AA7OK
Updated: 4-13-2014AV-640 Work

 

 

 




Likes & Dislikes:
1000+ QSOs

Likes:
-  Wire length  & shape is not critical.
-  'Ground Image' makes the loop functionally larger.
-   Tunes up with ease.
-   Static and lightning protection.

-   Not visible to the neighbors.
-   Works DX
      -  As Grounded Loop 160m & 80m
      -  As Inverted U, 40m to 10m

-   Very low maintenance
-   Cheap to build.
-    50 Ohm match on 80m & 40m: Grounded Loop

 Dislikes:
-  Maybe lower efficiency in the Grounded Loop configuration.
-  Less useful for DX above 80m... unless used as an inverted U 
-  Noise like any vertical
-  Tuning/Matching unit is required for the Grounded Loop config. at 160m and above 40m and when used as an Inverted U.

Summary:
-  This is a fun and very useful antenna for a suburban size lot.  It works with no fuss and no mess.

About 11/22/2013 My original Grounded Loop antenna came down in a wind storm.  On 3/2/2014: I have a new loop up and running but some refinements need to be done, as weather permits.  Pictured is the new configuration.  This antenna can be quickly configured as a Grounded Loop or Inverted U, with different radiation patterns given the configuration. 

Grounded Loop Antenna
with an option for configuration as an Inverted U.

The grounded loop antenna (non-resonant, unbalanced), works well on the HF Bands . On 160m & 80m 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. Four 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.

Notes on the Modified Half-Loop       L. B. Cebik, W4RNL

Grounded Loop webpage by G4NSJ

Grounded Loop webpage by OK1DQT

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-rhombic 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

Antenna & Ground Help by SGC

Diamond




In the Grounded Loop configuration, 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.  See the 1.8 and 3.6 MHz radiation plots below.

The antenna is supported by large fir trees native to the area.   As the trees sway in the wind, a system of pulleys and weights provide tension relief for the solid copperweld wire.

One can lift the far end from ground and operate the antenna as an inverted U.   The given dimensions allow the inverted U to radiate similar to a half square on 7.1 MHz.  See the 7.1 to 28.1 MHz radiation plots below.






 

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.

3d loop 80m

< The 3D EZNEC plot at 3.6 Mhz. This plot illustrates the familiar vertical radiation pattern.



  All plots calculated above 'real ground'        
Grounded Loop Plots:
Above 7.1 MHz the Plots are not as useful as the Inverted U Configurations as seen below
1.8 gnded Loop 3.6 gnded Loop

Basic configuration.

 Here is an idealized sketch with a raised counterpoise

Basic idealized configuration

Actual configuration.

The loop presently in use.  Dimensions are given above.  Note the raised ground system.

sketchup
 

         
Inverted U Plots:
Below 7.1 MHz the Plots are not as productive as the grounded loop configuration above.
7.1 U 14.1 U 21.1 28.1  
           


 

Wes

Member: American Radio Relay League

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)

 

 


 

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EPC 16921

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AV-640 40m to 6m


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.. The RF seems to be good for my garden.  I have a large city garden.

 
DXCC


AA7OK's Station:

FT-950

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

LoTW, QRZ & EQSL Pse.

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 Forecast

HF Radio Propagation Conditions:
http://www.ips.gov.au/HF_Systems/6/6/1
Hourly Area Prediction charts for your area.
HAP charts

 

House

A near scale representation of my antenna.


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