Take-off profile from JO55QX

(note -this blog is written in english, automatic translation works but reads clumsy)

Following the move to a new QTH it was time to rethink the antenna setup. JO55QX is close to the sea with strong winds. I also wanted to be able to operate remote and as the QTH is remote by itself, antenna robustness and stability were important parameters.

During my (long) love affair with amateur radio I have encountered a lot of VHF antenna designs. The electrical performance has improved tremendously since I got my license in 1979. One example are the DK7ZB antennas and for the 5P5T contest group we build all the antennas based on DK7ZB designs, but the antennas we build where made for portable use and with little attention to mechanical stability and robustness. They will not survive many seasons in the open environment.

Picture of antenna taken from Gorans web page

This has changed and new mechanical designs are becoming available. Antennas-Amplifiers founded and lead by YU1CF Goran is one of the producers of more mechanically robust VHF/UHF antennas.

I was looking for a medium size antenna with a gain on 144 MHz around 13 dB and preferably including a 432 MHz antenna on the same boom. The antenna of choice is a dualband 144/432 MHz yagi with a boom length of 5,6 m and antenna gains of respectively 15/18 dBi. It has shown some quite remarkable results on air, OV3T worked CT9 for a OZ 144 MHz tropo record of more 3200 km than with this antenna.

Thus, I ordered the antenna, and from ordering until it arrived took less than a week! There is no manual with the antenna, everything is marked by numbers and letters. It works very well, assembling the antenna took me less than 1 hour, and I made no mistakes 🙂

This is a high quality antenna. The boom is made of 30×30 and 40,40 mm square aluminum tubes and the elements are made of 8 and 4 mm aluminum tubes. Every single hole matches and all the screws and bolts fits perfectly. The boom assembly and the guy support and mast clamp are made from 3 mm steel plate and has a perfect fit with the boom. Check out more pictures of the antenna below.

This is not your well known light weight yagi. It weighs 9,5 kg and of course requires that you design your antenna mast for a the load -not to mention the work of lifting the antenna in place on the mast…. Remember that if you put 10 kg on top of a m mast compared to 5 kg, the extra load from wind pressure experienced by the mast is not twice as high but four times as high! However, as I now have just one yagi for 144 and 432 MHz instead of two, there is a positive trade off.

Also take a look at Gorans case studies on antenna designs, e.g. what is the effect of a 50 mm mast upon a 432 MHz horisontal yag? Read about it here.

But, regardless of all the nice mechanical details, the really big question is -how does this very nice aluminum gadget perform on air and during the heavy wonds of winther? That story will have to wait a little, -stay tuned!