Transmitter Testing

A transmitter that does not transmit is the worst failure a beacon can have, because it looks fine on the bench. This page is the verification sequence that catches it.

The order of checks

1. Frequency accuracy
2. Power output
3. Keying behavior (clean Morse)
4. Harmonics and spurious (with the right gear)

Frequency check without a counter

The SEARCH mode of a second beacon is a crude but effective frequency meter: sweep the band and see where the peak lands. A beacon transmitting at 433.92 MHz should peak within one channel step (12.5 kHz) of 433.92. A peak 100 kHz off indicates a calibration problem.

Power check with a dummy load

A dummy load (see Dummy Load and Bench Testing) absorbs the full power. With the load in place:

1. Measure the current draw during TX; +22 dBm should draw 110 - 140 mA extra.
2. If a power meter is available, verify the level reads within 1 - 2 dB of the setting.

Keying behavior

Morse keying must be clean: no clicks, no tails, consistent timing. Two ways to verify:

• Audio path: the Audio Jack feeds the keyed tone to a recorder; decode it with an app or by ear (see Reading CW by Ear).
• Receiver: a second beacon in RX shows the bursts on schedule and decodes them.

The 10-second listen

The most valuable test costs nothing: put the second beacon in fixed-frequency RX on the channel, and listen to 10 full bursts. Timing jitter, missing repeats, and drift all show up in the rhythm of what you hear.

Related pages

• Dummy Load and Bench Testing for the load
• Receiver Testing for the paired test
• Two Beacon Bench Test for the full procedure