[sdiy] AM reciver

[René Schmitz]

Hi Dustin and all,

About the easiest set you can make is a direct conversion receiver. 
Essentially this is nothing more than a ringmodulator and a variable 
frequency oscillator. This has the benefit that you can demodulate 
transmission modes that require a beat tone, like SSB, RTTY or CW. 
Something the cheap radios that you can buy dont have.

I haven't tried it yet, but I think with some care it could be possible 
to pull in LF utility stations on a modular, by using a ringmod and a 
sufficiently fast VCO. There is lots of stuff between 30kHz and 150kHz, 
like time signals 60kHz (Rugby UK) and 77.5kHz (DCF77 Germany) here in 
Europe, and stations  that send out digital modes on 139kHz (DCF39).
I've put up two examples here: http://www.uni-bonn.de/~uzs159/dcf39.ogg
http://www.uni-bonn.de/~uzs159/dcf77.ogg
They were received with a shortwave receiver, and a 5m wire antenna.

An example of a direct conversion set is here: 
http://www.qsl.net/vu2upx/Projects/dc_rx.htm Its for 20m, but if you 
change the tuning tank on pin 6 of the NE612 and the filter on the input 
it should work for other bands too. And you could perhaps use a variable 
cap, instead of the varicap diode. (But zehner diodes can be used as 
varicaps too.)

For receiving VLF below 30kHz, there is an interesting page: 
http://www.vlf.it lots of ideas there.

Cheers,
  René

dustin sedlacek wrote:
> does anyone know much about building a AM reciver ? i was thinking
> that it would be a intresting "noise source" and random sound
> generater

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159