View Full Version : SLH Antennas
rconaway
12-25-2008, 11:04 PM
Has anyone used an SLH (Stub Load Helix) antenna? I was just talking to a buddy in India and they are going to deploy them. One company that sells them is Turbowave, inc. I'm really curious how they compare to a simple vertical polarity high-gain antenna and how they would work with the bullets.
"how they compare to a simple vertical polarity high-gain antenna"
They aren't the stubby VPOL omni antennas you see on UHF walkie-talkies, they are merely compact circular polarized directional antennas.
Considering they are only right hand polarization...how will the opposite side work?
rconaway
12-26-2008, 10:54 AM
I have done a bunch of reading but am not sure how it works talking to a laptop versus SLH antenna to SLH antenna.
panamasteve
12-26-2008, 11:23 AM
CP antennas have their uses, but for "outside-in" applications they suffer greatly by apparently having the circularity reversed(chirality?) after passing through windows, reflecting off walls, etc. Also, keep in mind that there is inherent 3dB lower gain (for same number of elements) in a CP antenna which means a linear-polarized antenna with 10 dB gain will be half the size of a CP antenna with the same gain. That said after constructing hundreds of CP antennas for a WISP. The linear polarized antennas also change polarization, but it does not seem to affect the "outside-in" scenario as much. My .02 worth based on my experience. YMMV
rconaway
12-26-2008, 12:32 PM
Thank you for that. So are you saying that the primary use for an SLJ antenna is point-to-point and that a vertical antenna will work better with a laptop?
Yup....its nothing more than a compact directional CPOL
http://www.physorg.com/news5600.html
http://antenna.ece.vt.edu/product/SLH.pdf
http://www.wp-wireless.com/pdfs/WPANTCPB.pdf
It does not have any of the alleged omni or isotropic advantages of the WiFi Plus antenna.
http://forum.ubnt.com/forum/viewtopic.php?t=7022&highlight=
