February 2017: I thought it would be appropriate to take a comparative look at all four Sideband adapters. All four are made up of the same common building blocks. So what distinguishes one from the other? They all have two Local Oscillators making them effectively dual conversion receivers operating at a fixed input frequency of 100KHz (with one or two exceptions … see below)
82KHz or 118KHz
RA63C (465KHz IF) Local Osc. 447KHz
RA63E&L (455KHz IF) Local Osc. 437KHz
With only 6 valves, and one of these is a rectifier, the RA63 is the simplest of the four Sideband adapters. It is also the only one that can truly be called an SSB adapter since all the others are essentially Independent Sideband Adapters. The RA63 really was designed to satisfy the need for SSB reception and little else.
There are no crystal oscillators involved (with the exception of the D & K variants).
Both Oscillators are relatively simple, yet stable L-
There are however variations. The RA63C was designed for an IF of 465KHz whilst the
RA63E catered for an IF of 455KHz. The RA63D and K both employ crystal controlled
oscillators with the 1st LO oscillator being temperature controlled and running at
118KHz, and the 2nd LO using the same dual-
September 2017: Whilst repairing an RA63H and and RA63K I was able to perform some
tests around the filters. Unlike most modern SSB receivers, Racal’s adapters do NOT
employ crystal lattice filters. Instead, the Sideband filters use tuned LC elements.
This is probably why an IF of 18KHz was chosen. This also eliminates the often unwanted
side effect of ‘ringing’. It is probably overlooked by many, that the Low-