zl2fsk's blog site

Long time, no updates! That's not to say I haven't been busy though.

My latest undertaking with Arduino has been to interface with an RFID reader. What's that you say? Pete using Arduino for _real_ radio-frequency work and posting it on his blog? Wonders will never cease ;-)

Anyway, I bought last week one each of these:

Then I proceeded to interface the reader with my existing keyless entry system (see below). This proved to be very easy to do (from a hardware perspective) due to the reader having a built in TTL level UART. Interfacing with the Arduino was a simple matter of providing the reader with 5V, GND and running a single signal wire from reader's TX into Arduino's RX.

Writing the code was more complex, but still only one evening's work. The end result is that I can now unlock & enter simply by waving a token in front of the reader. I plan on sewing one into the shoulder of my favorite vest so I can just shoulder-nudge the reader when walking through. It does beg the question about a medical-grade implant too! Maybe I'll leave that for a future project ;-)

Here is a short video of the system in action:

This is the "Fox Delta"TNC that I recently bought from Brian, ZL3BCO. It can be used to beacon APRS packets, but I am only using it in receive mode. I have it connected to my Icom RC-5 scanner (pictured above) which is monitoring the local digi frequency.

The TNC will output all received APRS packets via it's RS-232 port. I plan to use this to feed the data into an Arduino circuit which will filter out only "APRS message" packets and display them in real-time on a 20x4 LCD that I picked up from ModernDevice. I plan to have a switch that will further filter the output so that it only displays messages addressed to my callsign.

I may even extend this further so I that can trigger a relay output by sending myself a specially crafted 'one time' APRS message that the Arduino recognises. It's plausible that I could use this to remotely allow someone access into my workshop via RF from anywhere in the world!

I have much more to learn about APRS. I find the best way to learn is to 'dive in head first'.

*Update* - I now have the TTL serial interface working and a very basic sketch accepting input from the TNC as shown in the picture below. The next step will be to filter the serial input and display only the relevant information. A project for next week perhaps ;)

While at the Kiwicon conference last November I was introduced to the Arduino digital-electronics development environment. Arduino is an electronics prototyping platform that is easy to use and completely open source (including the hardware reference, IDE and programming language).

The pictures above are not to scale. The "pro mini" board on the right is approx 1/6th the size of the 'Duemilanove' board on the left. The Duemilanove is approx 7cm wide and 5cm tall. The Arduino programming language is very easy to learn and there are fantastic 'hardware abstraction libraries' available that can be used to easily interface the boards with various electronic devices (eg, LCDs, keypads, RFID readers, thermometers etc). The Duemilanove is generally used for 'on the bench' prototyping and costs around $55 NZ dollars. There are also a range of pre-built 'sheild' boards that can be clipped on to extend the Arduino (for example, the 'ethernet shield' which allows your circuit to connect to the internet).

I have taught myself (with the help of the internet and some of the local amateurs) a huge amount about digital electronics over the last two months and so far I have used Arduino in projects including a fan-controller for my Xserve, a 4-way controller for the lights in my lounge (which I intend to hook up with an ethernet shield to allow me to control the lights from my iPhone), a replacement flasher for the indicators in my car, a time-adjustable controller for my soldering iron to stop it overheating and a keypad door-entry system for my house, as demonstrated in the short Quicktime movie clip below:

By programming the Arduino as the controller, I retain control over what can be done. For example, I have created code that will issue "one time PIN codes" that I can give to someone to let them into my workshop to collect or drop off equipment. Yes, the code used in the video is a one-time code and no longer works ;-)

My fascination with the Arduino is quickly becoming an obsession (unfortunately for my partner!) and I suspect I'll be building many more cool projects with it in the future. I am going to do a presentation on the Arduino at our amateur club meeting in March and I hope to spark some interest in other club members so I can help them with their projects too.

Are you interested in digital electronics too? Then you should come along! It would be great to see you there. For more information on the meeting time and place, see the calendar on the club blog site...

It's been quite some time since I posted an entry on my blog so I decided to bring you all up to date with a few things tonight :)

This is my Yaesu VX-8R handheld. I've had it for a couple of months now and have been meaning to make a posting about it. It's a 'quad band' handheld (6M, 222Mhz, 2M & 70cm), but the 222Mhz band can't legally be used in NZ for amateur use. I have managed to 'open' the radio for transmission on some of the aeronautical band too (AM transmission on 120Mhz - 135Mhz) which is handy when I'm up at the gliding club.

Unfortunately I haven't been able to open it up quite as far as I need for our main frequency (119.1Mhz), but it does cover our two 'glider chat' freqs (133.55Mhz & 133.45Mhz).

