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Clandestine Antennas for Amateur Radio. By Craig Bradley, AE6RR. “BY PROHIAS”. -••• -•--    •--• •-• --- •••• •• •- •••. Background. First licensed as WV6SVW & WA6SVW 1961 to 1967 No antenna restrictions (except parents) Life was good Relicensed in 2004 as AE6RR

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clandestine antennas for amateur radio

Clandestine Antennasfor Amateur Radio

By

Craig Bradley, AE6RR

“BY PROHIAS”

-••• -•--    •--• •-• --- •••• •• •- •••

AE6RR – Clandestine Antennas

background
Background
  • First licensed as WV6SVW & WA6SVW
    • 1961 to 1967
    • No antenna restrictions (except parents)
    • Life was good
  • Relicensed in 2004 as AE6RR
    • Main residence had minimal lot lines and CC&Rs
    • Vacation home in Truckee had CC&Rs but a large lot with some tall pine trees
    • Antenna prospects did not look good
    • XYL thought that I had lost my marbles
      • I was climbing up in the attic, on the roof, staring at trees

AE6RR – Clandestine Antennas

this presentation
This Presentation
  • Clandestine vs. Stealth antennas
  • What makes an antenna work
  • Multiband antennas
  • Possible locations
  • How well do they work?
  • RFI
  • QRO
  • Reference Material

AE6RR – Clandestine Antennas

clandestine vs stealth antennas

Clandestine vs. Stealth Antennas

What is the difference?

AE6RR – Clandestine Antennas

stealth antennas
Stealth Antennas
  • There have been many talks, books and articles on Stealth Antennas
  • They are “Hard to See”
  • Construction varies
    • Thin wire antennas in plain view
    • Towers and beams painted in camouflage colors
  • Scheme is to blend with the background and minimize visual impact
  • The antenna concepts in this talk can also be used to construct Stealth Antennas and others

AE6RR – Clandestine Antennas

clandestine antennas
Clandestine Antennas
  • Clandestine means “Hidden”
    • Should not be visible to someone that may be looking for it
    • May be hidden in plain sight (looks like something else)
      • Flag pole, rain gutter, fence, etc.
    • May be hidden in or on a structure
      • On top of roof
      • Attic, indoors, shed, etc.
    • If you have CC&Rs
      • Clandestine antennas will not need to be explained
      • Stealth antennas may be discovered
    • Once discovered, you will be a suspect
      • Increased surveillance may result

AE6RR – Clandestine Antennas

what makes antennas work

What Makes Antennas Work?

Get the RF in the Air

AE6RR – Clandestine Antennas

some antenna basics
Some Antenna Basics
  • Most of the RF is radiated from the high current portions of the antenna
  • The highest current is where the impedance is the lowest
    • At the feed point
  • The lowest current is where the impedance is the highest
    • At the end points
    • The ends have the highest voltage
  • The end points don’t radiate much RF
    • They do contribute to the tuning of the antenna
    • They act as “capacity hats”

AE6RR – Clandestine Antennas

bent antennas
Bent Antennas
  • If you don’t have space for an antenna why not bend the ends around?
    • You can get a lower frequency antenna in a much shorter space
    • The ends don’t radiate much RF so it doesn’t matter where there are pointed
    • The ends do have high voltage present so be sure to insulate them well

AE6RR – Clandestine Antennas

bent antenna example
Bent Antenna Example
  • Conventional wisdom says that you can’t bend an antenna back on it's self
  • SteppIR does not agree…

AE6RR – Clandestine Antennas

antenna tuners
Antenna Tuners
  • Antenna Tuner is a misnomer
    • It does not “tune” the antenna
    • It is an impedance matching device
  • Modern transceivers and amplifiers are designed to match a 50 ohm load
    • If the antenna is not 50 ohms you will have a miss-match (high SWR)
    • Most solid state transceivers will start to limit the output power if the SWR is higher than 2:1
  • A tuner will make your antenna “look like” 50 ohms to your radio
    • You will get full power out

