Adding AM mode – an after thought

By | 5th August 2017

For some reason not yet known I have decided to add an AM receiving mode to the rig, muRata 455KHz 6KHz wide filters are cheap and available so why not?

Ok, so I could simply detect the AM with a diode, filter the audio and job done – well having researched various methods I have chosen the synchronous AM detection method – more effort and parts required but far superior results.

I found several articles on Synchronous AM detection and found a very interesting and detailed blurb on the NE567 PLL chip, obsolete but very much like the NE555 there are thousands still in circulation at low cost – http://www.amalgamate2000.com/radio-hobbies/radio/ne567_tone_decoder_as_am_fm___de.htm

As the product detector will be built as a daughter board module for the 455KHz IF strip I will use the same approach for the AM detector, although I will never need to transmit in the AM mode I don’t see why I can’t make it a good AM receiver.

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