Amateur Radio

New toy

I picked up a few new toys recently.  I’ve been looking around for a small microcontroller based device to act as a combined remote face / DTMF generator for my FT897D.  The idea is that this device could interface with the FT897D via its CAT port, and allow me to adjust the frequency and mode, recalling the information from internal flash or an SD card.

The remote face would then be mounted on the front of the bicycle, and connect to the radio at the rear to allow easy bicycle mobile operation.  An extension of this would be control of a separate 2m radio, and a GPS to allow APRS from the bicycle.

The idea was to have the memory work like a relational database.  Rather than just recalling memory channels, and having a big long list, I could scroll through the repeaters by callsign, location (service area), or combined with GPS, proximity.  Modern flash technology would make this easily doable.

Likewise, for DTMF, rather than having to carry around a cheat sheet or remember IRLP node numbers, wouldn’t it be nice to just be able to scroll through a node list by country/region/callsign, select one, hit the “Call” button, put your callsign across and have it automatically dial the moment you raised the PTT?

I don’t have the ability to manufacture PCBs of the standard required for ICs such as most 32-bit microcontrollers.  SOIC is about as fine as I can muster, and prototyping services are expensive.  Thus I was looking for a stamp module or premade board.

Luminary Micro (now TI) make a few nice ones, and during my work at Laidley, I got to use the LM3S8962 Ethernet/CAN evaluation board.  One nice feature was that it had the JTAG built-in via a FTDI USB-serial chip.  However, the licensing for the board support package irks me — despite their code being useless on anything other than one of their chips, they still see it necessary to modify the BSD license adding a clause that prohibits its use on non-TI microcontrollers.  I had a crack at writing my own “free-software” Stellaris library, but haven’t gotten that far with it.

I happened to stumble on this board based around the STM32F103VET.  They were being sold on eBay for about $60 at the time, so I decided at that price I’d buy three.  ST’s driver library appears to be very liberal in its licensing (in fact they claim there is “no license”, I don’t know if this means “public domain”, or whether I treat it like BSD).

The LCD panel uses the Ilitek ILI9320 display controller with internal graphics RAM, and is capable of 18-bit colour.  The board also features a RTC backup battery, Texas Instruments TSC2046 touchscreen controller and on-board RS232 level converter.  The STM32 also functions as a USB peripheral, and can be programmed using the stm32loader bootloader script via RS232.

Interestingly, the LCD controller documentation states that no part of that documentation may be reproduced without written permission.  I’m not sure if writing an open-source driver classes as “reproducing” the documentation (as I’d be making documented #define statements in C).

The devices come with example source and have a pre-loaded µC-GUI demonstration on them.  So far I’ve managed to distill enough out of these sources to get working touchscreen, LCD and UART.  I’ll probably start looking at FreeRTOS next and seeing if I can get a workable device going.

STM32F103 board

STM32F103 board running a simple "Hello World" app

Hello world application for STM32

Hello world application for STM32

Guess now I had better start planning my application. 🙂

Gentoo/MIPS Progress update and LCA news

32-bit Gentoo/MIPS stages for both big and little endian systems are now available for MIPS-I, MIPS-III and MIPS-IV.  For now I’ve got these on my devspace, but I hope to get some of them out to mirrors as soon as possible.  I’d appreciate any feedback on this release.

The little-endian stages should work on Loongson systems.  All stages include a patched binutils binary (see bug #338405) which adds some fixes for errata in the Loongson 2F CPUs and the little-endian stages for MIPS-I and MIPS-III have this fix enabled in the CFLAGS, enabling their use on Loongson hardware.  They will also work on non-Loongson systems.

I’ve been doing quite a bit of testing with the little-endian stages in particular, and have had few problems with getting many software packages to work.

binutils-2.21 already includes the fixes needed, along with lots of other MIPS-related fixes… and so when that is released (they’ve already done a branch freeze for 2.21) I plan to build new stages based on this newer toolchain, and with the newer Perl release.  Current stages use Perl 5.8.8 since I found I hit a few snags at the time which I thought were better dealt with later (some package complained there was “something funny about this Perl version” and bombed out) as the primary concern for the Gentoo/MIPS port at the time revolved around gcc.

