Low Band Receiving Antenna                Comparisons

How I  compare Rx antennas.   It would definitely be up for debate as to how to compare low band receiving antennas at any given location. There are many factors involved such as available real estate, complexity, cost, portability, front to back ratio, and arguably the one that is most important to me, something W8JI calls RDF (relative directivity factor). RDF is the difference between the  maximum forward gain in the direction of interest and the average gain in all directions of an antenna.  Thanks to W7EL and his EZNEC program it is relatively easy to compare different configurations of antennas for their RDF. In my case I don't care how much real estate it takes for antennas as I live in farming country with at least 100 acres around me. I do have to take the antennas down in the spring because the fields are actively used for farming. I don't care too much about front to back ratio as there are not a lot of loud stations at my location  that I cannot separate with  20 db front to back. I am blessed to have an electronics shop as well as a welding/machine shop so cost of fabrication is not near as much a factor as it might be for some. So mostly I have found that it boils down to RDF and how can I get more while making it somewhat portable. I have found that my antennas when working properly do indeed perform with a signal to noise ratio that follows the comparison chart below. Tom W8JI makes similar comments on his outstanding website.


Comparison Chart of Different Rx antennas.    Gain, front to back, and RDF computed at 20 degrees elevation over average ground and at 1.850 Mhz. Because of the same elevation angle for all antennas, some will not appear as they would at maximum gain.

This site is protected against hot linking due to abuse so if you have trouble downloading the Eznec files by direct click contact k7tjr at arrl.net 

   Download Eznec file         Azimuth plot                       








90 ft. top loaded TX vertical 1.4 dBi 4.9

N/A Omni-directional

        360 degrees
K9AY loop -25.6 dBi 7.2 11.5 dB.         163 degrees
4 square of K9AY loops -22.2 dBi 9.1 18.9 dB.         58 degrees
10 Foot Dia. tuned loop 2.2dBi 4.0 6.8dB  F/Side Bi-directional         105 degrees
Flag -29.7dBi 7.4 22.8dB         146 degrees
Beverage 1000 Ft. -6.4dBi 12.3 31dB         63 degrees
Beverage pair 1000 ft.  400 ft. space -2.9dBi 14.6 40 dB         35 degrees
Beverage 910 Ft. -5.3dBi 11.9 15 dB         64 degrees
Beverage 500 Ft. -10.6dBi 9.0 23.9 dB         80 degrees
4 square Tx antenna 6.8dBi 10.7 25.5dB         99 degrees
Bsef Hiz vert array70x320 ------amplified 12.9 28.8dB         51 degrees
Inverted vee 120 ft. -1.08dBi .6 N/A omni         360 degrees
2 element hiz 50ft space -----amplified 9.0 35dB         137 degrees
TJR 8 element 200 ft circle Hi Z -----amplified 13.45 44dB         53 degrees

TJR 4 element of 8  200ft circle Hi Z 

-----amplified 10.8 19.7dB         80 degrees
330 ft circle 4 active of 8 Hi Z -----amplified 12.3 20.8dB         54 degrees
Beverage 300 Ft. -14.5dBi 6.5 9.9dB         89 degrees
Waller Flag -54dBi 12.2 32dB         84 degrees
Bsef=broadside end fire                

Link to K7TJR 8 Element Receiving Array   uses Hi impedance amplifiers and shortened verticals.

See  www.hizantennas.com  for parts and supplies for Hi-Z antennas  

 Animated 2 element array comparison.  Two Hi-z elements spaced 1/8 wavelength with varying phase delay.


 There are many pages on the web describing the K9AY loop. More discussion of it here is not necessary. With the exception that my observation is many people build this antenna and fiddle with the termination resistor to try for the ultimate. Some even make them remote control. My tests show that changing the termination from 330 ohms to 550 ohms only varies the RDF by .11 out of 7.2. Hardly worth ever worrying about for copying any DX unless you need the Front to back rejection for local noise.

      Larry W7IUV has a rather complete description on how to build the Flag antenna . The only comment I have about that antenna is that it seems really ground independent for those with really poor grounds and it is rotate able with great front to back for notching interference. Combine that with 7.4 RDF and it seems better than a K9AY.

     Jose Carlos has a complete discussion of his Waller flag antenna at   N4IS    to me the jury is still out on this one as it has such low output and I wonder about noise figure. Guess I will have to build one.

Tom W8JI has lots of coverage on Beverages on www.w8ji.com