The Antenna Story of DL3XM

From the HB9CV for 10m to the TITANEX LP7

I have small directional antennas on the roof of my house since 10 years. First a HB9CV for 10m which was set up from the no more required TV antenna material (22mm aluminum square hollow profile) in the spring of 1991. This antenna played very well, I succeeded to work my last, then still missing DXCC entities - XQ0X and VP8SSI. As the conditions became worse on 10m, the antenna emerged from a 10m antenna to one for 15m. However, the desire came up for more and so emerged a small 2 element homemade triband beam of Diemo - DL4LQM. It was then complemented by the WARC rotary dipole D3W by Cushcraft on the same mast. The mutual influences kept in boundaries, although both antennas were mounted only in an approximate distance of 50cm of each other.

In 1997, I however have increased to 3 elements and built a A3S in lieu of the 2 ele antenna. However there arose problems then in form of an influence between the D3W and the A3S, because both radiators were situated even more densely together. A way out above was not possible and so I did not succeed to achieve half-way bearable resonances on the bands. Whether I liked it or not, I had to remove the WARC antenna from the mast on the roof and have finally mounted it as a vertical dipole on my wood mast. This made a bit of a hard job of it on the WARC bands, but on 17 and 12m wishes were however left open.

The A3S at the place where now the LP7 rotates The D3W as vertical dipole on the wooden mast

In the last years I have however thought again and again about it, how the bands from 20 to 10m could be covered completely with one directional antenna. It stood however in the foreground that no larger load momentums could be induced into the roof timbering and that the assembling possibility on the walking board of the roof had to be taken into consideration as well. With these guidelines in mind the choice was taken for the LP7 by TITANEX. Weight and wind load differed only slightly from the A3S. The problem consisted only therein, how to assemble it on the roof. After a brain storming with Tom - DL5LYM, who had already gathered abundant experiences with the LP5, we realized that an installation must be possible on the narrow gangway of the roof.

And so lay the LP7 then in form of a 6m long cardboard tube on the court of my house on a beautiful day in March 2001 and had to be brought onto the roof yet!

The March and also still the April presented bad weather. The spring was a long time in coming this time. About an installation was not to be thought. The time was used to assemble the individual elements. After that followed a sample installation on ground level. Corresponding marks were placed on the boom where the individual elements were fastened. Everything fitted and the mounting technology well thought-out that it could go off at suitable weather.

On April 25, 2001 we've finally made it. After dismantling the A3S, the assembled elements and the boom were lifted at the western gable and taken off on the roof. After that the boom was screwed on the mast and the individual elements fastened one after the other on the boom. Everything worked as I have had it in my mind and the installation preceded drafty. However, the most difficult part was yet to come - the installation the auxiliary boom with the placing of the clamps and the cable connections to the even-numbered elements.

The first elements are mounted at the boom...

Thereby it showed that the included clamps are unsuitable for the installation under these conditions. One needed then three hands, because not only the clamps have to be placed, but simultaneously the cable connectors had to be placed below and everything had to be pressed together with the grip. And this all freely standing on the narrow walking board. Despite safety belt and rope apparently impossible.

DL3XM working freely standing

I have therefore used regular hose clamps in the kind like they are used at Cushcraft or also in the car industry (stainless steel version). There were no problems in putting on and tightening of the clamps - details see here.

All elements are mounted on the boom now

After all elements were joined with the auxiliary boom, the prepared stub and the cable to the station were fastened. The LP7 was ready for action! It now had to be proved whether the expectations were fulfilled.

The LP7 now in its full splendor

The first attempts yielded the expected results on 12m and 17m. The vertical dipole was still at disposal as a comparison antenna. When switching from the beam to the vertical, almost incredible differences emerged on these bands up to 5 S-units. The VSWR looks likewise very well, on both bands generally between 1.1:1 and 1.25:1. There is naturally no direct comparison possible to the beam on the other bands but purely subjectively I can say that the LP7 is in any case better on 10 and 15m than the 3ele beam and on 20m at least equally well. I can shore up my subjective estimate over detours in comparison with my Lazy Delta Loop, because the differences of the A3S to the Delta Loop are still a little in memory.

I have recorded here a WAV file where
V51AS can be heard on 12m in CW. I have switched repeatedly from the LP7 to the vertical during his CQ call. The difference can clearly be heard. The file was recorded on May 28, 2001 at 08.00UTC on 24.895 MHz. I had one more QSO with him in the evening of the same day on 12m SSB. To document that also in SSB, I have recorded a part of the QSO with switching between the LP7 and the vertical. Here now V51AS in SSB on 24.942 MHz at 16.10 UTC. The difference between both antennas is impressive!

I hope that I now still have long delight with this antenna and that I will be spared by storms. A first test in this regard has been given already. There were short blasts in a storm front with approx. 90 km/h, whereby there were no problems.

The antenna is rotated by hand. I have therefore set the standpipe on a portable-like fixture. The internal tubing sits on the roof timbering and can be turned by means of a lever under the standpipe fixture. The brake for ascertaining is not yet matured. I have to think of something better, although the temporary arrangement holds now already for 10 years! The antenna is locked in the park position (direction south) with a bolt, so that a sure hold at storm is guaranteed.

Thanks to Bernd - DF3CB for translation and final design!


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