Apr 292011
 

Well, the antenna I tuned up in my last post, I can say, while it doesn’t work that great on 80m, it did get a contact into Victoria this evening on the AWNOI net.  Terry VK2TEZ near Coffs Harbour gave me a 4-3 signal report, so still lots of room for improvement… part of that was due to static crashes from storms in NSW, but I think with a better tuned antenna, we should be able to get towards having a workable antenna.  At the moment the autotransformer I use has ~95 turns, with output taps at 0, 25, 50 and 75 turns.  I think one somewhere between 0 and 25, and/or some extra turns might help… so I might wind a new one and see where that gets us.

The headlight still continues to give me grief.  An interesting discovery though this evening.  Since the battery is no good, I’ve permanently mounted it to the bicycle frame.  This was achieved by removing the plastic bracket which is used to mount the headlight on the handlebars or on the helmet mount (using a rubber O-ring), and replacing this with a bracket bent out of a short piece of aluminium.  It fastens to the bicycle frame at the front right above the front wheel, using a bolt hole normally used for mounting rim brakes (my bike has disc brakes).

The upshot is that the headlight’s casing has a pretty good electrical connection to the bicycle frame.  Turns out this is a big no no with these lights.  Kiss goodbye HF if you do… you’ll get crap everywhere from 400kHz right up into the VHF.  I’ll have to do some further investigation, but I found that if I insulated the case from the frame, it helped on the 400kHz and HF emissions.  I think something parasitic is causing the 2m grief as this continues (that, or it’s less critical on the case being earthed).

For a while I thought it might’ve been something lurking around 415kHz… the standard IF frequency of most superhetrodyne receivers, but alas, can’t see anything there.  Otherwise it’d explain why it appears to be everywhere.  I definitely suspect it’s not supposed to be oscillating there though, so I think parasitic oscillations are the cause here.  I’m slowly researching my own power supply for the LED in this headlamp, so its days are numbered.

The insulation was achieved by breaking a cheap plastic picnic knife, drilling a couple of mounting holes, and mounting the headlight on that.  That quelled the HF interference quite a bit, and I was able to listen to the HF bands on my way into Brisbane.  At least it was nice to listen to something other than that sodding wedding in the UK.  (C’mon fellas, yes, great and all but can’t we just confine it to one station?)

I was concerned about the longevity of this arrangement however.  And as it turned out, I was right to be concerned.  It broke as I approached the Normanby Fiveways.  I went over a bump, heard a crack, and noticed the headlight dangling by the power lead.  I pulled over, threw it in the basket and grabbed the backup headlight.  At least there was one on the helmet, a 1W LED, so I still complied with local laws for night riding.  I didn’t have a mounting for the backup light, I just pointed it forward sitting in the bottom of the front basket, with it on flash as a warning to drivers.

Once at the destination, I reverted the headlight back to being directly mounted on the bicycle frame.  Interference was intermittent, but when it was acting up, it did wipe out 80m with S6 noise.  Not good when most stations are barely making S6 as it is.  I wound up turning off the main headlamp as for the most part I could see where I was going, and I knew the route.  As I got out of town this was less of an issue due to the lack of traffic, and of course I was on bicycle paths or the footpath for 90% of it.  That at least allowed me to hear what was going on with the net.

The other flaw I had was that the helmet’s speaker connections were acting up… wound up unplugging the earpiece side of the headset adaptor and using the internal speaker.  Thankfully I could still use the helmet’s microphone and the rest of the wiring harness… just not the speakers in the helmet.  I noticed this as I pulled out of my street, in fact I was aware there was a problem, but now I know where the problem is now.  I’ll get onto it tomorrow.  And I’ll look at a better way to mount this headlamp in an insulated fashion as an interim solution to a power supply replacement.

Apr 232011
 

Well, been some time now since I announced the start of some µClibc stages.  So far, not much has happened there other than the fact that I’ve successfully hard-locked the Fulong 2E system that I tried compiling on.  This is despite compiling with binutils-2.21 and using -Wa,-mfix-loongson2f-nop… which is usually enough to prevent lockups.  Clearly there’s further erratum that I’m hitting, I might try later on the Qube and see where that gets us, agonisingly slow might be better than the current pace.

Generic N32 MIPS-III little endian continues to remain unavailable due to an issue compiling Python 2.7, and unfortunately my N32 chroot on the Yeeloong broke when I upgraded glibc (the primary reason why I began doing a generic MIPS3 build on the Qube using Matt’s MIPS4 build).  I will get back onto this eventually.

