Clandestine Antennas for Amateur Radio

Clandestine Antennas for Amateur Radio
0 to 100 in 18 Months by AE6RR Clandestine Antennas for Amateur Radio By Craig Bradley, AE6RR “BY PROHIAS” -••• -•-- •--• •-• --- •••• •• •- ••• NCDXC June 08 AE6RR – Clandestine Antennas NCDXC, June 21, 2007

AE6RR – Clandestine Antennas
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 NCDXC June 08 AE6RR – Clandestine Antennas

This Presentation Clandestine vs. Stealth antennas What makes an antenna work Multiband antennas Possible locations How well do they work? RFI QRO Reference Material NCDXC June 08 AE6RR – Clandestine Antennas

Clandestine vs. Stealth Antennas
What is the difference? NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – 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 NCDXC June 08 AE6RR – Clandestine Antennas

What Makes Antennas Work?
Get the RF in the Air NCDXC June 08 AE6RR – Clandestine Antennas

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” NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – Clandestine Antennas

Bent Antenna Example Conventional wisdom says that you can’t bend an antenna back on it's self SteppIR does not agree… NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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 … NCDXC June 08 AE6RR – Clandestine Antennas

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) NCDXC June 08 AE6RR – Clandestine Antennas

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” NCDXC June 08 AE6RR – Clandestine Antennas

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) Type of line SWR at Load SWR at Input Total Line Loss RG-8X 19.91 5.24 6.0 dB Beldon 9913 20.33 10.01 3.043 dB 450-Ohm 2.47 2.41 0.137 dB 450-Ohm w/ 20 Ohm load 20.25 16.46 0.934 dB NCDXC June 08 AE6RR – Clandestine 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… NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – Clandestine Antennas

Want to get on more than one band?
Multiband Antennas Want to get on more than one band? NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

Types of Multiband Antennas
Trapped Verticals We already talked about verticals Horizontal Balanced Wire Antennas Fan or parallel dipoles Trapped dipoles Doublets G5RVs NCDXC June 08 AE6RR – Clandestine Antennas

Time to use your imagination
Possible Locations Time to use your imagination NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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! NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine 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 NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

How Well Do They Work? Results & Limitations NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

Antenna View from Front of House
End of G5RV Jr. VHF/UHF/1.2 GHz Whip Bend Point NCDXC June 08 AE6RR – Clandestine Antennas

Back End of G5RV Jr. Antenna Wire Tie Cord NCDXC June 08 AE6RR – Clandestine Antennas

G5RV Jr. Antenna Scan NCDXC June 08 AE6RR – Clandestine Antennas

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) NCDXC June 08 AE6RR – Clandestine Antennas

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… NCDXC June 08 AE6RR – Clandestine Antennas

The WAE Award How to “Work All Electronics” in your house
RFI The WAE Award How to “Work All Electronics” in your house NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

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 NCDXC June 08 AE6RR – Clandestine Antennas

Haven’t had enough RFI? Not for the faint at heart!
QRO? Haven’t had enough RFI? Not for the faint at heart! NCDXC June 08 AE6RR – Clandestine Antennas

If You Must QRO – Be Prepared
Solve your 100W problems first You may actually destroy some electronics My DOA 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 NCDXC June 08 AE6RR – Clandestine Antennas

Good reading and useful antenna information
Reference Material Good reading and useful antenna information NCDXC June 08 AE6RR – 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 Antenna Book Edited by Dean Straw, N6BV NCDXC June 08 AE6RR – Clandestine Antennas

Good Luck & Good DX de AE6RR NCDXC June 08 AE6RR – Clandestine Antennas

Clandestine Antennas for Amateur Radio

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