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

[Roger]

pc5m, Carel wrote:
> Hi Larry,
>
> Could you repeat your experiment with a subtle change: don't drill a hole
> through the discs but solder/connect the wire on both sides ? I think it
> will change your results. 
>   
One suggestion just to make it interesting...Do as before, but then move 
the disks out to about 75 or 80% of the wire length from the feed point 
and run the test again.

I'm finding this discourse quite interesting.

73

Roger (K8RI)
> Carel.
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Larry Benko
> Sent: Saturday, March 20, 2010 5:21 PM
> To: dezrat1242 at yahoo.com
> Cc: amps at contesting.com
> Subject: Re: [Amps] placement of RF choke bypass cap. (Results of
> experiment)
>
> 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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