On other news since the purchase of the MacBook I’ve been able to leave my Yeeloong sit at home running continuously to update the entire system.  Qt 4.7.2 gave me some grief — it seems at least on mipsel, qmake segfaults during the initial build of qt-core …

mipsel-unknown-linux-gnu-g++ -o "/tmp/portage/x11-libs/qt-core-4.7.2-r1
/work/qt-everywhere-opensource-src-4.7.2/bin/qmake" project.o property.
o main.o makefile.o unixmake2.o unixmake.o mingw_make.o option.o winmak
efile.o projectgenerator.o meta.o makefiledeps.o metamakefile.o xmloutp
ut.o pbuilder_pbx.o borland_bmake.o msvc_vcproj.o msvc_vcxproj.o msvc_n
make.o msvc_objectmodel.o msbuild_objectmodel.o symmake.o initprojectde
ploy_symbian.o symmake_abld.o symmake_sbsv2.o symbiancommon.o registry.
o epocroot.o qtextcodec.o qutfcodec.o qstring.o qtextstream.o qiodevice
.o qmalloc.o qglobal.o qbytearray.o qbytearraymatcher.o qdatastream.o q
buffer.o qlist.o qfile.o qfsfileengine_unix.o qfsfileengine_iterator_un
ix.o qfsfileengine.o qfsfileengine_iterator.o qregexp.o qvector.o qbita
rray.o qdir.o qdiriterator.o quuid.o qhash.o qfileinfo.o qdatetime.o qs
tringlist.o qabstractfileengine.o qtemporaryfile.o qmap.o qmetatype.o q
settings.o qlibraryinfo.o qvariant.o qvsnprintf.o qlocale.o qlinkedlist
.o qurl.o qnumeric.o qcryptographichash.o qxmlstream.o qxmlutils.o  -Wl
,-O1 -Wl,--as-needed                           
floatmath auto-detection... ()                                         
/tmp/portage/x11-libs/qt-core-4.7.2-r1/work/qt-everywhere-opensource-sr
c-4.7.2/config.tests/unix/compile.test: line 71: 25542 Segmentation fau
lt      "$OUTDIR/bin/qmake" -nocache -spec "$QMKSPEC" "CONFIG+=$QMAKE_C
ONFIG" "CONFIG-=debug_and_release" "LIBS*=$LFLAGS" "LIBS+=$MAC_ARCH_LFL
AGS" "INCLUDEPATH*=$INCLUDEPATH" "QMAKE_CXXFLAGS*=$CXXFLAGS" "QMAKE_CXX
FLAGS+=$MAC_ARCH_CXXFLAGS" "QT_BUILD_TREE=$OUTDIR" "$SRCDIR/$TEST/$EXE.
pro" -o "$OUTDIR/$TEST/Makefile"                                       
gmake: *** No targets.  Stop.                                          
floatmath disabled.                                                    
... etc for numerous other modules.

qt-4.6.3 builds without issues, but this is not sufficient for KDE 4.6.  I’m still investigating.  hyperestraier also fails to build, but only if you have USE=debug set, disable that USE flag and it builds without issues.

Fingers crossed, I can get Qt 4.7 and KDE 4.6 to build, and that there aren’t any issues.  Previously libkjs used to be quite unstable which is one of the main reasons I have not keyworded any release of KDE 4 for MIPS.  Yes, you could dodge around it and have a usable desktop, but I didn’t consider it working well enough for keywording.

Mozilla stuff will need some loving too.  I hope to upgrade to Firefox 4.0 on MIPS, see how that goes.  One of these days I’ll get onto tackling Thunderbird.  Sadly my life away from Gentoo intervenes and thus my plans frequently get put on the backburner as work demands my attention elsewhere.

Apr 172011
 

If you ever decide to put any kind of sensitive receiver on a bicycle, you’ll want to avoid this ugly duckling of the bicycle lighting world:

Nitelights Illuminator 900

Nitelights Illuminator 900

These lights are great from the illumination point of view, and they’re not badly priced either.  However, from an EMC viewpoint, they stink.  I was given one as a present some time ago.  The first night I got it, I mounted it on the helmet, charged up its battery, then went to work the next day.  That evening, tried using the radio on the bicycle as I rode home.  The interference rendered the radio totally useless.

At first I couldn’t figure out why the signals sounded so bad on receive.  I was stuggling to hear repeaters that were normally quite strong.  The only thing that was new was the headlight.  I got home, switched on the set in my room and tuned to 2m sideband, then put the headlight on flash.  The tell-tale static from the radio gave away the headlight as being the culprit.  Worst of all, the emissions weren’t conducted, they were radiated.

Since then I’ve spent the last few months trying to figure out ways to make this headlight less noisy.  The following page serves as a notepad, and I’ll keep adding to this as time goes on.

