Transcript Stealth Antennas

Stealth Antennas
David Treharne
N8HKU
March 10, 2005
Introduction
• Most Hams
want a large
antenna
• Most don’t get
one.
5-band-10/12/15/17/20 Meters, 11
Elements.
Price: $1159.95
Why Not?
• Cost: Antennas and towers are quite
expensive.
• Zoning: Restrictive covenants make it
difficult and expensive to put up a large
antenna array
• Space: Many homes/condos/apartments do
not have the space
• Spouse: Beauty is in the eye of the beholder
Solution: Stealth Antennas
• It turns out that an
antenna does not have
to be BIG to work
• It does not have to be
outside to work
• It does not have to be
high powered to work
• It does not have to be
permanent to work
What is Needed
• An attic, a porch, a deck, a flagpole, or even
a ceiling
• A tuner
• A good set of speakers or headphones
• Patience
• An occasional contest
The N8HKU Condo
• No outside
antennas
• Antennas covering
10m-80m, 144, 440
MHz
The Condo Antenna Farm
• SPI-RO trap dipole for
10-20M
• Isotron combo
antennas for 40M and
80M
• Cushcraft Ringo
Ranger 2m/70cm
Vertical
Getting the Antennas in the Space
Trap dipole
across the attic,
bent to “see”
Europe
Need to trim them to resonance
Metal can interfere with them
Resonance
of Dipole
after
Trimming
No tuner needed for
20m. Other bands
can be tuned,
including WARC
bands of 12M and
17M.
Other Antennas
• Isotron antennas
needed significant
trimming, and still
need tuning.
• Ringo Ranger had
horrible transmission
to the Tin Lizzy until I
moved it 1 ft over,
now great reception
Power
• May not be a good idea to run full power
– Interference potential with home electronics
• Issue with home stereo
– RF Exposure needs to be analyzed for both yourself and
for others in the house or in the adjoining units
• I performed a full analysis
– RF can get into your equipment
• Keyboard acts up on 10m
• Needed to add an isolation choke between my radio and
computer to keep RF out of the speaker system
Where have I worked?
• United States
– 40M/80M is within 1,000
miles only due to near
vertical sky bounce
– Oregon/Washington tough
• ROW:
– Russia, South America,
U.K, Germany, Israel,
Australia, Finland, Italy,
Croatia, Spain, Netherlands,
Japan
• All of that on SSB
– Contests help: late in
contest, all the Big Guns
have been worked, and the
operators listen better for
the weaker signals
• Many countries worked on
RTTY or PSK 31 as well.
– Can use less power
– Signals are stronger
– Less atmospheric
interference
Resources
•
•
ARRLWeb: Putting Up Your First Antenna Simple antennas for HF and
VHF -- and simple instructions for putting them up!
http://www.arrl.org/tis/info/antbegin.html 2002-02-05, 8498 bytes
ARRLWeb: Limited Space and Indoor Antennas
– techniques for building and using limited-space and indoor antennas.
http://www.arrl.org/tis/info/limited.html
•
The Care and Feeding of a Condo Antenna Farm
– The Care and Feeding of a Condo Antenna Farm 64 April 2001 In By Al
Alvareztorres, AA1DO
•
ARRLWeb: Antenna - Indoor
– techniques for building and using limited-space and indoor antennas.
http://www.arrl.org/tis/info/antind.html