Mar 312013
 

Recently I purchased a second hand Kantronics KPC-3 packet TNC. Brisbane Area WICEN make heavy use of packet at one particular event, the International Rally of Queensland, where they use the 1200-baud network to report the scores of rally cars as they progress through each stage.

Now, I’m a newcomer to radio compared to most on the band. I got my license in 2008, and I’ve only had contact with packet for the last two years, and even then, mostly only at a distance.  I had a hand-held that did APRS, and I’ve also done some APRS using soundmodem and Xastir.  Full-blooded AX.25 has taken me some time, and I’m slowly coming to grips with some of it.

One thing I wanted to try and figure out, is how to re-lay traffic from a host connected to the RF world, to a host on a local network.  I knew there was some protocol that did it, but didn’t know what, or how it worked.  Turns out the protocol I was thinking of was AXIP, which basically overlays AX.25 frames directly atop IP.  There’s also a version that encapsulates them in UDP datagrams; AXUDP.

The following are my notes on how I managed to get some routing to happen.

So, my set-up.  I have my FT-897D set up on 145.175MHz FM, the APRS frequency in Australia.  (I did go hunting for BBSes the other night but came up blank, but since APRS uses AX.25 messaging, it’ll be a start.)

To its data port, I have the KPC-3, which connects to my trusty old P4 laptop via good ol’e RS-232 (the real stuff, not pretend USB-RS232, yes the laptop is that old).  This laptop is on my local LAN, with an IP address of 192.168.64.141.

In front of me, is my main workhorse, a MacBook at the address of 192.168.64.140.  Both laptops are booted into Linux, and my target is Xastir.

First thing I had to do was compile the AX.25 kernel modules, and the ax25-tools, ax25-apps.  The userspace tools needed for this are: ax25ipd and kissnetd.

On the RF-facing system

This is the P4 in my case, the one with the TNC. First step is to get the TNC into KISS mode. In the case of Kantronics TNCs, the way to do this is to fire up your terminal emulator and run int kiss followed by reset.

Important note: to get it back, shut down everything using the serial port then run echo -e '\0300\0377\0300' > /dev/ttyS0. This sends the three-byte exit-kiss-mode sequence (0xc0 0xff 0xc0).

Configure /etc/ax25/ax25ipd.conf. Three things you’ll need to set up:

  • mode: should be tnc
  • device: should be whatever your serial device is (more on this later)
  • your default route: this is the host that will receive ALL traffic

In my case, my ax25ipd.conf on the P4 laptop looks like this:

socket ip
mode tnc
device /dev/ttyS0
speed 9600
loglevel 2
broadcast QST-0 NODES-0
# This points to my MacBook; d means default route
route 0 192.168.64.140 d

Once done, we start the ax25ipd service as root, it should fork into the background, and checking with netstat should show it as listening on a raw socket.

On the client machine

Here, we also run a AXIP server, but this time to catch the packets that get flung our way by the other system. We want Xastir to pick up the traffic as it comes in. Two ways of doing this.

One is to configure kissattach to give us a PTY device which we then pass onto ax25ipd, then run Xastir as root and tell it to use the AX.25 stack directly. Gentoo’s Xastir ebuild ships with this feature disabled, so not an option here (unless I hack the ebuild like I did last time).

The AX.25 tools also come with kissnetd: this basically generates several PTYs and links them all together so they all see eachother’s KISS traffic. So ax25ipd will receive packets, pass them to its PTY, which will then get forwarded by kissnetd to the other PTY attached to Xastir.

There is one catch. Unlike in kernels of yore, kernel 2.6 and above (3.x is no exception) do not have statically configured PTY devices. So all the AX.25 docs that say to use /dev/ptyq0 for one end and /dev/ttyqf for the other? Make that /dev/ptmx for one end, and the tool will tell you, what the other end is called. And yes, it’ll change.

Run kissnetd -p 2; the parameter tells it to create two PTYs. The tool will run in the foreground so make a note of what they’re called, then hit CTRL-Z followed by bg to bring it into the background.

vk4msl-mb stuartl # kissnetd -p 2
kissnetd V 1.5 by Frederic RIBLE F1OAT - ATEPRA FPAC/Linux Project

Awaiting client connects on:
/dev/pts/1 /dev/pts/4
^Z
[1]+  Stopped                 kissnetd -p 2
vk4msl-mb stuartl # bg 1

Now, in this example, PTYs 1 and 4 are allocated. I can allocate either one of them to Xastir or ax25ipd, here I’ll use /dev/pts/4 for ax25ipd and the other for Xastir. It is possibly best if you make symlinks to these, and just refer to the symlinks in your software.

