N0!! That's the equivalent series capacitance that correspond to -j5.6ohms
capacitive reactance! It would be much clearer if the analyzer would present
it in that form, since it clearly has determined the sign - since it's
indicating an equivalent capacitance.
Anyway, I stand by what I wrote you, Larry. I'd leave that TX antenna alone!
59.5 ohms real with 1.23;1 vswr IS JUST FINE! IMO
Have Fun!
73,
Charlie, K4OTV
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Larry
K4AB
Sent: Wednesday, December 10, 2014 7:10 PM
To: topband@contesting.com
Subject: Re: Topband: 160 Shunt-Fed Tower Readings
>I would like to know how you can get 15893pf from a 1000pf capacitor. That
>has to be a mis-read value there...gary maybe rounded off to 159pf??
That's a great question. Where is the analyzer actually getting that
reading?
73,
Larry K4AB
On 12/10/14, Tom W8JI <w8ji@w8ji.com> wrote:
>> I'm concerned about a few things:
>>
>> 1) I'm thinking the antenna is electrically too short. After all, the
>> Yagi at the top really isn't adding too much top loading. And I'm
>> thinking
>> adding a couple of top loading wires connected to the tower
>> might be beneficial.
>
> If you run any power, you will likely start to have problems with arcing
at
>
> the Yagi antenna elements where they cross the boom.
>
> This is because of the poor insulation, and because of the high voltage at
> the boom when on 160.
>
> The cure for that is to ground the elements to the boom though air coil
> inductors. Just five or ten uH would work OK, and not upset the antenna
> operation. This would also add 160 top loading.
>
>
>> 2) What exactly is the analyzer telling me when it says C:15893pF?
>> I'm far from an engineer, but something tells me that's way high. Or is
>> it?
>
> It is meaningless. It just means you are measuring almost where the
antenna
>
> is resonant.
>
> 73 Tom
>
>
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