Topband: 4 new radials...

[Jim Brown]

Hi Jim,

Yes, the variation with frequency that you saw was the transmission line 
behavior.  I'd say that the 1 MHz numbers are good.

73, Jim K9YC

On 2/10/2012 5:43 AM, Jim F. wrote:
> Hi Jim,
> Thank you so much for the reply.  Here is what I did.
> I tried an Autek RF-1 antenna analyzer to measure the 72 foot 2 
> conductor cable
> installed in my basement but the capacitance varied widely with frequency.
> I then went to an LC measuring circuit built from the Winter of 1993 
> Communications Quarterly that has an Oscillator running at 1.017 
> mHz and used it to determine the cable (capacitance per foot) in my 
> basement as a reference.  (24'/pf)
> Is 1/20 wavelength of 1.017 mHz =  ~ 215'  ignoring Vp ?
> I estimate that the cable going to the condo furthest away could be 
> over 100' and it measured a calculated 125'.
> Do you think that is reasonable  ?
> Thanks again,
> Jim / W1FMR
>
> --- On *Thu, 2/9/12, Jim Brown /<jim at audiosystemsgroup.com>/* wrote:
>
>
>     From: Jim Brown <jim at audiosystemsgroup.com>
>     Subject: Re: Topband: 4 new radials...
>     To: topband at contesting.com
>     Date: Thursday, February 9, 2012, 11:22 PM
>
>     On 2/9/2012 6:12 PM, Jim F. wrote:
>     > Using measured capacitance between the two conductors
>     >   of my cable ( 24pf / ft.) it was easy to calculate the lengths of
>     > cables going to the other 3 condos.
>
>     At what frequency did you make that capacitance measurement, and
>     how did
>     you make it?  When the frequency is high enough that the cable you
>     are
>     measuring is longer than about 1/20 wavelength (taking Vp into
>     account),
>     the behavior of the cable as a transmission line will cause
>     measurement
>     error.
>
>     73, Jim K9YC
>     _______________________________________________
>     UR RST IS ... ... ..9 QSB QSB - hw? BK
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