I downloaded and installed binutils last night, based on that day’s CVS snapshot.  I’m now trying to see if I can get qt-webkit to build (the biggest sticking point so far) using that, with the view of having a workable KDE-based desktop going on the Yeeloong and the Fulongs here before LCA 2011.  (For now I’ve got FVWM.)  In the meantime I’ll be keeping an eye on the binutils mailing list.

On the LCA front… I got formal confirmation of my payment on the weekend… so I’m definitely a go-er… I’m still trying to find out if I’ll be helping out with any stalls…

There’s a social meeting of the Brisbane Amateur Radio Club this Friday, wherein our involvement in LCA will probably be discussed — club president was supportive of the idea when we discussed it on our 2m net last Wednesday evening… we just need to figure out what we can do, who can do it, and what needs to be done.

I’ve managed to get fldigi going on Gentoo/MIPS, and so maybe interfacing one of the computers I have (either one of the Fulongs or the O2) to a radio transceiver… (perhaps one of the ships’ radios on the HMAS Diamantina… nice mix of old+new-er) decoding some RTTY or PSK31, is an option.  We’ll have to decide this formally.

Those who wanted to drop in… we meet at the Queensland Maritime museum this Friday (and every second and fourth Friday except fourth in December and second in January) at 7:30PM — entrance is via “Service Gate 2” off Lower River Terrace.  We meet in the lunch room under the bridge.  If anything is decided, we will likely make our final decision at the following business meeting, which happens a fortnight later.

BARC Meeting entry point

BARC Meeting entry point... via Service Gate 2 off Lower River Terrace

If Gentoo has a stall, it’d definitely be worth setting up one of the Fulongs there… and for that I’d want a reasonable desktop going (KDE, or maybe XFCE… I know people have done some stunning work with FVWM, but I’m not that good).  I look forward to LCA regardless… if neither Gentoo nor BARC are running a stall in the open day, then I’ll just have a look around and see what it’s all about.  I look forward to the event anyway. 🙂

You know you’re a ham when…

I stumbled upon this looking up information on magnetic receiving loops.  Content is below, with my comments added.

1. When you look at a full moon and wonder how much antenna gain you would need.

2. When a friend gets a ride from you and remarks that you have a lot of CBs in your vehicle, it turns in to an hour long rant on how ham radio is not CB radio.  (Not quite… but I have had people ask if that’s a “CB” on my bike, and I’ve responded no, it’s an amateur set.)

3. When someone asks for directions, you pause, wondering if long or short path would be best.

4. When you can look at a globe and be able to point to your antipode (and you know what an antipode is).

5. Your cell phone ring tone is a Morse code message of some kind. (Yep… my phone taps out “VK4MSL”)

6. You have accidentally said your Amateur Radio call sign at the end of a telephone conversation. (Almost did this once leaving a phone message back when I had a F-call… almost blurted out “VK4FSJL clearing the frequency”)

7. Your favourite vacation spots are always on mountain tops.

8. You notice more antennas than road signs while driving your car. (I do notice antennas a lot more these days when I’m riding the bike)

9. You have driven onto the shoulder of the road while looking at an antenna.

10. Porcupines appear to be fascinated with your car. (We don’t get porcupines in Australia and echidnas are rare in suburbia.)

11. If you ever tried to figure out the operating frequency of your microwave oven.

12. When you look around your bedroom of wall to wall ham gear and ask: Why am I still single? (This bloke can see his bedroom wall?!)

13. The local city council doesn’t like you.

14. You actually think towers look pretty.

15. Your family doesn’t have a clue what to get you for Christmas, even after you tell them.

16. Your HF amplifier puts out more power than the local AM radio station.

17. The wife and kids are away and the first thing that goes through your head is that no one will bother you while you call “CQ – DX” a few hundred times.