Initially when I used it I kept the battery in my shirt pocket.  This proved to be a fatal mistake, since the roughly ¼? power cable proved to be a very effective radiator of this interference.  I found winding the power lead up into a tight coil and moving the battery to the top of the helmet right behind the headlight helped things a bit.  Adding a 2.2mF capacitor in parallel to the headlight further reduced emissions to make it barely tollerable.

Then the battery pack died.  After a few weeks of non-usage, the cells collapsed.  So for a while the problem solved itself, I could no longer use the headlight.  The headlight’s battery pack runs at a nominal 7.2V (typical 8V).  Since I run a 12V supply on the bicycle, I set about making a step-down power supply that could drop my 12V supply down to 8V approximate to run the headlight.

Initially I tried using a LM7808 linear reg.  This worked, with one major drawback: the linear reg got bloody hot.  Turns out this headlight draws about 1A of current when at full brightness.  That means in order to drop 4V, the reg was dissipating 4W of power.  Ooops!  Poor thing.

I designed a crude switchmode power supply to do the work.  Using a voltage divider to provide a voltage reference, I used a LM311 comparator to detect when we were under voltage.  The output signal from this would pull down on the gate of a IRF9540N MOSFET which acted as the main switch.  Hysteresis was used to fine-tune the switching behaviour.  Capacitors at both sides would smooth the waveform.  470µF was used on the input side, 330µF on the output (we still have that 2.2mF capacitor not far away).  I also made liberal use of 100nF decoupling capacitors to try and control the rate of switching.

On the breadboard with a dummy load, my circuit performed pretty well.  A fairly smooth output with a bit of ripple at high load.  I mounted it in a box and tested it with the headlight, and presto, the headlight was back in service.  I mounted both on the bicycle directly, so as to minimise cable length and therefore radiation.

Since now the radio shared a power rail with the light, I knew there was potential for conducted emissions to cause problems as well as radiated.  The next evening I tried it out… 2m was lousy with the headlight turned on.  The good news is that it wasn’t much worse than before, but it still rendered the radio useless at times, particularly if the signal was weak from the repeater.

Recently, I added some 470µH inductors in series with the headlight and my switchmode power supply.  I also tried common-mode chokes to no avail.  A 1mF capacitor has been added in parallel to the 470µF capacitor in my power supply to further try and reduce the noise.

Low-pass filtering on headlight

Low-pass filtering on headlight: 2.2mF capacitor in parallel, 470µH inductor in series

Part of the problem was that I was shooting blind to try and find the interference.  Today, whilst tuning up the HF antenna, I decided to experiment and see what bands this headlight had an influence on.  To my (unpleasant) surprise, interference was severe right down to 80m.  I used the spectrum analyser built into the FT-897D to hunt for the culprit, and found it lurking at around 400kHz.  When the power supply initially starts up, it’ll be up around there, then it sinks down to 392kHz as the case warms up:

Noise from the headlamp detected around 400kHz

Noise from the headlamp detected around 400kHz

This appears to be the fundamental frequency for the switchmode power supply built into the headlamp.  It would appear to have a fairly sharp square-wave type pulse, as it contains very strong odd-order harmonics.  The same interference can be observed at around 1260kHz (3rd harmonic).

The fact that this frequency is so low, probably suggests it is being intermodulated with a parasitic oscillation at some higher frequency.  This I have not yet found, the CRO showed some other hash over the signal, but I will need to do some further investigation, probably with a more sophisticated spectrum analyser than the primitive one found in my transceiver.

I’d be interested to hear from others who have had issues with these headlamps.  In particular, interference to AM/FM radio reception or transceiver operation would be quite useful if the need to persue this with the ACMA ever comes up.  The manufacturer of the headlights has so far been unresponsive to my queries, so in the meantime I can only recommend that people avoid using these headlights if they intend to use any kind of radio receiver whilst riding at night.

In the meantime, I’ll be chucking further notes here as I find more on this issue.

Apr 172011
 

Well, I figured I better post up pics and notes on the improved antenna design for my HF bicycle mobile station.  I spent some time tuning it up today, and without resorting to the autotuner, I’ve successfully managed to tune up all bands available to me from 40m through to 6m.  80m still remains ellusive however.

The new design incorporates a version of the autotransformer used in the earlier attempt, using more turns of wire on the same size former, and multiple output tap points.  This allows me to accomodate a very wide turns ratio to match the antenna to various bands.

