Bluetooth KISS TNC for Android devices $50 with Li-Ion Battery (MobilinkD)

This looks pretty interesting.  It's a nicely done bit of integration, to provide a hardware TNC for APRS operation at a reasonable price as long as you have an Android phone or tablet handy.

There are several HTs with APRS built-in. I own a Yaesu VX-8DR.  However the user interface on the radio is very limited and there is no direct access to the TNC.  The APRS on my VX-8DR isn't all that useful to me because the GPS is external. The GPS from Yaesu is very expensive and reportedly doesn't perform very well: poor reception, high power drain.

A cheap, Chinese HT could be combined with this to make a nice functional APRS unit that is still pretty portable.  See my other posts about APRSdroid.

Features:

• Small battery operated TNC for attaching to an HT in a backpack style setup. 
• Connect to Android via Bluetooth serial protocol, so no cable needed to the phone or tablet.   Only an audio cable is needed to connect the TNC to the HT.
• Designed to work with APRSdroid, a great free or paid APRS application for Android.
• Has a 1,200 mAh Li-Ion battery for 48 hours of operation, includes USB port and battery management chip to charge the battery.
• Open source design.   Code and schematics are available.
• Easily hackable, microcontroller is Atmega 328 same as Arduino, An Arduino can be used to program it if you are building it from a bare atmega328
• Based on an AVR/Arduino TNC design that uses a real time OS (BeRTOS) by KI4MCW.  This has been on my list to build and experiment with for a while. https://sites.google.com/site/ki4mcw/Home/arduino-tnc
• Could reuse the hardware for other projects/digital audio protocols. The board is basically a battery powered Arduino with a bluetooth serial interface, and rudimentary audio input/output.

Mobilinkd's site:
http://www.mobilinkd.com/tnc/

Other side notes of possible interest

• Android Only - This will not work on iOS, because Apple doesn't have (or won't allow) Bluetooth Serial Protocol access from iOS apps.  Openness is the primary reason I have an Android phone instead of going with the flow and having a locked down iOS device like everyone else.
• The Yaesu VX-8DR GPS unit requires buying not only the GPS module but either a bracket to attach it to the top of the radio or the external waterproof mic unit. The external mic is also pretty overpriced. The connectors for both the mic, and the GPS are proprietary.
• The Yaesu VX-8GR had the GPS built-in and allowed getting the waypoints from the serial connector. However it has been discontinued as of sometime in 2013. It was going for a reasonable price, approximate $350 before it was discontinued.
• I've considered building a GPS for the VX-8DR using Adafruit's Ultimate GPS module which sounds pretty cool. However, the GPS parser in the VX-8 will only handle GPS sentences with the same padding as the Yaesu unit. It's possible that the Adafruit unit, which has an onboard microcontroller could be adapted to make it VX-8D friendly, but it's not clear if that is achievable, at least without a ton of effort.

Yaesu FT-857D Crashes (reboot loop) after programming a 4 character channel label with CHiRP

I found a small latent problem in the Yaesu FT-857D firmware which could cause the radio to crash and go into a reboot loop when a 4 character or less label was created using the free CHiRP radio programming software. I isolated the problem, the Yaesu FT-8[59]7 driver in CHiRP now works around the problem starting with daily builds around June 27th, 2013.

This blog post just archives the info in case someone else stumbles across the problem either by using an outdated version of CHiRP or writing their own software for manipulating the Yaesu FT-8[59]7 memory. This probably applies to the FT-897(d) as well.

The problem has to do with how the 8 character memory label is padded.  The older versions of CHiRP were padding unused characters with 0xFF.  An unused memory label defaults to eight bytes of 0xFF on the radio.   When a label is created for a memory (channel) on the radio, it is set to 'CH-NNN  '.  There is no way that I found, from the radio to create a memory label that wasn't space padded.  Padding with 0xFF for labels that are 5 characters or more doesn't seem to cause any issues. The corrected version of CHiRP now space pads the label out to 8 characters.  I believe G4HFQ's FTbasicMMO, only space pads as well.

Marco Filippi, IZ3GME the primary author of the FT-8[59]7 driver made the change within hours of me reporting the problem.  The very next CHiRP build had the fixed version of the driver.  The current release of CHiRP, 0.3.1 from April 2013, has the old driver.  Until a version later than 0.3.1 is released, you need to download a daily release.

I believe I'm justified in calling this a small bug in the Yaesu firmware, because when the radio accesses the memory with the 0xFF padded label, it goes into a continual reboot cycle with lots of clicking of relays and a beep each time it restarts.  From the radio itself, the only way to resolve this is to force a reset which will clear some of the settings and/or memory entries depending upon which reset is used.  My opinion is the radio's firmware should be a little more forgiving than this.

Note: if your Yaesu FT-857/897 ever does get stuck in a crash/reboot loop, you can still get into clone mode, and save a copy of the whole set of radio settings and memories before you reset it. 