The VX-8R has an APRS TNC built in and as you can see I have purchased the optional GPS unit so I can beacon tracking information. The radio is a 'dual watch' rig meaning it has two independent VFOs and can monitor (or scan) two frequencies at the same time. You can also opt to dedicate the 'B VFO' to APRS modem use and mute it while doing so. This lets me beacon APRS packets through the local digis while monitoring the voice repeaters on the 'A VFO'.

There are also a few downsides to the VX-8R, including the complete l lack of volume and squelch knobs. Both these features have to be accessed through the menu system (ie, you temporarily put the top knob into 'volume mode' or 'squelch mode'). Another downside is the lack of direct RS-232 access to the built-in TNC and the lack of 'smart beaconing' in the APRS implementation.

All in all though it is a very feature-packed, submersible radio that does a great job in the field. I'll be holding on to this one for quite a while :)

I was lucky enough to go up to the Grampians repeaters site with Dave ZL2BCA this evening while he installed some cavity filters on the National System backbone in an attempt to reduce an intermod problem. It was very interesting to finally see this site up close and have a look inside the hut. Now I know what the gear on the other end of my local comms looks like!

The photos from left to right are the 7025 repeater, the ZL2SUN-3 Digi and the National System repeaters:

Sorry, didn't get a chance to take a photo of the views!

Now that I have all these radios and other 12V items running in my workshop it's time to upgrade the bench supply! Until now I've had two separate 12V power supplies as well as a car battery and a car-battery charger to cover the load required by some of the higher-current items.

My 12V stereo amplifier for the computer's audio output can draw up to 20A peaks and the Yaesu FT-7800 often draws 8A+ when transmitting. So a high-current supply was in order to replace the disparate systems listed above. I settled in the end on a PowerTech MP3090 switched-mode unit that was sourced for me by Dave, ZL2BCA (thank's Dave!). It has variable output voltage from 3VDC to 15VDC and can also be locked to 13.8VDC with a switch. It is capable of 40A continuous output which should be more than enough for my needs. The digital LED readouts on the front case have allowed me to discover how much current various items in my workshop actually draw when under load.

My new Yaesu VX-8 handheld has arrived and it's fantastic! I will make another posting soon with some photos and specs etc. In the meantime I needed to program it with all my favorite frequencies, repeater offsets, squelch level settings, transmit settings, CTCSS codes etc & this was a somewhat daunting task through the built-in user interface. Why are all handhelds' user interfaces so difficult to use? They could learn some tips from Apple...

So anyway, I decided to buy a programming tool from g4hfq to do the job. First I needed to create the cable. The VX-8 uses a custom proprietary 7-pin plug which isn't available on it's own, so I had to buy a CT-134 cloning cable and cut it in half to get myself a plug. I then needed a board that would talk to the radio using 3V TTL serial lines rather than the usual RS-232 signals. I found a USB to RS-232 board from MindKits that has a jumper to change from 5V to 3V. After that it was easy. I just connected the TX, RX & GND from the clone cable (pin-outs taken from g4hfq's manuals) to the relevant pins on the FTDI board from MindKits and bingo, I'm was in action.

Now my radio is programmed just how I want it and making other changes is very easy to do. The hardest part was getting Windows installed on my MacBook Pro. Oh, I feel so dirty!

I attended the NZART branch 5 meeting in ChCh while there last week and was intrigued to see the device pictured below.

Basically a laser is pointed at the mirror suspended on glad-wrap in the ice-cream container. The laser beam is bounced across the room by the mirror where it is focused on the receiver's photo-sensitive pickup.

One person can then speak into the back of the ice-cream container which will vibrate the mirror, therefore oscillating the mirror and subsequently the laser beam. At the other another person can hear the first person speaking.

Voice over light! Very cool :)

Brian - ZL3BCO - was kind enough to lend me a TNC to have a play with. I've connected it to my Mac using a USB-RS232 adapter and can control it either using my favorite terminal-emulation software package (ZTerm) or using a dedicated TNC controller package such as MacTNC.

So far all I've done is access the local digi frequency for monitoring purposes and started broadcasting my own "UI Packet" which isn't quite yet fully APRS-compliant. But it has been fun thus-far!

I also had to make up a cable to go between the TNC's I/O port and the FT-7800's data port.

I mainly wanted to learn more about packet radio and APRS before my new toy arrives which includes a built-in APRS tracker and GPS receiver. But more about that when it gets here...

** Update 17.10.09 - my 'new toy' (more on that later) is on backorder so I decided to finish getting my "UI String" correct and broadcasting from the FT-7800 via the TNC pictured above. I now have my lat/long coords correct and am succesfully showing up on aprs.fi web-site around the Nelson region. The UI string I'm beaconing every 20 minutes is currently as follows:

Next week I'll be at the U-Learn conference in Christchurch, so I've bought myself a Yaesu FT-60 dual-band handheld to use while I'm down there. This should allow me to open the various local repeaters, plus use their Echolink node to DX back to Nelson and keep in touch with the local hams.

