Marshall Cross, W1HK, Bob Glorioso, W1IS, Bob Rose, KC1DSQ
Introduction
As authors of several antenna articles in QST1,2,3, presentations at ARRL NE Expo and publishing a book on wire antennas4, we often get questions from hams on their antenna problems. We also got a few from those who moved to homes with HOAs on how they can get on the air. The first question we ask is, “Do you have a large attic with few wires or no metal ductwork?” If they have a small or low attic or close wires and ductwork, there is a lower probability of installing a successful attic antenna without a great deal of experimentation. Thus, we decided to delve into alternate ways to get on the air with a stealth antenna over, on, or in the ground. Fortunately, one of our local ham friends, W1HK, had done a great deal of consulting for the “government” on these antennas so we asked him to join us.
Background
In the early 1900s, J.H. Rogers5 discovered that near-earth, on-surface and buried horizontal insulated wires could radiate and receive radio signals as shown below in his 1919 U.S. Patent. During the cold war the United States6,7,8, several of its allies9 and the Soviet Union10 conducted significant research and constructed thousands of buried antennas at command bunkers, missile silos and underground radio relay sites. Hundreds of technical reports and two major textbooks were written. The USAF even developed a set of “how-to” handbooks11,12 exploiting the two major features of buried antennas: their “hardness” to conventional or nuclear attacks and their visual covertness.
In the HF band, burial has three major effects on dipole antennas made from insulated wire: 1) it reduces the velocity of propagation along the dipole, the wavelength is shortened typically by a factor of 2 to 5. 2) the radiation pattern somewhat modified as compared to an above ground dipole in that it excites a strong vertically polarized ground wave signal off its ends. A resonant half wave dipole, buried a few feet in average soil is about 1/3rd the length of an above ground resonant dipole.
In 1969, the USAF’s Rome Air Development Center (RADC) made extensive measurements of buried dipoles and compared their performance with conventional above ground whip and dipole radiation properties using an aircraft13. They compared the measured values with calculations and concluded that the electrical and radiation characteristics followed classical electromagnetic theory.
To further explore the properties of buried antennas the reader is directed to a more recent text-book, “Antennas in Matter10.”
Design
There are a few on or in ground antennas mentioned in ham literature but most notable are the “Grasswire Antenna” by K3MT14, who explored End Fed and Off-Center-Fed designs and a more theoretical treatment by Silberstein, W0YBF16.
Expanding on this work we designed this antenna to work a few inches above, on, or a few inches below the ground while covering the HF bands, 80 to 10 Meters, Figure 1.
Figure 1. Layout – Under, On, or Over Ground Antenna
We chose an Off-Center-Fed configuration to get a good match on 80 meters to 10 meters. Using a Rig Expert and an EZNEC simulation, we found the impedance to be fairly high, 450 Ohms, too high for a 4:1 Balun normally used in an ==Off-Center-Fed antenna up 30 feet or more. But, a 9:1 balun is a perfect fit. Still, a 1:1 balun is needed to keep Common Mode Current on the feedline from radiating, changing the radiation pattern and detuning the antenna. The combination of a 9:1 transformer Balun and a 1:1 Choke/Balun is called a Hybrid Balun.
Simulations were done on EZNEC Pro2 for 80 meters with the antenna 0.16 ft, 2 inches, off the ground in the EZNEC model. The results, Figure 2, show that it looks like a “close-in” NVIS antenna. Most NVIS antennas for 200-to-400 mile communications on 80 meters are 40 to 60 feet high.
As is typical of low antennas, the impedance goes up as the height is decreased and electrical length increases. Simulations, of antennas of several hundred feet in electrical length have complex patterns with many lobes. The results for this antenna depend on height above ground, you get what you get. On the other hand, the unique vertical radiation off the ends does indicate it may be helpful for working DX! (See results below.) Since most of the energy is dissipated in the ground, the voltages at the ends are typical of a QRP rig and are not harmful to people or pets.
Figure 2. EZNEC Pro2 Simulation 2” above ground on 80 meters.
Putting an antenna near, on, or under the ground makes it resistive/lossy so radiation efficiency is very low, 1 to 5%, converting your 100-watt transceiver into a QRP rig. But, it is better than no antenna at all and it actually gets out. This antenna will work a few inches above, on, or a few inches below the ground.
