Saturday, February 21, 2015

Wyong field day 2015 - Damp but entertaining


The weather wasn't great for the big feature of the Wyong field day, the car boot sale. The ARNSW Home Brew group had a great display and spent time chatting with interested visitors. Here's John VK2ASU with Mal VK2BMS:


I showed the OpenRadio SDR on the home brew table:


While I didn't buy anything there were gifts of useful components from John and Stephen which are greatly appreciated! Some things I didn't buy:



It was great to retire to the classy bar:


For some tea, Jatz biscuits and cubes of cheese.

Built a larger quadcopter

The tiny drones are great for indoors, but to carry cameras I needed something larger. A collection of parts and a 450mm frame was ordered and finally it's flying.


I'm using a Fly Sky FS T6 transmitter and receiver and a KK2.1 flight controller.


Neither the remote or controller came with the interconnecting cable so I'm using single wire jumpers until proper cables arrive. The flight controller was recommended by Terry and is great because you can test everything and tune it by using its built-in LCD display and buttons.


While I can fly this thing the PI tuning isn't right and I'm getting oscillations while hovering. Lots to learn. Lots to learn.

Thursday, February 12, 2015

Tiny Quadcopters - Hubsan X4 and friends

We are having too much fun at the office (during lunch breaks) flying tiny quadcopters. The best of them seems to be the Hubsan X4.




A close second is a clone sold as the "Top Selling X6".


Both sell for about $40. The Hubsan you can order from China, the "Top Selling" is available at Paddy's Market in Sydney. Don't be fooled by the price saying $49 reduced to $45, they'll take $40 in a heartbeat.

For a little bit more, $50, you can get models with a camera:


Some drones like the UFO drone have a remote with buttons for taking still or video.


Great to have "High Agily Control":


The cameras are not great but kind of fun. Here's me checking the gutters.



The video is motion jpeg and seems to drop a lot of frames:


The trick to getting decent video with these tiny MJPEG cameras is to use a fast microSD card. Here's a recording with a Class 10 card and it's much better.



The motors are interchangeable and the other "consumable", the propellors, are available at low cost.

So far, I've learned:

  • Fly calmly, avoid dramatic corrections, and you'll be fine.
  • Expert mode, by pressing the left controller (mode 2) is more responsive and not really any harder to control.
  • The motors do die - I had one that went stiff after a crash, but are pretty easily replaced.
  • There is a "ground effect" and a "ceiling suck effect". Take off to about a meter in height and then get stable. Avoid the ceiling.
  • It helps to calibrate the accelerometers - the instructions explain this in broken English but it's worth doing. I've heard that calibration in expert mode is better.
  • If the video drops frames get a faster memory card. Class 10 works for me.

Flying indoors:


In a larger room:



Great fun.

Saturday, January 31, 2015

OpenRadio SDR kit build

Linuxconf this year in Aukland had a radio track where a low cost software defined radio receiver with some limited ability to transmit was launched. My kit arrived last week.

The OpenRadio SDR is based around the recently popular Si5351 oscillator which is controlled by an Arduino Nano. It's rather like the Softrock design but because the Si5351 has extra outputs there is ability to transmit digital signals modulated with shift keying. The software includes a beacon mode that can send a short message in, for example, BPSK31.


The OpenRadio SDR kit is lovingly prepared. As you can see above, the components are clearly marked and the makers have been kind enough to be generous with extra components - in particular I tend to lose surface mount capacitors and resistors from time to time.

The construction guide is first class. While there is some surface mount soldering required - a challenge for me certainly, they've been kind enough to pre-solder two of the most difficult devices.

I didn't rush the build and spent a few hours on Saturday doing a bit and then going for a walk. For me, everything worked first go.



The software in the Arduino is a great start but here's where this is where work can be done. You connect over a virtual serial port and get a simple menu for controlling the board.

0.3 Jan 31 2015 09:37:39
Starting up Si5351... Got Rev ID 1

RX Frequency (Hz): 8986000
TX Frequency (Hz): 26959500
TX/RX Relay State: RX
Transmitter State: OFF
Calibration factor: 1.00000000

RX Frequency (Hz): 8986000
TX Frequency (Hz): 26959500
TX/RX Relay State: RX
Transmitter State: OFF
Calibration factor: 1.00000000

MENU:
1: View current settings.
2: Change RX Frequency.
3: Change TX Frequency.
4: Toggle TX/RX Relay.
5: Toggle TX State.
6: Start BPSK31 Terminal
7: RX VFO Mode
8: Calibration Mode
9: Save Settings
A: Set channel (TX/RX frequency pair)
B: Start Beacon

For tuning around, at the moment you must use RX VFO Mode which gives you keyboard letters for tuning up and down, rather like PowerSDR but you must press enter after each.

RX VFO Mode, press q to exit.

    Up: r   t    y    u    i    o    p
  Down: f   g    h    j    k    l    ;
Amount: 1   10  100   1K   10K 100K  1M

I guess an interesting direction to evolve this would be to implement the protocol used by a popular rig and then SDR software could use Hamlib to control the board - certainly all possible.

My congratulations to everyone involved in this. I think it's a great idea brilliantly executed and I can't wait to see what people build on top of it. The idea of having an Arduino at the core makes it very accessible.

