Updated 14 November, 2009

Other Broadcast Equipment

Antennas

2coant

2CO in 1987

The original 1931 building and antenna are shown.
The antenna is one of 3 built.
The others are at Crystal Brook, S.A. and Perth, W.A.

The antenna is an example of the historic Multiple Tuned Downlead type.
This antenna predates the vertical mast and radial earth systems
developed later in the 1930s.

When 2CO started, it used the then lowest broadcast frequency
of 560 kHz in Australia.

The original power was 7,500 Watts.
Motor generator equipment was used to generate
the DC voltages for the original equipment.

The antenna has a sign on it;
"Manufactured for Standard Telephones and Cables A/Asia Ltd
Johns and Waygood Ltd Engineers South Melbourne"

The white building is the original 1931 transmitter building.
It has been demolished and replaced by a transportable hut with "Ifco"or similar on it.

2CO down lead tuning equipment.

The antenna current is about 11 Amps in each down lead.
The total vertical current over the 3 leads is thus around 33 Amps.

The huts are brick.

The multiple tuned down lead was developed in the early years of
Wireless to improve the effiency of long wave antennas.

The breakthrough was to use multiple (3)separate earths
each with its own vertical down lead and tuning coil.

The current is divided between 3 coils and earths thus
cutting by 3 the total current squared losses.

There are 6 parallel flat top wires strung between the 180 foot high masts.
The spacing between each adjacent flat top wire is 4 feet.
The wires are 230 feet long.
The 3 down leads are each made of 4 wires on a 4 inch circle.
2CO Antenna tuning box. This is one of 3; one for each down lead. <br>The function of the tuning inductor is also to<br>divide the antenna/earth current equally between the earths.
Johns and Waygood Masts - Anti-Fading Radiator

In 1938, just a few years after the 2CO antenna was erected,
the new Australian Broadcasting Commission had modern stations erected in the capital cities.

The new transmitting stations replaced the original privately built stations.
The new stations had tall anti-fading masts of approximately 200 metres height.
Some had their height electrically increased by a top capacitive armature and
an inductor in a tuning hut at the top.

The tall masts increased the range of the signal during the day and importantly increased fade free range at night from about 55 km to 150 km.

Johns and Waygood ceased mast manufacture in about 1965.
Their last mast was at Mt Burr, S.A.
It collapsed (and was rebuilt) during guy tensioning when the guy anchor block broke.

6GF bottom

This particular mast is only 123 metres tall.
It appears to be a shorter and less heavily constructed
Johns & Waygood version of its capital city brothers.
3wv top showing tuning hut and insulators

Shortened Antifading Radiator

An anti-fading radiator for the low frequency end of the MF broadcast band would be very tall.   An economical solution is to use a shorter mast with top loading, thereby saving around 50 metres height and a small fortune.

The mast shown is 660' ie 200 metres tall with an 18 metre diameter 4.2 ton capacitor structure on the top.   It is connected to the mast physically by long insulators and electrically by a tuning coil inside the hut just below.

The tuning hut, made of thick copper or brass, is entered via a trap door in the floor.
The tuning inductor is about 600 mm diameter and 600 mm long.
there is enough space to get past the coil to the trap door in the roof to go up to the top hat.

The 3 legs are made of 6" by 6" by ¾" steel.
Weight of structure and guys: 58 tons.

The station commenced transmission on 25 February 1937.
Similar antennas are at 6WN/6WF Perth, 6WA Wagin, 2CR Cumnock, 2GL Glen Innes.

In recent decades a similar result has been achieved using an insulated gap in the mast with a tuning coil across the gap.

3WV wire mesh
View of 3WV from the top loading capacitor in about the 1940s.
The building was made of triple brick wallls.
Photos kindly supplied by Mr Ray Leerson.
Ray's shoes
View from just below the tuning hut in 1971.
The building structure cracked up due to soil movement and was demolished when the STC transmitters were replaced by physically smaller Nautel units in 1990's.
Former 5KA 5AD, Cavan Rd Mast, Adelaide, 11 Jan 2007

Metter's Masts


Typical of many of the same type erected in 1950's.

This mast shown was standing 277 feet tall in April 2007.

Travellers on the Hume Highway can see a 312 foot example
of 3NE next to the Highway at Wangaratta.

The three pictures to the left and below were 5AD & 5KA
Cavan Rd Mast Base
Cavan Rd Mast now scrap metal in early December 2007

The mast was not standing in December 2007 when the site was revisited.

