Push buttons allow to raise or lower the currently selected frequency. Here, the MMIC and the output HF connector have not been yet soldered. PCB has been designed in order to be cut into two small boards that will be assembled face to face. The broadcasts of meteorological information by the German Weather Service via its RTTY transmitters DDH7, DDK2, DDK9 as well as DDH8, DDH9 and DDH47 serve exclusively for the safety of seafaring within the framework of the. The PIC is clocked using a 3.579545Mhz Xtal in order to get the 4800 Bauds RS232 speed.įor this application, the fixed frequencies have been hardcoded to receive the Hamburg RTTY 50Bd/450Hz weather programs on 4583.1KHz (DDK2), 7646.1Khz (DDH7), 10100.8KHz (DDK9), 11039.0Khz It sends weather reports, mainly for seafaring, with a transmission power of 20 kilowatts via RTTY with 50 baud.
I manage to reuse the XTal oscillator variable condensator to drive the push button inputs using two micro-switches and a metal clip put on the condensator axle. 10010 CQ DE DDK2 DDH7 DDK9, Hamburg, Germany w/RYs, callsigns, freqs. The AD-9835 DDS is driven by a PIC 16F84 which runs a polling loop looking for any frequency switch or push button changes.ĭefault frequencies are stored inside the PIC EEPROM and can be modified (5Hz up/down) by using any of the two push buttons. The use of a -10V power supply (germanium transistors design) requires to use a dedicated power supply. It appears that the receiver design allows for a quick and easy modification by reusing the frequency switch, the XTal sockets and the external diversity frequency input.
This device has been designed to replace the 6 Xtals bank of my RF520 HF receivers. Six frequencies PIC 16F84 driven AD-9835 DDS board