CT2JKO - Ham Radio and Local Weather - Station

Antenas (Antennas)

After some months waiting for permision, I finally installed my antennas on the top of the building, on 13th July 2008, according to my project):

Projecto de instalação no topo do prédio - PDF

At the moment I have two installed antennas on the roof of the building:

HF - Homemade Inverted V - 40m length - 80-10m with ATU - Fed by RG-213U

VHF/UHF - Diamond X300 - High gain Vertical antenna for the 2m and 70cm bands - Fed by Westflex 103

Some pictures of the building without the antennas:

And the roof after antenna installation!

Feedlines outside:

H.F. - Shortwave (Inverted V)

Balun (1:1 Choke Balun, rebuilt from a MFJ-918):

Antenna:

Barely visible!!!

Detail on the two sections of the inverted vee:

V.H.F. / U.H.F. - 2 m / 70 cm (Diamond X-300N)

The picture on the right shows the improvised guy lines I installed on May 2009 to avoid damage during strong wind days.

Antenna Installation Video - 13th July 2008 (WMV, with sound!)

(Firefox users: You may need this plugin to watch the videos properly).

Both antennas perform ok, better than before (outside my apartment's window, down below). I had a great improvement on my VHF/UHF coverage: Now I can work 300km apart repeaters with ease (5W output and receiving 9+++ signals), depending on propagation of course. On HF the first improvement is that I don't need to extend my antenna outside the window each time I operate (click back and see decomissioned equipment for old antenna installations) and now I feel I can work stations easier!

Now you can take a look at the graphs produced with the MiniVNA antenna analyser (borrowed from CT2JLF for a couple of days to test my antennas).

Correct prediction of the cable length from the shack to the roof: 48m:

SWR and impedance graphs for the Inverted V on all HF bands:

The minimum SWR is for 10Mhz as you can see, which is different from what I had designed it to - 3.5MHz. It should be ressonant at a lower frequency that that. This happens because of the small distance between the Vee wire and the roof, and it's not completely extended in the inverted vee configuration (some meters of wire, on the end of the legs, are bended and extended to another direction, because the roof is not big enough!), so that must be why it's behaviour is not as expected.

Now, to end this description, the beautiful graph for the 2m band - Diamond X-300N:

It is perfectly ressonant to the 145 MHz and SWR is quite aceptable along all the band.

Thanks for looking!