[TowerTalk] Omnidirectional antenna for domestic contests. Re: TowerTalk Digest, Vol 154, Issue 18

[Robert Harmon]

Joe,

So the laws of electromagnetic radiation physics do not apply to the 
east coast LOL !
I have been following this discussion and Jim is basing HIS 
contributions on actual data.
You are digging your self into a hole Joe.  Time to stop digging :-)

Bob
K6UJ




On 10/12/15 8:02 PM, Joe Subich, W4TV wrote:
> On 10/12/2015 10:50 PM, Jim Brown wrote:
>> But at lower angles (30 degrees and below), which is where most of
>> the stations we want to work in a domestic contest come in,
>
> While that may be true for you on the left coast (the land of fruits
> and flakes), it is most certainly untrue for those in W3, W4, W8, W9
> and W0.  Most QSOs for those in flyover country are at takeoff angles
> greater than 60 degrees on 80 and 40 meters.  However, that still
> argues for a height of roughly 50 feet for an 80/40 trapped or fan
> dipole (3/8 wave on 40 meters, 3/16 wave on 80 meters).  70 feet (60
> to 80 feet) is to be avoided due to the overhead null on 40 meters.
>
> 73,
>
>   ... Joe, W4TV
>
>
> On 10/12/2015 10:50 PM, Jim Brown wrote:
>> On Mon,10/12/2015 9:15 AM, Stephen Davis wrote:
>>> I was indicating what my actual results are, regardless  of what
>>> software indicates.   Also, if I had looked at software first, I might
>>> still have done the NIVIS based on other practical experience noted by
>>> others in the research I did.
>>
>> Nearly all published assessment of the vertical patterns of antennas has
>> been on the basis of what is called take-off angle -- the vertical angle
>> at which the antenna produces maximum radiation. That description leads
>> to a VERY false result.
>>
>> In the tutorial I referenced, I looked at both high angle and low angle
>> field strength (performance) as the height of horizontal dipoles was
>> varied from 30 ft to 135 ft. I looked at 5 degrees, 10 degrees, 15
>> degrees, and 70 degrees, picking data points off of a full vertical
>> pattern. I looked most at 80, 40, and 20M.
>>
>> In general, the high angle field strength is greatest when it is about
>> 1/4 wavelength high (65 ft on 80), and drops by only 1 dB if the height
>> is increased to 3/8 wavelength (90 ft on 80M) or decreased to 1/8 wave
>> (30 ft on 80). But at lower angles (30 degrees and below), which is
>> where most of the stations we want to work in a domestic contest come
>> in, the field strength increases by 4 dB between 1/8 wave and 1/4 wave
>> high, and another 2 dB going to 3/8 wave. High angle field strength does
>> not begin to drop much until you get higher than 3/8 wave.
>>
>> SO, repeating my statement, a low antenna does NOT work better for NVIS
>> than a high one, and a high one works MUCH better beyond a few hundred
>> miles. All of this is shown in easy to understand graphs in
>>
>> http://k9yc.com/VertOrHorizontal-Slides.pdf
>>
>> 73, Jim K9YC
>> _______________________________________________
>>
>>
>>
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