Fascinating tour round a museum of antique radio and TV museum in North Bloomfield N.Y.
https://www.youtube.com/watch?v=VkVz1BM … mp;index=3

I came across this fascinating site while looking up crystal radio sets.

It has loads of different designs made by the author, and an "antique" set made by his grandfather (pictured)

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http://www.hobbytech.com/crystalradio/crystalradio.htm

A demonstration with explanation of the super accurate Hewlett Packard (as was)/Agilent caesium clock. Of interest for geeks of laboratory instruments.  This clock was the type that proved the part of Einstein's Theory showing a difference of measured time between clocks travelling two ways round the earth. The accuracy will amaze you, guaranteed!

https://www.youtube.com/watch?v=eOti3kKWX-c

This next clock tested was the clock used on the Soyuz spacecraft - just to make a comparison.

https://www.youtube.com/watch?v=HKsjwT53yXw

This video is about the Mullard thermionic valve works in Blackburn, UK, in the 1950s.

I find it all utterly familiar, having been taken on industrial radio factory tours from my college, the Northern Polytechnic in London.

https://www.youtube.com/watch?v=-GgWIlvyEL8

Mullard was one of the major radio and radio valve manufacturers in that time. I can't remember just what dates were milestones for them, but I remember one of our lecturers saying they made a packet during WW2 on the 1154/1155 radio transmitter/receiver sets carried by the bombers of the time. Lovely coloured plastic knobs!. Like many others at one time, I had the receiver  set, which was by way of being a quite broadband communications receiver. It included a direction finder function, for which there was a special antenna.  I think this section was normally removed before the set was sold as government surplus.

Mullard valves were identified normally by the European nomenclature, so that a 6V heater double triode would be called an ECCxy, where E was the 6V, CC =two C, triodes, x was the base type and the y was the individual valve characteristic.

I found this video entertaining, and a nice explanation of superheterodyne  mixing and why it is the basis of all modern radios.

https://www.youtube.com/watch?v=hz_mMLhUinw

One point worth making, not in the video, is that changing the baseband frequency of the signal as it passes through the system means that the possible feedback loops are minimised.
For example, in the old fashioned TRF (tuned radio frequency) wireless sets, there was only one signal frequency, selected by the input tuning circuit, which was amplified successively by each same tuned amplifier stages. Thus a signal leaking from a more powerful later stage will get back into an early, more sensitive stage, and cause positive feedback and howling.

The superhet process means the signal at the same frequency as the sensitive earlier stages of amplification does not exist in the later stages, so feedback is eliminated. This is important in domestic radio, and far more so in the end-to-end amplification in a satellite payload, where input signals are very low, and outputs much higher.

I hope that is interesting - maybe details are inaccurate, but the principle is the thing.

I have several synthetic wine bottle corks (hic!) which consist of a smooth sleeve over a soft mass. I cut a piece of the inside plastic mass and found it makes a good pencil eraser.

May be useful to an old fogey, like me....