Another thing I learned about the FT-857/FT-897 firmware during all of this is that it is nearly impossible to get a pristine memory image from the radio.  The radio has three different types of resets which will clear all memories, some settings, and a "full microprocessor reset" which is supposed to return the radio to all factory settings.  However, the way this is implemented, the eeprom isn't really reset to a known default, just select bits are cleared marking all of the memory entries unused.  Most of the previous memory channel settings, including the label are still there, which makes things confusing if you were looking for clear, reproduceable state.

(Note: There probably is a way to completely clean the EEPROM to a known, reproduceable state, but you don't want to use it.   For some reason, Yaesu's firmware writers included a CAT command which would completely reset the radio including the specific calibration settings that are written into EEPROM for each radio.   Unforatunely, it's not that improbable to accidentally trigger this when using the CAT interface a lot, possibly with a baud rate setting mismatch.  Every FT-8[59]7 owner should use the service menu to record all of the calibration settings in case they are ever lost.  This has been documented on the FT-857 and FT-897 Yahoo group's.   There is also a few pieces of software, including a PERL script from 0xdecafbad.com for reading out the calibration settings over the CAT interface using the undocumented CAT peek command.

Hopefully I'll get around to posting and documenting more of the things I've learned about the FT-857d.  All of the information is out there, but not necessarily organized to make it easy to find.

References

• CHiRP Issue 937 (bug report for FT-857 crash
• 0xdecafbad's FT-8[59]7 Calibration Dumper - ft897calibration.pl PERL script
• 0xdecafbad.com Blog Post about the calibration dumper

Understanding the Arduino platform (You don't need a separate Arduino board for everything you build)

From time to time, I've heard some objections about using the Arduino platform to build things because of the costs. Arduino prices have come down, but it's also worth understanding you don't need an Arduino board for every project.
The Arduino is essentially a board that has an Atmel AVR ATmega328p microcontroller chip on it with a USB interface, power supply, clock crystal, and a lot of sockets for the pins in a (now) well known form factor that allows stacking additional board/modules called shields for additional functionality.
The older units had an FTDI USB serial interface chip on it which added significantly to the cost, but had some interesting alternative uses. Newer Arduinos use another Atmel AVR chip that has USB support built in, which winds up being less expensive than the FTDI chip.
The form factor (size of the board with pin sockets) makes it easy to get started and prototype but also adds to the cost.
The Arduino software environment also makes it significantly easier to get started with microcontroller programming.  There is an small, development environment for Windows/Mac/Linux which completely wraps the C/C++ compiler and chip programmer making it a simple push button operation to compile your sketch and program the chip.
The AVR microcontroller is essentially a full system on a chip, with an 8 bit CPU, a small amount of RAM, 32K of flash memory, a small EEPROM, and a TTL level serial interface.  There is even an internal oscillator so you don't have to use a separate crystal, or resonator, if you have an application where you don't need the timing stability offered by an external crystal.
Bare ATmega328P chips cost $2-4 in single quantities.  They come without any programming, so you need hardware to program the chip.
The Arduino gets around the need for having hardware to program the microcontroller chip by preloading a bit of firmware, a boot loader, that allows the chip to receive code over the USB/Serial interface and write it to the 32K flash to program itself.
An Arduino can be used to program bare AVR chips, so you can use one Arduino to create more Arduinos.
So the moral of the story, once you've built something using an Arduino, you don't have to dedicate a whole Arduino board to each device.  You can easily build your project with a bare AVR chip and only the supporting components you need for your projects.  Typically this can be done for less than $5.

Note: This post is another reply that I had sent to a mailing list that I thought would be worth preserving and sharing as a blog post.

Using an Oscilloscope to Check Your (Transmitted) Signal

N2NOV had posted that Tektronix now has a Youtube channel with videos on how to properly use an Oscilloscope.  Many years ago, Tektronix published a good free PDF, The XYZ's of Oscilloscopes. It was
good but a little dry compared to a video presentation.

Well equipped radio operators have a special type of dedicated oscilloscope called a service monitor which allows viewing your transmitted signal, by tapping the radio frequency (RF) from the transmission line. Recently I came across a Youtube video that showed how to build a very simple RF sampling circuit that would allow using a common oscilloscope to monitor the RF output of your transmitter (transceiver).  While this won't do everything that a dedicated service monitor would do, it's a pretty cool way to check your signal if you only have an oscilloscope.  The RF sampler circuit described should be less than $10 in parts.

Personally I find this sort of thing to be very cool.  Even if I had an unlimited budget for buying equipment. I don't have the room to store it in NYC.

• How to Use an Oscilloscope
• Tektronix Youtube Channel
• How to monitor your Ham Radio Transmitter using an Oscilloscope

Note: This will only be useful for monitoring AM and SSB transmissions. I hope to come across something not too difficult to build that would be useful for looking at the output of an FM transmitter like the type most commonly used on VHF and UHF.

