A few weeks ago, I've bought via ebay a military whip antenna for a few euros. The whip is a Racal ANT-129, collapsible in 8 sections, total lenght 260cm circa, and seems rated for 21-30MHz.
The base of the whip is terminated with a M10 screw (10mm metric), is very easy to find a nut for radio connection. I arrange a quick base with a camera tripod and a piece of wood. I've connected the whip with a wire to my Elecraft T-1 tuner using a 5m wire counterpoise. The antenna needs NO tuner for 21 and 28 MHz, (ok, SWR is not 1:1, but may be acceptable) and with tuner loads in 20, 17 and 12 meters. No way to use this antenna in 7MHz and less. The foto below shows me (left) and Nico "The President" IZ8KTL (right) near antenna, tuner and FT-817 in /P. Many nice QSO with european hams. (TNX to Carmine IK8GYQ for photo)
I've built a more stable support for my whip, I'll show it soon! Stay tuned.