Meet Mr Mast Master; courtesy Herald Sun 2 June 1992
(the file may take a little time to load)
3SR Mast

3SR Shepparton

Total length of the antenna was 425 feet.
3SR Shepparton; Metters Mast

This antenna appears to be from the same factory as the
5AD/5KA antenna in the photos above above.

I visited this station in summer 1968/9 with 3SR technician, Mr Smith, he told it was a Metters Mast but I forgot until reminded in 2008, then I had a flash back to 40 years earlier.   Interesting how the brain works.

This antenna was erected in about 1956 and dissused about 1987.
The lease on the site ran out; the elderly site owner refused to renew the lease.
Contracts were let for the construction of a new facility on the opposite side of Dookie Rd.
The site owner died; the new site owner/s were happy for the mast to remain, but it was too late to cancel the new contract.

Interesting mast 3HA on Mount Bainbridge

Built in 1941 this mast's height is 247', 75 metres.
Interestingly it is on top of a volcanic hill;
not considered ideal for MF but
half a centuary later for good real estate for FM transmission.
The FM signal has been heard in the Antarctic.

Tapered masts are not normally considered ideal for MF
due to the vertial profile of the current distribution along the length being less than ideal.
(The current drops off lower down than on a uniform cross section mast)
The mast is insulated from earth and has an insulated mounting for anti-twisting.

antitwistweb

3hamastweb

The original 1941 transmitter antenna power was 750 Watts, 10.6 amps.
The transmitter was powered by a small fuel oil generator.
Mast at AWA built station Bendigo

Mast erected for AWA

The mast left and guy below were erected for
an AWA station in about 1956 in rural Victoria.
The mast is about 257 ft (78 m) tall.

The mast has 4 sides, most only have 3 sides.

Below: The guy insulation and tensioning system
seems elaborate and expensive by modern standards.
It looks original.

The station, built to last in a red brick building,
originally had AWA 1 kW transmitters
very similar to the unit shown covered in sparrow droppings.
See AWA Transmitters page.

This antenna's 200 Ohm transmission line is described below.

youtube video of 450 ft 4 sided mast also built about 1956
1bobotweb2 Kangeroo hopped past 20 metres away after the camera was away

AWA 200 Ohm Transmission line

AWA built many AM broadcast transmitter stations using
6 wire 200 Ohms transmission line.

The inner two wires are the active, the 4 outer wires are the earthed screen.

200lineweb
AWA 200 Ohm Transmission line at Wagga Wagga

AWA built many AM broadcast transmitter stations using
6 wire 200 Ohms transmission line.

The inner two wires are the active, the 4 outer wires are the earthed screen.

Deeko Mast sections<br>3WL Warrnambool in 1992
Deeco Mast sections
at
3WL Warrnambool in 1992
6GF stand-by
& others

The mast height in the photo is 102 feet.

The building and antenna in this photo were replaced a year or two after this.
The wind mill in the background is now gone;
replaced by houses to the horizon as Warrnambool expands.

The transmitter was a 250 Watt solid state made by STC.
The site is still almost the same but different building, mast, and sign.
The water tank may still be the same.

The antenna was built of "Deeko" 6 foot (1.8 m) mast sections
that were for built several decades after WW2 in Sydney.
They were also used at Emu S.A. to support long haul shortwave communications for the Totem atomic tests.

The a.m. broadcast station mast at Alice Springs uses another sort of Deeko mast.

No doubt many thousands of these 6 foot sections were built.
After late 1960s the sections were made in 2 metre sections. The vertical tubes are centred on a inch triangle.
The weight varied between models up to 20 kg.
They are easily transported by utiliy or aircraft.

They can also be seen supporting radio and TV antennas and supporting hay shed roofs etc.

Deeko mast sections were used for many military installaions.
The large majority were used for H.F. (short-wave).
No doubt used for many smaller government broadcast towers and Non-Directional Beacons (NDB) for aircraft guidance.
ABC MF standby aerial at Kalgoorie is 108 feet of 6 foot sections.

After government disposal, they are in use at low budget radio stations, as well as TV reception,
amateur radio stations and supporting hay shed roofs.

A retired radio engineer told me that when he started work in the early 1950s many Deeco masts could be seen along the road from Darwin to Adelaide.

Deeko also went on to manufacture a stronger 2.0 metre long section. A problem with some sections was that the lengths of all 3 sides were not exact.
Tall masts could be curved like a banana unless packing shims were insteted.

Thanks to Andrew for requesting this photo.
deekoweb

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