VK4MSL/BM HF: The autotransformer

VK4MSL/BM HF: The autotransformer

 

Band Test Frequency Primary turns Secondary turns Approximate SWR Comments
80m 3.590MHz 1 90 Too high to measure This seems to get the strongest signals. Autotuner is able to tune from here.
40m 7.120MHz 26 48 ~2:1 +/- a turn on the secondary to cover the entire 40m band.
20m 14.210MHz 26 1 ~1.2:1
15m 21.200MHz 26 27 ~1.4:1 Slightly out, there is probably a better one.
10m 29.200MHz 26 27 ~1.1:1
6m 53.000MHz 26 52 ~1.2:1 +/- a turn on the secondary, able to hit VK4RBX with 10W from the driveway

 

On the top of the autotransformer are for selecting the secondary tap; one of 0 turns, 25 turns, 50 turns or 75 turns (caveat; I might be slightly out with my counts here).  Having done this I think in hindsight I’d have been better off moving the 0t one down to maybe 10t instead, as there aren’t too many bands that seem to work on the 0t setting.  The primary side is selected by means of a wire soldered on to a thumbtac.  The wire wraps around the tube with a piece of balsa wood for the pin to stick into.  You select the turn by piercing the insulation as you push the thumbtac through the wire and into the balsa wood behind.  Crude, but it works.

VK4MSL/BM HF: Primary tap

VK4MSL/BM HF: Primary tap

In place of the CB whip, I have taken a fibreglass whip and cut it down, stripped the winding, and used it as a support with a base-load spring to take any shock loads.  In place of the original antenna winding, is two sections of brass tubing which telescope out.  This allows for an antenna that can be partially dismantled and reassembled on the run, unlike the other antenna which was permanently fixed at 6′ length.

VK4MSL/BM HF: Mark II

VK4MSL/BM HF: Mark II

I have a third solid section I can insert in there too, which would further extend the antenna to 2.5m, but it becomes very top heavy when I do this.  The antenna can extend to 1.6m length, or for portable use I can throw a wire up into a tree, or support it using a squid pole and connect that wire to the autotransformer output taps.

I didn’t make any contacts while tuning the thing up, although I was hearing New Zealand on 20m quite strongly, and on 10m I could hear the VK8 (Northern Territory) beacon going quite well.  I tried a few calls on 28.390MHz, but had no contacts.

 

I’ve also re-inforced the antenna bracket.  Prior to doing this the antenna would sway wildly from side to side.  Yes, it meant the cars gave me a wide birth (something I greatly appreciate) but I fear had adverse affects on the signal, and probably was asking for trouble in the long run.  Putting a brace between the two brackets seems to steady things up just a little bit, and now I can rock the bike side-to-side quite violently without the antenna swinging too far.

I’m yet to go mobile with the new improved station.  Weather permitting, I shall give it a try Monday evening.  I have a meeting with Brisbane area WICEN.  Due to headlight QRM I may or may not be active while mobile, we’ll give it a shot, but I should be able to work portable once I get there.

Apr 102011
 

Well, I’ve done some tinkering with Gentoo/Prefix on MacOS X.  Not bad so far, although there’s a lot of packages not keyworded… (a bit like MIPS) and some packages I miss from regular Gentoo (e.g. crossdev).  However, we can work on sorting this out over time.

For those of you who aren’t particularly fond of going on a copy/paste fest from the documentation, I decided rather than sit there all night and manually do it, I’d code up a script to do it for me.  Behold: Gentoo MacOS X bootstrap script.

Usage:

$ export EPREFIX="${HOME}/.gentoo/amd64"
$ export CHOST="x86_64-apple-darwin10"
$ mkdir -pv "${EPREFIX}"
$ sh do-bootstrap.sh
Apr 092011
 

Well, today I got news that the Wireless Institute Australia has decided to change the cost of membership, not in the favourable direction either.  This, on top of a $1 increase in our annual license fees (to $66/year), and substantially blown out costs for obtaining a license.

For someone like myself, who is no longer a student but still not rolling in money, it means if we decide to get involved in this de-facto union, we’re coughing up $80/year.  That’s more than our radio license, which is expensive enough.  Now, I am not a member, never have been… and at the moment I find it hard to justify why membership to an organisation should approach triple figures, especially when one considers that amateur radio is a hobby.

Things like my membership to Engineers Australia, yeah fine, that’s considered a “professional membership” and I can write that off on tax.  (Although I am seriosly considering whether to cull that membership!)  The WIA however does not fall under the same umbrella.  I think things are getting a little extortionate.

Examinations are also a lot more expensive than they used to be.  Apparently if you’re going for a radio license today, you don’t get much change out of $300.  That’s for three examinations (two if you’re a Foundation candidate) and for a “callsign recommendation” (which costs $20 if you wish to choose a callsign, or $5 if you don’t).  If I had to cough up $300 back in 2007 when I went for my Foundation license, I would have left the examination paper on the table unmarked and walked away.  I would not have been able to afford it then, and I would not be a radio amateur today.

