Tuesday, 25 February 2014

HF Marker

A useful tool I built in 1999 is an “HF Marker”. This simple device produces a 10 MHz primary signal and lots of harmonics (even and odd). Two “divide by 10” IC’s (SN7490) produce 1 MHz and 100 kHz primary signals and also lots of harmonics. With this device you can calibrate frequency scales for example.

Harmonics that are available:

20, 30, 40, 50... MHz
2, 3, 4, 5 ... MHz

200, 300, 400, 500 ... kHz

A NE555 is used to produce a 1500 Hz tone that is “injected” via a 1N4148 into the modulator. You can here the tones with the receiver either selected to SSB or AM.


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