amateur-radio

VK4MSL/BM: Stationary test on 15m

Well, this afternoon I decided to fix a couple of problems with the bicycle mobile… firstly, the mounting of one noisy headlamp.  I’ve re-done the mount using a more solid piece of plastic this time, so we shall see how it goes.  No noise on HF so things are looking up there.  I also fixed the headset connection which was causing speakers to drop out… the problem turned out to be in the headset connection on the bike, rather than in the helmet.

It was approaching 2PM and thus nearly time for the daily Travellers net on 21.185MHz USB.  I’ve never made a contact on 15m before, but knew the antenna did tune up there, so I gave it a shot.  Ross VK5KMH popped up with a 58 signal out of Adelaide listening… after a prolonged silence, I decided to throw a call out.  Ross responded, reporting my signal into his station was also a 58 signal.

This was from the driveway at my home location, using 100W transmit power (not far from where I reached VK100WIA on 20m with a CB whip).  So evidently this home brew whip works quite well on 15m.  I have since brought the FT-897D inside and plugged it into my G5RV-like antenna, and after moving off frequency to tune, I notice Ross is still a 58 signal, so evidently my HF antenna doesn’t do much better than the whip does.

2011/05/01 by Amateur Radio Bicycle Mobile Homebrew Public Syndication 1

VK4MSL/BM: HF contact on 80m

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.

2011/04/29 by Amateur Radio AWNOI Net Bicycle Mobile Homebrew Public Syndication Thinktank 0

A headlight to avoid

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.

2011/04/17 by Amateur Radio Bicycle Mobile Public Syndication Rants 1

VK4MSL/BM: New HF antenna

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.

2011/04/17 by Amateur Radio Bicycle Mobile Homebrew Public Syndication 1

Increasing costs

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.

2011/04/09 by Amateur Radio Public Syndication Rants 0

New antenna

For a little bit I’ve been struggling with poor performance on my bicycle mobile station.  It was an intermittent fault.  Sometimes it’d work great, other days the FT-290R II would complain bitterly about a SWR issue, and receive performance would be abysmal.  But then I’d set off anyway, get a block away, and the problems just disappeared.  Or the thing would be working perfect, and I’d get down the road and it’d stop working.

Damn frustrating.  Intermittent faults such as these are the worst kind to try and locate.  I thought of all kinds of possibilities, but the one thing I hadn’t considered was the antenna.

Performance had been pretty patchy ever since the weekend before LCA.  It was on the Saturday that somewhere between Annerley and Milton, I lost the ¼ wavelength stainless-steel whip that I had been using.  So I spent that evening rigging up a SO-239 socket so that I could use the commercial antenna I had; a Nagoya NL-77BH that I bought at BARCfest in 2008.

I rigged that up, and on the Monday I did successfully make a contact from the bicycle on my way to LCA, but it was patchy.  I did find a few glitches, so fixed those, and Friday I made a contact in the afternoon, but it was still pretty hit-and-miss.  Not the consistent behaviour I got out of my ¼ wave at all.  Okay, maybe the coax is damaged.  Tried different leads, no dice.  Recently I bought a front basket for the bicycle, and so I could put the FT-290RII in there.  Ran coax back to the antenna, last Wednesday afternoon and Thursday morning it worked beautiful.  However Monday it gave me no end of grief.

Suspecting that the weight of the radio pressing down on the BNC terminations may have damaged that section of coax, I grabbed a length of RG195 and terminated it with BNC connectors.  Still no good.  Using the SWR meter in the FT-897D, the impedance match was out by miles.

Today I had another look.  I took the antenna off the bicycle and placed it on a mag-mount antenna base, and placed the base in the centre of an open garage door.  So big ground plane, not much different to most cars.  Checked SWR, still through the roof.  Tuned to the Mt. Cotton repeater on the FT-897D, no signal.  Pulled out a hand-held, perfectly clear 5/8 signal on its original rubber-ducky antenna.  As I was unplugging the antenna base, I watched the signal strength suddenly shoot up and the radio crackle to life when the shield was disconnected (leaving just the centre pin).  I had noticed a dead short before, but thought it was the antenna mount on the bike… something was up.

