Some additional notes and musings about the content on the RAE course.
Resistors
Resistors nowadays don't have coloured bands or markings. SMDs come on a long tape. They are placed by a numerical controlled XY machine onto printed circuit boards. [Pick and Place machine] Then soldered into place.
Q So why do we make you learn the 'colour code'?
A Well the code values gets used elsewhere. e.g. Cables denoting the number of the wire. Pins 1 to 9.
A Also you will be able to re-use old resistors for your projects. Most constructors these days re-use or re-purpose old equipment for their projects.
A lot of radio amateurs re-use older equipment to save cost etc. In doing this they need to identify components etc. One example is the conversion of a CB radio to use on the 10 metre band.
Resistor Failings
- Inductive value [VHF/UHF] - they are measurably inductive.
- Carbon Composition [very rare] - for non-inductive types.
- Capacitive value or self-capacitance [VHF/UHF]
- Power dissipation - heating. [Capacitors do NOT dissipate power]
- Radiative heat - some resistors come with a heat sink mounting.
- Volume/Potentiometers - variable resistors used to control the sound output. Log (logarithmic) types are used to vary sound level. But linear types are used for adjustment of voltages or currents. Some are multi-turn for precision setting of voltages/currents.
- Hair Dryer and Electric Blankets - heat dissipating at high or low levels.
- FUSES - Where the resistor melts to 'open circuit' and stop the current. This has its own 'issues' as the time to melt has an impact. Higher the current the faster it melts!
For more information find the informative article "Resistors" in Wireless World 1975-10-01 by R.A. Fairs, B. Sc.
Capacitors [Condensers in old docs]
Capacitors have a multitude of uses. "Super Caps" have a very large capacity value and can discharge high currents. Such that some trucks use them to start the engine. Charging from the normal truck battery when not needed.
At radio frequency they provide tuning for resonant circuits or parts of filters.
In pulse circuits they provide delay networks. [Differentiation and Integration]
They can also be used to "tune" an antenna. A "Capacity Hat" on the top of an antenna will reduce the frequency of resonance. Usually used on a short antenna to bring the resonant frequency down.
The majority of electrolytic capacitors get used as "decoupling" capacitors. Or as "coupling" capacitors. But at higher frequencies the ones used are generally ceramic. For filters and resonant circuits mica and air types are used. Being of higher quality and Q value.
For more information find the informative article "Capacitors" in Wireless World 1974-12-01 by R.A. Fairs, B. Sc.
Both are available on:- https://www.worldradiohistory.com/Wireless_World_Magazine.htm