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

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.