I`m a beginner, do not have extensive radio knowledge or equipment. I have been trying to build spiders using just a cable and then also advised connectors etc… but my reception is very poor compared to totally random find on my window.
our windows have metal angles when they finish drywalls to keep nice shape. I have found that when I put my strongly modified original antenna which came with the DVB-T dongles I get impressive results.
I would like to replicate this in my attic or maybe even adapt this phenomenon for my 1090MHz setup.
Would you know why is this setup gaining such a great result?
I will try replicate the window setup an cut piece of metal in 55cm ( for 1090 ) and 61.3cm ( for 978 ) and will place the wip DIY antennas in the middle of that metal strip.( to replicate the Window setup )
and will see if it performs the same as in the window
The most likely issue with the spider is an issue with the coax or connectors, check for pins being present when there is a hole on the matching connector and check that you don’t have shielding mesh shorting to the center.
You could check the radials vs the whip for resistance with a multimeter.
If there is a short between the whip and the radials you have found your issue.
As well there should be no resistance between the whip and the coax.
@jaymot @Slipstream232
Even if whip or radials are few mm off the correct length, it wont make the Spider so bad as it is performing now. Sure it is something else.
As @wiedehopf rightly pointed out, one possibility is that there is a short between shield and core which will show as short between whip and radial if tested by a multitester. The other possibility is that core is open somewhere so whip is not connected to Dongle. This may be due to a defective connector or using RP-SMA instead of SMA
I think the problem is the poor soldering job. I don’t think solder is needed on the radials for a 4-radial spider (which is actually a 1/4 wave ground plane): the screws should be enough to hold them on. But definitely redo the one that holds the whip in place. It’s probably not making electrical contact with the center conductor of the coax. The solder should ideally flow down inside the hole that the whip’s been stuck into to form a good electrical bond.
(I should talk. I’m a crappy solderer these days. I used to be very good when I was younger but I have vision problems and kind of shaky hands. Too much coffee every day, methinks.)
If you can find some flux paste you can apply some to the connections before soldering to get the solder to flow better. Just make sure not to get the acid flux used by plumbers, get the kind meant for electronics.
Also see Three Easy DIY Antennas for Beginners - #2 by abcd567 for an example of what it should look like. (Note that the instructions give measurements for 1090MHz not 978MHz.) Rereading the page I just linked to it clearly says “no soldering.” So get your solder-sucker or solder wick out and remove that stuff and see if it works afterward.
I have deployed 2 quick spiders per recommendation for 1090 and 978 and they work great. Reached 700 msgs/sec.
I`m running Raspberry pi 2 zero with Bullseye and it works great, CPU is at 15%.
The only issue I have is with 978Mhz, the reception oscillates from 0 to ~40msgs/sec not sure if it is normal behavior or some power related issues ( using OTG cable ) on my end.
