Kjell, SM7GVF (ex SM4GVF)
A new
EME antenna for 144 MHz was built in 2008.
Last February my 4 x 14 el DK7ZB home made antennas were
destroyed in the storm. I have good ideas on how to improve it, but
at the same time I wanted to try something else.
With the 4 x 14 el antennas, stacked 4,2 wide, 4,5 high, I measured
almost 1 dB to little sun noise from what I calculated, to which I
have no explanation.
The antenna shall sit at 23 m in my tower, so it is going to be windy!
2008-07-23
I am staring the project, after collecting 8 x 8 el I0JXX at SM5IOT,
Christer. Christer had the Yagies 2 high/4 wide, but I want to have
2 wide and 4 high, so I can use it for MS and other propagation
modes.
Here are some of the 8 el I0JXX antennas, some were bent in the
transportation.
These are the calculated performances with 4 high and 2 wide, 9,6 m
high and 3,4 m wide.
The array will have some 23,2 dBi gain, and still at 11 degrees
offset, I have 17 dBi, this is good for Meteor Scatter.
I am testing out the elevation mechanics, a dish actuator. The
readout will temporary be a potentiometer, SM5IOT-style. I have not
decided how to perform it, I want to have full computer tracking.
Azimuth will be a M2 rotator which interfaces to my PC:
The tower is in the background.
2008-07-29
I have almost made the frame ready, after several days hard work...
In this picture, the frame is at about 75 degrees elevation, beyond
the 60 degrees my system will handle (moon is no higher here).
I will go to the hardware shop, again,
tomorrow and get some more details. Hopefully the frame is
finished by noon, so that I can start checking out the antennas ant
mount them to the frame. I will measure them one and one. Then
follows all cables...
2008-07-30
Today I fine tuned the frame, I found out I should use the Parafil
wires differently, so I had to redo some of the work. Now I am very
close to finished with the frame.
2008-07-31
At
SM7EKU
we made the plates for mounting the rotator and the bearing in the
tower, I have forgotten to take photos, will come soon. I have not
mounted it in the tower yet.
2008-08-01
I made the final adjustments to the frame, it will now stand in its
position for some time... maybe I will do changes to it...
I aligned and measured all eight antennas this afternoon, I tuned
them to 144,220 MHz which is the center of my activity.
I had the antennas on a 3 m pole, and used a vector network analyzer
to adjust the T-match.
This is the typical return loss of the antennas after tuning.
2008-08-03
I have mounted the antennas to the frame.
While attaching the coaxes I was interrupted by a thunder storm,
that in no time gave me 7.6 mm rain, now the sun is shining again
(at 1430).
2008-08-25
Slow progress now. Today I mounted four antennas to one power
divider (one more to go) and replaced one Parafil wire with
stainless steel wire as I am suspicious to them.
I made a bench test of the rotator...
I am afraid the weather is not too good now, expected is some rain.
2008-09-05
Today, with the help of my friends SM7GGB and SM7EKU, the array is
up in the air.
SM7EKU
SM7GGB
The array is on its way up.
Finished.
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