Tnx Richard for the info.
I've got a small collection of doorknobs and will ck to see
if I can cobble up that much capacitance. I only run less
than 200 watts output, so won't need any HV vacuum caps. From
what I read, the inv L can be fed directly with 50 ohm coax, but
no mention is made of what the swr might be. In an open field,
made per the book, the swr might be much lower than mine. My ant.
has a lot of tall pines close to it.
I thought the "Q" of the antenna was not vry good since the SWR
curve is vry broad.
The choke you mention..is it made with coax coiled up at the feed
point..if so, any idea how many turns & coil dia?
Last night I made contacts into Minn, NY and PA, with 589 reports..
running a Viking 2 at 100w output. Oh, and receiving seems to be
good too...W1AW overloaded my SX-71 and other stns were cmg in
good as well...so some success.
Tnx, 73 de Bill K4JYS
----- Original Message -----
From: "Richard Karlquist" <richard@karlquist.com>
To: topband@contesting.com
Sent: Tuesday, October 1, 2013 6:14:12 PM
Subject: Re: Topband: 160m Inverted L High SWR
On 2013-10-01 14:08, Bill Stewart wrote:
> Good afternoon all,
> The vert. section is
> abt 55 ft & the rest is nearly flat horizontal. Total length is 130
> ft/6 in. I am using a
> 4 wire c-poise abt 9 ft high of which none are directly under the
> horiz. section.
> Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz.
> The SWR
This is exactly what you would expect. It corresponds to a drive
impedance
of something like 18 ohms, about right for a top loaded 55 foot
vertical.
You will need to put a shunt capacitor of about 2400 pF across your
coax,
and then increase the length of the L until you get the resonance to
1833 kHz.
I currently have a top loaded 60 foot vertical and this is very similar
to my situation. You will find that after proper matching, the
bandwidth
is really quite narrow, indicating reasonable efficiency.
You should probably add a common mode choke at the feedpoint if you
don't already have one.
Rick N6RK
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