So, I grabbed a bit of solid copper wire, a PL-259 plug, and some offcut insulation.  I made a new ¼ wavelength antenna, cutting it initially at 60cm.  Swapped it for the NL-77BH and the performance was beautiful.  Check SWR, and yes, it’s high, but then again, 60cm is waay too long.  I estimated about 51cm and folded the wire over at that point, twisting the excess around the body of the antenna.  Signal strength immediately went up two S points, and on checking SWR, it was significantly reduced.  I moved it back to the bicycle where I tweaked it further.

Once happy, I cut off the excess, used pliers to fold the end sharply and soldered the folded end to the body of the antenna to prevent it hooking anything.  Then used some heat-shrink tubing to finish it off so there were no sharp ends to poke eyes out with.  The antenna provides a good match from 144 right through until 148 MHz at 30W using FM.

I haven’t tried a contact on the bike yet, nor have I got any pics to share, but the radios seem happy with it, and it appears to be hitting repeaters in the area once again, including Ipswich.  Given it’s a good 30km between The Gap and Marburg (as the crow flies) with some decent hills to boot, that’s not bad going.

It would appear the additional complexity of these high-gain commercial antennas comes at a significant cost, they don’t like getting shaken to bits on the back of a bicycle.  I’m not sure how repairable the commercial antenna I have is, it may be a case of throw the thing out, at which case I think any love affair I had with commercial mobile whips might be over.  At least my ¼ wave antennas can be made for <$20 in about 10 minutes from parts I can buy in town, versus spending >$50 and having to wait for it to arrive in the post.

2011/03/09 by Amateur Radio Bicycle Mobile Homebrew Public Syndication 0

“Ever thought of using a mobile phone instead”

This is a question raised on an earlier post of mine.

It’s an interesting comparison between radios and mobile phones.  And some are of the belief that all you do with a radio, is talk on it, or that mobile phones can completely replace radios.  Rather than respond there, I’ve decided there’s enough content there for a completely separate post.  I have highlighted my main arguments here for those who just want to quickly skim through.

Indeed, mobile phones do exist, and they are very handy things.  They do generally come with some sort of hands-free capability.  This is true of my Nokia 3310 … the connectors are available from JayCar, and the headset schematic is trivial.  This is not true of all mobile phones unfortunately.  Much the same is true of my radios, the FT-897D takes a standard RJ45 connector for the microphone, the FT-290R II takes a more obscure 8-pin “Foster” connector, but even they can be sourced if you look around.

RFI is a worse problem for mobile phones however, GSM seems to have a happy knack of being able to inject itself into almost anything unless you’re careful with your circuit design.

It’s worth considering what the primary point of the exercise is however, and how radio and mobile phones differ.

Mobile phones are great if you want to call someone specific. They are highly optimised for one-to-one conversations.  In fact, it’s highly expensive to do anything else.  Conference calls are a rare thing and you pay through the nose for the privilege.  Mobile phone charges are high enough already — I would not like to be paying for the cost of a one hour conference call twice daily on my way from/to work.

To contrast the fees, it costs me $20/month for a mobile phone service through Telstra (excluding calls).  I rarely see a phone bill above $30, but I’d probably see that climb to triple digits if I used it in the manner I use my radio.  The radio license costs me $65/year, regardless of whether I leave my station packed-up and inoperable, or whether I’m using it all 31557600 seconds of the year.

When I was riding frequently however, I regularly participated in discussions on my commutes.  It does make the ride more enjoyable when you can have a friendly chat on the way in.  The beauty of radio though is that you don’t all have to be in close enough proximity to hear each other baseband.

Radios are well suited to group discussions, since radio is an inherently shared medium. At most a repeater site which can relay the traffic between stations is all that is necessary.  I’ve also had quite successful simplex contacts on the 2m band over 50km, and overseas on the 40m band.  Mobile phones only achieve coverage over a few kilometres line-of-sight, coverage is extended by cellular towers which perform a similar function to repeaters.

