[TowerTalk] Measurring at the antenna feedpoint
Eric Gustafson Courtesy Account
n7cl@mmsi.com
Mon, 8 Jun 1998 10:30:01 -0700
Paul,
Unless the Autek measurment port is balanced, I suspect that you
were having problems trying to measure an essentially balanced
antenna structure with an unbalanced instrument. This had the
effect pf making the instrument and probably the operator part of
the antenna system. You might want to try the measurement at the
antenna with a good 1:1 balancing device in line between the
instrument and the antenna.
73, Eric N7CL
>From: "Paul Ferguson" <Paul.Ferguson@pobox.com>
>Date: Mon, 8 Jun 1998 11:07:48 -0400
>
>When I put up my quad, I checked the resonance at the feedpoints
>using an Autek RF1. I used a couple of inches of wire to attach
>the RF1 to the loop feedpoints. Some of the results did not seem
>correct. The SWR was OK at the shack and the quad played well. A
>friend had a similar experience. Here is part of his message: to
>me:
>
>-----------------------
>
>I made the mistake of trying to measure impedance/resonance right
>at the feedpoint with the Autek RF1. I knew from experience with
>the 40 dipole that that's a bad thing to do. I'm not sure quite
>why. So I did two other things. I had an old Johnson Directional
>coupler. I stuck it right at the feedpoint (6" coax actually)
>with the signal lines running down to the ground and got readings
>that made much more sense. I also cut a 1/2 wave piece of RG8x
>and put the Autek at the end of that. It essentially reproduced
>the coupler results. It seems one can't make measurements and BE
>at the feedpoint as well. Body capacity effects I
>guess.
>
>--------------------------
>
>Have others had this experience. Does body capacity cause it?
>
>73,
>K5ESW
>Paul
>Paul.Ferguson@pobox.com
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