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[hfsig] Re: [Flexradio] The final nail in the coffin of Morse ?

Walt DuBose dubose at texas.net
Wed Jul 27 22:59:52 UTC 2005


"...In reality practical bandwidths on HF are governed by the bandwidth of the 
SSB filters provided in transceivers."

Actually, software designed radios such as the SDR-1000 can be programmed to 
have any bandwidth you want...this hams are not limited to the bandwidth of SSB 
filters IF they don't want to be.

"...Currently raw data rates as high as 25 kbps can be squeezed into an SSB
channel; although it gets ripped to shreds by skywave reflections and a raw
rate of 12 kbps is more realistic."

If you want robust date, say something that is 99.9% error free at -5 dB on a 
poor CCIR channel (about what we have on any skywave HF signal), about the best 
throughput you are going to get is 300-400 WPM in a bandwidth of 3.5 KHz

"...It seems to me that a prime use for high data rates would be video
transmission."

Perhaps video is you "bag", but I think most folks would like error free 
messaging as well as the ability to send other types of binary file as well as 
error free transmission of computer source code.

"...This should be achievable in a 7.5 kHz B/W"

Well not in the U.S. if the ARRL has their way and restricts bandwidth on HF to 
3.5 KHz.

I will give your that realtime streaming high qualitity video would be nice.

Walt/K5YFW

Trevor AKA wrote:
[deleted]
> The UK is fortunate in having no bandwidth restrictions on HF, we could in
> theory run 100 kHz B/W if we wanted to. In reality practical bandwidths on HF
> are governed by the bandwidth of the SSB filters provided in transceivers.
> Currently raw data rates as high as 25 kbps can be squeezed into an SSB
> channel; although it gets ripped to shreds by skywave reflections and a raw
> rate of 12 kbps is more realistic.
> 
> It seems to me that a prime use for high data rates would be video
> transmission. Full Motion Video with sound can done in a data rate of around 33
> kbps (very small picture slow frame rate but usable). This should be achievable
> in a 7.5 kHz B/W and something as exciting as Video transmission probably would
> encourage Amateurs to have a wide band filter fitted in their rigs. Signals
> this wide would be feasable on the 75 metre and 10 metre bands.
> 
> 73 Trevor M5AKA
> 





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