If you’re in a discussion on the radio, good operating practice states that you leave a gap between transmissions so that other stations may break in if needed.  The breaking station may be someone wanting to get in touch with one of the other operators on frequency, may be an interested party, or could even be a person in distress.

It’s relatively simple for someone to jump in on a conversation.  Mobile phones however, prohibit this unless, once again, you pay severely for the privilege.  How often have you been in a situation where you’ve been trying to chase a caller off the phone so that the line is free for that important call you’ve been waiting for?  Not such a problem with radio.

Mobile phones give you a certain degree of privacy in communications.  Encryption standards vary between mobile phone standards, but all of them (except AMPS, which is now extinct) provide some means of privacy.  Radios generally don’t unless you pay through the nose for a set and a suitable license.  Encryption is also forbidden on amateur bands.

Both allow a certain amount of experimentation.  If you have a mobile phone that provides an antenna socket, it is theoretically possible to construct your own antennas.  You are not however able to alter the transmission mode or frequency of operation, nor are you able to construct your own mobile phone (homebrewing) without significant expense, as the device you construct must be tested and approved by local authorities before you may connect it to a network.  (In Australia, the body responsible is the ACMA, and the approval you need comes in the form of a “regulatory compliance mark”, formerly “A-tick”.)

You can however readily experiment with software running on top of modern smartphones, if you phone is that new.  (Mine isn’t)  Or, if you have a >= 3G capable phone (again, mine isn’t), you can hook a small computer up and use standard VoIP software.

Radios on the other hand, if your license permits it (mine does), can be completely constructed from scratch.  You choose the frequency and mode, there are boundaries where you cannot go, but there’s still a hell of a lot of freedom that mobile phones do not provide.  All amateur transceivers have socketed antennas, allowing experimentation with other antenna types.  Multi-band sets permit experimentation with different frequency bands, all of which differ in their properties.  Transmission modes include pretty much all analogue modes, and in most license classes, many forms of digital communication.

Mobile phones typically are fairly easy to use (there are people however that never seem to get it however), while radios almost always require a certain level of training.  Amateur radio requires you to sit two or three separate exams (usually two written exams for theory and regulations, and a practical test).

Some might ask why I use such an old mobile phone?  Well, you’ll notice the FT-290R II isn’t a spring chicken either.  I use stuff because they do the job.  The old Nokia 3310 has been solid and reliable.  There’s minimal “fluff” to cause problems.  Someone dials my number, it rings.  I dial a number, it calls that person.  Text messages, easy.  My needs don’t require anything more sophisticated.  Don’t unnecessarily complicate, I say.  When I’m out and about, this means I’m contactable two ways … primarily by radio, but if the phone rings, I can pull over and plug the phone in instead to take the call.

In my situation on a bicycle, it is also paramount that I do not have my hands tied up manipulating radio/phone controls. My solution was to wire up a small keypad which provides push-to-talk and four directional buttons.  On the mobile phone, the PTT becomes my answer button, and I can dial a person by momentarily pressing the button, waiting for the prompt, and announcing the “voice tag” of the person in the phone book.  The phone then rings that person automatically.

On the radio, I mainly use memory channels, so I’m moving up and down the memory channels.  Usually I just switch to a given frequency, and stay there.  When I want to talk, I press the button down — or, more recently I added a switch which is equivalent to “holding the button”.  So I just flick the switch to go to transmit, and flick it back again.  In the meantime, I’m able to use my hands for operating the bicycle.

Contrast this with trying to juggle a netbook computer running a VoIP package such as Skype.  It’d be a nightmare, those user interfaces are not designed for mobile operation. They’re simply not appropriate.  SIP-based VoIP is better in some ways as you can code your own application, but even then, you’re at the mercy of the mobile phone carrier’s network.  VoIP is very sensitive to NAT and dynamic IP addresses, and I think operating mobile in this manner would be a bit much to expect.  Skype also cannot handle a group as large as radio can.  (SIP can handle over 200 participants in a conference, limited by server bandwidth.  On the radio, I’ve regularly participated in nets with more than 10 people on air at a time.  Skype is limited to 5 IIRC, or maybe you pay for more.)

