BRIEF HISTORY OF THE NEW ZEALAND ZC1
HF MILITARY RADIO TRANSCEIVER
was decided that New Zealand industries had the capacity to design and/or
manufacture a range of special purpose radio equipment including a field radio
to be known as the ZC1. There was
dissatisfaction with the reliability and range capability of the few existing
field radios held by the army. These were generally considered to be barely
adequate for training purposes. The
new radio had to be much better and suitable for both mobile and field base
special committee was set up with representatives from the army, industry,
Ministry of Supply and the Post Office to oversee the specification, design,
procurement of components and the manufacture of the new radio.
This committee reported in April 1942 that sufficient materials were now
available for the manufacture of 750 sets of the 1000 Mk I sets approved.
Considerable difficulty was being experienced in obtaining certain
components, especially meters. Difficulty
was also being experienced in retaining skilled technical staff. The ongoing
delays in commencing manufacture was causing the Draft Board to lose patience
and making it become ever more difficult to convince not to draft the radio
technicians required for the manufacture and testing of the radios.
problems were only improved in late 1943 after samples of the ZC1 Mk I were
tested by the Canadian Signal Engineering Establishment.
Such independent testing was a requirement under the provisions of Lend
Lease and the Canadians provided copies of their report to the American and
English authorities controlling war materials supply.
The report compared the ZC1 with a laboratory No. 19 set Canadian and
indicated that overall the ZC1 was superior.
The Canadian report particularly noted the following in order of
The ZC1 Mk I gave better:
both transmit and receive under normal and abnormal conditions.
- Decided saving in primary power due to low battery drain.
- Ease of operation in the field by even inexperienced operators, simplicity of dials and operating knobs on front panel.
- Accessibility in as much as servicing and replacement in the field is concerned.
- Capability of being able to trouble shoot speedily and easily due to separate send and receive circuits and increased space for assemblies.
- Flexibility as to type of aerial which may be used with sets.
- Simplicity of netting procedure, and tuning, indicated by a definite dip in plate circuit.
- Compact and light in weight approximately half the weight of the No. 19 and comparatively easy to install in any vehicle.
- Does not require extensive installing kits to set up for operation.
indicate after the Canadian report was circulated that the American Pacific
forces showed interest in acquiring a large number of ZC1 Mk II's for their own
use. Rather than outright purchase
completed sets were to be swapped for essential components required for the
manufacture of the sets. Although a
small number of sets seemed to have been supplied no major orders eventuated.
plans called for up to 30,000 ZC1's to be manufactured but in practice only
about half this number was ever built.
During early production runs each individual ZC1 took 60 man-hours to
construct. Initial production was 20 sets per week, with a production
goal of 2,000 sets per month at peak production.
It is not clear if this rate was ever achieved.
Delivery of the first batch of five hundred ZC1 Mk I's was planned for
Design of the ZC1 Mk I. is generally credited to Percy Collier and Bill Fever of Collier and Beale; a Wellington based radio design and manufacturing company. It was to at least some extent designed around components available at the time, largely those used in the manufacture of domestic radios.
The power supply use's a non-synchronous vibrator with two 6X5GT rectifiers in conjunction with a tapped transformer permitting switchable HT voltages to provide two different RF power outputs. Its power requirements are 12 volts at 4 to 6 amps depending on mode of operation.
In transmit mode a maximum of 2.75 watts RF output is achievable in standard configuration.
least three versions of the Mk I are known.
- The first version, produced in small numbers, was fitted with an aerial current meter. IF transformers with fixed cores and variable capacitors were used.
version, also produced in small numbers, used the same IF transformers but had a
plate with a watch holder fitted in place of the aerial current meter.
and most numerous version used different IF transformers with fixed capacitance
and variable cores. The watch holder is fitted directly to the front panel
without the need for a plate.
Serial numbers of sets are deliberately not in sequence to disguise build
numbers hence providing little clue as to date of manufacture or actual numbers
unit used a similar, but much smaller, case to the ZC1.
Two parallel 807's operating in class AB1 were used as an RF linear
amplifier producing 50 watts of RF. A
later version, the ZA1 MkII, differed in that the parallel 807's were operated
in class C and were modulated by a second pair of 807's fed from a 6V6 phase
inverter and a 6U7 microphone preamplifier.
mark of the ZA1 was produced in quantity. Official records indicate that it is
likely only twelve production ZA1 Mk II's were ever made being ordered, and
delivered, during mid 1943.
ZC1 Mk II .
The Mk II was a development of the Mk I and its design is generally attributed to J Orbell of Radio Ltd. The significant differences between the two are as follows.
The Mk II
is dual band having an LF band of 2 - 4 MHz and an HF band of 4 - 8 MHz.
A synchronous vibrator was used dispensing with the need for the two 6X5
The switchable HT voltage feature was dispensed with.
the ZC1 Mk II completed its service life without further change.
A small number were however manufactured with "flying rubber
leads" for use with the combined microphone headset as used by the No. 19
and No. 62 sets.
records show that the Mk II was originally planned to have a UHF transceiver
included in the design in a similar fashion to the No. 19 set.
This idea was not followed up, although prototype UHF modules for this
project were designed and constructed as a joint effort between Collier and
Beale and the NZ Post Office Radio Section.
Radio Ltd largely undertook production of the ZC1 Mk II with a significant number also being manufactured by Radio Corporation, sub-assemblies being provided by up to five other manufacturers.
The first issue of the ZC1 Mk I was in the Pacific at Guadacanal and it saw active service for the first time when NZ troops landed at Vella Lavella at 8am on the 18th of September 1943. Official records indicate that it performed well in the dense and wet jungle out performing many other types in use at the time. The Mk I also saw service on Stirling Island where once again good results were achieved. The NZ 3rd Division 2nd NZEF records show that they used the ZC1 in conjunction with the American 48 set with good results. However given the relatively small overlap of the frequency ranges of the two sets, the choice of working frequencies must have been limited.
was the only recorded active service seen by the ZC1, the Mk II version was
issued too late to see active service in WW2.
The ZC1 Mk II did see service with the NZ occupation force (J Force) in
Japan after WW2.
They were also issued to many Government Agencies and Departments including the Ministry of Transport, Civil Defence and the NZ Post Office. The Amateur Radio Emergency Corps (AREC) also received a significant number of sets and many were also disposed of as Army surplus. During the 1950's and 60's many NZ Amateur radio operators "cut their Teeth" using ZC1's on 80 Metres. Their owners extensively modified many of these ZC1's and numerous articles appeared in Break In during this period on improvements that could be made.
Collier and Beale produced a modification kit for the Mk II to make the set more suitable for small ships maritime use and large numbers of ZC1's were used in this service. The LF receiver section was changed to the AM broadcast band and the HF TX and RX sections to the marine band.
modifications included xtal control for fixed channel use, used by the MOT for
car to car communication for their traffic control cars, the Post Office for
point to point services and various organisations and individuals for Maritime
use. Changes to improve RF power
out and modulation depth were also common.
to Roy Symon of SPAM for his generous assistance with information.
to Fred Johnson, Bill Heinz and Reg Motion for their support and guidance.