Avoid This!!
HF Field Antennas
There is one law of physics that is unavoidable - Small Antennas have Small Signals !! (unless you're a dish). That's unfortunate, as high-dipoles and yagis are rather inconvenient for field work. That is what drove our search for something that is easy to put up and still works well.
Mag loops and low power are going to team up to ensure that no-one hears you when you call out. You will be buried below their noise-level. And hamstick dipoles and buddi-poles are convenient, but are either loaded or helically-wound, decreasing their efficiency. And if mounted horizontally, you still have to get them up high to work acceptably. A hamstick-dipole at 15-feet is going to disappoint. We have done many A/B switching tests in the field, and have verified this sub-par performance.
A full-sized dipole is the first choice if you can get it up to at least 0.5 W/L high. Below that, much of the power will be radiated more vertically than horizontally. 0.7 W/L high is better, and 1.0 W/L is optimum. 0.5 W/L gives you a 31-degree radiation takeoff-angle, 0.7 W/L gives 20-degrees, and 1.0 W/L is 14-degrees. (5-15 degrees is best for long-range work).
Here are the 0.5 W/L heights for the various phone-bands: 75m/136', 40m/68', 20m/35', 17m/27', 15m/23', 12m/20', 10m/17'. The heights for 0.7 W/L are: 75m/HaHa!!, 40m/95', 20m/48', 17m/38', 15m/32', 12m/28', 10m/24'. For 1.0 W/L, just double the 0.5-numbers. (492/mHz is used for the height-calculation, not 468).
From those numbers, it's obvious that other options are needed. A 1/4-wave vertical with elevated-radials (aka a Ground-Plane Antenna) is a really good choice, for several reasons. First, it has a low takeoff-angle, typically 20-degrees or lower (depending on height of the radials). Second, it is easy to erect (no really tall supports are needed). Third, the coax-run is much shorter. And the best part: it's a full-size antenna!!
The elevated radials eliminate most of the ground-losses that come with ground-mounted verticals, and just two elevated radials are the equivalent of 32 ground-mounted radials, and produce an omni-directional pattern. If you can get the radials up to 16-feet high, the takeoff-angle is a low 16-degrees!! Most of our mast-mounted installs have the radials at 10-13 feet high.
The 3 elements (the vertical radiator and both radials) are typically 1/4 W/L long, and the vertical-element can be either wire, a whip, or a combination wire & whip. Obviously, a non-metallic mast or a tall tree is needed). Start with the driven-element at 1/4 W/L and the radials slightly longer. Trim the radials (only) equally for resonance.
This is a very efficient radiator, and we have been impressed with the performance we've gotten with it, especially on 40m and 20m. On 40m, you have to get a dipole up to at least 70-feet high to outperform it !!
VHF/UHF Field Antennas
If you need a V/U antenna in the field, don't waste your time with a J-pole. They have no gain, and the radiation-pattern is not omni-directional !! Instead, use a great dual-band whip like the MFJ-1412, and get yourself some performance. It has the same gain as a Diamond X30 base antenna. Only $28 at GigaParts (half the price of the exact-equivalent Diamond 770). Very rugged (with a phasing-coil instead of a fragile loading-coil), and quite handsome-looking. Comes in black or chrome, with a versatile UHF-mount. I tune mine to perfection by removing 3/8" from the bottom of the whip - but they are quite good right out of the box. Lots of easy options for the ground-plane here on the site.