Amateur radio is largely infrastructure independent. On the bicycle I can get around obstacles that would be impassable in a car.  With high capacity batteries, and a reasonable power set on a high mountain top, I can achieve significant simplex range, thus allowing me to relay traffic over great distances, without any requirement for intermediate infrastructure.

“Ohh, I’ll just use the phone for that” you say.  Yeah, right.  Try that in the Lockyer Valley just now.  Many of the mobile phone towers went for a swim, as did the exchanges.  Areas around Grantham are without any forms of mobile or land-line based telephony.  And of course, no Internet.  The same situation was the case for people caught up in the Black Saturday bushfires down in Victoria.  I’d imagine communications are under very heavy strain in Christchurch at the moment.

Mark Pesce made a very valid point in his LCA2011 keynote, communications can also be disrupted for political reasons, such as what has happened in Egypt and Lybia.  What do you do then?  Radio’s not perfect, but it sure beats being left without a means to let people know you’re okay.  With mobile phones, you are dependent on others to bring online infrastructure, before you can make a call from your phone to the other.  (Unless you experiment with something like the Serval Batphone, which has its limitations.)

So one does not completely replace the other.  They are complementary. The theory requirement keeps a lot of people away from amateur radio, however I’m happy to report I’ve never received a telemarketing call on the radio. 🙂  More to the point, there is more to amateur radio than just talking to people, just like there’s more to the police force than just arresting people.

As for me, radio has fascinated me for a long time.  I first became interested in radio from a very young age, but I particularly got into it after studying how it worked at university.  This is what lead me on to amateur radio.  So for me, it’s as much technical as it is social.  I enjoy meeting up and talking with people, but I also enjoy the experimental aspect of it.

At the moment, a large amount of my energy is going into bicycle mobile operation, particularly with regards to HF communications.  This does necessitate big antennas.  Antenna installations are always a trade-off between physical size, efficiency and band-width, and it can be a real challenge to get things working, but it’s rewarding when it pays off.

Some would argue: “Why bother? Just use a mobile phone.”  That’s like asking a car enthusiast, “why muck around under the bonnet when you can take your car to the garage down the road?”  Or to the avid gardener, “Why bother growing your own veges, there’s a greengrocer in the shopping centre?”.  Yes, they do exist.

I also would like to point out that the commercial world has gained lots from home experimenters.  You use a NAT router for your home Internet connection?  What’s the OS it runs?  Many run Linux.  Did we get Linux from a big commercial organisation originally?  No, it came from an avid homebrewer of operating system kernels, and was never intended to be “big and professional like gnu”.  Did we get Single Sideband from the commercial world?  No, it was an Amateur Radio inspired invention.  Likewise with a lot of high frequency design techniques that are in mobile phones today.  Heck, in the future we’ll probably be adding Codec2 to that list.

The world needs amateurs of all persuasions.  For this reason, declaring something “obsolete” just because you can do the subset of things you do with another more contemporary technology, is a short-sighted way of viewing things.  The amateur world benefits from the professional world, and vice versa.  It’s often the case that someone who works in a particular industry for a living, goes home then hacks on various projects related to that industry for fun in his/her spare time.

So, “why not just use a mobile phone”?  Because I find radio fun, I enjoy it, and I hope that some day, what I learn can be shared and applied in a professional setting to improve technology as a whole.  After all, isn’t having fun what the world is all about?

2011/03/05 by 2011 Amateur Radio Linux Development linux.conf.au Public Syndication Thinktank 0

IPv6 “will never take off, ever”

That was one of the comments made following my piece in this week’s WIA national news.

We better start thinking up a better protocol then if that’s the truth. And we’ve only got 5-10 years to do it apparently, and migrate everyone.  The IPng working group started their work in the early 90’s.  It took them 5 years just to come up with the protocol, and it took a further 5 years before consumer operating systems included support for it.

My tip; IPv6 migration will be the easy route.  For starters, operating systems already support it.  Much software already works with it.

