[aprssig] Identifying TX Igates

Bob Bruninga bruninga at usna.edu
Mon Sep 19 14:00:16 CDT 2011

Steve Dimse Reports:

> ... icons are not a good idea for reporting functionality 
> because a station can have multiple functions...

> ... [but] Igates send out the IGate packet including the 
> number of stations it serves and the number of messages it 
> has transmitted; that is what the page reports. Any station 
> with a message cnt > 0 [thinks it is a TX Igate] though 
> [we] cannot guarantee they [actually have a working TX].

> [This FINDU.COM IGate function will identify] all iGates 
> heard in last 24 hr.

> http://www.findu.com/cgi-bin/igate.cgi?

Great function.  Thanks for reminding me!  

But, as you indicate, it is not conclusive either, since maybe 1% or less of
all packets are messages and the probability that a message has gone to an
APRS user in range of a given Igate in the last 24 hours is vanishingly

Although this data does pretty well prove a positive (those that actively
TXed a message in the last 24 hours), it does not help us identify the
negatives (Those RX only gates that do not).  It is interesting to see that
some are very busy though as TX gates!

Agreed that using SYMBOLS is not perfect for this distinction.  But unless
someone has a better idea, it is the best method we have...

Maybe someone could write a MESSAGE CRAWLER that then watches for MESSAGE
mobiles in one-hop range of IGates, and PINGS them with a message and then
gathers statistics on if the mobile ACKS it. (though again, we may not know
WHICH IGate was the TX gate0.  But that does not matter so what, since we
would get proof that a mobile DOES get messages in that area.

I think if we find an unidentified IGate that is RX only and is not using
the "R&" symbol overlay, we should encourage that operator to do so...

In the meantime, and while appreciating the feedback... Given that we have
had the R and I overlays for 5 years and 75% or so of all IGates use them, I
do not see any real reason why not to suggest also the "T" overlay.  I
checked, and presently no one on FINDU is using a "T" overlay on any IGate,
so it seems to be available.  If no one further objects, I will update the
SYMBOL table to include this option... http://aprs.org/symbols/symbolsX.txt

Thanks for the thoughtful feedback.


On Sep 19, 2011, at 11:39 AM, Bob Bruninga wrote:

> All IGate operators please read and consider action on this proposal.
> RX-only IGates kill the functionality of the APRS-IS as a universal
> And they give casual observers the impression that APRS has global
> connectivity, when in fact, that view has lots of invisible holes because
> RX-only IGates.
> Compounding this problem is that we have no way of knowing if people are
> using the right symbol for their IGate.  Are they using "I" because it is
> really  a TX Igate, or just because it seems logical?
> Using http://www.findu.com/cgi-bin/symbol.cgi?icon=Iamp&limit=2000 I see
> "I&" Igates
> Using http://www.findu.com/cgi-bin/symbol.cgi?icon=Ramp&limit=2000 I see
> "R&" Igates
> Maybe we need to have a 3rd symbol, a "T" Overlay so that operators of
> serious two-way IGates and indicate their dedicated intent to provide good
> APRS-IS local service.  These guys will take the trouble to indicate a TX
> Igate.  When we see one of those, we have proof-positive that the IGate
> includes a two-way TX capability.
> We could even go one step farther.  We could indicate the NUMBER OF HOPS
> that the IGate uses by default for IS-to-RF packets.  This could help us
> better manage overlapping IGate coverage...  So how about this plan:
> I& - is an IGate, but is ambiguous with respect to transmitting
> R& - means it is definitely an RX only IGate
> T& - Means it is definitely a TX IGate with one hop path only
> 2& - means it is a TX igate clobbering two hops in all directions
> 3& - means it is a TX SPAM GENERATOR , (or a legitimate special case)
> Etc..
> Should we do this???
> Bob, WB4APR
> An easy way to check an IGate is to find a mobile Kenwood, Yeasu or other
> two-way APRS messaging device on http://map.findu.com/callsign and then
> the internet send him a message.  If he gets it, then the nearby IGate is
> 2-way.
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