# ln -s /dev/pts/4 /dev/kiss-ax25ipd
# ln -s /dev/pts/1 /dev/kiss-xastir

Whilst you’re at it, change the ownership of the one you give to Xastir to your user/group so Xastir doesn’t need to run as root.

Set up /etc/ax25/ax25ipd.conf on the client. Here, I’ve given it a route for all WIDE* traffic to the other host. It might be possible to just use 0 as I did before, I wasn’t sure if that’d create a loop or not.

socket ip
mode tnc
device /dev/kiss-ax25ipd
speed 9600
loglevel 2
broadcast QST-0 NODES-0
# This points to my P4, attached to the TNC; d means default route
route WIDE* 192.168.64.141 d

Now start up ax25ipd and Xastir, you should be able to bring up the interface and see APRS traffic, more over, you should be able to hit Transmit and see the TNC broadcast your packets.

Some stations visible direct via RF

Some stations visible direct via RF (click to enlarge)

Mar 082013
 

Just recently, I managed to kill yet another hand-held. Not deliberately, just a combination of conditions and not adapting my behaviour to suit.

I have a Yaesu VX8-DR, which I mainly use on the bicycle for APRS. It isn’t bad, the GPS could be faster, and the Bluetooth is more of a gimmick (in that it only works with some Bluetooth headsets and is intermittent at best), but my biggest nit with it, is that you can’t charge the thing while it’s turned on.

This leads me to the bad habit of just leaving a DC power lead semi-permanently plugged into the side, with the other end plugged into the 12V supply on the bicycle. You guessed it… one bad day of rain, some water got in via the DC jack and basically destroyed it.  I’m pretty sure warranty doesn’t cover that kind of abuse.

I’m not in a hurry to buy another one.  In fact, I probably won’t.  I’m too clumsy to look after an expensive one, so better just to keep the two Chinese cheapies going (Wouxun KG-UVD1P’s).  This lead me to thinking about what I specifically like in a hand-held, and what features I’d look for.

Looking around, it seems the vast majority of sets out there are evolutionary.  An extra handful of memory channels, higher power, bigger battery, ohh look Bluetooth, and this one has {insert some semi-proprietary-digital-mode here}.  Yawn!

Most of them have tiny screens which can’t show a decent amount of information at a glance.  Digital voice is a long way being usable, with about 3 or 4 proprietary or semi-proprietary competing standards.  What about D-Star you say?  Well, what about it.  Nice mode, pity about the codec.  How about P25?  Same deal.

If a digital mode is going to succeed in Amateur radio, it’ll be necessary for a home base to be able to implement it with nothing more than a desktop or laptop computer loaded with appropriate Free Software and a sound card interface.  Not a silly proprietary “DV-Dongle” or some closed-source blob that speaks gibberish no other software can understand.

As for portable use; it should be possible for a hand-microphone that implements the mode on a DSP be plugged into an existing hand-held (like the Wouxun or Yaesu sets I mentioned earlier) to make it interoperable — open standards will help keep costs down here.

Until such a mode comes along (and they’re working on it — already making excellent progress on HF, keep it up guys!) there’s no point in pouring money into a digital mode that will be a white elephant in a few years.

By far the most popular mode on VHF and UHF is plain old FM.  The mode Armstrong made.  It’s everywhere, from your cheap $100 Chinese firecracker set to the most expensive SDR, they all offer it.  Repeaters abound, and it’s available to pretty much all amateur license classes.  And it works good enough for most.

The big problem with FM, is interfacing with repeaters.  In particular, the big use case with hand-helds and repeaters, is being able to recall the settings for a repeater where ever you happen to be.  Now you can carry around a booklet with the settings written in, and punch them into your radio each time.

This works better for some than others.  On the KG-UVD1P with its horrid UI, it is a tiresome affair.  The Yaesu VX-8DR and Kenwood TH-F7E aren’t bad, once you get used to them.  It’s still fiddly and time consuming, definitely not an option while mobile.  This is where memory channels come in.

