Topband: Simple motor driven telescoping aluminum vertical for low bands?

[Kristinn Andersen]

Hi:

Having been off the air for some 3-4 years due to broken radio and antenna,
I just got me an IC-746 and am now preparing for the winter season on 160m
from TF-land.  My situation does not permit much antenna farming, but I am
leaning towards a vertical on the roof of my house (metallic, 10-by-15m).

I came up with the idea of using two approx. 6m(20ft) sections of aluminum
tubing, where one is mounted as a base and the other can be extended  out
of it. Keep a motor (with reduction gears?) at the bottom and it would use
a threaded rod to run the inner tube up and down.  This allows me to (1)
adjust the length of the vertical for tuning purposes and (2) collapse it
during severe weather or when not in use.  Assume I will be using some type
of hat / top loading, as well as a low-loss inductor at the base.

Specific questions (other comments appreciated, as well):

- How would you suggest preparing the surfaces of the aluminum tubes so
that I don't run the risk of jamming them together, for example if they
bend a little?  Polishing?  Use some kind of lubricant (still assuming that
I will keep electrical contact or at least capacitive coupling...)?

- Suggestions for motors/gear?  Preferably something that is relatively
small.

73 de TF3KX, Kristinn.
                                                                           
                                                                           
                                                                           





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