Foundation Radio Amateur Licence - BDARS Online Syllabus

4. Transmitters and Receivers

Simple block or “concept” diagrams of a transmitters.

Identify the items in a simple transmitter block diagram and recall their order of interconnection:Microphone, audio (microphone) amplifier stage, frequency generation stage, modulator stage, r.f. power amplifier stage, feeder and antenna.

Technical requirements of radio transmitters
Recall that the frequency generation stage(s) (e.g. oscillator(s)) in a transmitter defines the frequency on which the transmitter operates.Recall that incorrect setting of these stages can result in operation outside the amateur band and interference to other users.

Recall that the audio (or data) signal is modulated on to the radio frequency “carrier” in the modulation stage of the transmitter block diagram. Recall that modulation is by varying the amplitude or frequency of the “carrier”, resulting in a.m. or f.m. modulation modes. Recall that speech can be carried by a.m./s.s.b. or f.m. and that data may be transmitted by means of suitable audio tones generated in a radio modem or TNC (terminal node controller).

Identify drawings of an r.f. carrier and amplitude modulated, frequency modulated and c.w. radio signals. Understand the terms carrier, audio waveform and modulated waveform.

Recall that the power amplification of the radio signal is carried out in the final stage of the transmitter block diagram. (r.f. power amplifier).

Recall that the r.f. power amplifier output must be connected to a correctly matched antenna to work properly and that use of the wrong antenna can result in damage to the transmitter.

Understand that excessive amplitude modulation causes distorted output and interference to adjacent channels.Understand that excessive frequency deviation will cause interference to adjacent channels.Recall the need to ensure that the microphone gain (where fitted) is correctly adjusted.

Simple block or “concept” diagrams of a receiver.
Identify the items in a simple receiver block diagram and recall their order of interconnection:antenna, feeder, radio tuning and r.f. amplification, detection/demodulation, audio amplification and loudspeaker or headphones.

Technical requirements of radio receivers
Recall that tuning of receiver is carried out in first stages of the receiver block diagram.

Recall that detection/demodulation (recovery of the original modulating signal) is carried out in the second stage of the block diagram and that audio amplification is achieved in the third stage.