Cruisers & Sailing Forums - View Single Post - Long-Distance WiFi Device

s/v Jedi · 20-03-2009, 10:04

A directional antenna is much better than omni directional even if it has just the same gain. The reason is that you improve the SNR (signal to noise ratio). The omni directional will receive everything around you, 360 degrees. If you limit your angle to say 60 degrees, you eliminate lots of noise which has the same effect as increasing gain. Look at your driver software: many drivers/utils show SNR or link-quality in addition to signal strength and see the improvement (other than gain) of a directional yourself.

We use a $50 Hyperlink Technologies yagi for outdoors use which has a 60 degree angle and 8 or 9 dB gain. We also have an 8 dB omni directional, also from Hyperlink Technologies. The yagi will improve the received signal strength 10-20% but it also improves our SNR 40-50% !! If you are at anchor and your swing is more than 60 degrees, you're in trouble (we switch to omni directional antenna). But in many places, like Caribbean, the wind is from the same direction 90% of the time and the yagi works just great. In many cases, I can take our wifi amplifier off with the yagi while I need it in the same location with the omni.

We even saw boats using those follow-me rotators like used for sat-dishes.

Cheers,
Nick.

20-03-2009, 10:04	#56
s/v Jedi Registered User Join Date: Feb 2009 Boat: Sundeer 64 - Jedi Posts: 1,520	A directional antenna is much better than omni directional even if it has just the same gain. The reason is that you improve the SNR (signal to noise ratio). The omni directional will receive everything around you, 360 degrees. If you limit your angle to say 60 degrees, you eliminate lots of noise which has the same effect as increasing gain. Look at your driver software: many drivers/utils show SNR or link-quality in addition to signal strength and see the improvement (other than gain) of a directional yourself. We use a $50 Hyperlink Technologies yagi for outdoors use which has a 60 degree angle and 8 or 9 dB gain. We also have an 8 dB omni directional, also from Hyperlink Technologies. The yagi will improve the received signal strength 10-20% but it also improves our SNR 40-50% !! If you are at anchor and your swing is more than 60 degrees, you're in trouble (we switch to omni directional antenna). But in many places, like Caribbean, the wind is from the same direction 90% of the time and the yagi works just great. In many cases, I can take our wifi amplifier off with the yagi while I need it in the same location with the omni. We even saw boats using those follow-me rotators like used for sat-dishes. Cheers, Nick.