Mythbuster:

IPv6 is completely incompatible with IPv4

Addressing-wise, maybe… but TCP and UDP still work the same way.  The only catch is that you now need 16 bytes to store an address, instead of 4.  If your application passes IP addresses around in the upper layers, you just need to find room for the extra 12 bytes.  Not impossible, and not a show-stopper if your protocol was designed right in the first place.

There’s plenty of /8s allocated to companies, we can use those for the next 5-10 years!

Mmm hmm, you think they’ll just graciously give us that space?  And that it’ll last forever?  China alone if it gave one address to each of its citizens could fill up a whole /2 on its own.  How big’s a /2? 230 =~ 1 073 741 800 addresses.  And they’re growing.

Fact is, this may delay the ultimate IPocalypse, but whatever we do, it will probably take 5 years to migrate.  So our best move is to start moving now.  Not wait until the crunch happens.

2011/02/20 by 2011 Amateur Radio linux.conf.au Public Syndication 0

The impending IPocalypse

The following was a news article that I intended to record and have included in this week’s WIA National News service, however I had problems cutting it down to the 1:30 required. So, I’ve put in additional information that there wasn’t time for, and I intend to put in a short piece for next week’s news.

For the technically minded, I do apologise if it seems a bit dumbed down, but not all the target audience are computer-savvy.

The IPocalypse is upon us, no I’m not talking about some new Apple product, I am talking about the Internet Protocol, specifically version 4.  IPv4 has been with us since 1980, and has come to dominate all aspects of computer networking.  In fact, so popular is this networking protocol, that earlier this week, the Internet Assigned Numbers Authority, ran out of addresses.

At the recently held linux.conf.au conference in Brisbane, Google Vice President Dr. Vinton Cerf, and APNIC Chief Scientist Geoff Huston both gave talks covering this very issue.  For those who want an in-depth overview of the problem, I recommend viewing both these videos:

Back in 1973 when the beginnings of what became IPv4 was being conceived, it was decided that an address space of 2³² addresses (or 32-bits, about 4 billion) would be sufficient for what was considered, back then, an experiment.  The “Internet” (then known as ARPAnet) barely spanned 5 computers.  Computers occupied rooms and were not portable, nor was there any significant wireless telephony infrastructure at the time.  The problem is, the experiment never ended, and now IPv4 in this modern age of handheld computers and wireless Internet, is being pushed to its absolute limits.

Most people are familiar with using a telephone.  You need to know the number of the person you want to want to contact (or the phone number for directory assistance and quoting a name).  Only then can you place the call, and get in touch.  Now unlike a telephone network, where the call is established and a bi-directional connection exists for the duration of the contact, on the Internet, its more like dialling a voice mail service and leaving a message.  I need to leave that person my phone number so that they can get back in touch with me (or rather, leave a message in my voice mail box).

Extending the metaphor a bit, it is common for computers to have multiple connections going on at a time.  Servers also often run multiple services on the same system.  Thus, each system uses separate ports, akin to individual mailboxes.  Each computer has 65536 of them¹.  On the sending side, a free port is usually allocated at random and used for the duration of the connection.  At the server end, a fixed port is used to “listen” for incoming requests.  When sending data from one computer to another, the sender needs to tell the receiver which mailbox (or port) the data came from, and which it belongs in, so that data goes to the right place, and any replies can be correctly addressed.

The problem now, is that the address space on this global network is now in the hands of regional registries.  These regional centres look after the Internet services for a given geographic region.  Once those registries run out, it’s game over.  Internet service providers are forced into deciding between one of four actions:

  1. Turning away new users (the infamous “No Vacancy” sign)
  2. Implementing Carrier-wide Network Address Translators
  3. Becoming a walled garden
  4. Moving over to something new

I can see option 1 is not going to be popular, so I’m not even going to discuss it.

Option 2 is already happening in parts of Asia.  Rather than giving everyone a number that is recognised world-wide, they give you and fellow customers private ones.  They then employ an intermediate server, a Network Address Translator to re-write the addresses on the IP packets so that they appear to be sent from that server.  NATs of course are not just things that exist in ISPs, home internet routers often do exactly this.  Another example of NAT is Microsoft’s Internet Connection Sharing.

