WW-II production of the ZC1 at
Radio Ltd as remembered by Ces Byrne ZL1AOD
(The following is a
transcript of a talk given by Ces to the Papakura Radio Club in 2001)
For this history of the ZC1 I am relying totally on 60 year old memories, so
bear with me, but by and large I think it is fairly accurate.
started work with Radio (1936) Ltd., the only factory that manufactured the
ZC1. The ancient four-storeyed building on Quay Street, Auckland, wasn't
really designed for radio manufacturing and it was a crowded place. Our big
precision lathes and power presses were located on the ground floor, which
also housed a large plating department, and the dispatch and inward goods
The first floor was mostly given over to administration. The second floor
dealt with domestic, industrial, and commercial electrical goods, trading
under the brand name 'Ultimate'. The third floor housed the machine
shop with its power presses, guillotines, welding and spray painting
equipment, coil and transformer winding equipment. It was an extensive
department and catered for the entire factory.
it is the fourth floor, the radio floor, that is of interest here. Six or
seven design staff were permanently employed there, headed by
under whose guidance this team turned out solid equipment. The "wiring line"
produced domestic radios and other equipment. When I arrived there it
consisted of 18 to 22 people operating on an assembly-line basis. From here
the radio moved on to the test department, where the alignment and functions
of the unit were checked.
Around 1940 the Government declared many of the materials required for radio
production "essential" (due to the war effort) and domestic production
ground to a halt. It became extremely difficult to purchase a new radio.
However one section still produced amplifiers and communication equipment
for schools, factories, hospitals and, of course, military camps. Later on,
towards the end of 1940, military people began visiting the design
department and rumours arose that something was afoot.
The Canadian WS19 set appeared on the designer's bench and we were told that
a local version of this unit was to be produced for the New Zealand forces.
Two or three of our staff and some from other factories were despatched
immediately to the United Kingdom and a team from our factory flew all the
way in a Douglas DC3, a tumultuous, lengthy flight. After four or five
months they returned and commenced work on the Mk-1. It was not easy to
produce because many other manufacturers were brought into the project and
perhaps this was the first time in New Zealand radio manufacturing that
subassemblies were mooted so that different factories could produce
particular units. It proved to be an excellent system.
Thus the first ZC1 prototype emerged. It was extremely robust; you could
drop them from a height and they would still operate. I've seen some that
were quite badly damaged and still operating fine. There were remote
controls that went with the ZC1. Also, and this was continued later with
domestic receivers, subassemblies were produced and mounted. A lot of work
went into progressing from the prototype to the final manufacturing process.
Every screw, every length of wire and every component had to be known. More
than a dozen prototypes were produced, and in each case every component had
to be detailed meticulously.
Many other companies were involved. People like Alex Harveys, who had never
seen a radio in their life, did the heavy metalwork; photoengravers dealt
with the screen printing; Akrad Radio produced the coils and RF chokes;
Radio Corp produced the condensers and resistors (perhaps the first time
this was done in New Zealand?); Swan designed the headphones and
microphones. The supply of batteries was enormous and Erg supplied most of
the batteries for the Services.
Power supplies and dial units were made separately, arriving at the factory
in quantity and assembled further down the wiring line. Special care had to
be taken here as the units were cadmium-plated and marked horribly by finger
sweat so special cradles were made to avoid this problem; the units remained
in the cradles until they were ready for final delivery. More staff were
taken on for the wiring line. All the wire was pre-cut and tinned, for which
a special department was needed. When the ZC1 first went into production we
aimed at thirty to thirty-five sets per day. There were many missed
deliveries in the early days. Sometimes the dial units didn't arrive,
sometimes it was the power supplies. Often sets were still going down the
production line, but were stored up in huge tiers because of a lack in
Still, we had to maintain our production level. The Defence Department
stipulated a definite number of units per month in the contract. The early
ZC1's had watch cases, old Westclox pocket watch cases, but they disappeared
so quickly that this idea was dropped. There was not very much in the way of
cosmetic changes to the face of the ZC1. Apart from the disappearance of the
watch case from the Mk-1 and the alteration of one or two switches, hardly
anything was altered from the original design.
