[TowerTalk] Takeoff angles HF VS VHF / F2 VS Es DE K0FF

[Tom Rauch]

Hi Tom,

>  And how do you KNOW that the peak was not at the
>  SECOND lobe (around 20 degrees) instead of the first?

I didn't, in the case of my installation in Ohio, any more than you 
know from your installation!

How do any of us know what the optimum angle is in our systems, 
and that it is not some spurious null or lobe causing the results we 
see?

How do you know your vertical on 80 doesn't have efficiency or null 
problems?

The problem is, we usually have no idea how any antenna really 
works at HF because gain and pattern is almost impossible to 
measure. 

We can be sure of a few things though, like a high dipole well out 
in the clear will be a reasonable reference antenna with nearly 
perfect efficiency. My 200 foot omni-tower on 160 meters had 4-6 
dB nulls in several directions, caused by a 300 foot tower 400 feet 
away. If I didn't measure FS, I never would have known that and 
been able to de-tune the tall tower.

I had a vertical with four elevated radials that was several dB 
weaker than the 200 ft tower. I never would have known that, if I 
didn't measure FS.

So how do we measure the FS and pattern of complex HF 
systems, and have any idea what we are doing? How often do we 
check simple systems? We don't, so all we have are opinions 
based on the antennas we have.

One opinion is just as good as another, unless one fellow clearly 
has more hardware and does more exhaustive tests.

 


 
73, Tom W8JI
w8ji@contesting.com

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