18. When you pull into a donut shop and the cops there on their coffee break ask if they can see your radio setup.

19. You refer to your children as your “Harmonics”.

20. Your girlfriend or wife asks: “You’re going to spend $XXXX on what???

21. You plan family vacations around hamfest dates.

22. When you see a house with a metal roof, and your only thought is what a great ground plane that would be.

23. You have pictures of your radio equipment as wallpaper on your computer’s desktop.

24. Every family vacation includes a stop at a Ham radio store.

25. The first question you ask the new car dealer is: “What is the alternator’s current output”?

26. You buy a brand new car based on the radio mounting locations and antenna mounting possibilities.

27. You have tapped out Morse code on your car’s horn. (I may try this if I ever mount a horn on the bike)

28. A lightning storm takes out a new Laptop, Plasma TV, and DVD Recorder, but all you care about is if your radios are okay. (Good riddance to the Plasma… they should be banned… I too have more concern for my radios…)

29. Your wife has had to ride in the back seat because you had radio equipment in the front seat.

30. Your wife threatens you with divorce when you tell her that you are going on a “fox” hunt.

31. Your wife says ‘the kids need to be fed’ and you first wonder what their impedances are.

32. When house hunting, you look for the best room for a radio shack and scan the property for possible tower placement.

33. When house hunting, you give your realtor topographical maps showing local elevations.

34. The real estate agent scratches his head when you ask if the soil conductivity is high, medium, or low.

35. You have Ham radio magazines in the bathroom.

36. When your doorbell rings, you immediately shut down the amplifier.

37. Fermentation never enters your mind when “home-brew” is mentioned.

38. Instead of just saying no, you have said “negative”.

39. You have used a person’s name to indicate acknowledgement.

40. You become impatient waiting for the latest AES catalog to arrive.

41. You have found yourself whistling “CQ” using Morse code.

42. You always schedule the last full weekend in June for vacation.

43. You walk carefully in your back yard to avoid being close-lined. (Make that step carefully around back deck to avoid tripping over feedlines)

44. You have deep anxiety or panic attacks during high winds or heavy ice.

45. You and the FedEx/UPS men are on a first name basis.

46. You really start to miss people that you’ve never seen.

47. Your exercise machine is a Morse code keyer.

48. You walk through the plumbing section at the hardware store and see antenna parts.

49. Your neighbours thought you were nuts when you ripped up your lawn to bury chicken wire.

50. Your next door neighbour thinks that your wife is a widow.

51. Your wife has delivered meals to your Ham shack.

52. If you sold all your Ham radio equipment, you could pay off your mortgage.

53. Removing snow from the roof of your car requires working around the antenna and wires.

54. You have never seen a Meteor Shower because you are inside on 6 meters when they occur.

55. If your radio equipment has a more advanced processor than your PC.

56. You hear about a pileup on the local news and you run to your radio equipment and start calling CQ.

57. If you install ferrite beads and place shrink tubing on your toaster appliance cords.

58. If your wife puts something on and asks “Does this make me look too fat?” and you reply with: “Honey you have an excellent front to back ratio with appreciable forward gain on the front lobes.”

59. If you think the half human / half machine individuals on a Borg Cube are really just a friendly group of electronic experimenters with similar interests.

60. You have no idea as to the weather forecast for tomorrow, but know the solar forecast for the next month.

61. If your blood type is RF positive.

62. You sell your dog to buy an amplifier.

63. Your XYL says communication is important in a marriage…so you buy another radio for the shack.

64. You doodle Hartley and Colpitts oscillators during boring meetings.

65. ..your boss asks if you understand? And you reply “QSL” !!!

66. You have been going to the library since you were three and the only shelf you ever go to has Dewey Decimal number 621.

67. You have invested more on your radio equipment than on your kids education.

68. You hire a babysitter to come over, and then you never leave the house-you just go to the shack so you can contest undisturbed.

