View Index by Level
RANDOM PAGE

SITE SEARCH

LOG
IN

SIGN UP

HELP

AM Transmitter


This is the AQA version closing after June 2019. Visit the the version for Eduqas instead.

To gain access to revision questions, please sign up and log in.

A2

Long Wave (LF Band) Transmitter

Drop the frequency to 40kHz and try it with ultrasound transducers; it works but the bandwidth is too narrow for good quality voice or music. It's fine for PSK31 digital text.

AM-LF-Transmitter.gif

AM-Transmitter.jpg

Design Goals

Input Transducer

Non Inverting Amplifier

Carrier Generator

Modulator

The Output

Amplitude Moduation

Ultrasound Version

Most ultrasonic transducers work best at about 40kHz but have a bandwidth of only one kilohertz. For voice AM, a bandwidth of at least 6kHz and preferably 10kHz is needed. The inadequate bandwidth results in muffled audio with the higher frequencies missing. Acceptable performance is possible by deliberately de-tuning the transmitter.

For digital text modes like BPSK31, the ultrasound transducers are ideal.

 

 

 

reviseOmatic V3     Contacts, ©, Cookies, Data Protection and Disclaimers Hosted at linode.com, London