[TheList] TheList Digest, Vol 48, Issue 4

Thu Apr 4 12:56:35 AEDT 2013

Re: The Right Co-ax
A bit of history for those that remember. I served my radio/television
engineering apprenticeship  with the well known firm of 'Collier & Beale
Ltd.' back in the 1960's - well known for the design and manufacture of the
ZC1 (WW2) the HF 'Sledge Set' that Sir Ed Hillary took to the South Pole.
The early VHF 2-ways radios of that early 60's era used 39ohm co-ax, it was
about 5/8th inch dia.  and used what was known as a 'Pye Elbow' coax plug to
terminate to the radio. Most other manufactures of both VHF and HF
land-mobiles used this impedance co-ax with these connectors for many years.
VHF antennas were always centre roof mounted, and the radios all 'valves'. 6
and 12 volt 'vibrators' were the norm for the H/T power supplies (no 24V
vehicles back in those days). It was not until the 1970's that 50 ohm co-ax
became the standard for mobile/vehicle antennas, with 75 ohm used for 'Base'
and Repeater site antennas (now most Base/Rptr. Ants. are 50 ohm also). 
History lesson for today.
John B