Antennas had to be made and wooden boxes for the spare valves. Australia
came into the scene and AWA Radiotron™ began producing the valves required;
6X5's in the earlier versions, the 6U7's, 6K8's, and 6V6's. The quality was
not the best and it became necessary to pre-test virtually everything (in a
dynamic circuit) before it went on the production line, so we created a
pre-test department for the task. I remember oil drums full of broken
valves, thousands and thousands of them, that didn't meet the requirements.
Vibrators and meters also proved to be unreliable.
About this time the Department of Scientific and Industrial Research (DSIR)
set up their own laboratory in our building. Many of our staff (secretively)
were utilised by the DSIR for building prototypes of radar equipment. Strict
security was insisted upon in the war years; nothing was ever discussed
outside the factory.
In addition orders were coming through for lots of other stuff, such as VHF
equipment, perhaps the first venture into that, including little
transceivers for the tug boats around the Hauraki Gulf. Some remote controls
for the lights around Auckland Harbour were also produced. Changes were made
to some of the flying boats that arrived here with UK equipment and most of
them serving in the Pacific had to be changed over to American style Bendix
At the same time Seagar Bros. and Mason Bros. started to produce 110 ft
trawlers for the American service in the Pacific. These required radio
equipment to be designed, made, and installed. Fairmiles were being made and
they also required radios. In general there was a large variety of design
and production going on this floor that was originally designed just for
plain old four valve to ten valve domestic receivers. Materials were in
short supply and we were low priority for materials from the USA and UK.
However, through the help of local manufacturers and by the good graces of
one or two American companies we still continued to get materials for the
After a year and a half the military reported back that there were problems
with some of the units in the Pacific. They were growing mould and fungus
inside them. We redesigned the plating and spray painting to tropic-proof
them all. That meant changing wiring, solder (fluxes were out because they
grew fungus), and utilising special paints over the sockets and wiring. They
had to be mechanically robust as well as electrically satisfactory. (When
they changed the solder, they also had to change the soldering irons because
they required more heat. I remember the little soldering iron boxes built of
fire brick and elements, you pushed the soldering iron in, it didn't have a
cord on it.)
Anybody that has tried to service a ZC1 knows how difficult it is to remove
the wires from the terminals but military specifications demanded that it be
done like that. The life expectancy of a ZC1 in service was only eighteen
months. That they are still operating is incredible, and I'm sure the people
involved in the original design would never have believed it.
The ZC1 needed both CW and AM phone communication. They had to have some
means of pre-setting frequencies so that a whole unit could be sent out, all
operating on the same frequency, and yet able to alter the frequency
readily. The power output needed to be adjustable since the power required
for communication had to be minimal, especially in the North Africa section
and the Pacific. The enemy was very good at DF'ing and could locate an
operating transmitter very quickly.
To give you an idea of how little signal was required for DF'ing, we at
Marconi were getting requests from the ships to quieten the receiver
oscillators because submarines were DF'ing on the receiver oscillator. At
sea, with sensitive equipment, you could pick up that oscillator in the
receiver; very little power could create a problem.
By the time the Mk-2 (1943) came out production was progressing smoothly at
a cost of about ŁNZ 450 a piece (about $40 000 today). Most of the
out-manufacturers doing the subassemblies had improved and the materials
were arriving with fair regularity.
Later on I entered the final test department with a Ministry of Defence Army
sergeant supervising me. I had to test each unit (using dummy loads and
other tools) for performance in receiving and transmitting, on all
frequencies. After a successful test they became the possession of the Army.
Now for a quick review of some of the more frequent problems I encountered.
The dial units were not always smooth in operation, and the machining of
them wasn't always the best. We whipped them out and had them machined
locally. Sometimes vibrators didn't start, although they'd been working
through the pre-test department. Valves often arced over, the old 6X5 in
particular would short over between cathode and filament. There was a
general downgrading of expectancies when the components began to arrive. For
instance, we had been used to the American Bradley relay; a lovely,
silver-plated unit, and the relays that arrived looked cumbersome by
comparison. But we had to use local materials. How many units did we turn
out? Somewhere between 20,000 and 25,000, I suppose. Production continued
until the end of the Pacific war, but there must have been thousands stored
away that never went into service. Some of them were sold off eventually to
other countries. Apparently a Mk-3 was in the initial stages of design, but
(happily) the war finished before production could commence.
HF radio activity during the war was all military, lots of propaganda
stations and lots of interference. Every staff member that enlisted was
guaranteed a job when they came home. The firm did a lot of work with food
parcels and other things for those people who were overseas.