Beware not putting the top yard inside small Teflon tubing. You will have an
infinitely high Z at the top and potentially lots of KV. It will burn through
the support line. 73 Clive GM3POI
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Richard
Beerman
Sent: 04 September 2018 17:18
To: Joe Subich, W4TV
Cc: topband@contesting.com
Subject: Re: Topband: Air wound coil
Rick and Bob, Thanks for such swift replies. Looks like I should try to
reinforce the 3/8” tubing (it’s pretty short) with a wood dowel or perhaps with
smaller or larger aluminum tubing. Then the fishing line method should be a
perfect solution using 24 or 26 gauge wire. Using this method, I think a
hairpin loop at the base of the vertical will help me achieve resonance. Thanks
again. Dick W5AK
> On Sep 4, 2018, at 11:36 AM, Richard Beerman <rbeersr@att.net> wrote:
>
> Top Banders, This discussion has been tremendously helpful to me as I also
> am going to put a DX Engineering 68’ vertical when the QRN subsides here in
> South Texas. Initially, I planned to install a large inductor (looks like it
> came from a BC transmitter) that I found at a local hamfest. My calculation
> is that this inductor has around 43 micro henries. According to various
> contributors, this is not a good solution. I actually did the same back
> around 1972 with a Hytower on 160 meters! It did work with a pathetic ground
> system and 40-50 watts from a Ranger II.
>
> Anyway, here is my question…. my vertical has 3/8” tubing at the top. Pretty
> flimsy to connect top loading wires except maybe small gauge wire. I am not
> sure how well small gauge wire will handle voltages that may appear at the
> top of a 68’ vertical. So, as an alternative, much like the Hytower does
> today, what would happen if I installed top loading wires of a larger gauge
> lower on the antenna where the tubing is more substantial? Any suggestions
> regarding where the top loading could be connected on the vertical and
> approximate length of the top loading wires?
>
> Thanks, Dick W5AK
>
>> On Sep 3, 2018, at 1:41 PM, Joe Subich, W4TV <lists@subich.com> wrote:
>>
>>
>>> Getting to six would result in a smaller top hat but may not be
>>> worth the mechanical hassle.
>> If the mast has traditional three way guying, the mechanical hassle
>> for a six wire top hat may not be that much greater than a four wire
>> top hat.
>>
>> If the top hat wires slope downward, keeping them to the minimum
>> length will result in maximum efficiency (and minimum "shielding" of
>> the top of the vertical element).
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 2018-09-03 7:20 AM, Paul Christensen wrote:
>>> I ran the same model in 4Nec2 as below but changed the hat from the
>>> traditional two wires to four, spaced 90 degs. Complex base Z is near
>>> 16+j0. Even though two symmetrical top-hat wires produce little radiation,
>>> four wires result in wires that are only 24 ft long to achieve resonance --
>>> versus 41 ft with only two wires. Getting to six would result in a smaller
>>> top hat but may not be worth the mechanical hassle.
>>>> "4Nec2 shows that with a 68 ft. thin radiator, resonance can be achieved
>>>> with wires roughly 41 ft. per side. With a ground field of 60 radials, 90
>>>> ft long on sandy ground, 4Nec2 reports a base impedance of 15.4+j2.5."
>>> Paul, W9AC
>>
>>
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