AVALA-01 SDR Transceiver

Probably the most ambitious radio project I have embarked upon is the construction of a software defined radio (SDR). After my less-than-successful experimentations with what became my Software Defined Hardware Radio, I decided to find an SDR "backend" design that was already proven and build that. After some investigation, I selected the AVALA-01, which was developed by

Tasic' Sinisa - Tasa YU1LM. His YU1LM/QRP website is a treasure trove of SDR-related designs. Tasa has gone on to develop SDRs for Genesis Radio. In fact, the Genesis Radio G40 (no longer available) is a direct descendent of the AVALA-01.

While could have fabricated my own printed circuit board (PCB), I obtained one that was pre-made from an overseas vendor for a very low price. I obtained most of the components through Mouser and spent about five weeks (October - November 2011) constructing the board. While there were some issues with differences between the schematic and the PCB, they didn't really present that much of a problem. The PCB I bought had some of the errors corrected and I had already learned about the other issues through others that has already constructed an AVALA-01. A very good on-line resource is the AVALA-01 Yahoo Group, of which I am a member.

The three photos below show my finished AVALA-01.

Note that the components for the output low-pass filter are missing. While the AVALA-01 was designed for operation on 40 meters, I wanted to use it as an all-band SDR transceiver. Instead, I constructed an external four-bank RF filter for the amateur bands.

After these photos were taken, I replaced the heat sink attached to the IRF510 with a custom copper heat sink modelled after that described in the original AVALA-01 documentation. I also had to remove the 3.5 mm stereo connector on the rear panel, as the circuit design places 12 volts on the ground pin of that connector.

I placed the AVALA-01 in an LMB Heeger OH-743 enclosure. In my humble, unbiased opinion, I think it looks rather spiffy. I still have yet to label the switches and connectors, though.

While construction of the AVALA-01 was rather straightforward, its tune-up has been far from easy. Due to being a direct conversion, I/Q SDR system, it must be adjusted to remove mirror image signals during both reception and transmit. After a lot of trial and error, I think that I have successfully obtained mirror image rejection on reception. There is still some adjust that needs to be done for transmission, though. While I have been able to successfully transmit into a dummy load and receive SSB signals, this problem has prevented me from transmitting oppenly. Access to a spectrum analyzer will probably be required to resolve this problem.

I have already used the AVALA-01 in two SDR set-ups. The first was a desktop SDR system, using a Dell Dimension Pentium 4 computer with two sound cards. I obtained a Creative Sound Blaster Live! 24-bit (SB0410) card cheaply off of Ebay to interface to the AVALA-01. It, unfortunately, only supports 64 ksps. It also presents an odd audio interface, with the line in and microphone in sharing the same line. I used a Turtle Creek sound card to provide microphone input and baseband audio output. The OEM Sound Blaster card that came with the Dell Dimension conflicted with the SB0410. I used a QRP2000 with an EIA232 interface to provide clock and keyline control to the AVALA-01. Below is a photo of the desktop SDR setup.

Since the AVALA-01 is close to the Genesis G40, I used the GSDR software to complete the system. I was never quite satisfied with this setup, as it behaved oddly, at times. Some GSDR features did not operate as expected.

Preferring Linux over Microsoft Windows and needing a portable system, I set up a laptop SDR. I am currently using a Toshiba Satellite L350, running Kubuntu 12. I am using the internal sound system for microphone input and baseband audio output. A Sound Blaster X-Fi Surround 5.1 Pro (SB1095) interfaces to the AVALA-01. The QRP2000 carried over to perform clock and keyline functions. Below is a photo of the laptop SDR setup.

On the laptop, I am using Quisk as the SDR software. It works very well with the AVALA-01 and the QRP2000. I was able to determine how to get the SB1095 working properly at 96ksps under ALSA. Below is the .asoundrc file to support that configuration.

pcm.radio96ksps { # This is the ALSA plug name to be accessed by Quisk

type plug

slave.pcm "radioFDX96ksps"

slave.rate 96000

}

pcm.radioFDX96ksps { # This is the full duplex plugin for transceiver at 96 ksps

type asym

playback.pcm "radioTX96ksps"

capture.pcm "radioRX96ksps"

}

pcm.radioTX96ksps { # This is the audio playback stream plugin for radio reception at 96 ksps

type dmix

ipc_key 1024

ipc_perm 0666

slave {

pcm {

type hw

card 1

device 0

}

period_time 0

period_size 1024

buffer_size 65536

format "S32_LE"

periods 128

rate 96000

}

pcm.radioRX96ksps { # This is the audio capture stream plugin for radio reception at 96 ksps

type dsnoop

ipc_key 1025