69. You occasionally buy a Playboy magazine and let your Mum find it , just so she can think that you are ‘normal’.

70. You’ll spend hundreds of dollars on a new rig, and then wander the hamfest pausing each time you pass the booth selling those $7 embroidered call-sign hats thinking “I wonder if they’ll take $6?”

71. When shopping for a new vehicle the first think you look for is space to mount the radios – you end up sitting in the front seat staring blankly at the dashboard area, feeling underneath seats, and poking around the back seat for ways to route the coax. If caught looking under the hood for holes in the firewall for your power cables, you tell your wife, “Nothing honey, just checking things under here.”

72. Your family has a special annual garage sale just to get rid of the boxes of wire, coax, and power adapters-but you pay your friends to “buy” the stuff and get them to quietly return it to you the following weekend.

73. The $10 bargain you got at the flea market that smoked up the whole house when you turned it on is one of your prized possessions.

74. Your wife has called you three times for dinner – then she calls you on the repeater.

75. When going on vacation, the first thing you think about packing is your hand-helds, chargers, scanner and frequency book.

76. The total number of radio related books in your home are five times the total number of all other books and magazines.

77. You visually check your outdoor antennas and coax once a week, regardless of the weather.

78. You have more certificates and licenses on the wall than your local veterinarian or dentist.

79. All the local cops know your vehicle on sight – “it’s the blue Ford with six antennas”. (“It’s that bike with the 6′ whip”)

80. You think an upside to gaining weight is more belt space for radios.

81. You immediately think of `tower’ when someone says the word – `erection’.

Some additions I’d add to the above list

82. When naming kids, you immediately think: Charlie, Juliet, Mike, Oscar, Romeo and Victor.

83. You prefer the grandkids call you Papa.

84. You plan your week around regular nets. (“C’mon, they’ll be expecting me on 3.590MHz in 15 minutes”)

LCA2011: I’m going… are you?

Hi all,

I’m in the process of registering for LCA2011… since it’s in my home town, I figure I may as well show up. 🙂 This will be the first LCA that I’ve attended, last one I was looking at going to was the one in Sydney a few years back … however at the time I just didn’t have the funds.

Now, with it in Brisbane (therefore no need for a hotel room), and having some money in the bank, there’s no excuse for me.

I’m not certain if Gentoo is organising a stall there or not this year, and there’s mention of the Brisbane Amateur Radio Club (of which I am a member), not sure what activities are going there either (this could be in error… I’ll inquire with the group and see what’s doing). If we have a stall… figured it’d be a good opportunity to get one of the Fuloong computers up and running as a bit of a demonstration of Gentoo/MIPS… maybe get my O2 running fldigi with my FT-897D decoding some PSK31 as well if BARC are involved. We shall see.

What is certain though, is that I’m taking the plunge this year… before the earlybird pricing expires in early November.

CQ JOTA 2010

Hi all,

This year I will be activating the Robertson Scout Den as part of this year’s JOTA. I’ll be working as a one-man band at least on the Saturday, working under my personal callsign of VK4MSL. Bands planned are:

  • 80m
  • 40m
  • 20m
  • 2m

I can also do 15m, 10m, 6m and 70cm and may have a listen there too… however the above listed bands are where I suspect most of the action will be. Modes will be FM and SSB. On 2m, we can be reached on the VK4RBR-L Echolink node (#284321). JOTA documentation lists as also contactable via VK4RBS, which at last check was on IRLP node 6408. However, it appears this node has been down for some time, and as such we will likely also be making use of other 2m (and possibly 70cm) nodes in the region. I can also do 2m SSB, however that was very quiet last year.

Hope to hear many young voices on the air this weekend… let’s see if we can push the average operator’s age well below 20. 🙂 And next time I’m in contact with ZL2JOTA, I’ll try to keep the topic away from asking about sheep (ahh well, gotta forgive inquisitive minds… you could hear the groans baseband).

