Elektor DRM RX

As you can see form the picture below this is a simple receiver. What you can't see it that there is an AD9835 DDS chip on the bottom of the board. This is the radio's VFO and is tuned via commands from a PC which are fed into the serial port you can see in the picture.  Unlike the other radio's I have it was designed with DRM in mind and so already has a 12KHz IF output.

The reciever can tune from 500kHz to 25MHz and is limited by the frequency of the reference oscilator (large silver rectangle) which in this case is 50MHz. The radio is somewhat deaf requiring quite a strong signal before it will produce any significant results. There have been improvements to the design which as yet have not been implemented on my unit.



So far I have only been able to receive the various offerings from RCI's Sackville relay on 9800 (and thereabouts) as this is commonly a rock crushing signal with me all the time. I have tried various other broadcasts such as DW from Sines and MOI from Kuwait but whilst they are received on my FT-840 at well over S9 the Elektor is unable to hear them.

Despite the size of the picture above the receiver is in fact quite small coming in at something like 4 inches by 6 inches. In the below picture I have installed it into a project box that I found on ebay. By sheer dumb luck I discovered that there are a small set of rails built into the side wall of the box that would accept the receiver.








I was stunned to be able to receive this transmission! Look at the signal level. It's barely out of the noise. This is what really sets DRM apart from regular shortwave broadcasting. As long as we have enough signal we get FM quality audio. If this were an analog signal we would be having a very hard  time even making out what station it was let alone listening to it. Check out the evaluation dialogue for this reception. You can just make out the DRM signal peaking at -80dB. I think the thing that saved this broadcast was the very low bit rate. MOI always sounds like it's on a phone circuit. It's audio quality is about that of a good AM station.