[Elecraft] PAR endz-fed

[David Gilbert]

Hi, Jim.

I had thought about that concept years ago when I was doing more casual 
QRP portable operation (camping, Flight of the Bumblebee-type stuff, 
etc), but I never tried it because I just assumed that the impedance at 
the end of a "dipole" (i.e., where the choke would be on the coax) was 
so high that you wouldn't get much decoupling at that point.  Have you 
been able to verify that a simple choke really blocks the shield current 
there?  Or am I misunderstanding something?

73,
Dave   AB7E



Jim Brown wrote:
> On Mon, 2 Mar 2009 10:16:27 -0800, Randy Cook wrote:
>
>   
>> HOW MANY OF YOU ARE USING PAR ELECTRONICS END FEDS 
>>     
>
> This is a VERY easy antenna to build. Why would anyone want to buy 
> what they can build in an hour for a fraction of the cost? See 
>
> http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf
>
> One half of the dipole is a quarter-wavelength of wire, connected to 
> the center conductor of the coax feedline. One quarter-wave from the 
> end where the wire is connected you add a ferrite choke that 
> functions as an "end insulator" for the coax, which makes the 
> section of the coax between the wire and the choke the other half of 
> the dipole. You do NOT apply a velocity factor when determining the 
> length of the coax between the wire and the choke. 
>
> If you're running 100W or less, the choke can be as simple as 10 
> turns of the coax around two 2.4-inch o.d. toroids, #31 or #43! I 
> used much bigger chokes to run 1.5kW. For 20W or less, a single 
> toroid is plenty.
>
> 73,
>
> Jim Brown K9YC
>
>