AE6RR – Clandestine Antennas

a word on swr
A Word on SWR
  • The Voltage Standing Wave Ratio (or just SWR) is the ratio of the maximum and minimum voltages on the transmission line
  • It is caused by the interaction of the forward and reflected voltages on the line
  • If your antenna and transmission line impedance matches your transceiver output impedance there will be no reflections
  • If the impedances do not match there will be reflections on the line
  • SWR is not a measure of how well an antenna radiates
    • Dummy loads have an SWR of 1:1 …

AE6RR – Clandestine Antennas

reflected power
Reflected Power
  • Gooch’s Paradox “RF Gotta Go Somewhere”
    • Stealth Amateur Radio by Kleinschmidt
  • It will “bounce” back and forth on the transmission line until it goes somewhere
  • It can be radiated as RF by the antenna (good)
  • It can be radiated as heat by the transmission line (bad)
  • It can be radiated from your station “ground” (bad)
  • It can be radiated from your microphone (burned lips)
  • It can go into your home electronics (bad)
  • It can go back into your transceiver and cause it to limit output power or cause heating or damage (bad)

AE6RR – Clandestine Antennas

a word on transmission lines
A Word on Transmission Lines
  • Transmission lines have losses
    • Usually rated as dB per 100 ft with an SWR of 1:1
    • The losses are much higher at high SWRs
  • Reducing Loss
    • Place the antenna tuner as close to the antenna as possible (lowest loss)
    • Use balanced line between the tuner and the antenna
    • Use low loss coax to feed the antenna (LMR-400 or 9913)
  • If you don’t lose power in the coax you have a better chance if it “getting out”

AE6RR – Clandestine Antennas

transmission line loss
Transmission Line Loss

The following table is for 100 ft of transmission line with an antenna impedance of 1000 Ohms non-reactive at 14 MHz (Source TLW program by N6BV)

AE6RR – Clandestine Antennas

unbalanced antennas
Unbalanced Antennas
  • Verticals or Long Wires
  • Require radials (more stuff to hide) or a good ground (hard to do)
  • May result in “RF in the shack” with bad grounds
  • May “stick up in the air” – harder to hide
  • You can “tune” the ground system but now you have created a balanced antenna…

AE6RR – Clandestine Antennas

balanced antennas
Balanced Antennas
  • Dipoles, Doublets, G5RVs, Loops etc.
  • No ground or radials required
  • Less chance of “RF in the shack”
  • Simple low cost construction - usually wire
  • Can be bent around to fit the space
  • Keep most of the radiation at the antenna

AE6RR – Clandestine Antennas

loaded antennas
Loaded Antennas
  • Loading coils can physically shorten an antenna
  • Highest current is between the feed point and the coil and the lowest current is after the coil
  • Maximum radiation will be from the portion between the feed point and the coil
    • Maximize the length of this part
  • Loaded antennas are more complicated to tune
    • Nearby objects will interact
  • If you want to get on 80M, you may need to consider a loaded antenna if space is limited
    • RFI noise may be a big problem here

AE6RR – Clandestine Antennas

loop antennas
Loop Antennas
  • Loop antennas can fit in many places
  • Outdoors may be hard to support it and keep it concealed
  • Indoor horizontal loops can run around the top of your room or around the attic
  • Small loops can be vertical and indoors
  • There are several companies that sell loops and many construction articles
  • You may need a special loop tuner
  • Many Hams have had good results with them

AE6RR – Clandestine Antennas

multiband antennas

Multiband Antennas

Want to get on more than one band?

