[Amps] placement of RF choke bypass cap. (Results of experiment)

[David Cutter]

The current is taking many paths across the surface of the disc to get to 
the other side.  Not sure what this means, but if you used a strip to reduce 
the number of paths, that might demonstrate something... I don't know what, 
but it would be an interesting comparison.

David
G3UNA



> 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
>