Hi windowwasher,i use a modular from the now defunct Emporium.
The first 5 sections have all broken so i now use an ordinary brush stale.The new gooseneck is pushed onto this stale(the diameter is slightly larger so fits nicely)i put a screw through this for a secure fit.I bought an alloy adapter with a threaded end fron cleantech and this fits into the brush end of the gooseneck.Then i use a plastic adaptor, screwed onto the exposed thread (this gives me any adjustment i need because the TV aerial is fixed at 45 degrees)
I had to make this concoction for a specific job that i do which you can see on my website.It is a tall building with deep sills and i needed lightness and reach.
I hope this all make sense.
PS i found the old aerial in a skip ages ago and found the purfect use for it.
PPs the brush stale is cable tied and then duct taped to the top section(No 6)