0-500 Khz converter to 4Mhz by CT2GQV This was part of a NAVTEX receiver experiment. NAVTEX signals are around 490 and 518 Khz so I first built an PLL oscilator for those frequencies (for a DC receiver) but the PLL never worked like I wished so the idea was first to make the conversion to 4Mhz and then built a direct receiver around that frequency. http://speakyssb.blogspot.com/2009/06/0-500-khz-converter-to-4mhz.html