Qtel and svxlink in Gentoo

Hi all…

It’s been a long time since I took over the maintenance of svxlink in Gentoo, and to be frank, I’ve done basically nothing with it because for the most part, it worked. Much development has gone on upstream, however no newer releases have been made, the only way to get the latest stuff is via SVN. This includes the somewhat experimental Qt4 branch.

Since Qt3’s demise, we’ve had to drop Qtel from the package… prompting bug #336993. There are also issues with initialisation scripts (bug #335307).

Consequently, I decided to try out this new Qt4 branch from SVN. For those playing along at home, the installation instructions are simple enough:

$ svn co https://svxlink.svn.sourceforge.net/svnroot/svxlink/branches/qt4/
$ cd qt4/src
$ make
$ sudo make install

At first, I found it wasn’t working… completely deaf and mute.  Vox didn’t show any sign of hearing my audio from the microphone… and I couldn’t hear anything back.  I tried some other ALSA devices… at this point Qtel only supported one audio device at a time.  Some tinkering, I found I could get it to hear me, but audio was very scratchy.

I had noticed this with aplay too… the problem being that the audio CODEC on the Yeeloong runs at 48kHz, and does not support other rates.  I managed to set up dmix to enforce a 48kHz rate (and give me software mixing as a bonus), then set up a rate converter atop this… but a snag, you can’t record from dmix, and Qtel (or rather libasyncaudio) expected a two-way device.  I suggested to Tobias that having separate microphone and speaker devices would be a good idea.  In double quick time he had updated the Qt4 branch to support this.

Some tinkering, and I managed to get it to hear me, but I was still effectively deaf.  It took some more investigation to track down some of the other issues, but eventually this morning I cracked it.  I had working audio both ways… but received audio was still very scratchy.  Further testing with aplay, after thinking I had solved the problem confirmed this.  More fooling around with .asoundrc ensued.  I finally tried an upgrade of the kernel to 2.6.36-rc7 (linux-loongson-community git HEAD).  Voila, rate converted sound out of aplay came through crystal clear.

I started Qtel and tested it initially on *ECHOTEST*, then on a local repeater (VK4RBR-L node 284321 / 147.950MHz FM) listening via RF as well. No problems there, it seems to be able to make contacts no problems at all. I will have to try svxlink itself at some point to see if I can successfully construct a node using the software, but for now my own node is back on the air after a long hiatus… and I hope to have new ebuilds in the tree.

In particular, svxlink will be split into a few packages.

  • dev-libs/libasync: Asynchronous I/O Library
  • net-libs/echolib: Echolink Communications Library
  • media-radio/svxlink: svxlink and remotetrx
  • media-radio/qtel: Qt Echolink client

I should probably try it on the O2 as well, but Qtel, libasync and echolib will probably get keyworded ~mips too, since they work fine on the Yeeloong   The others… well, I’ve got the parts to make an interface cable for the FT-897D here, in fact, enough for two.  The plan is to make up this interface cable, and try setting up a node on FM simplex.

There’s a second ‘897D as well… however it has a burnt out microphone preamp after a storm blew it up (and a blown up DDS chip, so no SSB or AM TX on this rig).  Miraculously, its finals seem intact as it’ll happily blast out 50W RF on 2m (with no modulation).  If the data interface works okay though, it may work well enough for a temporary 70cm node on one of the local repeaters, VK4RBC Mt. Coot-tha.

In the meantime, my personal node is now up and running again after a long hiatus… Look for VK4MSL in your client or dial  37 37 40 via RF.

Obligatary screenshot of Qtel in action

Obligatary screenshot of Qtel in action on the Yeeloong

VK4MSL/BM: First true bicycle-mobile contact: ZL3SV

Well… it seems my tinkering has paid off. This weekend was the weekend of the International Lighthouse Lightship Weekend… and also a federal election.

