Re: LF: active ant on metallic mast

[Gary - G4WGT <g4wgt@tiscali.co.uk>]

Roelof & All,

Just for your information I am using a PA0RDT Mini-Whip antenna for my grabbers, it is connected to 2 receivers via a passive 50 ohm splitter. The antenna size is 30 x 45 mm on the PCB. You can see my results at

http://myweb.tiscali.co.uk/wgtaylor/grabber2.html

The Mini-Whip is at about 9 metres high on a 1 metre PVC stand off arm attached to my main steel mast. The mast is 90mm diameter & the coax from the Mini-Whip runs along the stand off arm & down the side of the mast with my other coax cables from 3 other antennas & the rotator control cable.

The Mini-Whip coax is grounded at the base of the mast as is the mast itself. It seems to work very well. I have not compared the results with running the coax away from the mast straight down from the active antenna, could be a test I could carry out next time I have to work on the antennas.

73,  Gary - G4WGT.

On 7 February 2010 10:11, Roelof Bakker <roelof@ndb.demon.nl> wrote:

Hello Alan,

Thank you for the hands up.
Years ago an old hand told me that it made a lot of difference with the coax inside or outside the mast.
But I don't know if the mast was grounded at the bottom, up on the roof or what else.
So it is time to get a proper metalic mast and do some tests.

Besides my SLM's, I now have a PERSEUS SDR for two years, which is not only an excellent receiver, but also a rather sophisticated piece of test gear. It has level meter, whith a 0.1 dB resolution, which is not a toy but accurate to 0.1 dB for relative measurements. The bandwidth can be set to 5 Hz if you like, which allows level measurements down to -143 dBm. And a 40 MHz spectrum analyzer with the noisefloor at -110 dBm, which is great in tracking down wide band noise, off air antenna tests etc.

73,
Roelof, pa0rdt