What can you do if your radio signal isn’t quite strong enough to get through reliably? Move to higher ground? Get a better antenna? More power? Use very narrow bandwidth and very slow data?
Sometimes those are not options. Another way to improve communication reliability is to add redundant information so the message will still get through even if small parts are missing. FX.25 adds forward error correction (FEC) which maintaining complete compatibility with older equipment.
- [**AX.25 Throughput: Why is 9600 bps Packet Radio only twice as fast as 1200?**](Why-is-9600-only-twice-as-fast-as-1200.pdf) [ [*download*](../../../raw/dev/doc/Why-is-9600-only-twice-as-fast-as-1200.pdf) ]
Simply switching to a higher data rate will probably result in great disappointment. You might expect it to be 8 times faster but it can turn out to be only twice as fast.
In this document, we look at why a large increase in data bit rate can produce a much smaller increase in throughput. We will explore techniques that can be used to make large improvements and drastically speed up large data transfer.
Very few hams have portable equipment for APRS but nearly everyone has a handheld radio that can send DTMF tones. APRStt allows a user, equipped with only DTMF (commonly known as Touch Tone) generation capability, to enter information into the global APRS data network.
This document explains how the APRStt concept was implemented in the Dire Wolf application.
WB4APR described a useful application for the [QIKCOM-2 Satallite Transponder](http://www.tapr.org/pipermail/aprssig/2015-November/045035.html).
Don’t have your own QIKCOM-2 Satellite Transponder? No Problem. You can do the same thing with an ordinary computer and the APRStt gateway built into Dire Wolf. Here’s how.
AIS is an international tracking system for ships. Messages can contain position, speed, course, name, destination, status, vessel dimensions, and many other types of information. Learn how to receive these signals with an ordindary ham transceiver and display the ship locations with APRS applications or [OpenCPN](https://opencpn.org).
- [**WA8LMF TNC Test CD Results a.k.a. Battle of the TNCs**](WA8LMF-TNC-Test-CD-Results.pdf) [ [*download*](../../../raw/dev/doc/WA8LMF-TNC-Test-CD-Results.pdf) ]
Many have published the number of packets they have been able to decode from this test. Here they are, all gathered in one place, for your reading pleasure.
- [**A Closer Look at the WA8LMF TNC Test CD**](A-Closer-Look-at-the-WA8LMF-TNC-Test-CD.pdf) [ [*download*](../../../raw/dev/doc/A-Closer-Look-at-the-WA8LMF-TNC-Test-CD.pdf) ]
Here, we take a closer look at some of the frames on the TNC Test CD in hopes of gaining some insights into why some are easily decoded and others are more difficult.
There are a lot of ugly signals out there. Many can be improved by decreasing the transmit volume. Others are just plain weird and you have to wonder how they are being generated.
## Questions? Experiences to share? ##
Here are some good places to ask questions and share your experiences:
The github "issues" section is for reporting software defects and enhancement requests. It is NOT a place to ask questions or have general discussions. Please use one of the locations above.
