[Lowfer] Active Ants Redux

[Peter Barick]

>>> eric@willow.nutstreet.net 07/14/03 08:36PM >>>
>Well, it is based on the AMRAD active whip.  If you want to build the

> check http://www.amrad.org/lf/actant/ ... this 
>appeared in a September, 2001 QST article.
>Eric, KD5UWL
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Interesting, Eric,

I am familiar with the original AMRAD AA and read the full account of
it when it was released. I didn't know about the FAQs on "dumbing it
down," however. But your approach likely captures the essence of that
project and when used in a restricted RF environment (w.r.t. nearby
signals) may offer good results.

The genesis of that project began with a group of LF enthusiasts
meeting on Saturday mornings for coffee and engaging in "what if?".
According the the QST article, some were RF engineers and had insight to
the latest that semi-conductor technology had to offer. They began to
spec a design based on given parameters and that determined the active
component, an expensive FET fitting the bill. From there it was
prototyped and analyzed to meeting expectations. That's the nice thing
about such collaboration and we as amateurs get to copy it intact with
likely similar results or attempt changes for our needs.

I'd like to mention for others wishing to build the AMRAD Active
Antenna that pcbs are available at modest cost from FAR Circuits (see
that Web site). These boards, amp and PS, I believe, allow the amp to be
enclosed into a 1.5 in. nominal PVC pipe for wx proofing and remote
mounting, a must for good e-field pickup from the short 1-meter ant rod.
But as Eric noted, the original used a FET that requires a heat sink
(fabricated from flashing) to dissipate the heat likely from the 24V
supply.

Several on this list have built the original version from posts I've
seen. But another popular active ant from the 80s was that by Ralph
Burhans, also a LF'r, who died a few years ago. His work was in early
The LOWDOWN news letters. I found a three part series on his
experimentation of e-field amps in Radio And Television News of March
and April 1987. I built the one for LF using a J-310 FET and coupled to
the feed line by an audio xfmr. I'm still looking for that amp as the
wife cleaned up one day and it became one of the "missing." She was
properly "put on notice."  ;-)

Hope to find it for coming season and make comparison to my usual rx
loops.

Peter