The PF1 was a radical idea stemming from John Brinkley, the MD at Pye Telecom in the mid-1960s. He wanted to equip UK police with handheld personal radios rather than them having to rely on radios fitted in police cars. Equipment for UHF was totally new (in this market) at this time. Instead of putting the TX and RX in one unit a novel idea was used: put the RX in a unit that could be mounted in a breast pocket and have the TX, with a spring released whip antenna, as a separate unit that could be kept in another pocket when not used. Most of the time policemen listened and transmitter for less than 5% of the time. The TX was low power - only around 50-100mW, so base stations were needed frequently in urban areas. The RX used a plate antenna.
My very first project when I started at Pye Telecom was to make a 12.5kHz version. This was never implemented commercially, but it gave me a chance to play with both the RX and TX for some weeks and helped with my induction process.
The PF1 sold in thousands and transformed police communications in the UK.
See also Pye Telecom PF8 Handheld and http://www.pyetelecomhistory.org/index.html