APRS Reply Relays

[motormayhem]

Hey Guys,
I'm recently having some trouble where I can send messages / position packets, but not receive packages directed at me. I am however able to receive packets on the local network (WX stations, digits, etc) so I don't believe it's a decoding error on my side. Looking at my path I am using "WIDE1-1, WIDE2-2" and it appears I am relaying though a low level repeater, then a mountain top digi, then an Igate. I can't hear the mountain top digi from my location. I'm wondering if the path of response messages isn't getting back to me. How does the APRS system know what digi's/igates to send out a packet directed at me? Can I view the path say a message from SMSGTE is taking and where it is being broadcast on RF to get to me? My setup is a mobilinkd BT TNC to a Kenwood TM-V71A using APRSDroid. I'm a bit lost on how to troubleshoot this seeing as I am able to send/receive packets, just not messages directed at me from any service.

 

[AK9R]

A callsign would help us decode what's going on.

It's possible that the I-gate involved here is a one-way I-gate in that it receives APRS packets via RF and injects them into the APRS-IS, but it doesn't transmit APRS packets from the APRS-IS that are directed at users in the area.

A two-way I-gate knows to transmit packets directed to you because it knows you are in the area. Once you move out of it's area, it will stop transmitting packets for you.

 

[motormayhem]

The callsign is KF7EFI-9. So assuming the IGate is transmitting a packet, how does that get relayed? If I’m in a spot where I cannot hear the igate directly and am getting to it via a mountain top digi will a packet from the igate try to take a similar path back?

 

[talkpair]

It appears that WB7QMR-10 is gating the majority of your packets from RF to APRSIS. The symbol being used by that station indicates they are a receive-only igate.

N7HND also comes up as an igate, but there isn't a way to know from the symbol if it is an RX-only or a 2-way igate, as their main function is a digi.

This pretty much confirms W9BU comment about 1-way igates.

 

[motormayhem]

Interesting, surely a town the size of Tucson has a bi-directional igate. I played around with it a bit more directing my packets directly to K7TUS which is one of the larger digi/gateways and I believe is bi-directional. Looking aprs my path was “KF7EFI-9>APDR15 via K7TUS,qAR,N7HND”. What does the qAR,N7HND mean? I believe K7TUS was directly gating the packet or am I misinterpreting this? Still not receiving any messages directed at me. Is there a way I can see the path a packet from say smsgte takes to get to me to see if it’s trying to make it to RF? Looking at the raw packet for SMSGTE I see “SMSGTE>APSMS1,TCPIP,qAS,VE3OTB-12::KF7EFI-9” which I believe is the path into the internet, but can I see the path back to RF?

 

[AK9R]

q Construct

N7HND is the IGate.

 

[talkpair]

There is no way that I know of to see which station(s) are picked to gate message packets.

I did notice K7RST-11 has a comment about it being a UHF digi. I am guessing it's on 445.925, since KB7KFC-2 has that frequency in it's comment and has also heard K7RST-11. You may want to research that frequency and see if it has any special conditions.

 

[vagrant]

I could be wrong but...

A cursory look at APRS.fi and it appears that you do not have a "TX igate" in your area. As you are unable to RX messages via the Internet to RF that pretty much confirms it.

- There are digipeaters like N7HND which the nearby RX only igate WB7QMR-10 handles to get the packets to the Internet.
- There are various RX only igates that are using the symbol "I", but should actually use "R" like WB7QMR-10 does properly.

- A buddy nearby setup a TX igate "T" and he only RF transmits messages. His setup will also RX messages and position packets and pass those to the Internet. (He is intentionally not setup to be a digipeater as we have enough nearby.)

A possible solution would be for the Op to setup a TX igate at his QTH, presuming they have dedicated Internet access. Five watts of power may be fine considering the nearby digipeaters. I would only TX messages with it as another digipeater in his area is not necessary.

 

[motormayhem]

So I left Tucson last night to travel to central Az. Once I was about an hour out of town I was able to receive messages so yes Tucson apparently does not have a TX igate. I’m quite surprised given its size. I’m only in Tucson part of the year, but I may consider setting up one.

 

[vagrant]

Many hams are unaware, or do not use APRS. Be the hero, make it happen.

The nearby buddy who set his up told me that his station pushes quite a bit of messages. He did not provide a number, but he seemed surprised at the amount.

 

[talkpair]

It's really difficult for others to assess what is going on in your area without actually being in your area.

If I were you, I would do some research on TAPR...The Tucson Amateur Packet Radio organization. Look to see if any of any of the members are still local and active and run the problem by one of them.

That group has been around a while and I value their contribution to packet and APRS.

TAPR – Tomorrow's Ham Radio Technology Today