Thursday, June 29, 2023

CG Antenna GW-1000 APRS iGate has serious bugs

The CG Antenna GW-1000 APRS iGate gateway appliance contains faulty firmware which causes severe problems to APRS messaging worldwide.  The IS -> RF gateway feature must be disabled on all GW-1000 devices until the bug is fixed by CG Antenna, and firmware is updated on the devices.  Please contact the vendor for further instructions.

CG Antenna has asked me to publish this information so that owners of faulty iGates would more likely learn about the issue. They mentioned a special TTL level serial cable / adapter may be required for the update process.

Description of the issue

When enabled, the APRS-IS to RF (transmit) iGate transmits packets to the RF unmodified.  It does not use the correct 3rd party packet format documented in the iGate specification.  Because of this, other iGates near the faulty iGate assume all of those distant stations are active on the local RF channel, while in fact they may be on the other side of the world.

This causes the other local iGates to transmit APRS text messages destined to all of those remote stations to the local RF channel.  They're operating correctly - the unmodified packets sent by the CG-1000 seem like they would have been transmitted locally on RF.

When a lot of messages are sent, such as during the APRS Thursday event, the local RF channel will be seriously congested.  The CG Antenna GW-1000 device itself will transmit a high rate of packets, packets which are destined to remote stations and which should not be forwarded to RF.  The other iGates confused by the GW-1000 cause additional unnecessary traffic.

Because of the congestion many packets are also delayed long enough to cause the 30-second duplicate packet filtering window to be exceeded.  Packets sent to RF by the GW-1000 will be looped back to APRS-IS and redelivered everywhere in the world.  A single GW-1000 gateway in Switzerland caused delayed duplicate APRS messages to be delivered worldwide.

There are currently GW-1000 gateways operating elsewhere, but it is difficult to track them down and get them disabled.  They are hard to identify, because they send the packets to RF unmodified, without using their own callsign in the 3rd party packet frame like they should.


I have notified CG Antenna of the issue by email on January 14th, 2023, and they confirmed receiving the report on January 17th.  On February 4th they confirmed that they have to make a firmware update.  They have not published updated firmware on their downloads page yet as of June 29th, 2023. After 5 months, on June 21st, they updated their web site to note that the feature is faulty and needs to be disabled.

The bug has been present in the firmware since the launch of the product, but only became apparent when the APRS Thursday event got people to send more APRS messages, and some of those messages were originated near GW-1000 iGate.


Yes, the APRS messaging feature is brittle and it's easy to cause a bit of a mess.

If you produce and deliver a product like this, make sure it is easy for customers to upgrade the firmware without special tools. Be prepared to ship updated firmware in a timely manner if there is a serious issue.

If you wish to implement an APRS iGate, be sure to fully read the APRS iGate spec, and the details page, and fully understand it. If there's something that you don't understand, please don't do it before obtaining more information or help to understand it.

This is not the only current issue out there - there are other software causing similar issues. I'll make an update in the APRS iGate implementation tips document.

The issue was originally debugged and described in this APRS group thread.