[aprssig] APRS Messaging

Brett Friermood brett.friermood at gmail.com
Thu Jul 29 00:29:31 CDT 2010

On Wed, Jul 28, 2010 at 11:56 PM, Adi Linden <adil at adis.on.ca> wrote:
> I've read the docs you've recommended. I suppose I am interested in a lot more detail. In order
> for a message to make it from IS to RF, does the iGate need to listen to the complete IS data
> stream? Or is there a mechanism that allows an iGate to forward the "heard" list to upstream
> server(s) to establish a path for messaging?

The IS is smart. It knows which stations have been heard by which
IGates. When a message is
sent to an RF station, the IS forwards that packet to an appropriate
IGate which heard that station
recently. That IGate then transmits the message packet, which is
received by that station.

So, no. An IGate should not have to listen to the complete data stream
because the IS forwards
message packets to an appropriate IGate irrelevant of any filters
blocking most of the data stream.

> I tried sending message to my two messaging capable radios. One should have been gated
> through my iGate, the other via some other iGate while I was travelling. Neither message ever
> made it. I'd like to understand why. Especially when it comes to my own iGate I'd like to be
>able to configure it appropriately for messaging.

First, the particular IGate has to be configured for two way, as
compared to one way, operation. A
one way IGate only receives via RF and transmits to the IS. A two way
IGate has the ability to take
packets, usually messages, heard on the IS and transmit them over RF.
In many places IGates do
not function as two way, but receive only.

Second, an IGate has to hear an RF station before it can transmit to
it. This is because the IS
doesn't know where to send a packet until it knows which IGate(s) are
receiving that station. I'm
not sure of the exact timing, but an IGate also has to hear that
station fairly recently.

After making sure your IGate is set for gating to RF, try sending a
position packet from your
portable. Then if you send a message through the IS to your portable,
it should be gated to RF.

Hope that helps,

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