What may be indicated if a VHF radio operates normally but the transmitter produces nearly zero RF output in the high power mode on all marine channels?
• SWR (Standing Wave Ratio) protection circuits and why they exist in modern VHF sets • What happens to a power amplifier when the antenna system presents a very high SWR versus a good, matched load • Difference between antenna/load problems and power supply protection problems (like crowbar circuits)
• If the radio receives normally but has almost no RF output on high power, is the problem more likely in the RF output path or in the DC power supply? Why? • Which condition would cause the radio’s internal protection to deliberately reduce or shut down RF output to protect the final amplifier? • Does a well‑matched 50‑ohm antenna system increase or decrease the likelihood that the radio will protect itself by cutting power?
• Check which choice describes a condition that would cause a protective reduction of RF output rather than normal operation. • Identify which options describe a healthy, properly matched antenna system (good SWR, 50 ohms) versus a fault condition (high SWR, protection triggered). • Consider whether a crowbar power supply shutdown would allow the radio to "operate normally" on receive while only reducing RF output on transmit.
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