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

Jim Brown jim at audiosystemsgroup.com
Thu Dec 13 15:19:39 EST 2007

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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