Jerry, Probably the better way to look at it is that co-channel interference is on the same channel, and adjacent channel interference is immediately next to the signal you want.
We have some pretty good interference fighting technology in today's amateur equipment. Although some are claiming that digital HF voice is going to be successful, I have serious doubts about it the more I find out. Most of the digital signals that require very large throughput, which would include voice, tend to require some very good S/N ratios in order to work. For example, you might be able to send some slow digital messages on a very weak signal that has other ionospheric disturbances using Olivia or MFSK16, etc. While the throughput is relatively slow, you may be able to get this information from the TX to the RX. With the need to send more information, and therefore the need for a better S/N ratio, you just are not going to ever be able to do well with voice. At this point, a number of hams moved from RDFT to QAM OFDM for SSTV and from what they tell me, it is mostly because the latter works better and faster. But it still requires close to a 10 db S/N ratio and that means a very good signal in order to get any throughput at all. While we can not repeal the laws of physics, Shannon's Law, etc., we can only get a certain amount of throughput through a given bandwidth of signal. Wider bandwidth could possibly help, but with the expected restrictions on HF bandwidth, it will be much more difficult to come up with modes that can increase the data flow based on BW. 73, Rick, KV9U jgorman01 wrote: >This is not the same as on-channel >interference that increases the total noise level, which is what BPL >interference is. On-channel interference requires different >techniques to solve than co-channel interference. > >Better receivers (roofing filters, increased IM3 capability, etc.) are >all answers to co-channel interference, along with higher transmitting >power. On-channel interference is a whole different animal. It >doesn't do any good to have a receiver with an MDS of -140 dBm, an IM3 >@ 2 Khz of 120 dB, and brickwall filtering of 3 kHz when the noise >floor is -80 dBm due to BPL and the digital signal you want to copy is >at -120 dBm. The only answer to this is higher transmitter power! > >Perhaps you can provide some concrete data on how a digital signal or >digital processing techniques can eliminate the difference in signal >level (i.e. signal to noise ratio) between what you're trying to >receive and the noise floor at the receiver's antenna? > >Jim >WA0LYK > > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
