Topband: Voltage at top of vertical and scaling?

[Richard (Rick) Karlquist]

On 4/17/2019 1:40 AM, Ulrich Weiß wrote:
> Would like to know how to feed the relay at the top of the vertical...
> regards
> Uli, DJ2YA
> 


Run a single insulated wire from the bottom to the top of vertical.
Connect a 0.1 uF bypass capacitor from the wire to the vertical
at the top.  Connect another bypass capacitor from the wire to
the vertical at the bottom.  Connect the coil of the relay
across the upper bypass capacitor.

I like to spiral the wire around the vertical just to hold
it in place.  You can also use cable ties or electrical tape
to hold it.

Wind a bifilar choke on a large high permeability (EG #33)
toroid.  Connect one end of the twisted pair across the
bypass capacitor at the bottom of the vertical.  The other
end of the twisted pair from the toroid should also have a bypass
capacitor across it.  The conductor in the pair that is
connected to the vertical should be connected to ground
at the other end.  This provides a DC ground for static
drain purposes.  The other conductor is where you feed
in the coil voltage.

The reason for this arrangement is that the DC currents
due to the relay coil in the bifilar wires are equal
and opposite.  Therefore, the DC does not excite the
toroid and saturate it or magnetize it.  It also avoids
generating any voltage spikes when the coil voltage is switched
off.  About 25 turns on the toroid will work (not critical).

Rick N6RK