Antennas at Musick Point

by Ian Walker ZL1BFB – July 2005

Aerial view of Musick Memorial Radio Station in 1961

Looking south over the receiving towers at Auckland Radio ZLD Musick Memorial Radio Station in 1961. The direction finding (DF) antennas can be partially seen at the top right of the photo.

Remnants of the “J” insulator bases can still be seen on the side of the building. (If any one has some please donate them.) The pole shown on the northwestern side of the plan was a sturdy 80 ft wooden telegraph pole, while one of the same was on the northeastern side, but unseen on the plan.

The pole where the 600Ω main feeders came together in the east was a standard 30 ft telegraph pole with cross arms. There were five other poles along the grass paddock leading towards the car park. These had take off points to the respective antenna tuning boxes and feed points.

The height of the 600Ω was sufficient to allow the grounds keepers to ride the tractor without getting decapitated. Most of the insulators were of the Pyrex or glass type not seen nowadays. (We have some on display.)

This was in the early years prior to 1970. When the riggers on occasions had to drop an antenna for checking for joint failure etc., the feeders need not have been earthed, and sometimes the riggers forgot to advise the operators if changes needed to be made.

Receiving antenna layout at Auckland Radio, Musick Point

Receiving antenna layout at Auckland Radio, Musick Point

As can be seen, there were long runs of the 600Ω lines and on more than one occasion the operators didn’t notice the difference to the received signal; the feeders were almost as good as the antenna.

These overheads were finally pulled down in the early 1970s in favour of coaxial 50Ω cable, which was buried in ducting from the station and along the grass paddock to the antenna feed points. Great care was taken on installing this ducting so as not to disturb the great 500 kHz earthing mat.

This ducting has kept the coax in good un-weathered condition and re useable for our antenna systems. It is unfortunate that the ground plan of placement of the ducts is no longer at the station.

Originally the coax ends terminated near the centre of each dipole to a termination or tuning or connection box. These boxes were removed many years ago during the closure of the station. Also it must be remembered that this was a “receiving station” and therefore had no special requirement to isolate antennas from a local transmitter.

Long wires were the “in thing” then and as can be seen were indeed long. If they still remained they would have been an “Amateur’s Dream”. We, on the other hand, have transmitters at the site and have to reduce the hazards of intermods and crossmods as much as possible.

The feeder wiring as mentioned earlier was standard telephone single strand copper wire of 60-80 pound strain. Should there have been a break, the tarnished wire was cleaned and polished and then a “married joint” formed and soldered, or in later years a compression joint was formed.

The main antenna conductors were of a much heavier gauge and multistrand. This heavy duty wire, also known as 600lb, was used for most of the antennas. There is none of this antenna wiring left for us to attach to, so we have done the next best thing.

Quartz Hill has the gain over us here.

All antennas using the 600Ω line that were attached to the station originally went to “J” or the straight “pin” type insulators and either direct to the receivers or to a matching transformer network. The whereabouts of the latter are unknown as they were removed many years ago.

We at the station now rely on memories and old drawings (where possible) recorded and filed away to retain part of history. It would be great to have ALL the original antennas and mast, but we must be satisfied with what we have at present.

The long wires for the low frequencies (2 MHz and 500 KHz) were ideal for monitoring the HF bands of the Amateur service. I for one can vouch for that, as can some of the DX operators at the station, for with the transmitters being so far away from the receivers, DX was easy to listen to, and to work in the off hours. No wonder they had the success they did. For those who were active hams at the time most held DXCC on CW.

On the other side of the coin was the signal received from broadcast intermods, and the bad joints that appeared in the support stay wires to the various masts were a concern.

The west towers of ZLD as seen looking north from the direction finding aerials.

The west towers of ZLD as seen looking north from the low frequency direction finding site.

The east towers of ZLD, with the 2182kHz polein the distance, as seen looking north from the carpark.

The east towers of ZLD, with the 2182kHz pole in the distance, as seen looking north from the carpark.

This is where I spent a lot of my working days trying to find the faults. Sure the technicians dug up a lot of the earthing mat and made several fresh joints, the riggers attempted to clear the rusty and corroded stay joints and there were many hours spent trying to locate the sources by DF. (Those days were great.)

It wasn’t until we (the radio club) obtained permission to use the station that I discovered one of the possible source of the past years’ problems. The main water pipe from the town water supply to the station came to the water tanks on the belfry floor and to the ball-cock valve in the tank. Electrolysis had corroded this away at the tank almost completely. It was much rusted and had a small voltage across the joint. When I advised Telecom they had it re-welded up for us (well, silphossed or brazed, anyway).

But the problem was that tank had, due to its age, severe osmosis and later on we had to drain and block off the outlet pipe. This may have been one of the sources that had plagued the station operators over the years. This pipe was well earthed to the building and ground but there was a small difference in potential to the station earth, also being so high in the building it acted as a perfect antenna in itself. I also recall that most of the QRM was on that side of the building.

Back to the Antennas.

The earth mat is still available to us for the vertical antenna which is at the feed point of the old 500 kc/s receiving aerial, and uses the ground plane at its feed point. Also available are the two masts installed for the directional antennas. The masts are attached to this mat through the extensive underground system, which is in turn connected to the earthing of the station. Earthing of our Vee beam is also attached to this mat and it is hoped that better signals can be heard because of it.

It would also be nice to have an antenna strung between the two masts on either side of the driveway, similar to the old 500 kc/s antenna but we have to consider the general public who enjoy the open space, and also current environmental trends, so at present we do not want to do anything that may jeopardise any future antenna installations. (Update: a Marconi Tee aerial is now suspended between the two towers for use on the 630-metre amateur band.

Looking at the plan the antennas that goes from the station towards the garage can be seen. Originally it was the EMERADIO antenna and this could still be put in place. This was used for the monthly contacts with distant Post Offices from Whangarei to Gisborne to confirm that the station had communications with them in case of disaster, a scheme that pre-empted Civil Defence. The feed to the station from this antenna is still in existence but not in use.

It has been suggested using the present masts as vertical shunt fed antennas. This is not the first time I have heard this suggestion, and it is a good one, as it would give us a wider selection of antennas, without making too many visual changes to the area. This also can be attempted but we’re going to need an awful lot of manpower to achieve it.

As a receiving site it is great, but it needs to be developed correctly and within the concepts that we started out with, i.e. to create a station where hams can enjoy the hobby, experiment, learn and teach, and pass along experience gained over many years.

Basic electronics have not changed that much over the years. It still takes the RF signal to get from one place to the next to make communications. It still requires equipment at both ends of the path, and the equipment needs to be able to cope with the technology being handled.

Antennas at the station have been designed to fit our concepts and come in all different shaps and sizes and although satellite communication was unheard of in 1945, it is not an impossible thought for a future project, but we need to concentrate on getting the station functioning as an historical site before this can even be thought of.

The station and its surroundings must be preserved as an important historical site covering Maori and European settlement, as well as the technological advances from the mid 20th century onwards.