Simple Audio

There are several simple sine/triangle/square wave signal generators, with adjustible peak-to-peak voltage and voltage offset and duty cycle / symmetry. Their main use is for audio frequencies circuits and mechantronic circuits.

Frequency range is up to a couple of MHz, but at those frequencies the waveform is less than perfect. With most, the front panel controls give a vague indication of the operating frequency, but if accuracy is required then measure it with a scope or the frequency counter. The Levell contains its own internal frequency meter.

The sig gens are all based around the classic ICL8038, which is effectively a 555 timer with some wave shaping. Consequently the sine waves are noticably distorted at the peaks, and they are unsuitable for serious audiophile purposes.

ASCII

RF

For higher frequencies and when simple modulation is required, we have a Philips PM5390S. The key characteristics are:

  • 100kHz - 1000MHz
  • 50ohm output. At these frequencies 50ohm coax and 50ohm terminations are required if the amplitude is to be correct
  • accurate synthesised frequency and frequency sweeps
  • AM and FM modulation. The internal modulation is inflexible and sufficient for testing/simulating traditional old-school radios. External modulation could be used for more demanding purposes, but I doubt those are relevant at Hackspace

A quick play with it indicates

  • it is basically functional
  • since it is complex, it is useful to RTFM before using it!
  • it feels as if the internal attenuator or relays need cleanin
  • it looks like it could benefit from recapping the PSU

Unmodulated sine wave:

FM:

AM:

TV Pattern Generator / RF

We have a PAL/NTSC TV pattern generator with outputs:

  • SCART
  • composite video
  • RF, carrier frequency from 38-890MHz, which covers the IF, VHF and UHF bands. Can set channel or frequency

It is unlikely that those “obsolete” TV signals will be useful, so the main use of the device is likely to be:

  • a “complex” waveform useful when learning how to use an oscilloscope
  • an RF signal generator, albeit only a modulated signal not a sine wave
  • when testing an old TV or monitor

  • equipment/sig-gens
  • Last modified: 10 days ago
  • by tggzzz