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df9rb
23-07-2006, 10:18
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

jbriggs
02-08-2006, 15:49
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.


James

df9rb
22-08-2006, 12:47
Hello,

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