[978MHz] - help needed with DIY antenna

Also it looks like this one is shorted to the base of the coax connector, though I don’t know if it matters.

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.