So shortly after my last post here I got a OmniX now I know it says Tuned: 118-137, 148-175 & 225-900 MHz but I didn't think it would so bad in the 142mhz range. I listen to this system a lot https://www.radioreference.com/apps/db/?sid=2560 now the digital channels work nice but the analog ones are full of static which I didn't have before with the ST-2. Almost thinking of refurbing my ST-2 and putting it back up on the roof.
Antennas can be rather application specific in there operation, but the ST-2 is a difficult antenna to beat on average.
I build clones specifically peaked, targeted for certain frequency ranges as needed. There is not any magic to a well designed and implemented antenna.
A friend of mine said to me once, an antenna is just some pieces of aluminum, how much difference can there be...
There are some fine working antennas available from what I read, but it has been so long since I have purchased a commercial scanner antenna that I can't offer any first hand experience.
How long has it been since you stopped using your ST-2 and began using the OmniX? Is it possible (even remotely) that another RFI / EMI noise source has appeared in that time.... even something you inadvertently created such as by installing a noisy LED light bulb, noisy AC adapter / switching power supply / "wall wart"? Or something that has appeared in your vicinity as a new source of RFI, e.g. leaky CATV system, noisy electrical pole, neighbor got new washing machine (yep... there's another thread on how washing machines can be major sources of scanner interference).
The Omni-x are three dipoles in parallell. The elements seems to be tuned to 125MHz, 155MHz and 400MHz. It should also work at 3 times the tuned frequency.