It seems as if anything I do pick up is a combination of different broadcasts
That could be a major clue! There is a problem called intermodulation. It happens when you are too close to a powerful radio transmitter. I ran into a similar problem when connecting a very long simple longwire antenna to my radio. I listened to the garbled broadcasts for long enough to hear them call out the station name. It was a local AM talkshow. The answer was to put a broadcast AM filter between the radio and the antenna. You've got 25 AM stations in the area so its likely some of them might be too close to you.
Of course traveling outside the area works too. But its nice to be able to use your radio in your own home.
Though I'm not currently running that setup any longer (4 dongles for 2 different towers) I did have a setup doing that very thing. I used a small DIY 8-radial ground plane antenna crudely tuned to approximately 780 Mhz and mounted outside 25 feet high. I'm surrounded by high powered radio broadcast towers so I needed to add filters. The setup was antenna --> feed line --> FM Block --> AM Block --> LNA --> 4-way Splitter --> feeds to the dongles --> dongles (4) --> Powered USB Hub --> Active usb extension cable --> PC
Although the LNA is BIAS-T compatible I was never able to get it to work properly through the splitter so I drilled a hole in the metal case and soldered in power leads from a DROK voltage regulator that itself was plugged into the powered usb hub's power socket. This added the benefit of allowing me to vary the amount of boosting.
The antenna was made using 14 gauge house wire on a lid from a plastic jar, secured with solder, hot glue, and silicone.
I've listed the other parts I used below. The usb hub is no longer available from amazon but it's just a standard powered USB 3.0 hub. If using a hub, be careful of how it's powered. I've found it's better to stay with a wall wart style power adapter but your results may differ. I tried 3 different higher powered usb hubs that use the laptop-style power adapters and they ALL introduced a terrible amount of noise to the setup. The usb extension cable was to distance everything from the noisy pc and its power supply. I also added a bunch of ferrite rings to the ends of every usb cable and to the main feed cable end right before the filters. I don't know how much this helped but at the very least it gave me a positive placebo effect from it. :)
https://www.amazon.com/gp/product/B01N6SWUSJ - Feed Line Cable
https://www.amazon.com/gp/product/B01LE9LRPM - FM Block
https://www.amazon.com/gp/product/B01N9SHS7P - AM Block
https://www.amazon.com/gp/product/B07G14Q6XX - LNA
https://www.amazon.com/gp/product/B0077QMDGY - 4-way Splitter
https://www.amazon.com/gp/product/B07JZ2GQJF - Voltage Regulator
https://www.amazon.com/gp/product/B00VK9PRIU - USB 3.0 Hub - Now discontinued.
https://www.amazon.com/gp/product/B0179MXKU8 - USB 3.0 Active Extender Cable
https://www.amazon.com/gp/product/B07CJMQQWX - Ferrite Rings (though when I purchased them they were only $10)
https://www.amazon.com/Broadcast-Reject-Filter-RTL-SDR-Blog/dp/B01N9SHS7P/ref=sr_1_1?crid=ZD1NSKSC2DEY&keywords=am+broadcast+band+filter&qid=1685473152&sprefix=Am+band+fi%2Caps%2C158&sr=8-1 And yes I am only using one for the antenna, apparently when looking at the schematic it is grounded.