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[aprssig] APRS Message Idea

Keith - VE7GDH ve7gdh at rac.ca
Sun Mar 6 03:07:32 UTC 2005


Wes wrote on Friday, March 04, 2005 12:56 PM PST

> Also, there's another advantage to the decay.  Let's say that I send a message
> right now.  about 1 minute later, you send a message.  They collide because you
> pressed enter at the same time my station resent a copy of my message.
> Now in a fixed timing system where we each retry every minute, we will always
> collide.

I can understand viewing that as an advantage. However, even if you both sent a message at exactly the same moment and for the sake of argument, you were both going to resend it if not acknowledged at one minute intervals, they wouldn't always be transmitted every 60 seconds. The program you are using should be monitoring data from the TNC and not transmit while the frequency is busy. Unless the frequency was very quiet, this will introduce some randomness, and unless the two stations are very close together and using antennas of the same gain and pattern, the odds of them both hearing exactly the same stations all of the time would be fairly low.

Of course, if the frequency was dead silent, and both of you transmitted at exactly the same time and both had either the same fixed timing or the same decaying algorithm, there would be perfect doubles every time. Not much chance of the frequency being dead silent around here, though!

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"





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