Simple „world receivers“ do not leave the user with many more options than setting the frequency range, frequency and volume.
With technical progress, the features of shortwave receivers were extended more and more. In some cases, technically similar basic sets with additional features were offered at a higher price.
One of the most important elements of a shortwave receiver is a tuning knob that is easy to reach, has no backlash when it's turned back and forth, and can be operated for hours without fatiguating the operator.
Various approaches have been taken in order let the operator tune through a large frequency range quickly and to let him fine-tune the desired frequency in single sideband mode.
In some receivers, it is possible to select fine tuning by pulling out the main tuning knob, a very elegant solution. In modern sets with digital frequency processing and tuning by an impulse generator on the shaft of the tuning knob, different tuning speeds can be selected. With an electronic flywheel effect, the tuning increment is automatically increased when the tuning knob is turned faster.
Tuning is just as pleasant sufficiently heavy tuning knob running smoothly, which in itself provides a nice flywheel effect.
Many shortwave receivers work on only one frequency, but the need to be able to call up several frequencies in quick succession with high frequency constancy came soon, for example, to quickly check parallel frequencies to check for the best channel.
- Log scale: Originally, there was only the possibility to write down the frequency read on the quite inaccurate frequency dial; sometimes a log scale was provided for this purpose, so the numerical value on a 0 - 100 scale is noted in a logbook.
- Frequency presets with multi-turn potentiometers: in some „all wave receivers“, frequencies could be preset with multi-turn potentiometers, which preset the tuning voltage.
- Digital frequency memories: With the introduction of PLL synthesis technology in the receiving equipment, it became possible to store frequencies in digital form using digital memory chips. This is only possbible if the digital frequency information can be used to control the processor of the receiver's PLL unit. In the early yeas, a memory unit with four frequency memory channels had a price tag of US$1000 and had to be purchased as an external accessory, but later hundreds of frequency memories were available in cheap microprocessor-controlled scanner receivers, the sheer number of the memory channels which made it difficult to keep track of the memory content. Alphanumeric memories let the frequency memories to be labelled with the name of the station.
Direct frequency entry
With the advent of receivers with digital frequency processing, not only the realisation of digital frequency memories was easy, but also the possibility of directly entering a desired frequency with a numeric keypad.
The input sequences on different sets differ greatly; it is worth consulting the operating instructions.
In SSB mode (single sideband), not only single sideband transmissions without a carrier signal (mostly radio amateurs, military and commercial radio traffic) can be picked up, but it is also possible to tune the receiver exactly to the carrier of an AM signal and, with appropriate filters, to listen only to the upper or lower sideband. This technique makes sense if the reception is disturbed by a strong neighbour channel station, as it gives the possibility to listen only to the undisturbed sideband of the two sidebands with identical transmitted audio information of an AM signal.
This so called ECSS (Exalted carrier single-sideband) reception requires small tuning steps. Some high-end semi-professional receivers have the option of automated ECSS reception. The receiver locks onto the carrier frequency automatically at the touch of a button, it synchronises the BFO's subcarrier with it, and feeds the signal of one or the other sideband to the speaker.
Even in the 1930s, military equipment was equipped with a clock or at least with a place to put the signal man's pocket watch.
In the schedules of shortwave broadcasting stations, the transmission times are usually given in world time (UTC, formerly GMT (Greenwich mean Time)). Since there is a difference to the local time at least if you are not living in the London time zone, high-end receivers sometimes came with switchable clocks (local / UTC) or double time displays.
Professional and military listening stations were manned around the clock. In order to give the shortwave listener the possibility to record transmissions automatically during the night hours, several receivers were equipped with timer functions, sometimes with an additional socket to control a cassette recorder.
In the case of travel radios, the timer function was used more for the purpose of using the unit as an alarm clock while travelling.
World receivers for home and hobby use usually came with a tone control to improve the reproduction of music or speech. In receivers used in commercial communications, the main concern is the intelligibility of Morse code, radio teletype or voice transmissions, a tone control was sometimes omitted as unnecessary.
Simple tone controls work with a single „bass - 0 - treble“ control; higher quality sets have separate controls for bass and treble.
The use of a 5 kHz or 9 kHz audio filter to reduce the annoying whistling sound from neighbour channel stations, is also a feature found in some sets.
„All wave receivers“ covering the FM broadcast band have sometimes been equipped with a stereo decoder. The separate information for the left and right speaker transmitted by VHF stations is decoded and fed to the left and right audio channel at the receiver side, this gives a spatial listening experience.
On shortwaves and (apart from broadcasts in a special format used by some US stations) mediumwaves, stereo reception has not been implemented in the AM bands; so a receiver with stereo speakers also works in mono mode.