Construction
The wire, #14 Flex Weave from Davis RF or THHN from a hardware store is cut to deliver 30 feet and 70 feet of radiating wire between the insulators and a 9:1 UNUN, Balun Designs 9130sw. A 1:1 UNUN built as descrived in ref 4 or Balun Designs 1110d is connected to the 9:1 UNUN with a dual PL-259 connector. Figure 3. Since the UNUNs will be near, on, or in the ground, it is important to seal cracks or holes around connectors to keep the insides dry.
Figure 3. Antenna, 9:1 UNUN Coupled to 1:1 UNUN, and Coax Feedline
In our tests the antenna was stretched through the woods behind the W1IS QTH, 25 miles west of Boston, placed as close to the ground as possible despite the poison ivy.
To bury the antenna and coax in a yard, use a lawn edger to cut a slit through the turf and stuff the wire and coax into the slit. Close the turf and mark where the wire is because the grass will soon cover the hole. Do the same for the two UNUNs by lifting some turf and placing the UNUNs under the turf. Do the same for the coax run to the shack. A sweep of the SWR across the bands, Figure 4, shows that it has low SWR and can be easily tuned from 80 to 10 meters. This is expected because of the high loss in this antenna. Thus, a tuner with only a 3:1 SWR range can easily tune it on all bands.
Figure 4. SWR Sweep 80 through 10 meters.
The Proof is in the Results
Casual operating with 100 watts to the antenna for 16 days in April yielded the following contacts. A daily afternoon net on 60m SSB with stations from Maine to Southern New Jersey. CW QSOs on 40, 20, 17, 15 and 10 meters in 12 Countries and 4 Continents. Yes, Virginia, it really does work!
References:
1. Robert Glorioso, W1IS and Robert Rose, KC1DSQ “An All-Band 160-Meter OCF Antenna,” First place winner in the 160-meter LF or VLF Category of the 2024 QST Antenna Design Competition. Cover Plaque Winner
2. Robert Glorioso, W1IS and Robert Rose, KC1DSQ “A Portable 2 Element 40- Meter Wire Beam”, QST March 2022. Cover Plaque Winner
3. Robert Glorioso, W1IS and Robert Rose, “Portable 20-meter phased dipole beam” QST February 2022. Cover Plaque Winner
4. Robert Glorioso, W1IS and Robert Rose, KC1DSQ, Book “Wire Antennas 160 meters to 70 cm: Concepts, Construction and On the Air. 2nd edition” OCFMasters.com, and Amazon, 2025
5. J. Rogers, Radiosignalling System, USP 1,303,730, May, 1919.
6. R. Moore and W. Blair, Dipole Radiation in a Conducting Half-Space, J. Res. Nat. Bur. Stand. Vol. 65D, #6, Nov/Dec, 1961.
7. A. Banos, Dipole Radiation in the Presence of a Conducting Half-Space, Oxford, Pergamon Press, 1966.
8. W. Blair, Experimental Verification of Dipole Radiation in a Conducting Half-Space, IEEE trans. A&P, vol. AP-11, #3, May, 1963.
9. R. Mussett, Analysis of Buried Antennae, Rep. # EWP (P) (68) 2, British MOD, 1968.
10. G. Lavrov, Near-Earth and Buried Antennas, Sovetskoye Radio, 1965
11. A. Guy and G. Hasserjian, Design Criteria for Buried Antennas, D2-7760, Boeing Aircraft Co., Jan, 1961.
12. B. Gilchrist, Antenna Engineering Design Handbook for Buried Linear Arrays, RADC Contract F30602-85-C-0282, Apr, 1988.
13. J. Entzminger, Measured Performance of HF Subsurface Dipoles, RADC-TR-69-221, Jun, 1969.
14. R. King and G. Smith, Antennas in Matter, MIT Press, 1981.
15. The Graswire, K3MT http://f5ad.free.fr/Liens_coupes_ANT/G/K3MT%20Antenne%20gazon.htm
16. Richard Silberstein, W0YBF, “Subsurface Antennas and the Amateur” The ARRL Antenna Compendium #1, 1985
