Skip, Anyone attempting to connect to a PMBO is really no different than any other ham calling CQ in the hopes of receiving a reply, except that in the case of having a PMBO potentially on frequency it is more likely that a contact can be made. It is dramatically more efficient than any other third party traffic.
As far as your suggestions on scanning, are you suggesting that each PMBO have only one frequency and then to make up for the need to have many different frequencies available to meet the constantly varying propagation conditions, you would need to have many more PMBO systems in operation? My main concern is emergency communications planning and deployment so I do have a bias toward that end and I hope that most hams who want to see amateur radio survive also have a similar "bias." One of the things that I have tried to promote to the WL2K controller has been to increase the number of HF PMBO stations. (And for that matter the vhf/uhf only PMBO's as well). Especially for the lower bands 80 and maybe even 160, which will not tend to cause interference during daylight hours since signals do not travel as far and those bands are very lightly used. These new PMBO's could use the new SCAMP mode to eventually replace much or hopefully all of the Pactor modes someday. If you had an HF PMBO at least every 100 miles or so, they could handle traffic without requiring the use of the higher frequencies and that would free up those longer range frequencies for blue water and emergency traffic folks. Since Winlink 2000 is administered by one person for the entire worldwide system, they have indicated they do not have the ability to add many additional stations. Because WL2K is a proprietary system, they do not want any redundant system to "compete" with their system, even though it would be far better for the amateur community, and for emergency communications, to have many such systems in place that are not directly connected to each other. If one WL2K system failed, you would have other options. And yes, the chance of this happening needs to be placed in the calculus of emergency planning. By the way, I did not see any retraction of your claim that the WL2K had been infected by a virus, when in fact it had not. We need to keep a balanced perspective on what is or is not real. Because of such emotional views on this subject it seems that each side overstates the facts so that those of us in the middle have to try and figure out what is really true. Maybe that is normal politics, but I would hope that more discussion could center around practical solutions to ham radio's major reason for its existence ... emergency communications. And perhaps even more importantly, if you don't have those systems in place and used daily, contrary to what some people believe, they won't be there when you need them the most. 73, Rick, KV9U -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] Behalf Of Skip Teller Sent: Thursday, April 21, 2005 8:09 AM To: [email protected] Subject: [digitalradio] RE: Winlink Scanning > >>>By distributing callers across multiple scanned frequencies, the > incidence of multiple callers colliding on a single frequency is > reduced. Such collisions prevent the PMBO from connecting with any > of the competing callers, increasing time-from-request-to- > connection. If the callers cannot hear each other, then they don't > know to back off and the collision is extended in time -- further > increasing time-from-request-to-connection for all callers. If the PMBO is busy passing traffic on another frequency, he is not scanning, so the really significant delay in time-from-request-to-connection is always waiting for him to finish passing traffic and resume scanning. Once he resumes scanning, he is going to connect with the strongest caller that he can hear, even if there are multiple callers. The only way he would be unable to connect is if all callers were at the same strength AND timing. So, using scanning has a negligible improvement in the time-from-request-to-connection, and that would only apply to ONE of the multiple callers - the one that was successful. For the others, that time might be infinite. > > > > Because the PMBO stations are not allowed to broadcast, the client > MUST call a specific PMBO. If he does that on any of the alternate > frequencies of the PMBO, he cannot connect until the PMBO is > finished passing traffic on the frequency being used. The client > station may transmit continusouly for a connect, but he will not > achieve one until the PMBO finishes passing traffic and starts > scanning again and picks up the client station's transmission. > > > > The result of the scanning is that the Winlink client station > is "holding the frequency" for his own use and nobody can use it or > capture it while he is doing that. > > >>>If callers (which are always attended) refrain from initiating a > request on a frequency that is already busy or becomes busy after an > unsuccessful request, then the caller is not guilty of holding the > frequency. As I mentioned in my previous post, the problem is that a > Winlink-on-Pactor PMBO has no busy detector, and thus threatens QSOs > on any of its scanning frequencies with hidden-transmitter QRM. > Knowledgable operators wishing a QRM-free QSO would therefore tend > to avoid any frequency scanned by a Winlink-on-Pactor PMBO. Is a > PMBO "holding" its scanning frequencies? Legally, no; pragmatically, > yes. 14076.9 may currently be clear, but there's no way I'll call CQ > there. With scanning, the caller is holding the frequency whether or not he is "guilty" of doing so, which would only be the case if he were aware that the PMBO was busy and he kept calling. He may not be "guilty" of holding the frequency, but he is accidentally holding the frequency nevertheless, because he thinks it is clear and the PMBO is listening for a connect, when, in reality, that is not true. The PBMO is not listening (on the alternate frequency) for a connect. Eliminating scanning eliminates this problem. The hidden-transmitter problem is certainly real, but ONLY after the PMBO has been triggered to transmit. In practice, the MAJORITY of QRM, as you can easily observe on the waterfall, is not the hidden-transmitter, but the client stations transmitting, breaking up the QSO, waiting for a while, and doing the same thing over again. If they do trigger a PMBO to transmit, then the QRM generally becomes much worse, as can also be seen on the waterfall. If there were no scanning, then the calling client station would not be repeatedly calling on the alternate frequency, even if he could not detect weaker activity on the frequency, because he would be monitoring the same frequency the PMBO he wishes to contact is currently using. In fact, HALF of all the Winlink advertises frequencies would NEVER be used by Winlink if there were no scanning, unless the number of PMBO's doubled and scanning was eliminated. If half of the frequencies currently advertised by Winlink were eliminated from their system, then half of the PMBO's could be reassigned to the vacated frequencies, leaving a large block of frequencies available for everyone else to use without fear of a PMBO station popping up on top of their QSO like they do now. So, the real fair solution to the problem is: 1. Eliminate scanning. 2. Reassign PMBO to frequencies in a contiguous block, with a geographical separation of PMBO's on alternate frequencies, as much as possible, to lessen the chance of adjacent channel interference. This keeps the Winlink traffic handling capacity the same, frees up space for others to use, and eliminates the QRM to others by PMBO stations. The time-from-request-to-connection would not be noticeably different, if there is any at all. 73, Skip KH6TY The K3UK DIGITAL MODES SPOTTING CLUSTER AT telnet://208.15.25.196/ Yahoo! Groups Links -- No virus found in this incoming message. Checked by AVG Anti-Virus. 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