Now I realise that sets which stored more channels than you could count on one digit-challenged hand were considered a revolution about 10 years ago.  Back then the idea that you could basically control a digital counter, which would supply an address to an EEPROM that would spit out the settings to drive a PLL synthesizer and other control circuitry was truly remarkable.

Today, the EEPROM and counter have been replaced by a MCU that reads the keypad matrix and outputs to a LCD panel, but we’re still basically incrementing a counter that’s acting as an address offset into non-volatile memory.  The only change has been the number of channels.  The Kenwood set I had gave you 400.  The VX-8, gives you 1000 — which can be optionally grouped into 24 banks (by far the best system I’ve seen to date).  The Wouxun gives you a poultry 128.

The hardest thing about this is finding a given repeater in a list.  128 is more than enough if you don’t travel, or if you pre-programme the set with the appropriate channels in some logical ordering before you leave.  In there hints another factor; “logical ordering”, since there’s no way to sort the memory channels by anything other than channel number.

In this day and age, 1000 channels, linearly indexed, is a joke.  I can buy a 2GB MicroSD card from the supermarket for $10.   How much repeater data could you store on one of those?  FAT file system drivers are readily implementable in modern MCUs and a simple CSV file is not that big a deal for a MCU to parse.

It wouldn’t be difficult to build up a few indexes of byte locations to store in NVRAM, and have the CSV store frequency, call sign, a Maidenhead locator and other settings of all the repeaters in the country, then allow the user to choose one searching by frequency, by call-sign, or if the user gives their current grid square (or it derives it from a GPS), by proximity.  That would be a revolution.  The same card could also store a list of Echolink and IRLP nodes, and make a note of such nodes via RF so it can automatically suggest the nearest IRLP node, take you there, then dial whatever node for you after you announce yourself on the frequency.

I’ve seen more elaborate software written for 8-bit micros like the Apple II, the Commodore 64 and the Sinclair ZX Spectrum back in the day, so clearly not beyond today’s equally powerful AVR, PIC, MSP430 and ARM chips.  A STM32F103RE packs 64KB RAM, 512KB flash and a SDIO interface in a nice small TQFP64 package and costs less than $8.  Even for a Wouxun, that’ll maybe add no more than 20% still keeping it rather competitive with the opposition.

As for user interface?  We don’t need Android on there, although that could be nice.  A decent size resistive touch-screen with a reflective dot-matrix LCD would more than suffice.  This technology, thanks to mobile phones, is cheap enough to implement in this application.  The MCUs needed to drive them have also come down in cost greatly.

Even without the touch-screen — a LCD bigger than a matchbox would allow for text that is easily readable, menus that aren’t constrained in their presentation, and a generally nicer user experience.

SDR hand-helds will likely be the next big revolution, if they are affordable, but I feel that’ll be a way off, and for rag chew on a local repeater, I doubt SDR will be that much superior.  It certainly will push the price up though.

I suppose a start will be to try and come up with a suitable front-end device that can be bolted onto existing transceiver hardware, maybe something that drives the computer control port of a mobile rig such as the FT-857 or IC-706.

From there, it just takes one brave manufacturer to package such a device up with a suitable transceiver in a hand-held form factor to put something to market.  If they did so in a way that could keep this UI module open-source, even better.  Bonus points if there’s a bit of an interface that can take a DSP for digital modes.

Want D-Star, P25, FreeDV, Wongi?  You got it, just slot in the right module, load on the firmware into the UI module, and away you go.  Want to do something special?  Break out the text editor and compiler and start hacking.  The RF side of things can still be as it was before, so shouldn’t pose any more of a problem for regulators than a transceiver with a digital modes jack and computer control interface.

I’m not sure if anyone has worked on such a front-end.  Another option would be a cradle that takes a modern smart-phone or tablet, interfaces via USB to the set, and uses the smart-phone as the UI, also extending the phone’s battery at the same time by supplying the 5V it needs to charge.  Bonus points if it can feed the audio signal to/from the phone for digital modes and/or interfacing with BlueTooth.  A pocket APRS I-Gate and Echolink node, perhaps?  Whatever takes your fancy.

