VHF tends to be line of sight, with some exceptions. UHF is more so. Increasing antenna height would increase coverage area, or distance to horizon...
Using a distance to horizon calculation and using an approximate current height of 30 feet would give you just under 7 miles to the visible horizon. Adding another 10 feet is going to give you just under 8 miles to the visible horizon.
If your coverage issues are in that extra mile, then it would be worth it.
Also, if you are blocked by structures, and adding the 10 feet gets you above that, it would help.
If coaxial cable losses are your concern, you likely won't notice it with your ear. While couplings have some measurable loss, and the 10 feet of cable does too, it would be hard to notice without test equipment.
I agree that additional height may help and the extra coax shouldn't be noticeable. Another thing to think about, however, is your mounting. Adding to your chimney mast will also add to the leverage the wind has increasing the stress on the chimney. This may or may not be an issue for you, depending on the age, construction, and just how strong your chimney is (it looks OK, but we can't really tell if there are any existing cracks or the state of the mortar). Be sure to check it out closely prior to adding to your mast. Repeated checks over time is probably a good idea even if you don't extend the mast.
Not really worried about the amount it is heavy duty and antenna is very thin and does not move much and windy weather I had a gp6 on a 15 foot Mast on the same mount and it had no problem and the gp6 is definitely less aerodynamic
I was just wondering if the if the height was worth the extra loss of The Wire I'm not using a barrel connector I'm going to get a wire with an so-239 on one side but from what you're saying it sounds like the extra 10 feet is worth the loss from from the extra wire
Since your gonna replace the entire coax, I would suggest something good like LMR400 or the R.F.Davis equivalent but a little cheaper priced, Bury-Flex. Not sure what type coax you have now but just the coax swap could make a noticeable gain if you are currently running RG58 or 8x type coax. There are lots of coax "loss" charts and calculators on the net where you can see the exact amount of loss from different types of coax. Just be aware all "low loss" coax is not the same.
Looks like your chimney is functional, so getting the antenna up another 10 feet should help reduce soot and heat damage to the antenna.
LMR400 or 9913 could cut your line loss in half, doubling your output power and expanding your range as well. So it might be worth replacing the entire cable with new instead of patching in something.
And I'd have to agree: wind loading on that antenna may pull your chimney down, or in the least cause the mortar to crack and the stack to leak, which can cause a flue fire. Even the best and slimmest of VHF antennas (as from Antenna Experts) is "only" rated to 125 mph, because at that point the wind load on a plain strong fiberglass stick is enough to rip it apart, as well as tear it off whatever mount you can arrange.
On a wind day you may see half that wind--but you've got a long lever arm, and chimney repairs are EXPENSIVE.
Just saying. You may need a kludge--but there are good reasons to just not throw money out on one.