My 24hr reported position of the old #12 wire spider is between 40-45k. With this new antenna 30k has been achieved in just 6hrs run. Looks like its working fine. Lets see how this antenna perform on daytime busy traffic.
Got the so-239 from China and all the rest from local Lowe’s.
Drilled another 4 holes to the 239, the element holders are Terminal Lugs from electrical section of lowe’s.
The element is a 3ft 1/8 dia brass round, again from lowe’s.
After seeing photos of blueskyspotter’s Spider, I feel ashamed on the poor workmanship of my “Easy Spider”, made of a F-barrel connector, a nut, a tiny washer, and core wire (18 AWG) of RG6 coax.
After seeing the success of TomW’s & blueskyspotter’s Spiders with enlarged horizontal groundplane, I have decided to replace the tiny washer by a large washer. The F-barrel connector does not have a Flange, and has almost zero horizontal groundplane.
I have done some searching for that answer too. There is some empirical data in the side by side antenna comparison link from abcd’s comment above. The size of the copper disks were 2.5" [63.5mm] which compared favorably to abcd’s soda cantenna base of 66mm. Those numbers are close to the quarter wave at 1090MHz. Is that the answer? I don’t know. It’s my understanding that the angle of the ground plane wires (influenced presumably by any added horizontal ground plane disk) is a change in the antenna’s impedance. At 45 degrees, the impedance is ~50 ohms. Ground planes parallel to the center element (vertical in our case) have an impedance of ~70 ohms and when perpendicular (horizontal, in our case) ~20 ohms. I’ll bet very few of our antennas do a good job at impedance matching down the line so there may be some serendipitous impedance matching going. This answer is not terribly satisfying to me since a horizontal plane would theoretically move the impedance toward 20, not 70. The angle of the ground plane also influences the antenna pattern (sensitivity in our passive antenna case). This effect could either be a positive or negative depending upon the air traffic near you. There’s likely many here with more antenna knowledge than I; maybe abcd can share some insight.
Copper and brass will behave very similarly at the same diameter with thicker wire resonating at a lower frequency. The ground plane, if I remember correctly, can be as long as you want. With mine I had more luck adjusting angle to get performance than length. Receive only antenna design is just as critical as transmitting antenna design, with less danger due to minuscule power and voltage differentials.