Software Defined Radio (SDR) and its Implementation

Brandon GrahamW0GPR

What is SDR

• Instead of relying on RLC circuits, a raw, lightly filtered analog signal is converted to the digital domain to be further processed by digital systems

• RF Front End ADC/DAC Computer

R.F.Front End

High QualitySound Card

P.C., Laptop,Netbook, orEmbeddedprocessor

Antenna

I,Q

I,Q

Digital vs Analog

Digital• Discrete• Digital Signal Processing

DSP• Filtering• Phase• Frequency• Time• Power

Analog• Continuous• Filtering• Power amplifier

Flex Radio

• Manufacturer of SDRs for Industry, Military and Amateur use starting in 2003

• HF transceivers ranging from QRP to 100 watts– Flex 1500 – QRP/transverter IF– Signature series – Contest serious radio– *Flex 3000– *Flex 5000– *SDR 1000• *discontinued

“The Feel of the Radio”

“The Feel of the Radio”

Power SDR

• Graphical User Interface (GUI)– Radio’s buttons and knobs

• Signal Processing– Filtering, DSP, Audio input and output shaping, etc

• Rig control– Frequency, band, tuner

• Program interface– VSPs, VACs, out to digital modes, logging, ext. aux

“The Feel of the Radio”

“The Feel of the Radio”

Computer system/Software

• VAC– Virtual Audio Cable

• VSP Manager– Virtual Com/Serial Port

• Com-0-Com• DDU Til• Logging• Digital Mode Program• Remote Operation

• Processor• RAM• Screen usage• Quirks

The system setupFlex 3000

PowerSDR

VAC

DDU Til

VSP Manager

FL-DIGI

WSJT-X

N1MM+

Computer

Com SingleVAC Pair 1VAC Pair 2FireWire

Pros / Cons of SDR over Analog

• Pros• Filter visualization• Filter manipulation• Control of settings• Visually based displays– Panafall, etc.

• DSP systems and control

• Cons• Quirky• Visually demanding• Computer intensive• Software setup• Need for multiple

monitors and mouse• Not EmComm Ready

“Let’s Play Radio”

Remote Operation

• Controlling computer, not radio

• Everything must be powered up at radio and ready for control

• Easier with digital over voice modes

• Lag• Control of accessory

programs and screens

WebSDR

• University of Twente– Netherlands

• Website designed for internet linked SDR receivers

• Mostly centered on ham bands.

• http://websdr.ewi.utwente.nl:8901/

• http://www.websdr.org/

Other SDR Systems

• $20 Dongle– Nooelec.com

• SDR SoftRock• HPSDR• ANAN• Genesis Radio• Rfspace

• Google is a friend!• Always New stuff added• Experimentation vs.

“Solid Systems”• Many different

programs• http://

www.abrohamnealsoftware.com/products.php?cat=10