I guess the real answer here will be to come up with something and see if there’s any interest — the “throw it against the wall and see what sticks” approach.

Mar 242012
 

Prior to my road trip to LCA 2012 Ballarat, I bought a new toy, namely a Yaesu VX8-DR handheld.

At that point it turned up only just before I was due to leave, so I wasn’t able to get the accessories I wanted. I cobbled together my own 12V charger lead by snipping the original power supply and soldering on a cigarette lighter socket, but otherwise I used the handheld in its out-of-the-box configuration.

Having gotten back, I have purchased the FGPS-2 GPS module, CT-136 GPS adaptor and the BU-1 Bluetooth module.

Transceiver performance

The set works quite well. The antenna is pretty deaf and useless on 6m, maybe I can get a better after-market tri-bander whip, but on 2m and 70cm it works reasonably well. I’ve heard APRS traffic over distances of 100km, and even been heard on APRS by a digipeater some 90km away.

Audio quality is good, both transmit and receive. Plug in a pair of stereo headphones, and the wideband FM receiver sounds excellent; in stereo to boot.

Probably my biggest nit, is you can’t simultaneously charge and externally power the set. To charge, you must either detach the battery and drop it into a separate charger cradle (an optional extra) or turn off the set.

GPS Performance

When I purchased the VX-8DR, it was a real toss up between it and the VX-8GR. The reason I went the VX-8DR was because it had 6m, and Bluetooth. Having gotten the GPS, I’ve run into the problem a lot have reported; the GPS module is deaf as a post.

The VX8-GR doesn’t improve on this either. However, the good news, is that because my module is external, I can (1) mount it in a better spot, or (2) replace it with a better compatible module.  For VX8-GR owners, this is the end of the road, they can do nothing but moan to Yaesu.  I at least have options.

The module is mounted vertically inside the FGPS-2 casing. Usually with GPS modules such as these, they embed a small patch antenna, whose radiation pattern is perpendicular to the plane of the antenna surface. Being vertical, this means when you hold the radio vertically (as you normally would), GPS reception is poor because the radiation pattern is directly in front of the radio.

The radio seems to perform a lot better, if the radio is held with the screen facing upwards towards the sky. It’ll even work inside my house if I do this. It seems this is a screw-up on par with the iPhone 4.  Another alternative is to replace the module, the FGPS-2 apparently uses 9600 baud serial with NMEA format strings.  However, it seems the parser in the VX-8 is rather crude.  I have a module that does NMEA at 4800 baud, so I’ll either need to coax it up to 9600, or use a microcontroller to buffer and convert rates, and perhaps do some tweaking of the sentence format to make up for the VX-8’s shortcomings.

My hunch; if I make an alternative bracket to the CT-136 adaptor, I can nail this, and another problem, the inability to plug in the GPS and a headset. I have the CT-M11 cable, and thus I plan to make a bracket to connect the FGPS-2 to the end of this cable; allowing me to also plug in a wired headset.

Bluetooth

I bought the Bluetooth as an insurance policy to give me another means of interfacing a headset. Then began the fun of getting it to work with my headsets. I have a couple; a Bullant earmuff-headset, a lightweight mono Digitech headset, and a “MyTalker” headset.

The first was one set I bought some years ago, back when the Bluez was far less stable than it is today, and also long before I was into Amateur Radio or possessed a Bluetooth-capable phone. I tried pairing using a USB Bluetooth dongle, but had little luck, so they got put on one side. Also despite advertising being able to stream music, it only supports HFP and HSP profiles, so you get to listen to your tunes in 8kHz 8-bit mono. They are sold at some hardware stores, such as Mitre 10 The Gap (where I bought my set).

The handheld did pair with this set, but I couldn’t get PTT to work, and the headset itself also had a few faults; namely it was always noisy, and the broadcast receiver stopped working, so I’ve taken them apart for now to see if I can fix these issues. I can key the radio up using the radio’s PTT, but then both internal and headset microphones go live.

The second set is sold by Jaycar, catalog number AA2080. This would be my preferred set to use with the radio as it can pair with two devices simultaneously. It supports the same profiles as the earmuffs, but it’s at least more lightweight.

The BU-1 takes one look at this set, and turns its nose up at it, with the VX-8 giving up and displaying “PAIRING ERROR”.

