[hpsdr] Is DRM the only free Digital AM waveform?

[Tony Langdon]

At 01:18 PM 4/7/2007, you wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>
>A couple of us were discussing receiving and probably even 
>transmitting Digital AM signals with HPSDR or equivalent.  We are 
>looking for a good quality open source/free digital AM protocol that 
>we could implement.  However, the other person mentioned that he 
>wasn't sure if any of the waveforms/protocols were free.  He thought 
>that we'd have to license any that we wanted to use for transmitting.
>
>I found the following that appears to be free, however, I'm curious 
>if anyone else in the list has researched this area and/or has any 
>opinion on this topic:
><http://en.wikipedia.org/wiki/Digital_Radio_Mondiale>http://en.wikipedia.org/wiki/Digital_Radio_Mondiale

The DRM encoding is free.  There are now 3 variants that I know of - 
shortwave DRM, standard ham DRM (narrow bandwidth)and DRMDV which is 
a more robust ham version that has just been released.  However, some 
of the CODECs in use on the ham bands, namely MELP (2400bps) and 
MELP-1400bps have IP issues that may make it difficult for us to 
implement (especially since HPSDR would be delivering ready to run 
binary implementations).  It appears that Texas Instruments holds the 
IP rights on these CODECs, looking at the snippets of source I've seen.

I am just getting setup on DRM (ham variant using WinDRM) and DRMDV, 
so will be able to report more as time goes by.  There is also the SW 
broadcasting version, for which there is a free implementation in the 
form of Dream.  The shortwave version uses higher data rates, wider 
bandwidth (9-10 kHz as opposed to 2.5 kHz) and different CODECs to 
the ham variant.  It would be nice to have these modes built into 
HPSDR, this would certainly be an asset - just flip the mode switch 
and away you go - the versatility of SDR.

I look forward to the day when I can take a SDR (without needing the 
PC for processing) out into the field, with all the modes I need, and 
use a PC to update the radio as new modes, filters and other code 
become available.

73 de VK3JED
http://vkradio.com


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