This antenna was born from
the demand to use a loop for vlf operations in portable posting, avoiding the aid
of long wires to stretch. Up to a few time ago, I have used a circular loop for
the home activities, the output of the home-loop, thanks to its shape, it is slightly
higher, but irrelevant for a normal use.
How is it built?
The loop is composed by 5 pieces of galvanized-zinc pipe, of which 3 long 120 centimeters
and the remainders 2 about the half of firsts, the diameter is 3/4', connected between
them by 4 female-female aluminium RTA curves, these are usually used for the electric
fittingses, these are waterproof and can be opened. The inferior pipes are shorter
so to avoid the internal wires that circulate in the loop to escape inside a pvc
box. 4 dice stop the pipes to the box. It's important that the two shortest pipes
don't come to contact in the box, otherwise we create a real short circuit!
To shift more in lower frequency the antenna I have opted for an inside loop of
60 coils. These are formed by 60 poles flat-cable for PC peripheral. The advantage
to use the inspectable curves is the easiest way to insert the cable in every pipe
from the most comfortable position without having to face uncomfortable curves avoiding
boring cable insulator peel. I don't describe how to insert the cable, each will
use the more congenial to his own demands. Once ended the job, with a little of
patience, you must solder all the incoming wires from one pipe with those came from
other pipe, take care to don't connect the same wire, so that at the end you have
an unique wire in the loop that reaches the lengh of over 280 meters with 60 coils!
To the two open heads connected the cable to receiver, having care before finishing
the job to connect a pole toward the metallic loop.
We have now a square loop that will allow us to dearly receive VLF. It can directly
be connected to the SB of your PC for the first approaches to this type of listening.
In effects it's a little heavy, but once installed is not it anymore! I succeed
in carry it on the roof of my compact car without problems, I couldn't do that with
the circular one, and this is what I wanted.