Essential Test Equipment for the Shack
Why Test Equipment Matters
As an Advanced licensee building, modifying, and troubleshooting equipment, you need to be able to see what your radio is actually doing — not just what it should be doing. Good test equipment turns guesswork into certainty.
The Oscilloscope — Seeing Signals in Time
An oscilloscope shows voltage vs. time. You can see the actual waveform — sine waves, square waves, distortion, modulation, timing, etc.
Key Specs
- Bandwidth: The highest frequency it can accurately display. For radio work, you want at least 5× your operating frequency. Testing a 50 MHz signal? Need at least a 250 MHz scope.
- Sample rate (digital scopes): How many measurements per second. Should be at least 5× bandwidth.
- Triggering: What tells the scope to start drawing. Edge triggering on a rising signal is most common.
10:1 Probes
Standard scope probes divide the signal by 10 before it reaches the scope. This seems counterintuitive, but it:
- Increases the effective input impedance (less loading on the circuit)
- Extends the bandwidth
- The scope compensates by displaying 10× the measured value
The Spectrum Analyser — Seeing Signals in Frequency
While a scope shows amplitude vs time, a spectrum analyser shows amplitude vs frequency. This is essential for:
- Checking your transmitter for harmonics and spurs
- Measuring signal bandwidth
- Finding interference sources
- Measuring intermodulation products
Key Spec: Resolution Bandwidth (RBW)
This determines how finely the analyser can separate nearby signals. Narrower RBW = better resolution but slower sweep. To see a spurious signal just 1 kHz from your carrier, you need RBW well under 1 kHz.
Signal Generator
Provides a known, calibrated RF signal for testing. Uses include:
- Testing receiver sensitivity — feed in a known weak signal and see if the receiver can hear it
- Aligning IF filters — inject a signal at the IF frequency and adjust for maximum response
- Measuring filter response — sweep across frequency and measure the output