Are these antennas any good for around 100 watts transmitting power.
Band 2 Antenna RFS Type 828HP FM Broadcast

One for sale on E Bay £99

I think that is one of those circular polarisation jobs. Yes that should easily take 100 - it is rated at 30Kw.
http://www.rfsworld.com/websearchecat/d ... ?q=828HP-6
It looks like they are designed to be used in arrays.

It'll work, but not very well. These things are designed to be stacked. One on it's own will be 3dB down on a simple (properly matched) dipole! You're just going to be wasting power.

You really should be using something like a J-pole - easy to build and match, and (generally) does better than a dipole. It also doesn't look like a pirate aerial. Also consider the "flowerpot" aerial (look them up - they're very good). You can make a J-pole for <£10

Thank You for your replies, I wondered if they should be stacked for the big boys. it was if it would be a waste of time to use on its own with just 100w, and the answer is yes. thank for Albert H and Bton-FM

circular antena under 1000w is practical useless... minimum of minimum is 500w!