I also bought the MyTalker set from Jaycar, catalog number XC4894. This set is much like the earmuffs. It embeds its own microphone, but the unit itself provides a 3.5mm socket for you to plug in your own headphones, or use the supplied earphones (which are awful and uncomfortable, don’t use them). At the other end of the unit, is a lead terminated with a 3.5mm plug to plug into a music player. I’ve modded this set to be able to use an external microphone, switchable between a transceiver and the Bluetooth set, allowing a headset connected to a radio to also connect to a phone. I’m still working on this bit.

The VX-8 treats this set with much the same contempt as the mono headset before.

Today, I poppsed in and bought a more expensive set; this time I looked for A2DP functionality, Jaycar have one, catalog number AA2082. Like the AA2080 it can talk to two devices, unlike the AA2080 it supports AVRCP and A2DP. Also, not advertised, is it can function as an analogue headset; supplied in the box is a dual 3.5mm to mini-USB cable that can plug into the headset and allow you to use it with a non-Bluetooth capable device.

I plugged it into the bicycle’s battery to charge on the way home. When I got home, I read the instructions (which are in awful Chinglish). Basically, the English translation of the pairing instructions go like this:

  1. Hold in the MFB button (the centre one on the right ear-cup) in for several seconds. You will hear the voice prompts “Hello”, followed by “Enter Pin Code 0000 on phone”.
  2. When you hear the latter prompt, tell your device to start looking for the headset
  3. When it finds a device called “AA2082”, select it, and enter 0000 as the pin code

So, the steps I followed:

  1. Turn on the VX-8
  2. Hold in the MENU key to bring up the Set menu, then select BLUETOOTH PCODE
  3. Enter 0000 on the keypad.
  4. Hold in the MFB button on the headset until you hear the “Enter Pin Code” prompt
  5. Hit V/M on the VX-8
  6. After a few brief moments, you should see “PAIRING COMPLETE”, press PTT to confirm.

Having got this working, I notice a few things:

  • Stereo (A2DP) sounds a little weird, perfectly clear, but the compression is apparent. I’ll experiment with the laptop later to see if it’s the headset or the radio.
  • Mono works well, pressing MFB toggles PTT on the VX-8. VOX doesn’t seem to work, but no great loss as I find VOX to be a disaster when outdoors.
  • In mono mode, a buzzing is apparent on the received audio. This isn’t audible on transmitted audio, nor did I notice this on received audio when I tried using the headset with my mobile phone.
  • Range seems to be quite restricted, possibly due to where the module is installed it doesn’t get the reception it perhaps needs. A2DP suffers more from this than HFP, with drop-outs being frequent. Again, I’ll need to do some experimentation with the laptop, and perhaps some experimentation with the radio without the battery installed to see if that helps performance.

I’m tossing up whether I get one of these motorcycle Bluetooth headsets.  I ride on the bicycle quite a lot, and at the moment I use headsets embedded in the helmet that are home-built from old computer headsets.  The longevity of the microphone seems to be the biggest problem  I also am on the look-out for an earmuff headset for things like the Imbill car rally, ideally one that can do A2DP.  The Bullant ones I know can’t do this.  I see some earmuffs in the $400+ price bracket that offer Bluetooth, but no idea if that includes A2DP, and frankly, I shudder at that price.

The motorcycle ones are designed to fit a wide range of helmets, and they look as if they’ll fit a set of cheap regular earmuffs quite well.  They typically sell for about $200, support A2DP, multiple devices, and intercom.  Add in $30 for a set of earmuffs, and it makes this a much more attractive option.

More experimentation will be needed I think, but this is looking promising.  I’ll probably post up more details as I come across them.

It’d be nice if Yaesu had been a bit more up-front on what the BU-1 supports: the AA2080 supports both HFP and HSP, yet the BU-1 won’t touch it, the Bullant set supports the same profiles yet the BU-1 works fine with it.  The reasoning for this is not clear, but it does seem that it’ll reliably talk to A2DP capable headsets, so maybe that is a starting point for others.

Likewise with the CT-136, I’ll see if I can fabricate a bracket using the CT-M11 cable, and see where that gets me.

