[TowerTalk] Another Cage Question

[K4SAV]

Since you are using a using a tuner at the feedpoint, the resonant 
frequency isn't too important.  The antenna you have should be resonant 
somewhere around 2.0 MHz which is probably the reason you are using a 
tuner. Changing the vertical section to a cage moves the resonant 
frequency to 2.4 MHz and at 1.85 MHz decreases the real part of the 
feedpoint impedance by about 1.2 ohms.  EZNEC says the cage also 
decreases the gain by about 1 dB.  Part of that is 0.3 dB more ground loss.

Notes:
Cage was four #12 wires in a square, 4.5 ft between wires.  I assumed 10 
ohm ground loss in both cases, modeled over real average ground with an 
almost perfect radial system and a loss resistor.  Numbers calculated 
above will vary with the ground loss number.  Mininec ground cannot be 
used with this antenna.  EZNEC is very touchy when trying for an 
accurate answer.  Average gain error test is required.  Numbers less 
than 1 dB are of questionable accuracy.

Jerry, K4SAV


n9lah at comcast.net wrote:
> At the risk of fire up the cage machine again one related question. What will changing the 55 foot vertical section of my inverted "L" to a 6 wire cage from a single wire do? It is 55 feet tall supported 4-5 feet from my tower. The horizontal section is probably 70 feet  long and slopes down to about 20 feet and the antenna is tuned with an SGC 237 tuner at the feed point. 
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> I guess my question really is if it would really help much for the work involved. 
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> Phil 
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> N9LAH 
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