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.

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 :-)




Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Then the IM performance due to strong signals near the received signal
(inside the first IF range) would be even worse!

If they're near the received signal, then it won't make a lot of
difference as to whether the fitst IF BW is 1MHz or 2MHz!


But thanks for your response, for I see from their (unread) headers that
the Mongolian Hordes of stalking nonces are on my tail, as ever.