I'll try this again as I used the wrong email to reply. km1h@jeremy.mv.com
no longer exists.
Carl
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "rich kennedy" <astro_maryland@yahoo.com>; <topband@contesting.com>
Sent: Wednesday, October 01, 2014 8:48 AM
Subject: Re: Topband: 160M/80M Vertical - Using a capacity hat below a trap
Whatever is below the trap stays below and affects 80 only. You can add a
loading coil, hat, linear loading section, or whatever to shorten the 80M
portion and then add more wire or loading coil above the trap for 160.
It wont take much of anything to make up just 5'.
In more extreme cases realize that shortening increases losses and reduces
feed impedance plus efficiency which places more importance on the ground
system to keep overall losses tolerable; the hat has the least losses.
Carl
KM1H
----- Original Message -----
From: "rich kennedy via Topband" <topband@contesting.com>
To: <topband@contesting.com>
Sent: Wednesday, October 01, 2014 8:15 AM
Subject: Topband: 160M/80M Vertical - Using a capacity hat below a trap
I’m finalizing design for my 160M/80M shortened wire tree-mounted
vertical. An Unadilla 80M trap will be
placed approx. 65’ feet above the feedpoint; above the trap is another 20
feet
with a small cap hat. An autotuner
handles the Z matching for the anticipated 500 watts on both bands.
QUESTION: Can one install a capacitive hat directly below
the 80M trap to help shorten the length of the 80M section? For example,
shortening the 80M radiator to
60’ (from 65’) and making up ‘the difference’ with a capacity hat? Any
downside?
NOTE: Please omit suggestions about using a larger hat on
160M (sloping wires, etc.) – I know that it is much more desirable, but
that is
just not feasible here at K3VAT.
Thanks, 73, Rich, K3VAT
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