[Antennas] Broadbanding an antenna...

Thu May 24 12:05:10 EDT 2012

ARRL members can search the archives for the article. It can be found 
in "Hints and Kinks" April, 1992 QST. Search: "Load Tracking Network".
The author explains he designed a top loaded the short 160 meter 
vertical to be resonate for the top end of the band. He used a remote 
series motor tuned inductor at the base for better Z matching.
He further found that he could improve his match by adding a parallel 
L-C circuit which resonated well above 160 meters (about 3.4 MHz). He 
then tuned the base series coil for 1:1 at the high end of the band and 
got a 1.4:1 at the low end of the band (as I read it without further 
tuning the base coil).
Although he started out with and utilized a motor driven series coil at 
the base to establish a match at the upper end of the band, this doesn't 
to me appear to be necessary to re-adjust as he went down the band, once 
the L-C parallel circuit was in place. The added circuit had a 
reciprocal reactance curve to that which occurred as he went down in 
frequency.
Thus it would appear the added parallel circuit is as a viable way to 
improve the bandwidth of many other verticals that were tuned in a 
similar way, with or without a motor tuned base coil.
If someone else has a different take on the article or a different 
experience with a similar exercise, I'm open to your inputs.
Ray, W4BYG
On 5/24/2012 11:20 AM, C.Whitaker wrote:
> de WB2CPN
> Someone please explain, or define, "broadbanding"?
> Does this mean the antenna will show a low SWR over
> a wider range of frequencies without readjusting anything?
> Or does something have to be retuned every time the
> frequency is moved slightly. Why does the L need to be
> a variable?
> Learn me. I've been in the technical side of radio
> communications all my working life.
> Clete
> +++++++++++++++++++++++++++
>>> On 5/24/2012 9:42 AM, Andy wrote:
>> Rick Karlquist wrote:
>>>>> The technique cited only works with a variable inductor.
>> Um, why???
>>>> Andy
>> ______________________________________________________________
>> Antennas mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/antennas
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Antennas at mailman.qth.net
>>>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>>>> ______________________________________________________________
> Antennas mailing list
> Home: http://mailman.qth.net/mailman/listinfo/antennas
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Antennas at mailman.qth.net
>> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>