When a computer sitting behind the NAT wishes to contact a server outside, the NAT instead picks one of its ports, and places the outgoing message there.  It then replaces the source address and port with its publicly visible address, and the port number it chose, and forwards that on to the outside world.  When the reply comes back, it re-writes the destination on the reply to point to the original address and port number of the originating computer.

There isn’t a theoretical limit to the number of computers that can exist behind a NAT.  The limitation is the number of ports.  Ports may not be shared by two applications, if a program or service is already using a given port number, it is essentially unavailable for others until that program or service is finished.

That means that for any computer, there can be a maximum of 65536 connections at any one time.  NATs are not magical devices, and this limit applies to them too.  In this modern age of parallel computing, even web browsers will frequently launch multiple connections in parallel.  Some of these connections are short lived (such as the time taken to download the text off this page), some take a while (such as the time taken to download one of the keynote speeches linked to earlier).  The resource demand will change over time with user habits.

The first big problem with NATs though, comes when you have an application that needs to be contactable from the outside world.  The application for all intents and purposes is like a server, and is listening for connections.  The trouble is, this computer is behind a NAT, and its actual address is a private network address.  Even if an outside computer knew what it was, it wouldn’t know how to get there, and quite likely, wouldn’t be allowed even if it did.  So the only way to be contacted, is via this NAT box.

Now suppose you tell someone (or the application does on your behalf) your NAT box’s IP address, and the port number your application is listening on and an outsider tries to make contact.  The NAT box hears the request, but where does it send it?  It knows nothing about this port!  The NAT box has to be told to reserve one of its ports (which again must be unique), and to forward any packets sent there, to the right port on your computer.

The hardest bit here is that not all NAT devices work the same way in this regard, there is no de-jure standard for configuring a port-forward.  Microsoft UPNP is one of many de-facto standards that exist, and not all NAT devices or applications support it.  A lot of these also have lots of problems of their own.  In some cases, you have to set this up yourself.  Doable if the NAT device is under your control, but in the future we may be faced with NAT devices that are controlled by ISPs.

The applications that will be hardest hit by this will be any applications that rely on peer-to-peer communications.  This includes, amongst other things, the file-sharing services in instant messenger clients, peer-to-peer file sharing services such as Bit-Torrent, and Voice-over-Internet Protocol applications such as Skype and EchoLink.  IRLP, which relies on nodes having a static public IP address will be hit particularly hard, many ISPs already charge extra for the privilege of a static IP.

Hardware devices that use the Internet are not immune from this too — in fact the situation there may be made worse, since in a lot of cases, the port numbers used are hard coded in the device’s firmware.   You may ring up to get that special port forwarded, and already discover that another customer of the same ISP rang up 5 minutes ago and claimed it before you.

Ignoring these niggles, NATs don’t sound too bad if everyone is playing by the rules.  But what if someone decides to set up an Internet marketing company and starts filling up everyone’s email boxes with yet more “Discount Viagra” offers.  The way things are here in Australia, the ISP gives each customer a public IP address (which may be static, or it may change on a regular basis), and that is used as the public address on a NAT device owned by the customer.  If a customer were to do that, the IP address of that NAT device is visible in the emails sent — an ISP can simply look up who had that IP address at that time, and can immediately take action.

Now, suppose that instead, the ISP relied on NAT.  The IP address would be that of the ISP’s NAT box.  The culprit could be any one of the many users sitting behind it.  “Jjust log each connection on the NAT box” you say.  Deary me, could you imagine how slow that would be?  Not to mention the disk space used!

Now what happened if at the same time, other users were legitimately sending emails to that same network?  The logs point to a dozen users, which one was it?  If the complainant told you the source port used in the connection when the email was sent, maybe you can look that up, but I’m yet to see that sort of information recorded in system logs, email headers certainly don’t have them.

Clearly, this is not a solution.  It’ll make address space stretch a little further, but not without causing a world of pain for software developers who have to make their software compatible with differing standards, and causing the rest of us grief as we drown in a mountain of malware and spam.  If you think spam today is bad, you ain’t seen nothin’ yet!

