The technology of single sideband (SSB) indicators first got here to my consideration by way of ham radio again within the early Sixties. My name was then and nonetheless is WA2IBH. The most effective phonetic I had for that decision signal was “WA2 I’ve Been Had” however that’s merely a aspect be aware.
Most voice communication by ham radio again then was completed by amplitude modulation or AM indicators. Once you heard somebody on the air with an AM sign, the voice high quality was often fairly good. As I recall, the E.F. Johnson Viking Ranger transmitter was regarded as having the perfect audio high quality. In fact, once you had many indicators on the air on the identical time with totally different provider frequencies, heterodyne squeals had been an disagreeable truth of life which frequently degraded the intelligibility of the particular person whom you wished to listen to.
Enter into service, SSB.
To demodulate an SSB sign, a receiver must reinsert a provider sign to exchange the provider sign that the sender is NOT transmitting. The resultant sound is intelligible, however the thought of audio high quality is a misplaced trigger. A human voice in a demodulated SSB transmission is troublesome to linguistically describe. Maybe it is perhaps regarded as listening to a cross between Donald Duck and Mickey Mouse. An enormous enchancment, although, is that there aren’t any heterodyne squeals. All you hear from a number of indicators coming by on the identical time are distorted however intelligible voices. It is a MAJOR enchancment. Nonetheless, the acceptance of SSB in ham radio was not universally enthusiastic.
Brief-wave receivers produced up by the Nineteen Fifties would have automated achieve management (AGC) in-built, however the response instances of the AGC perform weren’t nicely suited to SSB service. Trendy AGC designs have “quick assault and gradual decay,” which means that the receiver achieve is decreased in a short time upon arrival of an excessively sturdy sign and that receiver achieve is subsequently restored slowly. Since SSB indicators have amplitudes which might be “spiky,” which means excessive peak amplitude to common amplitude ratios, the AGC circuits of those older receivers may very well be “pumped” by SSB indicators, even when the receiver weren’t tuned precisely to the SSB sign’s actual frequency. Reception of just about anything may and infrequently was very badly affected. Trendy AGC management is significantly better.
Many non-SSB customers confronted by AGC pumping incorrectly assumed that SSB customers had been responsible of “splatter,” the descriptive time period for the spectral unfold of an overmodulated (> 100%) AM transmission. Derogatory phrases resembling “splatter sideband” and “foolish sideband” had been in widespread use.
Right now, ham radio voice communication is dominated by SSB.
John Dunn is an electronics advisor, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York College (MSEE).
Associated Content material
- Single sideband technology
- SSB modulator covers HF band
- Ham radio within the twenty first century
- Newbie and ham radio
The publish Single sideband technology, Half 2 appeared first on EDN.
