#AMRAD Active Antenna Project Page
AMRAD members have been
trying out various receiving antennas. The active E-Field probe has
proven to be simple and effective. An earlier design was tinkered
with to improve its performance. The result is the AMRAD Active LF
Antenna. Several were built up and it has been put on a set of
printed circuit boards. A construction appears in the September, 2001
QST. The amplifier transistor is biased up to as high a current level
as possible to obtain the best performance in an RF dense urban
environment. The result is the heat sink that is made out of a piece
of copper water pipe.
[[!img ActAnt1.jpg align="right" size="" alt="K0BRA Active LF antenna assembly"]]
We have posted some additional construction information to this web page to help in the construction.
ARRL has granted permission to post the QST article here. You may also find the QST article on the ARRL website at http://www.arrl.org/files/file/Technology/tis/info/pdf/0109031.pdf.
To help with gathering parts
for your AMRAD Active Antenna project we have put together two parts
sheets with more detail on the parts and sources. Print these out as
you travel hamfests, local stores, dumpsters and the internet and
check off the parts as you find them. We have included a lot of the
mechanical parts you will need also. We had originally used a
Signal Transformer power transformer since they had confirmed, by
phone, that they would accept orders for single transformers.
Since then they have changed their policy and now require a $50
minimum order. I had an email from Jon Lerner at Mitchell
Electronics saying they would like business from radio amateurs and
were quite willing to sell single units. I ordered one and
tested it. It had almost half the capacitance and looked to be
a good replacement for the Signal unit. After testing it is
concluded that the Mitchell design is better for our use. The
Power Supply Parts list has been updated to now reflect the
transformer from Mitchell.
##[Power Supply Parts](psparts)
We have been getting some questions about the whys and hows of the antenna. We have compiled an
FAQ. You can download it as an Acrobat
[[!img actant.png align="left" size="" alt="K0BRA Active LF Antenna deployed"]]