Topband: Air wound coil

[Clive GM3POI]

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 at contesting.com] On Behalf Of Richard Beerman
Sent: 04 September 2018 17:18
To: Joe Subich, W4TV
Cc: topband at 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 at 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 at 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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