Gareth's Downstairs Computer wrote:
On 02/12/2017 16:01, Rob wrote:
Gareth's Downstairs Computer wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Barlow was the (south-African) manufacturer who made the Barlow Wadley
XCR-30 portable shortwave receiver, an implementation of the Wadley loop.

OK, then mea culpa for referring to it previously as the B-W loop.

There are of course other receivers that use the same method, e.g.
the Racal RA14 and the Yaesu FRG-7.

Today there is no reason to use this design anymore, as we can make
digital frequency synthesizers and this have a much narrower roofing
filter at 45 MHz or so IF, improving the receiver performance.

I go for flywheel-loaded slide rule scales, not yet worked out how
to interface such things with a digital oscillator!

Spinning knobs and flying pointers are much more natural to me than
digits clicking over :-)

It is quite common to use shaft encoders to interface a spinning knob
to a microcontroller that sets the frequency of the synthesizer.
Normally a numeric digital readout is used with those, as it is usually
more convenient than a linear scale. However, there is no reason why
you could not mimic a linear scale on a dot-matrix display.

In fact, today usually an SDR is used with a "waterfall" display, that
looks like a linear scale where you can see all nearby transmissions
at the same time and can tune by sliding it to the position you want
to listen to using a spinning knob. But unlike a classic receiver
(without panoramic adapter) you can SEE what you will be tuning to,
making it much more convenient than just blindly tuning around.