🔍 Key Concepts

• Temperature coefficient of a crystal: how many Hz the frequency changes per MHz of crystal frequency for each degree Celsius change • Relationship between crystal frequency and transmitter output frequency when harmonics or multipliers are used • Unit conversion between Hz and kHz, and understanding whether the frequency should increase or decrease with a negative coefficient

💭 Think About

• First, for a 1 MHz crystal, how many Hz does the frequency change for each 1 degree C rise, given -4 Hz/MHz/degree? Then, what is the total change for a 6 degree rise? • Your crystal is 1000 kHz. How does its MHz value affect the total frequency change compared to the per‑MHz figure? • If the transmitter output (5000 kHz) is derived from the crystal (1000 kHz), what factor relates the output frequency to the crystal frequency, and how does that factor affect the frequency change?

✅ Before You Answer

• Make sure you apply the -4 Hz/MHz/°C to the crystal frequency in MHz, not to the 5000 kHz output directly. • After finding the change at the crystal frequency (in Hz), multiply by the same factor that relates the output frequency to the crystal (harmonic/multiplier), then convert the final change from Hz to kHz. • Check the sign and size of the change: with a negative coefficient and higher temperature, the output frequency should be slightly lower than 5000 kHz, not hundreds or thousands of kHz different.