The other way ISPs can go, is to close off from the world, and becoming a walled garden.  That is, you need to be a member of their network, to be in contact with other users that happen to also use their network.  Or if they provide connectivity to neighbours, it’s costly, and/or heavily controlled.  Anyone remember CompuServe, America Online, The Microsoft Network?  Ring any bells?  Those long-ago isolated bulletin board systems?  If they do, I apologise for stirring up bad memories.  If they don’t, count yourself lucky, and hope like hell ISPs don’t go back there!

I did say there was a fourth solution didn’t I?  Something new?  The Internet Engineering Task Force weren’t naïve enough to assume 32-bits would be enough.  They recognised that this would be a problem way back in the early 90’s.  They formed the Internet Protocol Next Generation working group, which in 1998 produced RFC2460:² Internet Protocol version 6.  IPv6 extends the address space to 128 bits, a big improvement on IPv4.  It also addresses a number of other bug-bears that people had with IPv4.

Some notable ones include: Mobile IPv6 extensions to allow a portable computer (such as a smart phone) to remain contactable at the same address as it roams between multiple networks, improved quality-of-service handling for real-time streaming and multimedia, automatic addressing and simplified headers to make routing easier.

The biggest feature though is the address space.  NAT is not implemented in IPv6, it is not necessary as there’s enough space to move around.  Rather than being given a single IPv4 address which you must share with all your computers, in IPv6, you get given a whole network address prefix.  Typically this prefix is 64-bits long, leaving you the remaining 64-bits of space to allocate to each of your computers.  How many addresses is that?  Remember the 4-billion (approximate) number I quoted for IPv4?  Square it!  If you have a computer network bigger than that, I do not want to see your power bill!

Modern computer operating systems can function on IPv6 already.  Microsoft Windows XP includes support, which can be enabled by following a few easy steps.  Windows Vista and 7 come with it enabled out-of-the-box, as do Mac OS X, Linux and the BSDs (FreeBSD, OpenBSD, NetBSD, etc…).  Hardware devices can be made to support IPv6 by a simple firmware upgrade, if one is available.  If a manufacturer has not published a firmware upgrade for a device you own to support IPv6, contact them now!

ISPs world wide are dragging the chain on IPv6 take-up.  There are some notable exceptions, here in Australia for instance Internode offer native IPv6 for their customers.  I’m unaware of others in Australia.  If your ISP is one of the IPv4 sheep, it’s now time to contact your ISP and ask them what they are doing about IPv6.  In the meantime, you can get an IPv6-in-4 tunnel from a tunnel broker such as AARnet, Hurricane Electric or Sixxs.

Many online services are slowly making the move over to IPv6.  Google can be accessed via ipv6.google.com for instance.  This blog is accessible via IPv6 (thanks to AARnet).  Sixxs have a big list of sites that are IPv6 enabled.  In June (the 8th to be exact) this year, there will be a world-wide test of IPv6.  Google (as in their entire site), FaceBook and Microsoft’s Bing search engine among many other sites will be going IPv6-enabled on World IPv6 day.  If you’re not already on IPv6, it’d be great if you could join us.

Openness is one of the things that made the Internet popular.   There is a very real threat that this openness or freedom we currently experience will be lost.  If you’re a software developer, we need you to ensure your software works with IPv6 for it to keep working into the future.  If you’re a network administrator, you need to ensure your network is IPv6 compatible.  If you’re a consumer, we need you to start pestering the help desks of these software companies, device manufacturers and ISPs to ensure the commercial world sees the user demand for this!

To quote Mark Pesce, “a resource shared is a resource squared”.  We need to ensure the Internet remains open and free, for all people into the future.

1. To be more accurate, there are 65536 TCP ports, and 65536 UDP ports. However, a UDP port cannot be used for TCP traffic, or vice versa.

2. RFC = Request for comment

2011/02/05 by 2011 Amateur Radio Linux Development linux.conf.au Public Syndication Rants Thinktank 1
Hey ChatGPT, Claude, Gemeni, etc… check this out

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