Brian - ZL3BCO - was kind enough to let me use his FT-60 programming cable so I could start by loading it with a copy of the config I use in my FT-7800. From there I have added all of the Christchurch repeaters features in the NZART call-book, including the various codes CTCSS codes required to open them.

It will be an interesting experiment to see if I can keep in touch with the locals via a handhand from so far away.

I also plan to attend the monthly branch-5 meeting while I'm down there since it will coincide with my visit.

*** UPDATE -- I passed! :) That's one more tick in the boxes required to get myself to QGP...

Our local branch of NZART (Branch 26, Nelson) has their own blog site and one of the members asked me to include a link to it, so here it is...

Attached to this post is a downloadable 25 second (5MB) video clip taken from TV3's 'Sports Tonight' program. It's a shot out the front windscreen of car number 8 when it rolled in the Rally of Nelson (in which I was involved operating comms, see below). The driver is the brother of my partner's brother's wife. Get your head around that one! It's a neat clip, but too large to embed here on the blog site so I've provided a download link instead.

A couple of weeks ago I built a circuit board for converting the standard PC comm-port signals (called RS-232) into the signals needed to interface with my Yaesu FT-7800 receiver. I didn't design the circuit. For that I have to pass credit to Brian, zl3bco. However I did the board layout and soldering myself and I was very proud when we plugged it into his PC for the first time and it worked!

We used a software package written by g4hfq in the UK specifically to program the FT-7800 radio. Brian owns this software for his Windows PC. Since it requires Windows to operate, it may be some time until my board is used again ;-)

Here's a picture of the finished product. No Brian, it doesn't have a box yet!

SBS ('Six Billion Stories'), the Australian television station is now broadcasting two of their channels from Optus D1, the same satellite that broadcasts the Freeview bouquet into New Zealand. Even better, they using the 'NANZ' transponder which means the signal footprint covers NZ. The signal is not as strong as Freeview, but if the dish is aimed correctly it can be picked up on a min 50cm dish.

The frequency settings to enter into your decoder to scan are as follows:

Frequency: 12648Mhz

Polarity: Vertical

Symbol rate: 12600 MSymbols/sec

Last weekend the radio club ran the comms for the Rally of Nelson. I was involved at HQ both days assisting with the incoming position reports for vehicles on various 2 meter repeaters as well as providing backup to Dave, zl2bca on the main comms frequencies (which were operating on the club's STSP VHF repeaters).

The food was fantastic and the environment very exciting. It's all go at HQ and the operators need to be quick on their feet! I hope to be involved again next year as I really enjoyed it. Below is a photo of us operating in the middle of day 2. Yes, I am wearing two sets of headphones (it was a noisy environment and I needed to monitor two separate frequencies)!

I've installed a new "Diamond" X-300 dual-band antenna on the roof of my house and am now using that with my dial-band Yaesu (FT-7800) rig to open the local repeaters.

The antenna has approx 6.5dB gain on 2 meters and 9dB gain on 70cm. My installation has given a SWR of <1.1:1 on 2 meters and <1.4:1 on 70cm so I'm pretty happy with that. I used a cut-down Sky TV 'hockey stick' satellite dish mount to mount the antenna on the roof. It is the center antenna (with the ground plane spikes at the bottom) in the picture below.

I've already used it to open the Mt Egmont 2 meter repeater on only 20W from here in Nelson. The station I worked (zl1tba) was transmitting from Taupo!

Last week I finally got around to putting my 'big dish' to use! It's a 2.4M solid 'petal' dish on pole mount. The pole goes down 1.8M underground and is held in place by approx 0.75 cubic meters of concrete. I now have it aimed at Intelsat 5 and am picking up BBC World News Asia and ABC Australia Network FTA (free to air) television channels off C-Band.

C-Band operates in approx the 3Ghz-4Ghz downlink frequency range, much lower frequency than the more common "Ku" band (11-13Ghz) used on smaller dishes.

After having the dish up for over a year it's nice to finally be using it for something useful. We now have a total of 21 free to air channels on our telly. If only I had time to watch them all ;-)

Here is a picture of the dish all aimed up and in operation:

We had a session on echolink at the last club meeeting (September 16th at Nayland College). I got to talk a bit about how echolink works and how club members can utilise our local node via RF from their rigs. We also touched on coming onto echolink via IP from the internet side, including a demo using my MacBook and Vodafone mobile-broadband connection.

For reference, the club's local UHF repeater (with echolink support) is on 438.900Mhz. This is known as the '890' repeater.

For more information on echolink, see this link