so ive been running a little rubber duck on my FT-70D around the house just to get a feel for the local repeaters and honestly its been fine for close stuff but theres a couple machines about 35 miles out i really want to hit reliably and i know im leaving a lot on the table with what i have now

been looking at base antennas and keep coming back to the comet GP-9 and the diamond X510N, both seem well regarded but theres like a 40-50 dollar spread depending on where you look and im trying to figure out if thats meaningful or just brand loyalty stuff. the GP-9 is rated 9.7dBd on 70cm if i remember right and the X510 is something like 8.5, but ive heard those numbers from the manufacturers arent always... honest

also my mounting situation is a bit awkward, i have a chimney bracket from an old TV antenna install and the mast is only 1.25 inch OD so i need something that'll clamp to that without a bunch of adapters. anyone dealt with that? and does it matter much where on the roof i put this thing or is higher always just better

had a GP-9 for about 6 years before a storm took it out, replaced it with an X510 and honestly couldnt tell a meaningful difference day to day. both hit my local repeaters fine out to about 40 miles with 50w. the gain specs from comet and diamond are both a little optimistic but its not like theyre lying by 3dB or anything crazy, just typical marketing rounding. either one will be a massive step up from what you have now

on the chimney mount question, the GP-9 clamps down to 1.25 inch no problem, thats a pretty standard size. higher is generally better yeah, but you also want line of sight toward whatever repeaters youre trying to hit, so if your roof has a ridge in the way that actually matters more than raw height sometimes

i went through this same thing last spring and just ended up ordering the X510 because someone local had one and let me compare it side by side with a cheap comet dual bander they had up. the diamond just felt more solidly built when i had it in my hands, the radials locked in better. no idea if that translates to RF performance but i havent had to touch it since i put it up and we had some pretty gnarly wind this winter so thats something