AE6RR – Clandestine Antennas

required equipment
Required Equipment
  • If you want to operate on multiple bands with a simple antenna you will need an external Antenna Tuner
    • Most internal tuners will only match an SWR of 3:1 or less
    • You will need a good external tuner
    • Auto Tuner preferred
  • You can easily get a simple antenna such as a dipole to resonate on a single frequency
    • With a tuner, it will load on many bands (higher frequency)
  • Multiband antennas
    • Can be complex
    • Are very difficult to get working close to other metal objects
    • Clandestine antennas will likely be near many unknown objects
    • Will probably have a high SWR on some bands

AE6RR – Clandestine Antennas

types of multiband antennas
Types of Multiband Antennas
  • Trapped Verticals
    • We already talked about verticals
  • Horizontal Balanced Wire Antennas
    • Fan or parallel dipoles
    • Trapped dipoles
    • Doublets
    • G5RVs

AE6RR – Clandestine Antennas

possible locations

Possible Locations

Time to use your imagination

AE6RR – Clandestine Antennas

indoors
Indoors
  • Can be done but should be your last choice
    • Limited space will require very compact antennas
    • Loops and bent wire antennas for the higher bands may be possible
    • Small current loop antennas may be usable
  • RFI will be a problem (Transmit & Receive)
  • RF exposure to you and your family will be higher
    • QRP may be required
  • The XYL may not consider your creation “decorative”
    • You won’t see indoor antennas on HGTV or in home decorating magazines

AE6RR – Clandestine Antennas

attic
Attic
  • If you have an attic that you can get into this may be a good possibility
  • Large attics can offer many opportunities
  • You may be able put a small beam in a large attic
  • You don’t have to worry about the effects of weather
  • Attics may contain HVAC ducts and wiring that can affect the performance of your antenna
  • RFI is a consideration
  • Be careful not to step through the sheet rock!

AE6RR – Clandestine Antennas

in the yard
In The Yard
  • Verticals can be hidden in trees
    • You will have to deal with the radial/ground problems
    • Vertical dipoles may be possible in higher trees
    • Flag pole and bird feeder antennas may be possible
  • Thin wire between trees or from a tree to the house may work
    • Thin wire is easy to break and you may have to replace it often
  • You may be able to string wire along the top of a fence
    • An antenna this low will probably be good for NVIS not DX though

AE6RR – Clandestine Antennas

on the house
On the House
  • Rain gutters have been used by some
    • You will have to bond all of the sections together
    • Corroded connections can generate harmonics and RFI problems
    • This system will probably be unbalanced
  • You could run a wire around the house under the eves
    • May not be very effective on a stucco house

AE6RR – Clandestine Antennas

tv antennas
TV Antennas
  • A TV antenna could be used as a vertical
    • The TV lead-in (300 ohm line) could be part of the antenna
    • The actual TV antenna is a capacity hat
  • FCC regulations state that HOAs must allow TV antennas
  • You could use a log periodic for VHF/UHF
    • 6M, 2M, 220, 440 and 1.2 GHz
    • It looks like a TV antenna and will receive TV signals

AE6RR – Clandestine Antennas

on the roof
On The Roof
  • A wire antenna is very hard to see from the ground if it is low to the roof
    • This is the highest location on the house
    • This location has the least RF obstructions
  • Two story houses are even better
    • The antenna is higher and harder to see from the ground
  • You can build a very good dipole or multiband doublet on the roof
    • By bending the ends you should be able to cover 40 through 6 M
    • Use chimneys, vent pipes and other existing items on your roof for supports

AE6RR – Clandestine Antennas

how well do they work

How Well Do They Work?

Results & Limitations

AE6RR – Clandestine Antennas

what worked and not
What Worked and Not
  • 20 M Ham Stick Dipole in the attic
    • My first try
    • I couldn’t hear much (weak signals and lots of RFI)
  • 20 M Wire Dipole on the roof
    • Worked great (good SWR and DX)
    • Single band though
  • Parallel Dipoles on the roof
    • Only would load up on lowest band
    • Tried a couple with no good results
    • More wire on the roof for people to see

AE6RR – Clandestine Antennas

back to basics
Back to Basics
  • Next I went back to the 20 M Dipole and added an auto tuner
    • Worked on 20 – 10M
    • More than one band finally
    • But what about 40M?
  • Tried a 40M Dipole with bent ends and the tuner
    • Worked good on 40 and 15M
    • Not so good on 20M but it would load

AE6RR – Clandestine Antennas

my bent antenna
My Bent Antenna
  • Finally tried a G5RV Jr.
    • Half size G5RV (51 ft.)
    • 16 ft. 450 ohm ladder line
    • Balun to 50 ft of 9913 coax
    • Auto tuner
  • The last 6 to 8 ft of each end is bent at about a right angle to the main portion of the antenna
  • This antenna works on 40 through 6 meters and fits in less than 40 linear feet
    • 15M is the worst band but it does work
  • I have been using this antenna for over 3 years

AE6RR – Clandestine Antennas

antenna view from front of house
Antenna View from Front of House

End of G5RV Jr.

