To facilitate input selectivity the RA17 is provided with a High-Q preselector covering the range 500KHz to 30MHz. Because of the High-Q nature of the preselector, selectivity is quite sharp such that if the 0.5 - 1MHz setting is selected and the MEGACYCLES dial is swept through the entire range you are unlikely to hear any chuffing except at 1MHz. Even then, this will be dependent on the position of the AE TUNE knob. The same obviously applies to all the preselector switch settings.
The AE TUNE knob only has 180 degrees travel. Let’s call that 9 o’clock though to 3 o’clock. On a correctly aligned RA17 the following can be used as a starting point …
1 - 2MHz setting: 1.5MHz will be around 11 o’clock.
2 - 4MHz setting: 3.5MHz will be around 10 o’clock.
4 - 8MHz setting: 7MHz will be around 10 o’clock.
8 - 16MHz setting: 14MHz will be around 11 o’clock.
8 - 16MHz setting: 18MHz will be around 10 o’clock (see below).
16 - 30MHz setting: 18MHz will be around 2 o’clock.
16 - 30MHz setting: 28MHz will be around 10 o’clock.
There is a deliberate overlap in all the ranges, which is why 18MHz can be peaked on two preselector ranges.
Whenever the desired MHz falls within the overlap, always use the lower range (8 - 16 for 18MHz) because by nature of the circuitry involved, this will give higher selectivity and higher gain. There is no substitute for experience. Experiment with these settings and use what is best for you.
Many people have said that the RA17 is terrible for receiving SSB signals. One thing is true, the RA17 does not have a product detector, therefore resolving SSB requires a bit of practice and judicious use of the input attenuator and the RF/IF gain control.
To resolve SSB, do the following …
DO NOT use AVC. Set the System Switch to NORM and the BFO on. On the RA17 and RA17L etc. the BFO should be set to -0.5 for USB and +0.5 for LSB. On the RA117 the settings are reversed due to the additional IF conversion. Use the input attenuator and/or the RF/IF gain control to keep the signal level such that the detector is not overloaded. If you do this correctly, the quality of SSB will be better than you might have imagined. If you use AVC, then the overall gain is elevated with an element of gain compression resulting in distortion when resolving SSB. An IF bandwidth of around 3KHz is ideal for SSB reception. What IF bandwidths are available will depend on what model of RA17 you have.