HAM Cheat Sheet 2026

The 30 highest-yield HAM facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Why does the 30–300 MHz frequency range have the most stringent RF MPE limits for the general public? → Human body dimensions resonate most efficiently with wavelengths in this range
2. Which of the following describes the function of a circulatory in a repeater system? → It isolates the transmitter and receiver when sharing a single antenna
3. Which of the following describes the term 'baud rate' in a digital communications context? → The number of symbol state changes per second
4. Which amateur band is sometimes called the 'WARC bands' along with 17 and 12 meters? → 30 meters
5. Under FCC Part 97, what is the maximum transmitter power level permitted on the 60-meter band for Amateur Extra licensees? → 100 watts ERP
6. What is the characteristic impedance of a lossless transmission line determined by? → The ratio of distributed inductance to distributed capacitance per unit length
7. Which filter type provides the sharpest roll-off at the cutoff frequency but exhibits the most ringing with pulsed signals? → Elliptic (Cauer)
8. Which ITU region includes the contiguous United States? → ITU Region 2
9. Which solar metric is most directly correlated with HF propagation conditions? → Solar flux index (SFI) at 10.7 cm
10. What is the purpose of neutralization in an RF amplifier circuit? → To cancel unwanted feedback through internal capacitances that can cause self-oscillation
11. A MOSFET used as an RF amplifier exhibits a gate-to-drain capacitance (Cgd). What circuit effect does this primarily cause? → Miller effect multiplying the effective input capacitance
12. What is the primary purpose of a key-click filter in a CW transmitter? → To smooth the rise and fall times of keyed pulses, reducing occupied bandwidth
13. What is the approximate velocity factor of standard RG-213 coaxial cable? → 0.66
14. A buffer amplifier is placed between a VFO and subsequent amplifier stages primarily to: → Isolate the oscillator from load variations that could cause frequency pulling
15. What is the purpose of a Beverage antenna? → A long-wire receiving antenna for low-frequency directional reception
16. What is a 22,000 picofarad (pF) capacitor's value in nanofarads (nF)? → 22
17. What is the purpose of a balun at the feed point of a dipole antenna fed with coaxial cable? → To prevent common-mode current on the coax shield
18. What is the purpose of pre-emphasis in an FM transmitter? → To increase the deviation of higher audio frequencies before transmission
19. Which type of filter response has equal ripple in the passband and a steeper rolloff than a Butterworth design? → Chebyshev filter
20. What does the term 'pileup' describe in amateur radio DXing? → Many stations calling simultaneously to work a rare DX station
21. Under FCC rules, which of the following is a prohibited amateur radio transmission? → Encrypted messages to conceal meaning
22. What is the approximate gain of a typical 5-element Yagi antenna over a dipole? → 6 to 9 dBd
23. What is the lowest frequency in the 80-meter band at which an Extra class licensee may operate single-sideband phone? → 3.600 MHz
24. Why should an amateur transmitter generally steer clear of 14.100, 18.110, 21.150, 24.930, and 28.200 MHz frequencies? → A system of propagation beacon stations operates on those frequencies
25. What is a collinear antenna array designed to achieve? → High directivity toward the horizon by stacking vertical elements in phase
26. What type of antenna produces a circularly polarized signal? → Helical antenna in axial mode
27. What is the maximum RF power density allowed in an occupational (controlled) environment at frequencies between 30 and 300 MHz? → 1.0 mW/cm²
28. What is the primary purpose of a DSP notch filter in an HF transceiver? → To eliminate a single interfering carrier or tone from the received audio
29. What is the primary advantage of a Chebyshev low-pass filter design compared to a Butterworth design of the same order? → Steeper rolloff in the stopband
30. What is 'auroral propagation' and which amateur bands does it most affect? → VHF and UHF reflection off the ionized aurora borealis, mainly affecting 50 MHz and above