This is a simple, compact, and easy to build 2m/70cm Delta Loop antenna, easy to transport (it is just wire and a connector) and for attaching to a window or in tree branches. The loop consists of a copper wire, ca. 0.8mm diameter, of 210 cm length. The ends are connected to an antenna connector, in my case a PL connector for a 50 Ohm coax antenna cable. It can be fine tune using the area of the resulting loop.
I found an inverted Delta Loop works on both bands, if the upper edges of it are about 30cm apart, which makes it a narrow loop. Hence you can simply attach 2 suction cups at the upper part of a window, and hang the loop wire over them, for the inverted delta loop, as shown in the picture. I also attach a .nec file for the xnec2c open source antenna simulation software, and the resulting simulated antenna radiation pattern. I found the antenna is doing a decent job. It is worthwhile to experiment with different placements, because this can make a difference of one to two S units (or 6-12 dB), as usual at these frequencies. And finding a good position is much easier with this small antenna than with a larger Yagi antenna. This also means that finding a good position can give as much gain as a Yagi antenna.
Many greetings, 73, Gerald, DL5BBN
Nec files for the antenna simulation:
2m/70cm Delta Loop
2m band radiation pattern
70cm band radiation pattern