[Top] [All Lists]


To: <>
Subject: [TowerTalk] MEASUREMENTS
From: (Ward Silver)
Date: Fri, 25 Jun 1999 22:17:18 -0700 (PDT)

> 1  I thought antennas realized gain through the change of it's radiation
> pattern.[ ie it reduces the power in some undesired directions and directs it
> in a desired direction - vola!! GAIN. If true --- antennas with different
> gains must have different patterns.
> 2   If antenna's have different patterns will they not be effected differently
> in a "real world" ground enviroment??

To answer both questions at once - it's a question of relative difference
and K2AV addressed this well.  If we were testing a combination of quads,
logs, yagis, and something else, then I would not expect all the antennas
to be affected the same by the local environment.  However, check out the
table that lists the element configurations - 3 on 20, 3 or 4 on 15, and 4
to 7 (I think) on 10-meters.  The only real variation is on 10-meters.
These antennas are all birds of a feather and the 24' boom set is almost
identical.  Pattern variation is minor and differences in the interactions
with the local environment would also be expected to be minor.  Notice I
said "differences in interaction" and not "interaction" would be minor.
It's a key point.

> 3 If the same antenna [ in this case a c-3 ] is installed and tested two or
> more times [ and the data repeats within 1 db ] it is reasonable to assume
> that its pattern and the "world" [ignore measurement calibrations] have not
> changed. Thats what you have experienced and no reasonable person would have
> expected major changes. It is a major leap tho to assume a much different
> antenna would measure higher or lower only due to the antennas gain and not
> due to the "test fixture"reacting to a different pattern.

All I suggested is that the multiple measurements indicate insensitivity
to local ground conditions as experienced at our site when wet and dry.  I
would not suggest that a salt water or solid rock site would play the
same with respect to absolute measurements.  It just eliminates one
variable from the mix, that's all.

I certainly hope, too, that there will be more tests and that our initial
foray will be just that.

73, Ward N0aX

FAQ on WWW:     
Administrative requests:

<Prev in Thread] Current Thread [Next in Thread>