured inductance and 8% in unloaded Q.