On Tuesday, I bought a trailer for the bicycle … this is primarily so that I can transport groceries, etc… to home since I’ve got the place to myself for a few weeks and need to be independent. Being so low to the ground, the trailer is hard to see, so I made the decision to move the CB whip over to the trailer, not only does it now radiate a signal, but it also alerts drivers to the trailer’s presence.

I was up to 3AM figuring out how to mount this antenna on the trailer… but eventually I cobbled together a mounting, moved the homebrew autotransformer over, and hey presto… I had nailed the propagation and visibility problems all at once. SWR is still horrid with the CB whip on the trailer, but the autotransformer brings it down to a manageable <15:1 SWR, which the AT-897 can deal with easily.

On the way to the event, I had the station on 14.200MHz… I heard a Chinese station… a BT call, and also later, a New Zealand station. Didn’t make any contacts until I got to the Bulwer Island lighthouse (AU0003) where I made contact with VK5SR, Cape Jaffer Lighthouse (AU0007), registering a weak 53 signal.

On the way home this evening, I first started hunting for a 40m tap on the autotransformer… found one that gave me a 10:1 SWR on 7.080MHz… Okay, not great, but better than the >25 I’d get otherwise.

Around Bardon, I was hearing some VK7 stations, tried to make contact, but I was in amongst their noise floor. As I got to Ashgrove, I tuned around and heard VK3ARK, Cape Liptrap Lighthouse (AU0037). Managed to make contact, and initially registered a 56 signal, but quickly dropped off as I rolled down the hill towards St. John’s Wood… by the time I hit Royal Parade I had dropped off completely. They got that I was mobile, not sure about the bicycle bit… but never mind. 🙂

I travel to the end of the road, trying to put out a few calls, then when I join the bike path I pause, and have a tune around… a very loud signal on 7.145MHz just about blew me away. I listened for a bit as I cycled… it was Gary ZL3SV, in the South Island of New Zealand.

He was in contact with a US station in New Jersey at the time. I could just make out the US station, however Gary just about blew me off the bike… so I waited for a break and called in. 2 others also jumped in… VK4FMVC and VK3BOT. I was barely able to hear VK3BOT, couldn’t hear VK4FMVC (40m can be like that). Gary could hear me though… he was getting me a strong 58 signal. When I checked the S meter briefly, he was registering 59+. This was around 7:00PM (UTC+10).

I was doing 100W at the time… running off a 9Ah SLA battery. I suspect I’d be lucky if even half of that was being radiated by the CB whip… Gary mentioned he was using 200W into a 1500′ centre-fed sloper… undoubtedly an excellent system. I’ll have to see about sending a QSL card over to NZ. As I continued home, there was also a VK6 station that joined us on the frequency, however I didn’t get to make a contact there… and I was nearly home.

I don’t think I’ll make HF a regular habit on the bike, but I’ll consider doing it again sometime. I’ll also see if I can document the setup a bit more… as it’s showing a good deal of promise. This was one contact I really didn’t think I’d be able to make.

VK4MSL/BM HF: Second stationary test contact

Well… after borrowing an antenna analyser and tweaking a few things… I made my second stationary contact using the bicycle mobile station on 20m.  This time, using 20W transmit power.  I now know where to place at least one of the taps on this autotransformer for 20m use. 😉  The station borrows heavily on the “Wonder Whip” style concept, where an autotransformer provides a means of matching the wild variances in impedance of the antenna, to something reasonable for the radio to cope with.

Shown here, is the station, exactly as it was during this contact.  The fibreglass 6′ CB whip has been spray painted yellow to make it more obvious, I plan to put a flag on there so that it resembles a bicycle safety flag (a big one) so it arouses less suspicion.  Click on any of the photos for a closer view.

VK4MSL/BM HF: as set up during the contact

VK4MSL/BM HF: as set up during the contact

This weekend was the day of the Remembrance Day contest, which is one of the major contests ran by the WIA.  Tuning around on 20m, I heard Kirby VK7KC booming in a S8 from the apple isle.  At first I tried contact with 5W, no dice… then 10W, then 20W… no luck.

