I think Ed made my argument much more succintly than I did. The only thing he forgot was how any "whitespace/holes" in frequency or time would be synchronized at both ends of a conversation.
It does no good to sync your transmissions to these "whitespace/holes" in your end when the person on the other end, perhaps across the country, has different "whitespace/holes" he/she must utilize to hear. You have to sync your transmissions to the "whitespace/holes" at the distant end. Pretty difficult to do. The only way to do this would be if the different BPL vendors could somehow use a very accurate time base nationwide to assure their "whitespace/holes" were synchronized. Jim WA0LYK --- In digitalradio@yahoogroups.com, "Richard \(Rick\) Karlquist" <[EMAIL PROTECTED]> wrote: > > > -----Original Message----- > > From: digitalradio@yahoogroups.com > > [mailto:[EMAIL PROTECTED] Behalf Of expeditionradio > > Sent: Sunday, October 01, 2006 7:39 PM > > To: digitalradio@yahoogroups.com > > Subject: [digitalradio] BPL-Busting Modes/Techniques > > > > > > BPL-Busting Modes/Techniques > > > > The Digital Voice formats presently in use by hams are not designed > > to be resistant to QRM from BPL (Broadband over Power Lines). The > > OFDM digital voice methods require a much higher S/N than SSB. > > > > In fact, most of our present digital and analog modes are not > > resistant to BPL intereference. However, such BPL-resistant or > > BPL-Busting digital techniques could be designed into new digital > > communication formats for HF and VHF. > > Here is what ARRL's Ed Hare, W1RFI, had to say about this subject > (cross posted from the "BPLandHamRadio" Yahoo group with Ed's consent). > In particular note the comment about "white space": > > Quote: > > > If BPL were simply a number of static carriers, > > digital-signal processing could, in theory, remove them. > > > > Unfortunately, they are modulated, and generally > > modulated fast enough that the carrier itself is > > only a small portion of the energy. The rest is > > ever changing digital information which is, to > > other systems, noise. It will appear as noise > > and the techniques used to remove carriers cannot remove BPL. > > > BPL is typically 40 to 60 dB greater than the > > ambient noise in an area. As noise, it is uniform > > vs frequency. If DSP could copy signals 60 dB > > below uniform noise, we would be using it right > > now to pull signals 60 dB out of our present noise levels. > > > BPL is designed to be spectrally efficient, pushing > > the Shannon limit on the amount of data that can be > > sent on a given communications channel vs frequency > > and noise. There really is no "white space" into which > > other communication can be interleaved. > > > The BPL industry cannot even develop a standard > > to prevent different types of BPL systems from > > interfering with each other, on a channel that they > > fully control. How can we expect that radio users > > can develop techniques to overcome it? > > > And even it it were possible to sneak a bit of > > information through on the channel occupied by BPL, > > what will happen the next time a different > > unlicensed use also uses the same channel? > > > The premise that licensed operation must constantly > > adapt to accomodate unlicensed use is flawed, which > > is exactly why the FCC has rules that place the burden > > of resolving interference on the unlicensed source. > > If the FCC had vigorously enforced its rules, we would > > not be seeing Part 15 noise nearly as rampant as it is. > > > Ed Hare, W1RFI > > ARRL Laboratory Manager > > Unquote > > Rick Karlquist N6RK > Rick Karlquist N6 > 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://standraise.corp.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://standraise.corp.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/
