[TowerTalk] Is it worth it to move 2El Quad from 50ft to 100ft?????

[n4kg@juno.com]

Higher is NOT always better....N4KG

More comments inserted below.

On Tue, 16 Oct 2001 <jaw@lion.cc> writes:
> 
> If you have flat terrain you would sure see an big improvement. 
> Compare the vertical radiation diagramm for both heights (see the 
> chapter "The effects of Ground" in the ARRL Antenna Handbook) and 
> you will see the difference.
> 
> For 20 Meters this means:
> 
> 50 ft high (0,75 lambda): a main lobe just right up at 90 degrees - 
> this is only usefull for short distances and a waste of power for 
> DX. The second lobe is at about 20 degrees, still rather high for DX.

	The ground reflection pattern includes a lobe straight up.
	The free space pattern of the antenna is focused forward.
	The radiated pattern is the vector product of the free space
	antenna pattern and the ground reflection pattern.  

	An MUF of 30 MHz will support takeoff angles up to 24 
	degrees on 20M.  An MUF of 45 MHz (typical midday MUF
	at high sunspot levels) will support takeoff angles up to 40 
	degrees on 20M.    N4KG
> 
> 100 ft.high (1,5 lambda): The highest lobe is at 57 degrees, much 
> less power at 90 degrees. Your lower lobe is at 10 degrees. That 
> sure makes a difference on DX !
> 
> 73s Juergen - OE5CWL
> 

	The lobe at 57 degrees will not be supported by the
	ionosphere. It is also wasted energy.   N4KG

	SNIP

   My TH7 at 40 ft has always been stronger to Africa
   than my Telrex 3L20 at 75 ft by 6 to 20 dB, even
   during Low Sunspot Activity.  It is OFTEN stronger
   to Europe during the afternoon.

   ANY horizontally polarized antenna more than 3/4 WL
   above ground will have 2 or more lobes in the vertical
   plane with NULLS between those lobes.  The way to
   fill in those nulls is with a lower antenna whose main
   lobe coincides with the NULL in the pattern of the 
   higher antenna.

   Bottom Line:  It takes HIGH and LOW antennas to
   cover ALL the angles supported by the ionosphere.

   People with only ONE antenna never seem to "get the picture".

   Tom  N4KG

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