Part of this is the agreement that the WIA has entered into with the ACMA.  The ACMA apparently demand that the fees be representative of the cost of the service or some such nonsense.  Once again, I say, this is a hobby.  We’re not commercial enterprise.  We are not using radio communications to make money (in fact for most of us, it’s quite the opposite).  It is therefore not reasonable to treat us like one of your commercial clients.

Some would argue that one needs to support the hobby.  Here I whole heartedly agree.  You don’t however encourage people to join in if you make it financially out of their reach.  Supposing the WIA made the annual cost $200 instead of the near $100 it is now… would they expect to nett more members?  This seems to be the logic, that the status quo will get people rolling in.  Newsflash: it won’t.  It’s probably worth noting that there are some amateurs who will not join no matter what the cost – they believe the organisation is too union-like for their tastes.  This is understandable, and thus perhaps there’s this image problem that may be why attracting members is such a problem.

I myself try to support the hobby by being an active member, lending support to the clubs around me, and generally sparking interest that may entice others to come join us.  Part of this is why I take the callbacks for the WIA news service of a Sunday morning (0900 on 147.000MHz FM).  I hope that by encouraging others to get involved, the community can grow.  This requires minimal expenditure of funds on my part, and I think, is more effective.

Paying $80 to some group in Victoria probably won’t change much around me… but getting out on the bicycle with the radio on board… someone tuning around suddenly hears “VK4MSL bicycle mobile”… Hang on, haven’t heard that before… curiousity gets the better of them and some activity is generated.  Or if not that, it’s the general chit chat between groups about the projects they’ve been working on.

If the bands sound like a ghost town because we’re too busy earning a quid to afford membership fees, then the radio community will die, people will ask “What’s the point?  There’s nobody here!”.  The repeaters here in Brisbane already remain dormant most of the time, and activity on HF is sparadic at best.  Do we really want to encourage this?

I think we need to consider why people aren’t getting involved with their local clubs.  Do we perhaps adopt a model like some parts of Europe, wherein your membership to a given club includes membership in the national body?  Bundle some packages up to offer services more cost effectively?  I for one don’t care for getting involved at a administrative level and magazines aren’t of great concern.  I recognise however that the WIA provides funding for things like public liability insurance and major club projects.  Maybe for those who aren’t interested in politics, there’s room for a non-voting membership that just funds the services needed by our clubs without all the frills?

Whatever happens, it is clear to me that the current trend is not sustainable.  The group and the community at large will continue to hemerage as the populace grows older and daily necessities compete for a chunk of our bank balance.  I think this area by far, is in dire need of reconsideration.

Apr 012011
 

Alrighty… AU$40 and two bus trips later later and I’ve now got MacOS X 10.6.3 installing.

Interestingly, this MacBook’s DVD drive seemingly does not like this disc.  Whilst waiting at the bus stop, I figured I’d fire up the machine and have a look at the disc.  Powered on, inserted the disc, the moment it got to the log-in prompt it spat the disc out.  Fine, maybe that’s a “feature”.  I log-in, then re-insert the disc.  It sits there for a bit longer then spits it out again.

Right, down I march back to the NextByte store where I bought it, cantankerous MacBook in one hand, receipt in the other to try and sort out this disc.  It was then the machine decided it loved the disc so much, it wouldn’t eject it.

10 minutes later in their service centre (no charge thankfully) they managed to extract the disc, re-insert it, and it was happily reading it at that point.  It was suggested that these machines do not like being moved when the disc is spun up.  Probably related to the angular momentum developed by the disc and fine mechanical tolerances owing to the form factor.  I looked at doing an install, but as I was walking down the street I did notice that the drive made the odd noise or two, so I decided discretion was the better part of valor, cancelled, ejected the disc and shut down.

Get home, placed the machine on a flat surface, and repeated the steps earlier.  It did the same “spit the disc out” stunt 3 times in a row.  I have it installing from an external DVD reader, which seems to be putting along nicely — and at least the disc won’t get stuck in this one.  I’ll investigate the internal drive later.

It happily accepted other discs, and if need be, I’ll burn a copy of the Snow Leopard disc as a working copy, at least then I’ve got the original if disaster does strike.  The good news is most of the stuff on this machine will be involving network traffic and not the DVD drive.  And I’ve been informed from two sources that the disc I have includes the Xcode IDE with gcc, so I should be able to put Gentoo/Prefix on next.

And I thought Macs “just worked”? 😉