I tuned off, and tried a different tap on the autotransformer… bingo, that sounded a bit noisier… I hit the button on the autotuner to clean up any last issues with the SWR, then tuned back and had another go.  Eventually after some perseverance, contact was made.

Below is a shot of the FT897D showing the frequency and S-meter reading shortly after the contact was made…. I was weak into Tassie, but that didn’t matter to me… as far as I was concerned, if I got outside metropolitan Brisbane, I was happy.

FT-897D frequency and S-meter during contact with VK7KC

FT-897D frequency and S-meter during contact with VK7KC

I haven’t yet tried other bands, although I’ve figured out some tap points for 6m, 10m and 15m… and some possible maybe points for 40m although I think the antenna will be very deaf down there.

On 80m it’ll probably be a mostly receive-only antenna, with maybe a Tx range of under 10km… if it’s enough for me to know what’s going on with the AWNOI net before I get home … and to maybe get a message relayed to VK4SD so I don’t get hassled about a late note, it’ll be great. 😉

The transformer still uses a map pin pushed though to select the tap… I’m not sure how well this will go long-term, and I think moving towards using banana plugs (or at the very least, alligator clips) will be a better solution.  Switches are another possibility.  Something that will be a more reliable connection than a pin pushed through a wire.  Shown here, is a close-up of the rear basket, the autotransformer is shown underneath the antenna bracket… which helps provide a bit of capacitance.  I find having it close up against the bracket helps, although I made provisions to be able to hang it vertically too (thereby reducing the coupling).

Rear basket showing homebrew autotransformer

Rear basket showing homebrew autotransformer

For now I’ll probably solder the centre conductor of the coax in place of the map pin, so that it’ll stay put until I can find a more convenient solution.  At least I have something on HF that works to a moderate degree.  I’ll probably give it a try next weekend on my way to the Queensland Maritime Museum, where I’ll be operating the Bulwer Island lighthouse as VK4MM in the International Lighthouse Lightship Weekend.  Hopefully I can stir up 20m sufficiently so that there’ll be some activity when 00:00 UTC rolls around.

VK4MSL/BM HF: The autotransformer

Well, I did some experiments this weekend regarding the bicycle mobile station using an autotransformer to match the shortened end-fed whip (6′ 27MHz helically-wound) to the 50ohm impedance my set demands.

I haven’t tried this on the bike itself… these were done in my bedro^W(ahhem) “radio shack”… with the antenna and its bracket sitting on a wooden chair connected to a longer bit of coax than I’ll probably use on the bike.  I will have to try this on the bicycle (ideally with an antenna analyser) to get a better idea of performance, and the up-coming Remembrance Day contest may provide a good opportunity to gauge performance, as the bands will be sufficiently “busy”.

The autotransformer is a simple design… about 50 turns of cheap speaker wire (~1.5mm diameter; ~0.2mm insulation thickness) on a 42mm OD PVC pipe section about 160mm long.  The pipe has small holes down its length, drilled at a spacing approximately identical to the wire centre-to-centre spacing (2mm).  The two extremes of the coil connect to the antenna and the metal antenna bracket respectively, the latter also connecting to the braid on the coax going back to the radio (about 30cm RG58C/U coax).  The centre conductor of the coax connects to a short piece of wire which is soldered to a small map pin, which is simply pushed through the wire’s insulation, piercing it and poking through the hole in the PVC pipe… I can select any turns ratio from 1:1 to 1:50, achieving a very wide matching ratio.  (On paper, able to match >10kOhm impedances to 50ohm.)

Early testing seems to indicate the ability to obtain good SWR figures on 6m, 10m, 20m and 40m.  80m (the holy grail for me) eludes me… and I suspect the actual radiated signal will be very low down to most stations… but if I can cover parts of metropolitan Brisbane with it, I guess I’m doing okay.  The fact that this antenna got down to VK5 with 100W up it, is a promising sign… perhaps with the autotransformer, it may do better.  Then again, it may do a lot worse… We’ll see.  Plan is to try and get it up and running before the ILLW… so that I can stir up some activity on the bands on my way to the Bulwer Island lighthouse (AU0003) before becoming VK4MM and operating a station there.

