For a more robust Mode B short-wave broadcast using 16-QAM for the MSC then only the AAC codec can be used - no SBR (see audio page for more information).
 

Mode C and Mode D

Only used on short-wave and demonstrate the trade off between making the signal robust against fading and multi-path signals and the actual data carrying capacity.

Audio quality can be poor and comparable with AM broadcasts as many broadcasts can only use the AAC codec as there is insufficient data rate to support both AAC and SBR codecs.

With Mode C and Mode D broadcasts using a high protection level then the audio quality (bandwidth) audio can sound worse than AM and obviously there is no possibility of including multimedia with these broadcast.

Although the audio may be poor quality (not much better than cell phone quality); provided there is sufficient signal-to-noise ratio at the receiver then the audio will not have any of the characteristics propagation fading or distortion of an equivalent AM signal.

 

 

 

 

 

 

 

Mode E

Using 4-QAM gives between 37.3 - 74.5 kbps (depending on protection level), and for 16-QAM gives between 99.4 - 186.4 kbps.

 

- DRM broadcast modes -
drm011001.jpg
DRM30 has 4 transmission modes, referred to as Mode A, B, C, and D.
DRM+ Mode E (VHF - 100 kHz bandwidth).
 
Mode A is most likely to be used on medium and long wave using ground wave propagation for local broadcasts where propagation conditions are benign. Can be used on short wave with stable path and for local broadcasts on 26 MHz (reception via ground wave).
 
Mode B is the most common mode for single hop short wave broadcasts and most broadcasts within Europe tend to use this mode. Night time or international medium wave broadcasts (via sky wave) may use Mode B instead of Mode A.
 
Mode C for long path multi-hop broadcasts on short wave. For example direct broadcasts from New Zealand or Australia being beamed into Europe.
 
Mode D is the most robust and could be used for Near Vertical Incidence Skywave (NVIS) broadcasts where the radio signal is broadcast upward and the ionosphere reflects the signal back down. This mode is little used for broadcasting in Europe but UK radio amateurs have recently been allowed to broadcast in the 5 MHz band to asses whether NVIS could be used for national coverage. NVIS is common in the tropical short wave bands as it gives considerable area coverage with a single transmitter located in the centre of the broadcast area.
 
Mode A and Mode B
 
At the bit rates available for Mode A and Mode B using AAC and SBR frequency enhancement, gives 15.2 kHz audio bandwidth (close to VHF-FM radio) at the DRM receiver but thanks to AAC compression only requires 9/10 kHz of radio spectrum to achieve this.

Only the higher bit rates available in Mode A and Mode B could be described as ‘near FM quality’ - the main selling point of DRM. However to achieve these higher bit rates the protection ratio has to be kept low so the received signal is more susceptible to interference or fading.

 

 

 

 

DRM30 modes
 
  mode  
                    propagation                    
  data rate  
 error protection 
A
 minor fading
 highest
  lowest
B
as ‘A’ plus selective fading
middle
low
C
as ‘B’ plus severe fading
 low
 middle
D
  as ‘C’ plus severe Doppler shift
 lowest
highest
 
 
 
 
Typical bit rates available when broadcasting in 9 kHz channel.
 Protection
level
  Mode A  
  64-QAM 
   Mode A  
   16-QAM
0
 19.6 kbps
 15.2 kbps
1
 23.5 kbps
 18.3 kbps
2
 27.8 kbps
 21.6 kbps
3
 30.8 kbps
 24.0 kbps
 
 
Typical bit rates available when broadcasting in 10 kHz channel.
 Protection
level
  Mode B  
  64-QAM  
   Mode B  
   16-QAM
0
17.4 kbps 
 11.6 kbps
1
20.9 kbps 
 14.5 kbps
2
24.7 kbps 
---
3
27.4kbps
---
 
 
Typical bit rates available when broadcasting in 10 kHz channel.
 Protection
level
  Mode D 
  64-QAM  
   Mode D  
   16-QAM
0
9.1 kbps 
 6.9 kbps
1
10.9 kbps 
 7.5 kbps
2
12.9 kbps 
---
3
14.3 kbps
---
 
 
Typical bit rates available when broadcasting in 10 kHz channel.
 Protection
level
  Mode C  
  64-QAM  
   Mode C  
   16-QAM
0
13.7 kbps 
 9.1 kbps
1
16.4 kbps 
 11.4 kbps
2
19.4 kbps 
---
3
21.5 kbps
---
DRM background
COFDM
FAC
SFN
MSC
SDC data 1
Multimedia
Bandplan
DRM future
DRM audio
FAC sync
DRM multiplex
DRM modes
SDC data 2