May 162011
 

This weekend just gone I was at Imbil helping out with the International Rally of Queensland, reporting scores for the car rally there.  This was my first look at packet radio in action.  Prior to this I had enabled the amateur radio options in the kernels I built, but never tried actually hooking radio to computer.  I shall be posting some notes on how I got this working…

zhouman ~ # uname -a
Linux zhouman 2.6.35.7-lm2f-nb #2 Wed Oct 13 00:42:58 EST 2010 mips64 ICT Loongson-2 V0.3 FPU V0.1 lemote-yeeloong-2f-8.9inches GNU/Linux
zhouman ~ # ifconfig sm0
sm0 Link encap:AMPR AX.25 HWaddr VK4MSL
inet addr:172.31.32.1 Bcast:172.31.32.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:256 Metric:1
RX packets:365 errors:0 dropped:0 overruns:0 frame:0
TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:24236 (23.6 KiB) TX bytes:6850 (6.6 KiB)

zhouman ~ # mheard
Callsign Port Packets Last Heard
VK4EA-9 sm0 6 Mon May 16 17:59:12
VK4NRL-9 sm0 1 Mon May 16 17:58:40
VK4VP-1 sm0 8 Mon May 16 17:58:38
VK4RAI-3 sm0 9 Mon May 16 17:57:58
VK4TIM-9 sm0 14 Mon May 16 17:57:56
VK4TDI-1 sm0 2 Mon May 16 17:57:39
VK4DC-1 sm0 15 Mon May 16 17:57:07
VK4TEC-9 sm0 120 Mon May 16 17:56:08
VK4FY-1 sm0 18 Mon May 16 17:54:38
VK4RMO-3 sm0 1 Mon May 16 17:54:33
VK4RGC-3 sm0 3 Mon May 16 17:52:48
VK4RC-1 sm0 8 Mon May 16 17:51:29
VK4FIL-1 sm0 4 Mon May 16 17:46:44
VK4RIL-13 sm0 4 Mon May 16 17:45:43
VK4RBR-3 sm0 5 Mon May 16 17:42:59
VK2RDO-3 sm0 2 Mon May 16 17:41:19
VK4RRC-13 sm0 3 Mon May 16 17:36:39
VK2JUB-1 sm0 2 Mon May 16 17:34:44
VK4BNQ-1 sm0 1 Mon May 16 17:26:58
VK4LDA-9 sm0 2 Mon May 16 17:24:59
VK2POO-9 sm0 9 Mon May 16 17:21:24
VK2XFL-9 sm0 1 Mon May 16 17:21:09
VK4RSR-3 sm0 1 Mon May 16 17:20:04
VK4IE sm0 1 Mon May 16 17:15:04
VK4ALJ-3 sm0 1 Mon May 16 17:15:00
VK4HPW-9 sm0 5 Mon May 16 17:13:23
zhouman ~ #

Set-up consisted of:
Linux kernel on Lemote Yeeloong, latest soundmodem driver, Yaesu FT-897D, homebrew interface cable plugged into Yeeloong’s onboard sound card, USB serial driving BC547 in interface cable for PTT.

zhouman ~ # cat /etc/ax25/soundmodem.conf
<?xml version="1.0"?>
<modem>
<configuration name="FT897-D">
<chaccess txdelay="150" slottime="100" ppersist="40" fulldup="0" txtail="10"/>
<audio type="alsa" device="plughw:0,0" halfdup="0" capturechannelmode="Mono"/>
<ptt file="/dev/ttyUSB0"/>
<channel name="Channel 0">
<mod mode="afsk" bps="1200" f0="1200" f1="2200" diffenc="1"/>
<demod mode="afsk" bps="1200" f0="1200" f1="2200" diffdec="1"/>
<pkt mode="MKISS" ifname="sm0" hwaddr="VK4MSL" ip="172.31.32.1" netmask="255.255.255.0" broadcast="172.31.32.255"/>
</channel>
</configuration>
</modem>
zhouman ~ #

I’ve shut it down for now, but I’ll give it a bit more work on 145.175MHz tomorrow. Once I get something working, I might set something up using the O2 or one of the Fulongs (probably the latter) and see about getting soundmodem back into Gentoo.

Update: After hand-editing the ebuild to enable APRS support, I can successfully report that not only is soundmodem working, but so is Xastir on my Yeeloong, as can be seen on aprs.fi.