Hello, > Once an effective, simple and robust SELCAL standard is developed (again > IMHO it should be a logical extension of the >existing RSID and Call ID > standards) it could eventually be parlayed into a more modern and > effective variant of ALE. By using RR for the nice SELCAL idea. I'm not sure it would be very easy if you need a symetrical acknowledgment. If it is only a one way transmission without any double acknowledgment it is much more easy. RS ID and CALL ID are public sources. So...
73 Patrick ----- Original Message ----- From: "aa777888athotmaildotcom" <aa777...@hotmail.com> To: <digitalradio@yahoogroups.com> Sent: Sunday, November 22, 2009 4:18 AM Subject: [digitalradio] Re: Getting serious about ALE for non-encomm digital hamming > I've gave PCALE a very good try. As implemented it suffers from several > problems: > > 1. It is equipment specific and intensive. You either need an SGC tuner > set up for bypass-on-receive (the only brand I am aware of that has this > capability) or a special antenna that is resonant and efficient on each > band you plan to scan. You can also set up RF switching to bypass the > tuner on receive but that becomes even more complex. There was a computer > controlled tuner on the market that could be controlled by MARS-ALE but > MARS-ALE is not available to mere mortals and the tuner itself was buggy > and is now out of production. > > 2. The link margins necessary for the calling waveform are pretty > substantial. Those used to the relatively robust nature of RSID or any of > the other common digital modes will be sorely disappointed. Even Winmor, > while better than ALE, requires substantially better conditions for > success. > > 3. The software itself is relatively complex to setup and operate. I'm > sure Andy will argue to the contrary :-) However IMHO it's significantly > more involved than just firing up Fldigi and banging away at some Olivia > or PSK. > > 4. The widely shared nature of the ham bands makes collisions inevitable > given the automation inherent in ALE (automation that is the whole point, > in fact) and the limitations of even the best busy channel detection > algorithm. This issue tends to generate a lot of hate and discontent. > However this ought to be the least worrisome issue. With an appropriate > band plan (which already exists for PCALE) the carnage can be limited to > just the ALE calling channels and anyone who wants to use ALE should be > expected to sign up for a certain amount of interference and not be > whining about it as long as it stays on the calling freq's. > > In lieu of full-blown ALE consider the following idea: > > I'm no software engineer and beggars can't be choosers, so forgive me for > making the following related suggestion (Patrick already laid into me on > this once!) Consider that RSID is great for identifying the mode and that > Call ID is great for identifying who is calling. Both use signaling > standards and waveforms that are very simple and robust. But what is > missing is an equivalent SELCAL (selective calling) signaling standard > using waveforms and formats similar to RSID and Call ID. Imagine you > wanted to find somebody monitoring the 3KHz of USB spectrum at 14070KHz > dial freq. You could find a clear spot in the waterfall and transmit the > SELCAL which contains the call sign of the station you wish to reach. At > the receiving station the SELCAL enabled software would function in the > same manner as that currently done for RSID, i.e. detect the call, > display/sound a notification and provide automation for tuning and > answering under operator control. > > Once an effective, simple and robust SELCAL standard is developed (again > IMHO it should be a logical extension of the existing RSID and Call ID > standards) it could eventually be parlayed into a more modern and > effective variant of ALE. By using time synchronized band scanning and > transmission (similar to WSPR et al) probability of intercept can be > substantially improved. Neither the SELCAL or time synchronization > represent new technology and both derive from proven, similar > implementations. So if one were to make a SELCAL on 80M, for example, once > the spot on the waterfall was chosen by the operator (because we can't > rely on unreliable busy-channel detection technology) the SELCAL > transmission would occur at say for instance 10 seconds past the minute. > Synchronized scanning would put all stations on 80M at 10-15 seconds past > the minute, 40M at 15-20 seconds, and so on. > > The last piece would be to perfect busy channel detection and automate the > selection of empty places on the waterfall, but this part of the puzzle is > useless with SELCAL (very useful by itself) and synchronized > scanning/transmission. And once this last part was perfected we are back > to requiring special tuner/antenna solutions. > > > > > > ------------------------------------ > > Suggested frequencies for calling CQ with experimental digital modes = > 3584,10147, 14074 USB on your dial plus 1000Hz on waterfall. > > Announce your digital presence via our Interactive Sked Pages at > http://www.obriensweb.com/sked > Yahoo! Groups Links > > > >
