Likes & Dislikes:
1000+ QSOs
Likes:
- Wire length is not critical.
- 'Ground Image' makes the loop
functionally double in size.
- Tunes up with ease.
-
Static and
lightning protection.
- Not visible to the neighbors.
- Works DX 160m - 20m
- Quiet
receive
- Very low maintenance
- Cheap to build.
- Not particularly directional
Dislikes:
- Relative low efficiency.
- Not useful for DX above 20m.
Summary:
- This is a fun and very useful
antenna for a suburban size lot. It works with no fuss and
no mess.
Grounded Loop Antenna
The grounded loop antenna (non-resonant, unbalanced), works well on the HF Bands and is relatively quiet. On 160m it acts much like a vertical with a counterpoise. On higher bands it seems to radiate like a vertical and somewhat less like a traditional vertical loop. It is oriented in the east to west plain. I like to think of it as a FAT vertical.
Various and sundry radials provide for an extended counterpoise on the ground side of the loop. I have experimented with different configurations of radials. All the radials and return wires are mostly 0' to 4' above actual earth. Three buried 8' ground rods provide for a direct earth connection. Static charges are grounded out with this antenna design.
Inspired by:
The
Novice Antenna Notebook, The Half-Wave Grounded Loop
by Doug DeMaw, W1FB
ARRL 1988 First Edition pg 87 – 88.
Grounded
Loop webpage by G4NSJ
The Half-Delta Loop, A Critical Analysis and Practical Deployment by John S. Belrose, VE2CV and Doug DeMaw, W1FB. ARRL: QST Sept 1982 p28-32
ARRL’s Wire Antenna Classics. The Tilted Half-rombic Antenna by AA2PE, Ch 5 p 5-10.
Antennas Away
from Home, Figure
2 "The
half rhombic..." by
Joel R Hallas W1ZR QST 3-2010 p 45.
Efficient
Ground Systems for Vertical Antennas, by Archibald C. Doty,
jr., K8CFU, John A. Frey W3ESU and Harry J. Mills, K4HU. ARRL:
QST Feb 1982 pg 20 – 25
AM
Elevated Radial Systems Radio
Guide Aug. 06
Theoretical LOOP plots, given approximate dimensions.
Of course these plots do not account for the real world of my
house lot.
This antenna radiates like a single element vertical. The loop is referenced to ground at any and all frequencies. This has an effect on the angle of radiation from the antenna at any given frequency. We are forcing the position of waves created on the loop (at the feed point) to be maximized for current.
The antenna is supported by large fir trees native to the area. A system of pulleys and weights provide tension relief for the thin steel cable wire as the trees sway in the wind..
Basic configuration.
I have
settled on this counterpoise layout
based on EZNEC demo results
and my operating experience.
AA7OK's
Station:
Locator:
CN87wp
Rig: Yaesu FT-950
Interface: SignaLink USB
Software:
HRD/DM780
Winkeyer WKUSB by K1EL
Iambic Key by
www.K8RA.com
TransMatch:
MFJ
Feed: Short/ High Quality Coax
This illustration draws the comparison between a ground mounted vertical (Marconi) and the ground mounted loop. In both cases the "earth image" of the above ground vertical elements, complete the antenna electrically. The grounded loop is a ground image antenna. It is always a half loop with the other half an Earth Image. The term grounded half loop would be an accurate descriptor. This antenna is inherently unbalanced like a ground mounted vertical or an elevated vertical with a counterpoise.
< The 3D EZNEC plot at 1.8Mhz (given my approx.. 80m loop). This plot illustrates the familiar vertical radiation pattern.
Member: ARRL
Certifications: Extra Class
& FCC
Commercial
Some College Degrees and Certs.
Info: QRZ.com
KB6AEC
(8/23/83), KG7EN (5/29/90), AA7OK (9-21-03)
I am also using an AV-640 Vertical by hy-gain for 40m - 6m. It is mounted 11.5' or 3.4 meters above ground.
The AV-640 is an RF 3/8 wave radiator. Using EZNEC it can be determined that 10 to 13 feet is a good height for the upper HF Bands. 15m is my favorate. The RF seems to be good for my garden. I have a large city garden.
Buddy was one of the world's greatest dogs and was my friend. He was frequently featured on my ATV transmissions.
HF Radio Propagation Conditions:
http://www.ips.gov.au/HF_Systems/6/6/1
Hourly Area
Prediction charts for your area.
HAP charts