One of the often overlooked aspects of amateur radio is the importance of being able to monitor the quality of your outgoing signal and to ensure that you aren't transmitting an excessively wide or out-of-band signal. The UK licence states:
"Whatever class of emission is in use, the bandwidth occupied by the emission is such that not more than 1% of the mean power of the transmission falls outside the nominal modulated carrier bandwidth."
Things are slightly more "nailed-down" in the USA where regulations state for transmissions below 30 Mhz, any spurious emission must be at least 43dB below the mean power of the fundamental emission, and for 30-224 Mhz, unwanted emissions must be at least 60dB below.
This can be quite daunting to the newly licensed amateur as new professional test equipment can cost many thousands of pounds and is often extremely complicated to setup. Many clubs have suitable test equipment available but I decided to get my own.
At the recent Ofcom sale (as mentioned in previous posts) one of the items that I purchased was an Aeroflex/Marconi 2945 Communications Test Set. I managed to purchase it for considerably less than I have seen them online so was quite happy with that!
The 2945 can perform a wide range of tests from 0-1Ghz at up to 150w (more with external attenuators). It also includes a spectrum analyzer and tracking generator but of particular use is the transient and harmonic analysys tool.
I am still learning this device but I find it incredibly useful to be able visualize exactly what I am transmitting and when building transverters etc, to see that I am actually transmitting something at all...