My Spider gets complicated


#1

I don’t know how will this antenna works when its UP.
http://i734.photobucket.com/albums/ww341/revadan/IMG_2522.jpg
http://i734.photobucket.com/albums/ww341/revadan/IMG_2524.jpghttp://i734.photobucket.com/albums/ww341/revadan/IMG_2526.jpghttp://i734.photobucket.com/albums/ww341/revadan/IMG_2528.jpg

#adsb


#2

ars longa vita brevis :wink:


#3

Give it a try. I am hopeful it will work better than standard SO239 Spider due to enlarged horizontal groundplane.
Nice & neat built! Very crafty. Looks like a flower.

Please see this thread for testing of a similar Spider by planefider forum member TomW:

Click here: Planefinder Forums - Side by side antenna testing

http://forum.planefinder.net/attachments/2015-06-13-08-10-18-jpg.2186/


#4

A little solder on that center conductor and you’re going to be good-to-go :mrgreen:


#5

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. :slight_smile:


#6

@blueskyspotter:

From where you got all this special hardware?
(1) The SO-239 flange has holes for 8 screws. Normally it is manufactured with holes for 4 screws.

(2) The copper petals are not cut from a copper sheet, as these have screw terminals for slanting radial. It looks to be from some heavy duty electrical wiring terminal. Am I right?


#7

Congratulations! This is as I expected.

TomW also got improved results by enlarging horizontal part of groundplane (1"x1" Flange of SO239) by adding a copper washer of larger diameter, as shown in the photo I posted in my previous post.


#8

Got the so-239 from China :slight_smile: 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.


#9

Super. Well, looks like it’s time to make another antenna. :slight_smile: Only change will be to use an N connector.


#10

After seeing photos of blueskyspotter’s Spider, I feel ashamed on the poor workmanship :frowning: 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.


#11

Time to visit Lowe’s… :slight_smile:


#12

Have to wait :frowning:


#13

Really? What about home depot…


#14

Just curious why brass over copper?
Isn’t copper more conductive?

Very nice design I like it!


#15

I’m guessing with the recent changes you haven’t been able to determine whether there has been a real performance increase (or decrease). Any updates?


#16

What is the optimal size for the horizontal ground plane on a spider?

I’m looking to make a few changes to one of my feeders and a better antenna is always a good idea!


#17

Here is a good post to look at.

ads-b-flight-tracking-f21/built-my-first-antenna-and-doubled-my-coverage-t19517.html


#18

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.

Edit note: had a couple of numbers switched.


#19

This antenna is a work of art. Not that it might be any more effective that the soldered 8 leg spider, but I hid mine in the attic out of view (where it works very well it seems).

A couple of questions.

Does anyone think that maybe using solid copper wire (12 gauge) might be equal to the brass rod?

Can you provide measurements of length of brass rod prior to bending?

Thankfully an antenna designed to receive isn’t as critical as one for transmission.


#20

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.