[TowerTalk] 43 Ft Vertical on 80/160 DX-Pedition

[Grant Saviers]

Here are a few numbers from a 20 minute modeling exercise with EZNEC

43' vertical modeled as a 1.75' diameter conductor and adding 4 top load 
wires at 47 deg angle to ground each 13.5' long and a perimeter wire at 
their ends:

resonance 2.9Mhz  Z= 14.2+j7.8

at 1.9Mhz    Z= 5.2-j183   (over perfect ground, wires 0.1" dia)   (Z= 3 
- j590 w/o top loading)

I think EZNEC does a pretty accurate analysis for such antennas.  I was 
concerned that the effect of a perimeter wire was overstated, but some 
references I've recently found show that they do dramatically affect the 
results.  My 80m 40' vertical measured right on the analysis.

The loading improves when 1. wires are as horizontal as possible, 2. a 
perimeter wire is used, 3. larger conductors, 4. more wires.

This quick and dirty model shows it takes less top loading to resonate a 
43' vertical on 80m, and more for 160m.  Get EZNEC and design what you 
need.  Using a heavy duty 43' stick is important to handle the loads 
from the wires.  b.t.w. any Al above a top hat is nearly useless.

Grant KZ1W

On 4/3/2011 1:46 PM, Jim Lux wrote:
> You might wan to talk to W4EF about this sort of strategy.   I think he's been using the guys as top load scheme in his desert sojourns for top band contests.
>
> Theres sort of a tradeoffs too, depending on the angle on the guys.
>
> On Apr 3, 2011, at 8:32 AM, Mike Fatchett W0MU<w0mu at w0mu.com>  wrote:
>
>> I spoke to one manufacturer of these and they are working on a version
>> with 3 or 4 top guys that are a combination of wire and "rope" to
>> effectively create top loading.  They are not sure just how much of an
>> effect it would have and are going to field model it.  This is an
>> interesting concept.  DXE has some top hats but they are for the heavy
>> duty verticals which are not very travel friendly.
>>
>> On 3/28/2011 1:25 PM, Grant Saviers wrote:
>>> Top loading the 43' will increase its radiation resistance and thereby
>>> the efficiency.  DX Eng has some top hats in their catalog.  Some of the
>>> Antenna Compendiums have articles.   It's an interesting question to
>>> model this for 160 - 40m.  Perhaps there is a "magic" guy number and
>>> length that preserves some sort of 40m match.
>>>
>>> My 40' vertical for 80m had 8 x 6' 0.375" Al horizontal  tubes as a
>>> capacity hat to resonate in the center of the 80m band.
>>>
>>> Grant KZ1W
>>>
>>>
>>> On 3/25/2011 7:45 PM, Jim W7RY wrote:
>>>> Great article!  thanks for sharing.
>>>>
>>>> 73
>>>> Jim W7RY
>>>>
>>>>
>>>>
>>>> --------------------------------------------------
>>>> From: "Al Kozakiewicz"<akozak at hourglass.com>
>>>> Sent: Thursday, March 24, 2011 10:12 AM
>>>> To: "Mike Fatchett W0MU"<w0mu at w0mu.com>;<towertalk at contesting.com>
>>>> Subject: Re: [TowerTalk] 43 Ft Vertical on 80/160 DX-Pedition
>>>>
>>>>> Have you read Phil Salas' article on base loading for this antenna on his
>>>>> website? http://www.ad5x.com/images/Articles/Match160.pdf
>>>>>
>>>>> Al
>>>>> AB2ZY
>>>>> ________________________________________
>>>>> From: towertalk-bounces at contesting.com [towertalk-bounces at contesting.com]
>>>>> On Behalf Of Mike Fatchett W0MU [w0mu at w0mu.com]
>>>>> Sent: Thursday, March 24, 2011 1:04 PM
>>>>> To: towertalk at contesting.com
>>>>> Subject: [TowerTalk] 43 Ft Vertical on 80/160 DX-Pedition
>>>>>
>>>>> I am aware of the issues with this antenna on 80/160.  I was curious if
>>>>> adding a wire T to the top would improve the performance on these two
>>>>> bands.  I am unclear what the length of the T would be or what effect
>>>>> the T would have on the 30/40.  I am not concerned so much with 10m-20m
>>>>> as we will have other antennas for those bands.
>>>>>
>>>>> W0MU
>>>>> _______________________________________________
>>>>>
>>>>>
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