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

It’s a fairly simple transceiver

It uses few circuit variations

It does not use software

Why the BITX20?

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

It uses a range of circuit variations

It is a more modern design

It introduces digital techniques

Why the SoftRock RxTx?

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