View Full Version : Synchronous DRM Transmissions

23-07-2006, 09:18
Hi all,

I found the following DMR stations to be synchronous:
RTL on 5990 and 6095 (not 1440); losing audio for a short moment when changing frequ.
DW from Wertachtal and Sines; mostly even not losing audio when changing frequ.
BBC from Norway and Great Brtain; mostly even not losing audio when changing frequ.
VoR on 12060 and 15780; losing audio for a short moment when changing frequ.

Switching between the frequencies is very fast sometimes even without
audio drop-outs.

Adding the DRM-signals from two radios tuned on the different frequencies was possible for some minutes then the frequency drift between the two receivers is to high (only +- a few Hz is OK) and Sync is lost.

Will DRM-receivers be able to use the MFN-feature (multi frequency network) (when they ever come)?

The screenshoot shows the waterfall from Sines and Wertachtal in the upper part, only Sines in the lower part.

Bernd, DF9RB

02-08-2006, 14:49
There are some papers on diversity receivers and MFN's from BBC R&D, although almost 2 years old they are of interest

bbc diversity & MFN white paper and presentation (http://www.bbc.co.uk/rd/pubs/whp/whp-pdf-files/WHP094.pdf)

receivers can look for other frequencies during the time the FAC information is repeated (this is normally static), or a receiver with 2 front ends, (like a high end FM RDS receiver) could also use MFN's.

Personally I think diversity reception from MFN's should be included in high end DRM receivers as there is a benefit. Cheap Rx should still have the ability to switch to the other frequencies listed in the AFS list.


22-08-2006, 11:47

VoR from Taldom and DW from Sines were synchronous for about 10 minutes today! Only the MSC CRC LED changed to red for a second and new audio was back also within a second when switching between VoR and DW. The new label followed within a few seconds. This was working even with different bitrates (17.10 kbps DW, 20.96 kbps VoR) used. Changing frequency was like a good old analog receiver would have been used!

I think DRM has some unused potential which could improve the acceptance of the listeners - only the broadcasters have to implement .......

Bernd, DF9RB