[TowerTalk] Half Wave?

[jimlux]

Are we talking a Yagi or a dipole?

We're also talking about a 4 foot difference - I would think you would 
have a hard time measuring the difference in the radiated far field.
(that's about 6% or 11 degrees of phase)
You *might* be able to measure the difference with a TDR or careful 
reflected power measurement on the feedline, because the feedpoint Z is 
slightly different. But he says "rocky soil" - which means it's probably 
not a salt water marsh acting as a perfect mirror.

But in terms of the radiated signal...
Let's say the return loss of the soil is 10dB - you're looking at 
combining a reflected signal at 31% amplitude with a slightly different 
phase - it's the difference between  .31 or .31*cos(11 deg)
Cosine(11 deg) is 0.98 so the difference between .31 or .304
So the "voltage gain straight up" is 1.31 or 1.304

I will buy a cold frosty beverage of choice if you can repeatably 
measure the 0.04 dB change in any one hour period.  (because over many 
days, and many temperatures, you could probably get that kind of 
precision, and I don't want to buy unlimited beverages... I might buy 
you one anyway if you attempt the measurement...<grin>)





On 1/17/19 12:37 PM, Peter Voelpel wrote:
> A 1/4 wave length height IS exactly a cloud warmer.
> At least 3/8 wave length height is necessary for a lower take off angle.
> 
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Keith
> Dutson
>
> My experience is that 1/4 wavelength is okay to avoid a cloud warmer.
> However, higher is always better for DX, aka lower take-off angle.
> 
> 



> -----Original Message-----
> From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of Warren Wolff
> via TowerTalk
> Sent: Thursday, January 17, 2019 11:47 AM
> To: towertalk at contesting.com
> Subject: [TowerTalk] Half Wave?
> 
> Greetings:   My understanding is that a yagi should be at least 1/2wave
> above ground to avoid warming the clouds.   So, considering that thought,
> how much does an antennasuffer if such antenna is 63 feet up instead of 67
> feetfor 40 meters over VERY rocky "soil"?   Thanks, Warren; W7WY
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