Tuesday, April 19, 2011

Stephan Schaa on what we need to see in DRM RXers

Our own Stephan Schaa (developer of the Pappradio) posts to the DRMNA Yahoo! Group about what is needed in DRM receivers, where we are, where we need to be and what can be done about it!:

"I think the problem with the DRM receivers lies in the self-understanding of the DRM Consortium itself. They always wanted receivers where you don't have to tap in numbers or rotate the dial. They always wanted receivers with very few buttons and with station lists. ( The reason is clear: in digital you have to wait some time to get audio, especially in the DRM implementations that I have seen so far and with no audio and no optical help to tune to a DRM station it's very difficult to tune) Besides that they set the priority to telescopic-antenna and portable radios. And there starts the problem.

With only few DRM Stations on the air, newcomer manufacturers with no or only little knowledge about shortwave, telescopic-antenna only at indoor use (because the batteries where drenched out very quick) and the "station list only" usability concept it's almost impossible to get good radio sets.

So what has to be done to build a good receiver?

1. Build a very good HF frontend. Someone of the DRM consortium told me that the people from radioscape always said: "If we have some problems at the HF section quality, this is no problem. We "repair" everything in the software part." And this is - of course - rubbish! In digital shortwave you need every single amount of original data that you can get out of the air! Every "selfmade" HF frontend problems will cause dropouts in audio! So a good HF frontend is essential

2. As all chipsets now are using "general purpose" DSP chips or ARM designs and all radios that have been manufactured have not been pocket receivers but more kitchen rack receivers the manufacturers should provide a external (magnetic) antenna or at least a good working antenna jack. I have got an Himalaya 2010 DRM receiver. Within some hidden menus it's possible to change the antenna input for longwave and mediumwave to telescopic antenna. And with this set on it's possible to use an external antenna for long- and mediumwave, too. You would wonder how much difference it makes to use a small 30cm broadband active loop antenna instead of the build in very small loopstick antenna. Besides the bad quality of the loopstick antenna in the Himalaya there's way too much selfmade noise inside the 2010 RX. With an external antenna only 1m away from the RX I get a lot of stations that have been under the selfmade noise before.

3. The commercial success of DRM radios would be much better if they would also provide good reception on analog shortwave, too. AM demodulation is always build in these devices. If the HF frontend would be ok, external antennas possible, the speaker and amplifier section good and if the manufacturer would invest a little bit more into good usability (keypad and tune-wheel, maybe SSB, software sync-detector and a responsive basic mini-spectrum-display to help put up the antenna better), the sales would be at least 4 times higher than now (or even more) .

4. Software updates: have always been possible in the old DRM sets, but have never been made. So people are disappointed.

So in one sentence: better frontends, external magnetic antennas, general purpose radio instead of "almost DRM only" RX and better usability with tuning wheel, more buttons for direct tuning and a "helping display". This would be my wishlist for a good DRM receiver."

Well said Stephan!