Here are the results of the experiment:
1.) Dipole was made with #10 bare copper wire each side 12.0" long.
2.) Disks are 2.02" diameter x 0.01: thick copper with hole in center
for #10 wire.
3.) 8ft. of RG-316 coax with 3 common mode chokes (Z>300 ohms at 200
MHz)was calibrated at the far end in order to measure actual dipole feed
point impedance.
4.) Tests were done in my basement with at dipole height of about 3.5'
and 4-5' of clearance to other objects.
Test #1: Bare dipole
Fres = 236.20 MHz, Z = 71.5 + j0 (468/length = 234MHz)
Test #2: Dipole going thru center of disks and soldered with disks
placed 4.0" both sides of the center of the dipole.
Fres = 223.55 MHz, Z = 65.7 + j0
Test #3: Dipole going thru center of disks and soldered with disks
placed 8.0" both sides of the center of the dipole.
Fres = 199.01 MHz, Z = 44.3 + j0
Test #4: Dipole soldered to top edge of each disk with disks placed 8.0"
both sides of the center of the dipole.
Fres = 196.89 MHz, Z = 43.9 + j0
Conclusions:
1.) The difference in frequency between tests #1 and #2 or #3 and #4 do
NOT allow for the dipole length to be increased by the extra 4" it would
take if the current went around the disks.
I have pictures if anyone questions my setup etc.
73,
Larry, W0QE
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