Tuesday, December 8, 2009

new low frequency ideas part 2 (RX)

There is another added bonus on CB crystals for low frequency operation. At least for the 136kHz band.

A CB-channel 22 TX crystal (27225kHz) would result in a frequency of 138.9kHz, just 1.1kHz off the upper band edge and 3.2kHz off the lower band edge.

Given the fact that the two last frequency divisions (see the earlier blog entry) resulting in 4 (two flipflops) it appears somewhat obvious to use just this crystal in a direct conversion SDR receiver.


  1. a CCIR colour burst crystal on 4433 kHz divided by 32 lands you at 138.5, that should do fine as well for a LW SDR

  2. yep, nice one. with a 74hc4060 there even is an on-board oscillator.