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Oct 23

New Satellite Antennas

After finishing my rotator interfaces, I have started with designing and building my satellite antennas.

First of all, I am restricted to a maximum 2m boom due the placing of the satellite mast, near de edge of the roof.

Now looking for a basic design that fits on a 2m boom.

Started gathering information on antennas, my favorites are DK7ZB antenna designs..
They never let me down in the past, so a thumb rule.. “Why change a winning team!?”

As for sats, they operate in a very wide frequency range, specially on 70cm..
Most GOOD designs are mostly low impedance ones, and they are very likely to behave very narrow band.
So I looked for a broadband design.

Most 50ohm designs of the DK7ZB are broadband,, In the terms, of < 1.5 VSWR on the band edges.

I took one of those designs and start playing with these designs in EZNEC (Wonderfull software from Roy Lewallen W7EL)

As the designs on DK7ZB are optimized to work on the lower portion of the 70cm and 2m band (432 and 144mhz) I first needed to rescale the designs to the upper part of 2m (145.900mhz) and (436mhz).
These portion of the bands, are mostly used for Satellite operations.

But still these antennas have to be very broadband, because of for example AO-7 is using 432mhz for uplink (TX!) so a good VSWR is still needed here.

Also a big challenge is to place all elements in the way that a X-Yagi can be made, and also a boom/mast clamp can be mounted.
Here I had to play with the element distances, and after every tweak I had to observer the sidelobes etc. etc..

Anyways, I have came up with some decent designs, and so time came to build them!

As for the DK7ZB designs, In the past I always semi constructed they antenna for testing..
But after building loads of these designs, I have build the 70cm version straight away.

After building these antenna’s, I have measured the VSWR, and they where spot on!, Just perfect on the desired frequency 😉

 

Here testing the 2m version

2mantennatest

Finished contruction of the 2m X-Yagi

2mantennaready  Finished the construction of the 70cm X-Yagi70cmantennaready

70cmsatdipole satarray2 satarray1 satarray3

 

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