AOR ARD9000 User Manual download pdf (Page 23)

Mode MSC Protection Bandwidth Interleave MSC Coding DC offset

B Normal 2.5 Short 16QAM 350

Robust lowers the transmission BPS by changing 16QAM to 4QAM. Speed raises the

transmission BPS by changing Mode to A, MSC protection to Low and Interleave to

Long 2 seconds. Long interleave requires additional sync time. Voice requires 2.5kHz

bandwidth for the 2400 bps CODECs. 64QAM on a HF channel requires a higher SNR

and minimum multi-path to perform well. MSC Protection A, B and E provides different

levels of forward error protection (FEC) to protect the MSC from the detrimental effects

of QSB/QRM/QRN. B is higher than A with E (known as D in DRM) for Near Vertical

Incidence Skywave (NVIS) transmission where the signal is transmitted with a very high

angle of radiation short path propagation. In practice, however the extra protection for

this mode appears to have limited results. In DRM, Mode A is used for ground wave

propagation where Mode B for single hop/multiple hop propagation. The default mode

“B” on HF has shown to have the best overall performance. Mode E has been shown to

be the most robust in the presence of multipath and weaker signal levels.

Note: A BSR request may be made using different (larger to smaller QAM constellation)

DRM TX settings. This is sometimes done under poor band conditions in attempt to get

the request through lower SNRs. However, the originating station responding to this

request must send the response to this request (“Send bad segment report”) in the same

DRM TX settings it was originally sent.

DRM RX Settings

Default settings are:

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 32 33

No comments

AOR ARD9000 User Manual Page 23