[TowerTalk] 80 meters antenna!!

Thu, 6 Mar 1997 22:46:35 -0300

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Dear friends from the Antenna Reflector,

I have just raised my HF2V vertical and it is working OK on 80. I am
not a big gun but now I can be heard to some areas of the word (at least).
Now I have to finish my EWE this weekend, but it's gonna be easy since
the transformer is ready (thanks to N5UL and IK4WMG for the help).

Of course my antenna improved but I live in a city called Niteroi in the Rio
de Janeiro Area. I have mountais (300meters high) in the  Asia and the South
of Africa directions (including VK0, ZS, V5, JA etc). It's not so
critical on 20 but on 80 it is for sure (because the signals come at the
same noise level most of the time on this band). If I don't change the location during the weekends I'll never work some areas of the world on 80.

Thinking about that I thought in another place 100km from my house. A very
special place 50m away from the beach and no mountains all around. This
place is a summer house which belongs to my mother and almost nobody goes
there. During the carnival holidays I operated there on 40 meters with
a dipole 3 meters high (lower than the house) and 100W and was capable of
working many JAs, ZLs,HL, etc ...
Now I know what a good location represents. Thus so a new place
was chosen for dxing on the low bands.

I told this story to start a new one. Which antenna would fit a 35m x 15m
lot? I have two ideas for an 80 meters antenna:

1) A vertical antenna 50 ft long (project provided by KF4HK from COMTEK) with 
capacitive top loading with 50 radials running 90 degrees with the vertical element. For reception two EWE's for 80, one to the south and the other to the north.

2) Two dipoles at 10m, one being the director of the other. The space between them could be 15m. According to the EZNEC, there is a forward gain and the antenna has more gain at 30 degrees with the advantage of providing a F/B ratio (important to avoid the  LU QRM). ALso according to the model the antenna does not have gain at 90 degrees. It sounds that the antenna does not receive a lot of noise from thunder storms as the dipole does. The computer also gives me an SWR of 2.3 for each dipole. I was expecting a dipole flat SWR! I am including the file PY1CASM.EZ with my idea for those people who have the EZNEC program. It looks like a low two el. beam for 80 meters.

The number 1 for sure will work! The number two is just a computer model and
I am not quite sure it'll work and for this reason I would like to receive some opinions and ideas about these two possibilities. To raise a tower in that place is impossible!!! I have to go for a wire antenna or a short vertical with top loading.

The soil is beach sand!

73 and anxious for a reply,

Carlos - PY1CAS
E-mail: silver@ax.apc.org
        csilver@lilas.riosoft.softex.br

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