[Antennas] Broadbanding an antenna...

[Rick Karlquist]

What he ends up with is the known broadbanding technique
consisting of putting a parallel LC across the antenna.
The series L is simply a fixed loading coil   This was discussed
in QST Technical correspondence circa 1980.  It splits a single sharp
dip in SWR into two shallower dips.

Rick N6RK


Ray wrote:
> 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
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