VK4MSL/BM: Photos of the current setup

Well, I’ve been riding a lot between West End and The Gap, and I get a lot of questions from people on the band about my setup. I was doing some repairs… one of the wires to the PTT had disconnected, luckily there was a 0V return via other connections… and so while I had the bike outside fixing that (it was too dark in the garage) I took the opportunity to snap some photos.

The light was fading at the time, so the pictures aren’t particularly great… I’ve touched them up to make them brighter, hence there’s a bit of noise in the photo… The last two showing the HF setup, required a flash (which I was trying to avoid due to the aluminum and reflectors)… and of course I didn’t spend time putting the FT-897D in the back… maybe later when I get everything tuned up and actually do make a true bicycle-mobile contact on HF (this one was not made mobile).

VK4MSL/BM on 2m

VK4MSL/BM on 2m: side view

Above, is the station in its entirety… fairly simple. The antenna is a plain 2m ground-plane, formed using a tunable mobile whip cut for 145.700MHz, the aluminum angle bracket makes up one counterpoise, and an additional counterpoise hangs out the back. Adjusting the angle has an influence on the SWR… in this arrangement, it works nicely.

VK4MSL/BM: Closeup of rear basket

VK4MSL/BM: Closeup of rear basket

Shown here is the rear basket where the FT-290R II (or FT-897D for HF) lurks… along with a 9Ah gel cell battery, which also powers the tail light. I haven’t been very neat about the cables. Two leads run from the front controls, the grey one (shielded) carries transmit/receive audio and the PTT, the blue one (Cat5e UTP) carries the four directional buttons — with spare wires connected to 0V. A DB15HD (“VGA”) connector terminates the cable at each end.

VK4MSL/BM: Radio controls

VK4MSL/BM: Radio controls

Remember how I mentioned the hand-mic in the last station was going to be temporary? Well… this is the arrangement here. Shown here is the PTT switch (red) and four directional buttons. Not all radios make use of all buttons … the FT-290R II uses only the up/down buttons, the FT-897D uses the right-hand button in addition for the “fast” button. Homebrew microcontroller-based radios I build will probably use all five shown for a menu interface. There’s no display in front of me, so don’t ask for an accurate signal report, I can tell you whether it’s a Q3 or a Q5, but any S-meter reading will be a wild guess. Future expansion of this may include a small potentiometer for a local volume control, and a small microcontroller-driven LCD that could be used to interface to the FT-897D’s CAT interface… but this is just early days.

Now… I did say I managed to mount a HF antenna on here and make a contact with it. The contact into VK5 that yielded this QSL card was made using a 6′ long CB whip… the station looked a lot like this:

VK4MSL/BM: HF Antenna

VK4MSL/BM: HF Antenna

The flash was needed here, took me a while to figure out where I had put the bracket (I don’t plan to ride with the HF antenna or bracket mounted very often). This is fortuitous in a way since you can now more visibly see the 2m antenna. The CB antenna mounts on a nearly identical bracket. I don’t bother with the radial out the back, as there’s no way I’ll make one long enough that would be practical. The antenna will need some work, in particular, either addition of a base-load coil, or modification, to make it resonant on the amateur bands.

VK4MSL/BM: Closeup of basket with HF mount

VK4MSL/BM: Closeup of basket with HF mount

With a small base-load coil, I should be able to make it a half-wave end-fed on 6m… some more and I should be able to make an end-fed quarter-wave on 10m. This will be the subject of future experiments. This tuning section will probably mount on top of the mounting itself, underneath the spring shown on the right.

And to answer the number one question I get from non-radio amateurs… no… I do not have a camera on my helmet (this is not a camera)… I am not broadcasting video. Kindly don’ t act like someone excited to be on television… you’re not. 😉