Good Tutorial on TCP/IP Diagnostics using Traceroute

MTK, just sent me this today.  It's a presentation and paper by Richard A. Steenbergen, from 2009 that covers the finer points of diagnosing TCP/IP networking problems with Traceroute.  It looks like it was originally presented as a tutorial at NANOG.  Why am I posting this?  If you tried to google "traceroute tutorial" you'd get tons of fairly lame overviews that show some traceroute output and attempt to explain it. 

To quote one of the intro slides:

Few people are actually skilled at interpreting traceroute.  Most ISP NOCs and even most mid-level engineering staff are not able to correctly interpret a complex traceroute.  This Leads to a significant number of misdiagnosed issues, false reports, etc, which flood the NOCs of networks world-wide.  The false report rate is so high that it is almost impossible to
report a real traceroute-based issue through all the noise.

There is a lot of nitty gritty practical details in here. Even if you rarely use traceroute, you'll learn a lot from this. This is one of those rare, good presentations and papers to file away so you can refer back to it and hopefully use to enlighten others.

• Presentation: A Practical Guide to (Correctly) Troubleshooting with Traceroute
• The Paper: Traceroute, PDF, 20 pp
• NANOG listing for the tutorial, includes a link to a .WMV video 

Hope This Helps.

Hams, Yahoo Groups and private message archives

Someone asked about learning the Yaesu VX-8 on one of the mailing lists I subscribe to. I sent the following response which has got general advice about Yahoo groups which seem to be popular with ham radio people. The most important bit:

If you are a member of any active Yahoo group that has useful information to share, consider lobbying the group's owner to make the message archive public.  It makes the information more accessible and should cut down on some of the redundant questions.

Please spread the word. The more information that is easily searchable the more we all benefit. 

Here's the original response:


I have a Yaesu VX-8DR and would be happy to answer questions about it.It has a lot of features and the manual isn't always as straightforward as it could be. I've learned a lot from reading the VX-8 Yahoo group for the last 2-3 years.

I suggest joining the Yahoo VX-8 Group, and then reading some of the old message traffic.  Many of the questions about the radio have been asked and answered since it came out.  Also check through the files and links section of the yahoo group.  There are some documents people have put together on working satellites, APRS and the ISS, etc.

Yahoo groups seem to be pretty popular for hams and there appears to be one for most popular radios.  If you have, or are considering purchasing a particular radio, check to see if an active yahoo group exists for it.
Then join it and look through the message and file archive.

Unfortunately one drawback of Yahoo groups is by default the message archive is only accessible by  members.  This means Google and the other search engines can't index the information stored in them.  The result is it's harder for you to search for answers to your questions.  You'll need to go to the Yahoo group and use its search function to look for answers.  (I still recommend using google to search for answers that might be available on the open internet in blog posts, open forums, etc.)

If you are a member of any active Yahoo group that has useful information to share, consider lobbying the group's owner to make the message archive public.  It makes the information more accessible and should cut down on some of the redundant questions.

Here are a few groups that I belong to that I'd like to get opened up:

• Wouxun_KG-UVD1  Wouxun KG-UVD1 (2)(3)(6) and KG-UV920R
• Yaesu VX-8R
• Yaesu FT-857D
• Uniden BC346XT
• Uniden BCD396T
• Uniden BCD396XT

There's a lot of knowledge locked up in those groups.

Hope This Helps,
--Rob

APRSDroid, freely available APRS app for Android phones

Here's another post that I've sent to a mailing list, that I thought might be worth sharing more widely. Many more people have Android phones with a built in GPS than have APRS capabilities via their radios.  This could be a useful tool in the toolbox for those who do public service events.

The APRSdroid application provides APRS functionality for Android Phones. An installable .apk as well as the source code are freely available from the developer's site.

• http://aprsdroid.org/

The same application is also available in the Android Market for $4.50, which is an option for supporting the developer.

The app enables sending and receiving APRS beacons and messages via a data (internet) connection to the APRS-IS network.  Map data is also downloaded from the internet.  (This mode requires that you have cellular data coverage.)

The app can also generate AFSK tones for sending ARPS beacons and messages via a connection from your phone's earphone jack to your HT's microphone. Note VOX capability is needed.  The ability to decode AFSK tones isn't implemented yet, so it's not a complete software TNC replacement. However, it's on the requested feature list.

I was successful in making a straight-through connection from my Samsung Galaxy Nexus to my Wouxun KG-UV2D.  My Yaesu VX-8DR had no problems decoding the packets from APRSdroid via the Wouxun.   I need to go out to some open spaces to test how well it will be picked up by actual APRS digitpeaters.  It can be pretty hard to get APRS beacons out on NYC streets.   In general 2 meters can be pretty spotty on the streets in NYC. 70cm does a much better job of being reflected off of buildings, which is expected.

An alternate version of the application that uses pre-downloaded offline maps is available. This can be handy in places where there is no cellular coverage. I was able to get APRSdroid loaded and running on the Kindle Fire using the offline maps version (OSM).  The Kindle Fire is really too limited of a device to be useful for APRS since it doesn't have GPS or cellular data service.  However, it does have a 7" screen which would be useful for

iPhone users: I've seen similar apps listed in the app store, but I have no experience with them.