Is there anyway to cut or eliminate all the static on an inv-L?
Hi all,
Rain, snow or even wind can cause a static build-up on any
non-grounded conductor in the air. If that conductor is your antenna,
noise can be produced every time there is a fast change of the electric
charge on the antenna. The fast changes in charge can be either from the
collection of charge from from the rain or snow, or when the potential
difference between you antenna and ground becomes sufficient to cause a
breakdown somewhere, discharging the antenna. That discharge most likely
occurs in the first semiconductor in the front end of your receiver,
which is often a diode used just for that purpose. Sometimes T/R
switching diodes or or antenna input switching diodes can serve the dual
purposes of limiting the voltage passed onto the more sensitive first
active stage of the receiver, and the switching function. In any case
the discharge, as long as it is not too big, does not cause damage but
does cause noise.
There are three easy ways to prevent the static build up and discharge.
1) Shunt the antenna with a high value resistor. High enough that no
significant amount of received signal is dissipated, and if it is also a
transmit antenna, no significant amount of transmit power is dissipated.
2) Shunt the antenna with an RF choke.
3) Make your vertical or inverted L into a folded monopole, so that one
part of it connects directly to ground.
All three of these methods keep the antenna DC potential equal to
ground. Any static charge picked up from rain, snow, wind is immediately
drained to ground.
DE N6KB
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