G0OPB 80 metre array


Picture Shows Tony G0OPB adjusting our Dxpedition 80 metre 2 element phased array at my QTH. The vertical at the far right ( in the distance), is my Titanex V160S 160 metre vertical.

We used 1/8 wavelength spacing and a pair of Titanex V80S full size verticals. For grounding we found that at least 16 1/4 wave radials were necessary to achieve the 37.5 ohm base impedance of an efficient vertical set up.

Whilst this was set up we also experimented with rolls of fence wire 1 metre wide as an alternative grounding. We found that just 4 66 ft lengths could drop the feed impedance to 37.5 ohms - the same as 16 1/4 wave radials.

We decided to use the fence wire on our Dxpeditions as it was much easier to lay and also did not suffer from people tripping over wires in the middle of the night !

This is a super set up with a wide forward lobe and good forward gain. It was ideal for our 80 metre operations from D68C, 3B9C and 3B7C where the majority of what we wanted to work fell in the wide forward lobe.

We had two set ups, one optimised for the SSB and and another for the CW end of 80 metres.
G3SED 2008 antenna array
G3SED Antenna set up March 2008
This is my current Antenna set up
although it can change from week to week !

Starting at the top the antennas are :-

* Cushcraft D40 rotary dipole at about 85ft high.

* Trident TA17M-3L 3 element 18 MHz optimised beam.

* Force 12 C31XR on a 30ft boom.

* Centre fed doublet with open wire feeders ( 80 metres long )

* Titanex V160S 87ft Vertical - click on thumbnail below
K9AY crossed rx loops
K9AY - pair of loops mounted at 90 degrees.

Picture shows Tony G0OPB and myself adjusting a pair of K9AY receiving loops mounted at 90 degrees, prior to our 3B9C Dxpedition

It was fascinating to hear the huge rejection from the back of the loops once the matching resistor was adjusted for optimum front to back.

Broadcast stations on the medium wave could be switched on or off at will by changing from one loop to the other.
Titanex V160S @ G3SED
Titanex V160S 87ft Vertical

The secret of a good vertical is the ground system or local ground conductivity. Many people view the vertical as a space saving antenna, when in fact in the average location it requires much more space than all other antennas if you are to achieve the low ground losses necessary for really low angle radiation