Perhaps it would be more useful to connect the ends through coils that
would bring the antenna nearly to resonance on 160 and by their choke
(neglecting distributed C to make into traps which may not be a perfect
assumption) effect disconnecting the added wire on the higher bands. The
choke will be more effective on 80 through 30 than 20 through 10 meters
because the distributed will likely make the choke series resonant
somewhere in that range and above that resonance it looks capacitive.
I'm sure I've read about such chokes in Pat Hawker's antenna topics volume.
73, Jerry, K0CQ
On 4/8/2011 3:46 PM, Steve Hunt wrote:
Art,
If you mean extending the ends off at 90 degrees to the main dipole at
the 25ft/30ft level, that's fine. Just think of it as adding end
capacity loading to an electrically short dipole. The important thing is
that it raises the resistive component and drops the capacitive
component of the feedpoint impedance - both of which significantly
reduce the VSWR and loss on the open wire.
But note that we are focussing on 160m here - there will be a "knock on"
for the other bands which will likely be detrimental. On the higher
frequency bands there will be much more current in those low extensions
than there is on 160m, and that means the "effective height" of the
antenna will be lower.
73,
Steve G3TXQ
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