~~BOOKMARKME:on~~

uYagi

The u stands for either μ or ugly :)

During geekcon08, Dror Gil asked for help building a UHF power amplifier so he could transmit old-time Israeli TV-shows from his DVD to a portable TV. I suggested not using a power amplifier at all, but just connect an antenna to the DVD RF output jack, which was rated at about 10mW output power.
The first attempt was made by connecting a single wire radiator to the RF jack:

vertical radiator

connected to the DVD's RF out port
length calculated using L=λ/4

This antenna worked quite well for close distances, a bit better than not using any radiator at all. We could receive good video and audio to a range of about one meter.
I suggested replacing the antenna with a Yagi antenna. This kind of antenna is directional, and “focuses” most of its energy at a single direction. I built it quick-n`-dirty style, and it ended up like this: This worked surprisingly well, we were able to transmit old-time TV shows across the room! Here is a short video taken by Dror demonstrating this achievement:

Statue Antenna

During geekcon I also erected a portable amateur radio station. It used a vertical antenna by using a radiator made of brass cut to a certain length for 2m communications. The supporting metal statue was acting as a ground plane. I achieved an SWR a little less of 1:2, and made a QSO using the Jerusalem repeater with Ronen, 4Z5AB. I operated the station with an IC-208H.