VHF/UHF/1.2 GHz Whip

Bend Point

AE6RR – Clandestine Antennas

back end of g5rv jr
Back End of G5RV Jr.

Antenna Wire

Tie Cord

AE6RR – Clandestine Antennas

g5rv jr antenna scan
G5RV Jr. Antenna Scan

AE6RR – Clandestine Antennas

dx results
DX Results
  • Worked – 2004 to Present (a few were with other wire or mobile antennas)
    • 162 Entities
    • 370 Band/Entities
    • 36 CQ Zones
  • Best DX with G5RV Jr.
    • Scarborough Reef - BS7H (20M CW)
    • Andaman Is. - VU4AN/VU3SIG (20M SSB)
    • Chalogos - VQ9JC (20M CW)
    • Peter I - 3Y0X (40M SSB)
    • St. Brandon - 3B7C (20M CW)

AE6RR – Clandestine Antennas

relative performance
Relative Performance
  • You will be a Little Pistol Station
    • You will not hear all of the stations that the Big Guns hear
    • You will hear a lot of RFI
    • If you wait for the best propagation, you have a chance
    • CW and PSK-31 will help
    • When conditions are good, you will hear a lot of DX
    • Sunspots help…

AE6RR – Clandestine Antennas

slide39

RFI

The WAE Award

How to “Work All Electronics” in your house

AE6RR – Clandestine Antennas

receiving rfi
Receiving RFI
  • You will hear most of the electronics in your house
    • TV sets
    • Computer networks, routers, etc.
    • Switching type wall warts
    • Battery chargers
  • Ferrites may help on some devices
  • In a pinch you may need to turn things off to work that “rare one”
    • Identify the culprits ahead of time

AE6RR – Clandestine Antennas

transmitted rfi
Transmitted RFI
  • Worst RFI receivers
    • Phones, cordless and regular, answering machines
      • 5 GHz cordless phones seem to be better
    • Home Theater amplifiers, stereos, etc
      • Rear channel speaker leads are great antennas
    • X10 Power Line controllers
    • Paper shredders
    • Burglar alarms
    • Sprinkler controllers
  • Check Jim Brown, K9YC’s material on ferrites and applications
    • Filters and ferrites may help
  • QRP (PSK-31 and CW) may be solutions

AE6RR – Clandestine Antennas

slide42

QRO?

Haven’t had enough RFI?

Not for the faint at heart!

AE6RR – Clandestine Antennas

if you must qro be prepared
If You Must QRO – Be Prepared
  • Solve your 100W problems first
  • You may actually destroy some electronics
  • My DOA list @ 1300 W
    • One answering machine ($50)
    • One Ethernet interface for LaserJet Printer ($300)
    • Max power is now 600 W
  • Burglar Alarm
    • Bell would ring at power levels over 300W
    • Solved by a .01uF capacitor
  • Seriously consider RF exposure levels!
    • Limit duty cycle

AE6RR – Clandestine Antennas

reference material

Reference Material

Good reading and useful antenna information

AE6RR – Clandestine Antennas

some good books on stealth clandestine antennas
Some Good Books on Stealth/Clandestine Antennas
  • Stealth Amateur Radio
    • By Kirk Kleinschmidt, NT0Z
    • ARRL Publications
  • Low Profile Amateur Radio
    • By Al Brogdon, W1AB
    • ARRL Publications
  • ARRL Antenna Book
    • Edited by Dean Straw, N6BV

AE6RR – Clandestine Antennas

good luck good dx

Good Luck & Good DX

de AE6RR

AE6RR – Clandestine Antennas

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