Tower story
Preparation phase
When I decided to purchase a house and move to Kasperske Hory I automatically
supposed I will be "radio-active" from there. Of course, man can put a multiband
vertical antenna on the roof and live with it forever, but it is not my case.
I am used to have "working" antenna and don't want to retreat from this standard.
Of course the dream to have the "best" antenna is just a dream... The location is
not optimal for demanding DX work on both HF and VHF (in mountain 730m ASL, but
there are nearby hills over 1300m).
The family was not very happy when I announced there will be a tower close to the
house (they asked the crazy question whether it is really necessary!). Anyway,
they accepted it...
There is a law in Czech republic (recent modification) saying antennas and antenna
supporting towers up to 15m high don't need any permission and also it is not
necessary to inform authorities about it. Also, my property is not very large
an neighbours would never accept too high tower, so I decided to keep that 15m limit.
There are several possibilities how to build the tower. I prefer self supporting
models (more work, more expensive but reliable, forever.) Some people try to
bargain used tower from electric distribution company but I decided to purchase
a brand new tower from manufacturer. There are several advantages: you can buy
tower exactly as you need it, it is not necessary to paint it (manufacturer
guarantees at least 20 years without care) and they can deliver it in front of
your house. The disadvantage is only one - the price.
I took a 15m standardized model from SEG company, 20 kN top load (they produce
12 kN model as well, but just for any case...), 400x400 mm top, surface zinc covered. Because it is a
standard model I got from them also all other information (like concrete basement
dimensions). It consists of 2 parts: lower to be fixed in basement (3m) and upper (12m).
I prepared some drawings about the tower - where to be situated, what modifications
I need, drawings for other mechanical parts - platform, rotor holder,... I bought
a material, cut the parts and Dusan OK1VKX welded all together (tks!). The SEG
company helped me to zinc other parts as well.
So I had a tower, but how to put it up? I call 3 different firms, they promised,
but never started or postponed it... I don't understand it, perhaps it was just
too small job for them they are simply not interested about business, hard to say.
So finally I decided to organise all on my own.
Hole into Earth
Each solid tower needs a solid concrete basement. The SEG documentation says the
hole should be 2m deep size 2.1 x 2.1m. I don't feel to be strong enough to do that
manually (I tried it already for smaller one in Holysov when I was younger so I know
what I say - really hard work) so I asked local firm to help me. The excavator did
the work in about 2 hours - how easy!
Lots of concrete
The basement needs about 7.6 cubic meter of concrete, that means about 17 tons
of concrete mixture. If you simply put the lower part of the tower into the hole
and later put that amount of material on it, you will never have it perfect
vertical - the mass will move it on side. So the first step was to situate it
(with family help) vertically and put some concrete (500 kg) on bottom to fix it in
position.
After several days when it becomes solid I ordered 7 m3 from cement factory.
Bad luck - the car was not able to arrive close to the hole, so I had to transport (10m distance)
all that amount manually (uffff... 2 hours of hard work).
The crane
It was the relatively easiest job - I ordered the car crane, the operator moved
upper part in the position, I fixed the screws (48 pieces) and done, all in half an hour. The tower is standing!
Finalizing
I prepared additional grounding system (2 plates about 15m away) - not only against
lightning but also to improve it for radio performance. There is also a pipe coming
from the house for cables. When both done I did "concrete hat" - 1 x 1 x 0.6 m block
that comes above the terrain. The remaining space has been filled by soil.
Cables
The cables comes from house by underground pipe up through concrete hat. There is
a provision that rain water cannot get into the pipe. I have 4 cables here: 2 coaxial
cables (one HF, one 50 MHz), one for antenna rotor (7 wires) and one for relay box
control (7 wires).
First antenna installed has been a 3.5 MHz dipole. Tuned exactly to 3.55 MHz where
the SWR is close to 1:1.0, of course in SSB part of the band it is worse, up to
1:4.
The 50 MHz Yagi followed soon.
It is a 6 element model from ZX Yagi (Germany). It is very robust and made from
high quality material, I am sure it survives the strongest wind I can expect here.
The boom length is 6.3 meters, not bad also for HF beams...
Here you can see me adjusting the antenna on test stand (gamma match for best SWR)
Phase 1 - done!
Both antennas on the tower, SWR excellent - first target reached! I stop further development
for winter season, esp. to give my neighbours time to get used. Dreaming for one
additional HF beam to be placed just bellow the 50 MHz Yagi...
Phase 2 - done!
The intention was to put on the tower a beam for 24.9 MHz band. But because of poor solar cycle maximum I decided to choose 18 MHz. I had a nice 5 ele Yagi for that band in Holysov already - why 2 beams for the same band? So I moved the beam from Holysov to Kasperske Hory...
Jarda OK1DNJ helped me to replace a rotator pipe for a longer one (in order to better separate 6m and 17m beams).
Here you can see how the 17m 5 ele Yagi was assembled and adjusted (there is no sufficient space bellow the tower so I hanged a boom at 4m height and installed elements from ladder).
And finally both Yagies placed on the tower. Finish for now!! (what's the next step?)
Next progress (august 2021): a 10 element Yagi OK5IM for 144 MHz placed between the 2 old beams.
How much is it?
Just rough numbers:
Tower, delivery - 40 000 CZK
Material, zinc - 3 000 CZK
Excavator work - 2 500 CZK
Concrete, delivery - 23 000 CZK
Crane work - 2 500 CZK
Antenna rotor - 30 000 CZK
TOTAL 101 000 CZK = 4 000 EUR = 6 000 USD.
So that's the current state. I will put more information here as the story
continues...
