The DH6LS/DF9CY 28 MHZ "PILE-UP CRACKER"
After dismantling the 144/432 MHz EME Array we decided to put up something very much different. On the 8 August 1998 we got it up and running: A full size 8 element antenna for 28 MHz in 21 m above ground. We purchased this antenna from GB Antennas and Towers in Brielle, PA0. In fact we were intended to put up 2 antennas, but some mechanical problems kept us from doing so. Eight meters above (!) there is a tri-bander FB33 by Fritzel Antennas (DL). First indications are having a superb system running there. In the August 1998 EU CW contest the 8 element behaved like a PILE-UP CRACKER ... More information will follow here. The big events will be the CQWW SSB and CW contests.
Here is an image with the system extended by another multiband monster ...
Problem with the 8 element: We were not able to get the antenna into resonance with the element configuration as it was intended to be. No good SWR was observed and no tuning was possible at all. We had to move the first director in front of the driven element in order to get resonance. With proper designed yagis the first element shall match the element to the wave accelerating elements in the front. You have to have enough elements. We observe good gain and a good front/back ratio now.
I have measured all dimensions of the antenna and I will recalculate it with EZNEC 2.0, which I purchased recently for dimensioning my 50 MHz antennas.
Have a look at the contest results
|The Antennas in operating position on top of the old military tower which has a weight of 4-1/2 tons. The 28 MHz Antenna is at 21 m above ground and the Fritzel FB33 is 8 meters above this at a height of 29 m. It does not look that big on the image, but it is a real monster.|
|Here is Soenke DH6LS mounting the FB33 antenna. It is still 17 m up in the air, when the mast is in down-position.|
|Another view of the 8 element for 28 MHz in the air. You see the ropes keeping the antenna tips up.|
|First impressions show a clear difference in performance. In some cases the tri-bander shows the same amount of signal - specially with Es short skip signals - but in some cases the 8 element receives about 15 dB better. A reason for this may be the low elevation angle of the main lobe over the horizon. In a good opening in August 1998 the 8 element produced a heavy pile - up on 28 MHz from the U.S.. We tested it against the FB33 and the DX stations' report the same as we see on the receive side. Nevertheless the FB33 is already a good antenna, the eight element makes it.|
Text and All Images are Copyright by Christoph Petermann DF9CY
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