[Lowfer] active whips

[Douglas D. Williams]

That is the $10,000 question.

Back when I was active on HF, I had a 260 foot long "inverted V" antenna,
fed with "ladder line",  with the center up about fifty feet above ground,
and directly above my house. I used this antenna on all bands with a manual
MFJ "antenna tuner". I was able to get WAS and 90 something countries
operating barefoot HF (mostly CW) with this arrangement, before I lost
interest. It was good for DX on 10 MHz and above, and more for "local"
ragchewing on the lower bands.

I decided to give this antenna a try for LF listening and constructed an
L/C impedance matching box, i.e. "antenna tuner", which I still have, based
on an old Ralph Burhans article in Popular Communications, which I had to
go to my local university library and make grainy photocopies of.

I constructed the L/C "LF antenna tuner" with such a range of L and C that
I could tune from 10 kHz to over 500 kHz with my inverted V antenna, with
the end of the ladder line tied together at the "tuner", thus making a
fifty foot high monopole with a large, sloping capacity hat. The lower
I ventured in frequency, the more narrow the bandwidth became. There was a
*very* definite peak in band noise when I adjusted the "tuner" to achieve
the proper L/C combination for 50 ohm impedance matching to my receiver
(whatever it was at that time...I forget) at whatever frequency I had the
receiver tuned to.

I had some success with this antenna as an LF receive antenna, but not
much. Why? Because it was a long wire antenna that was stretched over my
house and was very good at receiving whatever QRM was being generated in my
and my neighbor's houses. If I lived in a more QRM quiet environment, my
long wire antenna would have probably done quite well.

This is a big reason why I enjoy this hobby. Everyone's situation is
different and what works for me may not be ideal for you. The trick is
finding what works best in your RF environment, and making the best of it.
:-)

73, Doug KB4OER










On Thu, Jan 24, 2013 at 4:18 PM, JD <listread at lwca.org> wrote:

> So, do we need an active whip or just a better matching network to
>>>> overcome losses?
>>>>
>>>
> That's the bottom-line question there, Kurt, and I'd kind of say it
> depends on the properties of the antenna you've got.  Provided it's not
> picking up unwanted local noise sources and/or if it has desirable
> directional properties for what you're trying to receive, then try first to
> match it better or use a buffer amplifier such as I did.  That's all an
> active whip is...a bit of antenna with buffering that improves matching.
>  If matching merely brings up as much noise as it does signal, then you
> might want to try an active whip for itse ability to be located at just the
> right spot.
>
>
>
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