[TowerTalk] 160 inv L....data....need some experience....

john at kk9a.com john at kk9a.com
Thu Dec 13 16:44:41 EST 2007

I agree with K9YC, this data makes no sense.  Perhaps your analyzer is 
effected by a nearby broadcast station.  What SWR do you get by transmitting 
into it?

John KK9A

To: "Tower Talk List" <towertalk at contesting.com>
Subject: Re: [TowerTalk] 160 inv L....data....need some experience....
From: "Jim Brown"
Date: Thu, 13 Dec 2007 12:19:39 -0800
List-post: <mailto:towertalk at contesting.com>

On Thu, 13 Dec 2007 13:16:09 -0600, John wrote:

>Resonant at 1820 KHz....

>Z......100 ohms

>L......9.5 uH

>C......900 pf

>SWR with above data is 4:1

>What does this tell me?

I don't trust this data -- it doesn't make sense. First, 9.5uH and
900 pF resonates at 1.722 MHz. Second, if it's 100 ohms at
resonance, that's a 2:1 VSWR, not 4:1. Third, 100 ohms at
resonance for the antenna you describe doesn't sound right -- it
ought to be on the order of 30-40 ohms, depending on the loss in
your ground system.

Perhaps you are misunderstanding the data readout in whatever
analyzer you are using.

If the C and L numbers are good, so the antenna resonates at 1722
kHz, it would look like a significantly higher value of R and some
value of L at 1820 kHz.

How did you decide that resonance was 1820? Lowest SWR? Zero
reactance?  Does your analyzer give you R + jX? If so, what are
those values in 20 kHz increments between 1700 and 1900 kHz?


Jim Brown K9YC 

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