20cm aluminum foil antenna for 10m operation

[David], DL1DN, is an amateur radio enthusiast with a penchant for low power portable (QRP) operations. Recently he was on the move and found the 10m spread was wide open. Not discouraged at having forgotten his antenna, he tinkers with a makeshift one using a 20 cm piece of aluminum foil (see video demonstration under the break). [David] wasn't completely off guard, as he had the charging coil for his 20m portable antenna, but was missing the telescopic whip. He calculated that the length of the whip should be about 20 cm for a 10 m operation and crumples a sheet of aluminum foil the approximate length. He tunes it to length by rolling the tip to shorten the "whip" until he gets minimum SWR.

[David] QRP portable whip antenna schematic [David] describes this style of portable antenna in another video, using a more conventional telescopic whip as the radiating element. The charging coil is constructed from common PVC pipe and insulated wire. Although not necessarily the most efficient antennas, they can do the trick when portability is a major concern. For a different approach, here is a QRP Hackaday.io portable antenna project using a magnetic loop antenna. But for the ultimate in QRP, check out this transmitter we wrote about back in 2013 that only uses voice power to operate.

What unusual items have you used as makeshift antennas? Let us know in the comments below. Thanks to [mister35mm] for submitting this to our advice line.