[TowerTalk] remote antenna switch

David Robbins K1TTT k1ttt at arrl.net
Mon Mar 13 16:59:18 EST 2006

> At 10:26 AM 3/13/2006, larryjspammenot at teleport.com wrote:
> >What are the cases for a remote coax switch with unused antennas being
> >Grounded, or UNgrounded? For example, I have a 5-band quad with an RCS-8V
> >remote coax switch. So there are four unused bands on the quad with one
> >active, since I have five separate feedlines.
> Grounding is nice for dissipation of static.
> Of course, one can also dissipate static with a suitable RF choke (so that
> it's an open circuit to RF)to ground.

of course for yagi's built with certain types of matches there is no need
for either of these.

> You might want to ground or not ground because it would change the
> interactions among elements (I use this to make automated measurements of
> interelement impedances in my phased array)
> Depending on where the switch is located (electrically!), "grounding" one
> of the incoming feedlines has the effect of either shorting, opening, or
> putting some reactive load on the antenna it's hooked to.

leaving an open ended feedline will also have the same effect depending on
the length of the line.  you can only eliminate the effect by routing to a
dummy load that matches the feedline impedance.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net

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