[qrp-l.org] Antenna Question for you guys

[Dan Romanchik KB6NU]

The 37.5 inches at the top (or to the right in the diagram) is  
actually the antenna. The 16.5 inches at the bottom (to the left in  
the diagram) is a matching stub. If you could measure the impedance  
along that section, you'd find that it varies from 0 at the shorted  
end to very high at the top. Whoever designed this antenna has  
determined that the point at which the impedance is 50 ohms is 1-1/4  
inches from the shorted end.

That's the long answer. The short answer is, "Yes, it's necessary."

73!

Dan KB6NU
----------------------------------------------------------
CW Geek and MI Affiliated Club Coordinator
Read my ham radio blog at http://www.kb6nu.com
LET'S REALLY MAKE THE ARRL THE NATIONAL ASSOCIATION FOR HAM RADIO

On Aug 17, 2008, at 12:20 AM, Jerry Felts wrote:

> I have a old Kenwood TR 7500 I guess it is. I just stuck a 19in whip
> in the antenna jack and it does just fine. No problem hitting the
> repeater, but hey I can see the hill its on from my front porch. I
> don't care that much for repeaters but just have it, price was right.
> So tonite for some unexplained reason instead of trying to clean this
> mess up and make my wife happy I built the twinlead Jpole. Plan to
> just tape it to the window with about a 4 ft long feedline and thats
> probably 2 feet longer than I need. I got the plan from this webpage,
> which was posted not too long ago.
> http://www.qsl.net/wb3gck/jpole.htm
>
> My question is what does the 1.25 inch stub at the bottom do?? Is it
> necessary? Its late for me I have to get up early to go fly RC Gliders
> so I'll put it up tomorrow.
>
> So like whats the stub for?????
> -- 
> Jerry - NR5A - South Dakota
> www.freewebs.com/nr5a
>
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