Foundations Of Amateur Radio

Foundations of Amateur Radio At a recent local HAMfest we set-up a table to measure second and third harmonic emissions from any handheld radio that came our way. The process was fun and we learnt lots and in due course we plan to publish a report on our findings. When we received a handheld, we would disconnect the antenna, and replace it with a short length of coax and connect it to a spectrum analyser. We would then trigger the Push To Talk, or PTT button and measure several things. We'd record the actual frequency and how many Watts that the transmitter was producing and then record the power level in dBm for the base frequency, double that frequency and triple that frequency. In other words, we'd record the base, second and third harmonics. This resulted in a list of numbers. Frequency and power in Watts are obvious, but the three dBm numbers caused confusion for many visitors. The most perplexing appeared to be that we were producing negative dBm numbers, and truth be told, some positive ones as well