yeah the radials are almost certainly your culprit there. 4-5 on the ground is basically nothing, you really want at least 16 to start seeing the pattern clean up and even then elevated radials behave differently than buried ones. I ran a GAP Titan for a while and the noise floor was miserable until i got serious about the ground system, put down 32 radials around 15-16 feet each and it transformed the antenna. still noisier than my dipole on receive but the transmit performance was genuinely better for DX at that point. the inverted V isnt giving you great low angle radiation either though, its more of a compromise antenna all around. if you ever get a chance to try a proper dipole flat top at even 50 feet versus a well-built vertical with a decent radial field it gets more interesting. but for most suburban installs the wire just wins on noise alone, thats just the reality