[BC] RPU antennae

[Mark Humphrey]

On Sun, Nov 28, 2010 at 12:02 PM, Tom Spencer <Radiofreetom at gmail.com> wrote:

> 11m HF RPU would be roughly the same as the infamous CB antennas - and a 1/4 wave whip is ~108".  And I wasn't thinking in terms of a loop antenna, but verticals.  a 5/8 wave ground plane base antenna is about 20 - 25 ft tall, IIRC.
>
> I did mention using a beam antenna at the base / studio, as well, and did acknowledge that such an install would be extra.
>

I like the idea of using a Moxon Rectangle for a receive antenna.  At 26 MHz, this would measure 13.6 by 5 ft.and provide about 3 dBd of gain -- but with a cardioid pattern, you would need a rotator or multiple antennas mounted on opposite sides of the tower.

I used four Moxons (one on each side of the building) to feed a 161 MHz RPU receiver at One Liberty Place in Philadelphia. They're placed a few inches behind the window glass on the 61st floor (where WRNB's transmitter is housed) and need to be manually switched depending on the sector of the remote broadcast, but they're very compact, and the high front/back ratio helps to suppress RF noise coming from elevator machinery in the core of the building.   I'm not aware of any commercial products of this type, so I built them from copper plumbing pipe and elbows and used short pieces of fiberglass rod as insulators.  In an indoor environment, PVC pipe works well for the support. 

You can find links to Moxon information here:
http://www.dxzone.com/catalog/Antennas/Moxon/

I'm working on a prototype of a CP crossed-Moxon for the FM band which might prove useful in some translator installations.

Mark