8 element beam on Rohn 25g

[tunercars]

I'm looking to put an eight element beam on top of a 150 ft Rohn 25g Tower And possibly put a colossal 10K antenna on a sidearm at 100 ft What I want to know is is that too much weight for the tower The rotor is going to be at the bottom of the Tower so it's easy to work on the tower is going to be guyed every 30 ft

 

[Quiksilver]

I believe wind load would be more a factor than static weight. Here's some info for your reading enjoyment:
Rohn 25Ga
Rohn25Gb
Wind load ref

 

[nomadradio]

If your plan includes ground-wave, you may find that you're too high. Had a customer who fancied talking ground wave. Good thing, since this was during a sunspot minimum. Hiked is 4-element quad up from 80 feet to 120. Found that he picked up a handful of stations that had been outside his range, but lost a few of them that were closer. Ended up dropping back down to 80 feet and picked up those closer stations like before.

As for skip, once you're a full wavelength or two above ground the difference gets kinda small going higher.

73

 

[Crawdad]

Looking at an Elevation plot for an 11m 3 element Yagi @ 80ft Above Ground Level


And then the same @ 120ft AGL

The Take-off angle of the strongest lobe dropped a mere 2 degrees (from 6 to 4) by raising to 120ft from 80ft. Unless the extra height would help to clear nearby obstructions, it doesn't seem worth the extra effort and expense. The Law of Diminishing Returns kicking in.

 

[BC Coyote]

As for skip, once you're a full wavelength or two above ground the difference gets kinda small going higher.

I experimented with this years ago. If you are only interested in talking DX, there is no point in putting an antenna more than ONE wavelength high. There is absolutely nothing to be gained by going higher UNLESS you are doing it to clear solid obstructions such as a building or hillside which might block the antenna's view of the horizon.

Trees blocking signal don't seem to be much of an issue in the real world at all.......in fact at my current QTH I have two antennas, an A-99 at 40 feet to the base, and a horizontal delta loop at 35 feet AGL. There are massive 150 foot fir and cedar trees all around them, yet I can still talk DX no problem at all, even at barefoot power levels with the amp off!

And, no, I can't put antennas in the top of the 150 foot trees due to the fact that I live on a remote island with 360 degree exposure and we get hurricane force winds several times a winter. Anything up in the tops of the trees gets shredded in short order!