"Michael A. Terrell" ) writes:
TRABEM wrote:

Thanks Paul,

My old Drake C line had a multiple ganged permeability tuned inductor
mechanically coupled to a variable cap.

One of the assemblies tuned the front end, one peaked the driver
stage, etc.

It covered from 1 Mhz to 30 Mhz with a half turn on the front panel
preselector control. Most likely the variable C and L tuned together
maintained a desirable Q across all the bands.

I was hoping for something similar, but have no idea where to get
permeability tuned inductors today.

Regards,

T


Fair Radio used to have some in their catalog, and they were used in
all of the old Delco (and some other brands) car radios of the '60s and
'70s.

I thought it was the norm for car radios to be permeability tuned, right
up to the time synthesizers came along. No manually tuned car radio
that I've looked at had a variable capacitor, with the exception of
a relatively recent one that had a frequency counter for the readout.

Car radios would be the best source of the mechanics, at least for
front end tuning and not oscillator use. Of course, the issue isn't
changing the permeability of a coil, that's easy with a tuning slug,
but making it easy to do that from a front panel control, ie the knob
doesn't move in and out. The pre-synthesized car radios would proved
the mechanism. But you did see the occasional article in the old
days about making up such a mechanism, though those tended to be
for oscillators where there was more fuss because they wanted/hoped
for linear tuning.

Michael VE2BVW