[Lowfer] FW: The Wm's

[Bill Ashlock]

Hi again JB

A simple way to determine the Rac of the antenna system is to assume 100% transmitter efficiency and measure the antenna current. Then use the power formula to calculate Rac. If you measure the Q of the loading coil on the bench you can convert this value to Rac. Subtract that from the total antenna Rac and you have the Rac of the antenna itself without loading coil. I would highly appreciate to seeing your value as our ground systems are quite different.

I just now remembered that the NYC broadcast antenna I mentioned had cages on all four elements (Right Dave R?). That would be easy for me to do up here and would reduce the coil inductance required, hence reduce the Rac of the coil, by at least 2x. Also might reduce the electric field reaching the ground even though that counterpoise would be about 20ft above ground, considering the height of the two support trees. Can't wait to try this!

Bill

> From: weazle at hurontel.on.ca
> Date: Thu, 3 Nov 2011 09:50:45 -0400
> To: lowfer at mailman.qth.net
> Subject: Re: [Lowfer] FW:  The Wm's
> 
> Hi Bill,
> 
> The counterpoise wire is insulated and was just laid on the ground when it was installed.
> Years have passed in that time, so it's well matted in with the uncut grass in that part of
> my property here.  Each end of the counterpoise is connected to the ground rods at the
> base of the towers which support the antenna and it's also connected into the grounding
> at the feed point.  Buried parallel to the counterpoise and about a foot below it is a 20
> foot length of 0.5 inch copper pipe in the "black goo" soil there.
> 
> I've never measured the Rac since I've no equipment to do so.  I do have a RF ammeter
> (current xfmr) on the ground lead of the loading coil-variometer, but it's only relative and
> I just kept on changing things to get the maximum reading.  The final of the tx is coupled
> to the bottom end of the loading coil-variometer through a three turn link coil for D.C.
> isolation and matching purposes.
> 
> Based on the reports and captures I've received, it appears to be doing a fine job!
> 
> 73, J.B., VE3EAR
> 
> LowFER Beacon "EAR"
> 188.830 kHz. QRSS30
> EN93dr
> 
> 
> 
> 
> 
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