[Radio Wrangler]

The H2900 receiver was quite remarkable in a number of ways, thedesigners were obviously aware of several limiting factors that weren't fully appreciated elsewhere for a nuber of years.

I thoroughly enjoyed taking that prototype apart to look at how they'd done various things and to measure individual sections. The 2N4391 JFET, I'd used a lot an an analogue switch, but they showed it made a decent high dynamic range amplifier and its wide area made for more than just low RDSon. The mixers were a fair bit plainer than the diode rings developed by Hugh and Guy, but the Marconi tea were working several years earlier. I had to make a synthesiser which could keep up with the mixer, and without the luxury of a bank of crystal oscillators. In the and, I'd learned all I could from 'Sosin's Folly' and I didn't fancy using it with thumb wheel decade switch tuning and about a second to lock up. So I passd it on so someone else could have some fun exploring it.

Cerainly the FDM telecomms test industry understood phase noise and reciprocal mixing in the early seventies.

By the way, phase noise is a misleading simplification. The idea of a carrier sitting amidst a pedestal of noise is wrong. The illusion of a carrier is caused by finite resolution analysis. Look more carefully and it's noise all the way in, there is no carrier, just climbing noise. And this fits with the mechanisms of oscillators.

So it isn't a measurement of how much noise there is, a wideband power meter will tell you that, it's amatter of how steeply the muck-heap is stacked.

(I;m reminded of a bit by Terry Pratchet, when one character asked another about the flat Earth on the backs of four giant elephants standing on a giant turtle, and just what was the turtle standing on? The reply was "I've got news for you IT'S TURTLES ALL THE WAY DOWN )

David

David