[CambridgeWorks]

Exactly. Original design 10ss is late 60s, free running oscillator, reasonably stable generally. There was then the option of the switchable crystal filter module. The 360 channel model is a further development, as it has an effective capability of tuning through that number of channels. Scale calibration will hardly be good enough to select say 123.45Mhz though. Designed for use as a general purpose monitor rx for business use or for the richer aircraft enthusiast to listen in. Park air was started by Fred Parker, G3FUR from Stamford. His first portable ventures were using Japanese am/fm portable radios that were converted for airband am and often sold at airshows. He was well into modern design, hence some of the early fet front ends. One I remember had dual gate mixer and tuned circuits of tinned 18swg wire tuned with quality ceramic preset trimmers. We used to wind the coils in batches, using a drill bit.
At this time valve tx were made, typical models 50z and 50x.
His first venture into solid state tx was for Nipper aircraft Castle Donington, the model was I think 20A It was available as a transportable. This was one I helped build a few of. About 3 or 4W rf iirc. 20 crystal controlled channels with 4 additional switch selected plug in sockets on the front panel.
I think one was offered on this forum a few weeks back.
I spoke to Fred earlier this year and he still was as bright as a button! He must be in his 90s by now.
The company is now called Park Air Systems, owned by Northrop Grumman and located at Market Deeping, near Peterborough.
These days there are some advanced products for ground radio offered. Nothing is for airborne use. Back in 1969, there were 7 full time, including Fred, plus several part time, including a secretary and 3 or 4 Airworks Services radar technicians from North Luffenham Midland Radar. They were usually involved modifying the portables or assembly work on their rest days from the 24hour cover at work.
Nowadays, the workforce is maybe 100 to 150 in a custom built factory.
A google search will provide more information and marketing videos.
Rob