Antennas

The antennas used at this station are shown below:

quagi

Single Quagi

 

array

Twin Quagi 1.1m Separation

 

dish

3m Diameter Dish f/D=.28 with 408MHz Quagi Feed

 

horn

1420MHz Pyramidal Horn

 

helical

1GHz Helical Antenna

 

1420_Feed

3m Dish with 1420MHz Cylindrical Waveguide Feed

 

C_Band_Dish

3m Dish with C Band Feed

 

dish2

60cm TVRO 11GHz offset Dish

 

80cm_dish

80cm TVRO 11 GHz offset Dish

 

The system below has a 30m separation between the Antennas along an E-W Baseline

arm2

West arm of 408MHz Interferometer

 

Arm

East arm of 408MHz Interferometer

 

 

 

Receivers and Signal Conditioning

There are a number of receivers and spectrum analysers that are used for making observations.   The total frequency coverage available is from a few mHz to 18GHz.  The primary receiver used for almost all observations  is an Icom-R7000 shown below.  An DC – LF output  signal is derived from the receivers AGC circuit by linking  to the diode that drives the S meter. The output impedance is kept high by a series 10kW resistor no minimise circuit loading. 

A coax connection carries the signal to an analogue signal processing unit for amplification and filtering.

 

R7000

Icom - R7000 Communications Receiver

 

unit

Analogue Signal Processing Unit

 

From the antennas, signals are either fed directly into the receiving room or passed through an 18dB Gain low noise wide band (10MHz – 2 GHz)  line driver . RF signals pass through about 30m of low loss 50W  URM 67 coaxial cable into the receiving room. A wideband variable attenuator (shown) is connected between the coax and the receiver.


The Icom receiver has a number of demodulation options, the AM   (~4kHz BW) and the Wide FM  (180kHz BW) are used most often. The difference in detection sensitivities are compensated for in the Signal Processing Unit (SPU). Using the wider detector bandwidth is the best option when increasing the signal to noise ratio if used in conjunction with a low bandwidth filter (long time constant) in SPU.

The SPU has a number of functions including amplification / attenuation, filtering / time constant, level shifting, signal inversion, logarithmic compression  and audio signal level measurement with a proportional DC output. The output from the SPU is delivered to conventional meters both inside the room and sent back to the location of the antenna for remote reading. Another output is fed to an 11 channel 12 bit ADC (Pico ADC11/12) for  data logging in a PC.

Data processing in the PC relies mainly on Excel with image making / mapping software from Stanford Graphics.

 

There are a number of Spectrum Analysers covering frequencies from 10 mHz to 18GHz and these are used mainly in developing equipment and antennas etc rather than for long run observations.

Instrumentation

Instrumentation

 

PC

PC for Data logging & Analysis

[Temperature control equipment of head amplifiers is also shown]

 

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