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[aprssig] kenwood d7a and packet RX

Wes Johnston aprs at kd4rdb.com
Thu Mar 3 13:05:49 UTC 2005

The thread yesterday about battery life got me thinking about how you receive
packets with a d7a with the battery saver on.  You don't... unless the
frequency stays pretty busy and prevents the reciever from going to sleep.

I don't own one, but I seem to recall on a yaesu ht I owned you could adjust the
"sleepy" time.  Is there such a way to do this with the d7a?  Make it as long as
possible, say 30 seconds of silence before the receiver will go to sleep mode.

Now, what I'm about to say is NOT for your main wide digi, but could certainly
be implemented on a smaller scale such as a temporary digi put on air to
support SAR.  Every TNC has an AXHANG paramater.  This parameter allow the TNC
to have a longer TXdelay when used thru a voice repeater, since if the repeater
is off air, it may take it .5 to 1 second to come up.  And repeaters have a hang
time of 2 to 5 seconds.  So the drill is that if no packet has been heard in,
say 5 seconds, we'd need to use the extended TXdelay to make sure the voice
repeater was on the air before actually sending the packet.

Now, if we apply this philosophy to a digipeater who is talking to an audience
of handitalkies that are in sleepy reciever mode, we can make the digi keyup
the first time with a long enough TXdelay to allow all the HT's to sample and
wake up.  Subsiquent packets transmitted by the digipeater would not have the
extended TXdelay.  Only after XX seconds of silence (coordinated with the
sleepy timer on the HT's), does the digipeater use the longer TXdelay.

Of course KISS TNC's can't do this, so the solution there is that the host
software would send a bogus packet ahead of the first packet... to allow the
HT's to see something on RF and make them wake up.


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