frequency_sweeper

Frequency Sweeper

HF Swept Frequency Generator for Crystal Filter Alignment, Tuned Circuit Q-evaluation, etc.

Reference Links:

• 555 Timer Tutorial
• JF1OZL Sweeper
• VK2ZAY Sweeper
  • G0UPL LED Varicaps

These reference web sites were a great help. Thanks to Tony, Sunamura, Alan, and Hans for your assistance.

WORK-IN-PROGRESS

PLEASE BE PATIENT

For some time I have been considering design and construction of a simple HF swept frequency generator to use for Crystal filter evaluation, LC filter alignment, and tuned circuit Q-factor evaluation.

First objective of this project seems to be the design and construction of a DC ramp generator that will drive a varicap (voltage variable capacitor) for sweeping an oscillator over a range of frequencies. There are a number of candidates for this, but the old standby 555 timer chip seems readily available, reliable, and is easy to work with.

I do want the voltage ramp to be linear, so a constant current source will have to be devised for the ramp itself. This can be done with a simple NPN transistor, two resistors, and two diodes.