The WS52 would be considered part of the WS2 line of sets, based on the original numbering scheme from the 1930s (until things got out of hand during WW2), which was:
1 - "front line usage" (as close to the enemy as you use wireless), WS1, WS11, WS21. Intended to be Battalion to Brigade and within RA Regiments.
2 - Brigade to Division (WS 2, WS12, later the WS12HP that led to the WS53), probably also included the WS22 as a 'short range set' for divisional units and the Artillery (because the WS21 was deeply crap).
3 - Division to Corps (WS3, WS23, WS33, WS43 (Canadian). WS53 (developed from WS12HP), WS63 (Australian, I think, unless that was the 113)
4 - Corps to Army (Abandoned)
5 - GHQ to Home WS5(LP), WS5(HP)
6 - Army Chain (>1,000 miles) three were built: Aldershot, Gibraltar & Hong Kong. (Replaced by No.5HP, Marconi SWB 8E & SWB 11, (and WS 15 which was later renumbered to E 10 in the Larkspur Era (30kW SSB transmitter)).)
7 - AFV set to replace the Daylight Signalling Lamp & flag waving.
8 - Company to Battalion (once Wireless was seen to be a Good Thing), WS8, WS18, 48 (US) 58(Canadian), 68 and finally WS31 (Wireless sets split further to Platoon level with the 38, 78 & 88 sets)
9 - AFV sets (anyone getting a WS9 (British _or_ Canadian) into a WW2 AFV must have been a magician - though there was a 'vertical stack' case made for it). Canada (Marconi) took the British ST&C design and reworked it to something very much better that took readily available valves. To avoid confusion it was redesignated the WS52.) AFV sets continued with the 19 & 29 (Canadian).
What was the question again?
Ah! WS52 and the change in frequency range compared to the WS No.9.
The AFV sets were originally limited to 1.875 - 5.0 MHz (WS7, WS9, WS19 Mk.1) which was woefully inadequate and increased to 2.0 - 8.0 MHz that allowed overlap with the Infantry (and other users). The WS52 (and 62) were given a rather wider range so as to be usable as "Rear Link" sets and work to the WS12/R107 and WS53/R107 in Division and Corps.
The RF Amplifier No.2 was developed to boost the output of a standard WS19 to allow that to be used for Rear Link working, while the Canadians developed their own WS19HP that was a very different beast but arrived too late to see much service in Europe.
Best regards,
Chris.