images

The two feed system photos were taken in my previous location, which was half way

up on a hill in one of the south eastern hills suburbs of Perth, Western Australia.

This location was quite scenic, overlooking most of Perth. HOWEVER , from the

Radio Astronomy point of view it was an enormous challenge. Virtually any, even

minor VHF / UHF emissions from anywhere in the Perth area arrived with good

signal strength and some with absolutely overpowering strength.

By default I became a RFI expert, tracing nasty , often intermittent interferences

to sometimes most unexpected sources. Using the much needed wide bandwidth

was rarely possible,at least not on UHF. This is why I finally migrated to 1400MHZ,

where RFI was much less troublesome. On the minus side, the flux density of most

radio sources with synchrotron type emissions is considerably weaker at L-band

frequencies than at UHF . But there is fortunately quite a large number of "thermal"

sources observable in L-band with relatively high flux densities.

About 18 months ago we decided to move away from suburbia , approx 100km north

of the city centre into a " semi - rural" area. The antennas were rebuilt, along with the

rest of the equipment. There is no significant RFI noticeable here, but there is of

course no escape from the everpresent cell phone repeaters, ours here is about

3.5 km direct line-of-sight. Therefore the precautionary measure of installing the

1/4 wave cavity filters between LNA 1 and LNA 2.

The equipment rack , from top to bottom (right) :

VLF receiver, 0 - 100KHz

UHF receiver (not in use at present)

125MHz I.F. receiver ,phase switched (for 1400MHz)

1400MHz receiver (used previously)

A /D converter attenuators

8 channel dc amplifiers / integrators,etc.

HF receiver 100KHz - 32MHz

The other equipment is for test and construction purposes only,

as well as for the receiption of weather satellite pictures on 137

and 1691 MHz. All equipment, with the exception of the HF-Rx

is " home brewed ".