[aprssig] what is RELAY, WIDE, TRACE, etc?

Bill Diaz william.diaz at comcast.net
Mon Aug 2 13:44:44 EDT 2004

See below:

>-----Original Message-----
>From: aprssig-bounces at lists.tapr.org 
>[mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Larry Cerney
>Sent: Monday, August 02, 2004 10:49
>To: 'TAPR APRS Mailing List'
>Subject: RE: [aprssig] what is RELAY, WIDE, TRACE, etc?


>Good questions.  I'll try to answer some of them.

>[Larry Cerney] There is no difference between RELAY and WIDE.  

I beg to differ.  A digi can be set to RELAY only.  It would NOT respond to
an Unproto path of WIDE, or WIDE2-2 etc but it would respond to RELAY, or
RELAY,WIDE2-2 if the packet not yet been RELAY'd by that digi.

>That being
>said, there is a difference in how they are used.  One would 
>expect there to
>be many more RELAY's than WIDE's.  The reason is if a low 
>powered station
>beacons its position and can not be heard by a WIDE, the RELAY stations
>would repeat it in hopes that a WIDE will hear.  One low 
>powered station
>beacon may produce 3 or 4 repeats by RELAYS depending on the 
>density of APRS
>stations.  So, using RELAY,WIDE is asking RELAY stations hearing the
>beaconing station to repeat the beacon to a WIDE.  

If you have multiple digi's set to both RELAY and WIDE and they can all hear
the originating station using RELAY,WIDE it is not unusual for each digi to
digipeat the orignal packet twice, once as RELAY and again as WIDE. 

Here is an example heard in the Chicago area:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,W9AZ-15*,WIDE <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,RELAY,W9AZ-15* <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,N9WYS-15*,WIDE <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,N9WYS-15,W9AZ-15* <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,W9AZ-15,WB9WOZ-15* <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

N9BH>APW275,W9AZ-15,KC9DJM-12* <UI R>:
:KA9HRO   :test.... is somthing not working here?{015

Due to this ping-pong effect it may make sense (under some conditions) to
use specific digi's rather than generic RELAY, WIDE or TRACE.

>The reverse, WIDE,RELAY is never used.  If a station 
>beacons its position into a WIDE the WIDE would
>repeat it and all RELAY stations would repeat it as well.  
>So one stations beacon using WIDE,RELAY may very well 
>generate 15 or 20 repeats of the original beacon.  
>Not a good thing.  WIDE,WIDE and WIDE2-2 are 
>pretty much the same thing.  Both limit the number of 
>repeats of a beacon to two.  The first WIDE that hears 
>the beacon will repeat it and remove the 
>first WIDE.
>A second WIDE will than repeat it again and that will be the end of it.

>The digi protocol is all about getting the beacon out to be 
>heard, but still conserving the bandwidth.  It serves no use 
>for anyone to hear 5 or 10
>copies of a single beacon.  

Exactly.  A common occurrence when you can hear multiple Digis responding to
both RELAY and WIDE, at least in my area.  YMMV.

 Bill, KC9XG

>[Larry Cerney] Hope this answer some of your questions.
>Denver Igate

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