Transcript Document
Technical talks for 2008 The design of HF Transmitters, Receivers, and Antennas. The format of the talks The talks will be semi theoretical Speakers should be available for discussions afterwards or on other weeks Some will want a deeper understanding Others just want to use technology confidently Practical examples will be used where possible Suitable group projects will be identified Anonymous feedback forms will be used Reference designs In order to retain our focus we will regularly refer to the circuit diagrams of two kits. The BITX20 and the SoftRock 40/80m. BITX20 Picture from Hendricks QRP Kits Why the BITX20? It’s a fairly simple transceiver It uses few circuit variations It does not use software We will learn to break down “big” circuit diagrams (next) Don’t Panic! BITX20 bidirectional SSB transceiver A BITX20 single stage We will learn to break down small circuit diagrams even smaller. (Another day) SoftRock RxTx 40/80m Picture from Nicolas M1HOG.com Why the SoftRock RxTx? It uses a range of circuit variations It is a more modern design It introduces digital techniques SoftRock Receiver Many of the same principles are used in the: The SDR Transmitter (avert your eyes for now if you like) SoftRock Transmitter These circuits were just to set the scene. We will come back to them during the following talks:- Fundamentals Current, voltage Conductors, resistors Potential dividers Kirchoff's laws Signals & test equipment DC / AC Signal Generators Graphs, Time, Amplitude, Frequency, Phase (using visualisation tools) Oscilloscopes (practical to follow) RC Bridges & Grid Dip Oscillators Electric and Magnetic Fields Electric fields, capacitors Magnetic Fields (Using visualisation tools) Magnetic Materials, Inductors and Transformers (Bifilar winding, Baluns) Analogue circuit design Diodes, Transistors (Bipolar, FET), Valves Transistor circuits: Common emitter, emitter follower, common base, biasing, feedback. Transistor pairs: Cascode, long tailed, mirror. Introduction to integrated circuits ICs are not scary: lets look inside Operational amplifiers & their internal design Gates, flip-flops, transmission gates The first commercial op-amp, the K2-W 1952 http://www.ieee.org/portal/site/sscs/menuitem.f07ee9e3b2a01d06bb9305765bac26c8/index.jsp?&pName=sscs_level1_article&TheCat=2171&path=sscs/07Fall&file=Lee.xml Analogue signal processing Superhet (supersonic heterodyne) receivers Mixers (multipliers). Single / double balanced Filters (RC, RC active, LCR passive) Filter design with passives or op-amps Electro Magnetic Fields (e.g. radio waves) Transmission lines / coax cables Propagating EM Fields Fundamental Antenna theory (dipoles) Antenna matching / tuning Phased arrays / Yagis Digital signal processing Digital Communications e.g. PSK31 A/D & D/A, Shannon’s law, sampling theory Some more logic circuits Direct Digital Synthesis (DDS) Digital filters and their design Demonstrations of digital signal processing These will be non-theoretical demonstrations of signal processing using a Field Programmable Gate Array (FPGA) demo system. If interested this can be followed up with more detail and a live demonstration of programming