[TowerTalk] Guy wire interaction - Murphy's in the details

[km1h@juno.com]

On Fri, 09 Apr 1999 20:18:59 GMT k2av@qsl.net (Guy Olinger, K2AV) writes:
>
>>
>>Using a HP-4271B and 1/4" grips I measure 1.24pf @  1MHz.
>>Using an antique Tektronix 130 LC Meter I measure the same within a
>>needle width on the 0-3pf scale.
>>
>
>Are we assuming that all these insulators are alike at RF? Since they
>are manufactured en masse by umpteen manufacturers for power poles,
>likely (??) without regard for RF characteristics, why should we
>assume how they play at RF?


Most are made by one source these days. I used one made in 1998.


>
>Isn't it basically bothersome to have two HP's giving such variant
>answers to what seems a simple measurement.


Only to those who dont care to find or hear the answer. IMO it is not the
equipment that is in question either, rather the test fixture and
accuracy of the setup.




>
>Does the measured capacity stay constant 1 Mhz through 30 Mhz?


Hmm, I guess then that you are not familiar with some test equipment
parameters?
Basic C meters use 1KHz as the bridge oscillator. Better versions use
1MHz and 10MHz. The higher the test frequency the more the cost and the
better the real readings are at the frequency of interest.  Modern HP LCR
meters can go for $ 10K or more. For most HF use the basic 1 to 100KHz
test freq offers acceptable accuracy. I bought my HP at an auction for
too good a price to pass up.

>
>Also does it matter where one connects to the grips to measure
>capacitance?

Good question. Tom and I have both measured at the same point. I was not
about to drag a complete guy assy into the house either ( all made up for
another 100' tower and lying in the yard) . I opted to build a simple
test jig with one insulator and 2 grips only.

73  Carl  KM1H
Hoping we can have discussions on this reflector without whiners and I
dont mean you either Guy!




>
>Guy.
>
>73, Guy
>--. .-..
>
>Guy Olinger, K2AV
>k2av@qsl.net
>Apex, NC, USA
>
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