Clandestine Antennas for Amateur Radio

1. Clandestine Antennasfor Amateur Radio By Craig Bradley, AE6RR “BY PROHIAS” -••• -•--    •--• •-• --- •••• •• •- ••• AE6RR – Clandestine Antennas

2. 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

3. 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

4. Clandestine vs. Stealth Antennas What is the difference? AE6RR – Clandestine Antennas

5. 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

6. 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

7. What Makes Antennas Work? Get the RF in the Air AE6RR – Clandestine Antennas

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. Multiband Antennas Want to get on more than one band? AE6RR – Clandestine Antennas

21. 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

22. 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

23. Possible Locations Time to use your imagination AE6RR – Clandestine Antennas

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. How Well Do They Work? Results & Limitations AE6RR – Clandestine Antennas

31. 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

32. 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

33. 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

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

35. Back End of G5RV Jr. Antenna Wire Tie Cord AE6RR – Clandestine Antennas

36. G5RV Jr. Antenna Scan AE6RR – Clandestine Antennas

37. 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

38. 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

39. RFI The WAE Award How to “Work All Electronics” in your house AE6RR – Clandestine Antennas

40. 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

41. 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

42. QRO? Haven’t had enough RFI? Not for the faint at heart! AE6RR – Clandestine Antennas

43. 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

44. Reference Material Good reading and useful antenna information AE6RR – Clandestine Antennas

45. 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

46. Good Luck & Good DX de AE6RR AE6RR – Clandestine Antennas