VK6VZ WROTE:
"To give you an idea how poorly verticals perform here on 160m, my friend
VK6IM has a 70' top loaded vertical (no inductor, just a large capacity hat)
for 160m with an earth mat of 40-plus full size quarter wave radials under
it. In most geographical locations, this would leave a low dipole for dead
on DX - but not here - I work DX easily VK6IM can barely hear/work..."
VK3AJJ writes:
This is not the most scientific of comparisons. I am a firm believer that
the most important part of the lowband antenna system is the set of ears
under the headphones. It may well be that vk6im is lounging back in his
armchair without headphones, with Tchaikovsky playing in the background
whilst chatting with his wife when listening to the dx (not to mention
gegraphical and local noise differences). On the flip side your neighbor
could have "big bertha" humming away in the cellar and the extra 10kw will
make his vertical / dipole seem very impressive indeed. The only true
comparison (and even this is not perfect) is to have both test antennas
available at the one qth for switching by the same operator under near
identical propagational / local noise conditions.
I often laugh when I read an antenna review in a ham magazine and the
writer concludes the antenna is a winner when he makes 3 or 4 contacts into
Europe and is S9 (with no other comparative antenna switching). I could be
s9 into the ea3sf stacked yagi system on 20m with my mobile whip and as a
result announce to the world that I have discovered the latest and greatest
dx-ing antenna.
Another important (non-scientific) factor in Amateur antenna performance is
ease of construction. It may well be that a perfectly constructed vertical
array will out perform a dipole every time but probably not if I build
them!! I am not an engineer and thus the more complex an antenna system
becomes the more likely it is that I am going to make a mistake which will
impede its perfortmance. Any moron (yes thas me) can get a dipole antenna
working efficiently - a vertical system is however far more complicated and
thus room for efficiency impeding errors is greatly enhanced (thus warping
later comparison).
Another key "unscientific" question in antenna comparison is what is the
antenna's purpose?? Is it to work DX or is it to have the highest
theoretical gain over a comparative antenna. Often a simple but sound
performing antenna will work more Dx than its sophisticated rival simply
because the operator is at the radio instead of tinkering with the 4 square
switching system in the backyard. How often do we hear guys say they will
be on topband in a big way but because they set their antenna goals to high
never actually make it on air?? (I of course concede that a lot of these
guys enjoy the tinkering more than the Dxing and thats fine.)
This post is not intended as a shot at Steve (or VK6IM who I don't know)
but simply highlights some of the more practical (as opposed to
theoretical) aspects of antenna comparison.
Paul (vk3ajj)
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