Sunday, January 25, 2015

Raising antennas with a drone

Stephen, VK2BLQ, has suggested we try holding an HF vertical up with a drone but here's another idea for antenna installation in tall trees.


I'll have to improve my skills a bit but it's a great way to combine two hobbies.

Good value laptop for ham radio use - Lenovo X201

Recently there have been a constant stream of second hand Lenovo X201 laptops on ebay here. David Rowe mentioned when he visited that the X200 series is the last "good" Lenovo laptops from a technical Linux using perspective. Here's the one I picked up for $240 but they range from $200-$300.


I like these for the following reasons:


  • Solid build
  • Easy access to the hard drive - one screw and it pops out of the side.
  • Old style boot, not UEFI, so you can install old Windows
  • Fairly compact
  • Tolerant of high RF (My old MSI netbook goes a bit crazy when transmitting)
  • Decent CPU - i5 with quad core can keep up with DSP tasks
Mine came with a pretty dead battery so I paid another $40 to get a new 9 cell replacement. I had a 240GB SSD handy so I used a USB key with a gparted live linux system on it to dd copy the internal disk over to an external drive case and then swapped the drive. (These little bootable USB utilities are a very useful tool in the kit).

As you can see above, I'm dual booting Ubuntu for WSPR but also keeping Windows 7 around for the Windows only software I sometimes need to run.

Saturday, January 10, 2015

Skypi 40m transmitter controlled by Raspberry Pi

Just saw this interesting gadget called a Skypi from RadWAV.


It appears to be a 1W carrier transmitter for 40m that plugs in to the GPIO socket on a Raspberry Pi. The board requires 12V and it produces 5V to power the Raspberry Pi board via the connector.

They've modified existing software to control the frequency and carrier so that it can transmit WSPR, RTTY and CW. For CW they can read a key plugged in to the board.

Note that this is not a transceiver, which is a pity. They offer an optional output socket for a receiver and the board switches the antenna to that port between transmissions - there's demonstration audio of how it sounds.

It's great that RadWAV has created this product but I'd really like to see at least a block diagram of it. The documentation is sent to you by email after ordering.

Personally, I'm hanging out for the OpenRadio SDR which is being launched at Linux Conf AU which starts on Monday 12th Jan.

The SkyPi kit is US$85 or US$185 assembled including the receiver output port.

Sunday, December 21, 2014

Copper pipe loop for 40m

Inspired by the work of Peter, VK3YE, I visited the local hardware store to get bits for a 40m loop antenna. Purchased a 3m length of copper pipe, some hose clamps, some copper saddles, a piece of dowel, and a plank of wood. Here's the result:


The variable capacitor is clearly not going to be able to stand much power but at 20W it doesn't appear to be arcing. This capacitor has a reduction drive and I'm using a switch to add a bank so that I can tune both 40m and 20m. Joining the tuning shaft to a dowel rod with a piece of plastic pipe and cable ties worked out quite well although there's a little slippage.


Matching stub:



Tuning is incredibly sharp but a very low SWR is achievable.


The offset of the tuning stub was a guess but seems to be reasonably close to 50 ohms. I had a pre-arranged contact with Stephen, VK2BLQ who could hear me reasonably well.

Reception seems excellent and of course the very narrow bandwidth leads to nice low noise.

Update

Had a visit from Bob Bray who liked both the shed and the loop antenna, although I suspect he wasn't impressed with my impression of a circle.


Robert John Bray is a prominent astronomer who has been honoured by having a main belt asteroid named after him.

Update - motor drive tuning

I've changed capacitors and added a 36RPM motor drive and a box to switch direction. The drive is still way to fast and now I'm looking for a reduction gear or multi-turn capacitor of some sort.


Friday, December 12, 2014

Built an Ultimate3 Beacon

This week an Ultimate3 QRSS/WSPR kit beacon kit I ordered arrived and this morning it was easily built.

The display is super crisp.



I ordered mine with the 30m low pass filter.


The whole thing runs on 5V so I chopped an old USB cable and have been running it from a USB charger or battery.

It's a great kit, with very clear instructions and it came together very smoothly. Mine was missing one small capacitor but it was no trouble finding one in the shack.

The software is very well done and everything is set up using two push buttons placed in just the right spot for your fingers while holding the board with the display facing you.

Amazingly this does WSPR as well as lots of modes:

- QRSS mode (plain on/off keyed slow CW)
- FSK/CW mode (frequency shift keyed slow CW)
- DFCW mode (dual frequency CW)
- WSPR mode (Weak Signal Propagation Reporter)
- WSPR-15 experimental WSPR mode with 15-minute frames
- Opera modes (8 speeds)
- PI4 beacon mode
- Slow-Hellschreiber (frequency shifted slow-Hell)
- Full-speed Hellshreiber
- Half-speed ("DX") Hellshreiber
- CW (plain CW)
- FSK (0-999Hz shift, fast-speed FSK CW)
- Customisable FSK patterns
- manually-keyed CW/FSK transmitter

I ran Hellshreiber for a while but it didn't look too good on fldigi in the house, now I'm running 20WPM morse but that's not decoding perfectly either - my guess is that the signal is so strong that AGC is messing with it but I'm still trying to figure this out.