Poor performances with Spider antenna


#1

Hi everyone,
I’m new here and I start tracking plane with an Raspberry and a dvb stick.
I have build a spider antenna but I may have made a mistake because with virtualradarserver I see know between 0 and 6 plane. :confused:
With the original antenna (from the usb stick) I saw between 15 and 30 plane.

I live in a n appartment so I use these things to connect my raspberry to my antenna.
Antenna — CableFlat cableCable to stick

Do you think I use some wrong materiel? :question:
I’ll try tonight without the flat cable just to test and I’ll put pictures of my antenna just in case I made something wrong.

Hope you guys will have some idea to help me improve my installation

Thanks


#2

“Flat” coax can have poor performance at 1090MHz so that is the most likely culprit.


#3

:unamused:
Thanks for your answer.
Do you think a filter and/or an amp like LNA4All would help?
Or do you have an idea to connect the antenna to the rasberry without making holes in the windows or the wall?


#4

It is a tricky problem. You want to avoid cables that have large losses. If you can find a flat cable that has low losses at 1090MHz then that would be best, but I don’t know if they exist. Adding a preamp is not a great solution if you can avoid the cable losses some other way.

In the past I built a wooden spacer that fit between the window and the window frame so I could run a cable through the spacer but keep the window closed.


#5

Try this: Antenna – cable --stick inside the apartment. Check activity.

If you get more hits inside w/o the flat cable it is definitely the flat cable, and it becomes a matter of getting the cable out the window. OBJ suggested a spacer to allow the cable thru. If you do that you can lock the window with either a bolt-on window lock or an appropriate length of wood, dowel or PVC pipe to keep the window from opening.

If you have another antenna to use, try it. That will indicate if the spider is working. They are easy enough to make.

Make sure the connections are ok


#6

Hi,
First I had a problem with Virtualradarserver. It was listening on the port 30106. When I put it back on 30003 the number of plane get back to normal.
So with my new antenna and my flat cable I have approximatively the same result than with the stock antenna.
I tried without the flat cable and my rate msg/s doubled.

I will figure a way to connect my antenna without the flat cable.
The spacer is a good idea but I want to be able to close the windows.
I will work on it tomorrow.

Thanks for your advices.

With the flat cable
http://nsm07.casimages.com/img/2017/06/26//mini_17062611091319655615115348.png
Without
http://nsm07.casimages.com/img/2017/06/26//mini_17062611092019655615115349.png


#7

If you can do a little woodworking, get a small board that fits across the bottom or side of your window (depending on whether it’s vertical or horizontal) on which you can close the window. Drill a hole large enough to fit the cable fitting.
For security purposes you can put a window lock or bar in the window track.


#8

could also look at pre-made purpose built option, company like MFJ has a variety of options for ham radio and other communications users facing same situation…
example. mfjenterprises.com/Product. … d=MFJ-4604
I have some other MFJ items, but have not tried this one out personally - opting for the “hole through wall” solution.