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

[Larry Benko]

Darn, I just finished cleaning up the experiment and it is now in the 
trash.  I didn't think there were any follow up test to do.  I did the 
test at 33% and 66% of the distance from the center and am quite sure 
that doing it at 75% or 80% will result in an even lower resonant 
frequencies with a lower real part to the feedpoint impedance at 
resonance.  As far as soldering wires to disks without a hole I really 
believe there would be no change since I soldered a fillet to both sides 
of the disks before.  However I will let someone else have a turn with 
this test if anyone wishes.  The test could be more easily done with a 
short vertical on a metal plate.

Larry, W0QE

Roger wrote:
> 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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>>   
>>     
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