[TowerTalk] 40 meter vertical ant

[K4SAV]

 VK3QI wrote:
..."Why not rephrase the question slightly and take away the issue of mast
support height?

You have a 66 foot tree (or wooden mast) from which you can properly hang a
vertical dipole."....

A 66 wooden pole wouldn't do it, the bottom of the wire would be 
touching the ground.  You could make the wire into a half sloper which 
would give gain in some directions but loss of gain in other directions. 
--------------------
..."Alternatively you can have a 33 foot high vertical monopole with 66 
radials ON THE GROUND"....

With 66 radials over average ground it should have a gain of about -0.9 
dBi at a take-off angle of about 26 degrees.  It will do much better if 
you happen to live in an area with very good ground.
-----------------------
..."Alternatively you have a 33 foot high vertical monopole WITH ITS 
BASE AT 33
feet high with a significant number of quarter wave radials almost
horizontal to the ground."....

Talk about a theoretical question.  You would never be able to construct 
this, but regardless, if you could, with 16 radials and average ground, 
the shape of the elevation pattern will be similar to that of a 5/8 wave 
antenna, but with less gain.  Take-off angle is very low, about 16 
degrees but with only about 0 dBi gain.  Below 15 degrees it may beat 
the ground mounted vertical by 2 or 3 dB.  At elevation angles between 
22 and 60 degrees, the ground mounted vertical will beat it.  The higher 
you locate this antenna, the lower that first lobe becomes, but higher 
angle lobes form which are stronger than the low angle one.
-----------------

...."In which order would you expect performance to be?".....

For transmitting and for low angle DX and in the direction of best 
performance for each antenna:
1. A dipole at 60 feet.
2. An elevated radial vertical at 33 ft.
3. A half sloper. 
4. Ground mounted vertical.
If you use the antenna for stateside contacts, or for receiving, the 
order will be different.  The last three are within 3 dB of each other 
at very low angles.  The dipole is significantly ahead of the other 3.  
If you raise that dipole by an additional 20 feet you can pick up 
another 2 to 4 dB.

---------------------
..."Will the ground conductivity, both near field and far field now be 
the significant factor?"....

It's always a big consideration, but with 60 ground mounted radials, or 
16 elevated ones, near field loss should be less than a dB.  Far field 
loss is always significant but there is nothing you can do about that.
------------------

Jerry, K4SAV

Peter Forbes wrote:

>Hi All,
>
>Why not rephrase the question slightly and take away the issue of mast 
>support height?
>
>You have a 66 foot tree (or wooden mast) from which you can properly hang a 
>vertical dipole.
>
>Alternatively you can have a 33 foot high vertical monopole with 66 radials 
>ON THE GROUND
>
>Alternatively you have a 33 foot high vertical monopole WITH ITS BASE AT 33 
>feet high with a significant number of quarter wave radials almost 
>horizontal to the ground.
>
>In which order would you expect performance to be?
>
>Will the ground conductivity, both near field and far field now be the 
>significant factor?
>
>Cheers
>
>Peter   VK3QI
>
>
>
>----- Original Message ----- 
>From: "Tom Osborne" <w7why at verizon.net>
>To: "Towertalk" <towertalk at contesting.com>
>Sent: Monday, February 12, 2007 2:41 PM
>Subject: [TowerTalk] 40 meter vertical ant
>
>
>  
>
>>Hi all
>>
>>I have a 40 meter vertical with a bunch (50 or 60) radials.  I also have
>>been thinking of putting up a 40 meter vertical dipole.  Is there any
>>advantage to either or antenna.  Which works best for long haul contacts?
>>Thanks and 73
>>Tom
>>
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