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wi-fi antenna
I am about to raise the new mizzen mast on my old Van de Stadt ketch
and I have been thinking about some other possible uses for the mast head. Would it make sense to place a wi-fi antenna up there to make better use of the hot spots that may be available in some communities? Any suggestions for other hardware on the mizzen would be appreciated. I am already putting a spare anchor light and VHF antenna, but I know I will think of something else, when it is too late. Tom |
wi-fi antenna
On Tue, 1 Apr 2008 18:16:23 -0700 (PDT), "
wrote: I am about to raise the new mizzen mast on my old Van de Stadt ketch and I have been thinking about some other possible uses for the mast head. Would it make sense to place a wi-fi antenna up there to make better use of the hot spots that may be available in some communities? It makes a lot of sense if you do it right. The potential problem is the long run of cable up the mast which will create a lot of signal loss even with the very best LMR400 cable. The soulution is to use a weatherproof wifi bridge at the masthead which supports Power Over Ethernet (POE) technology. POE allows you to run ethernet cable up the mast instead of coax cable. Two units that I have been successful with on my boat are the Senao 3220-EXT and also the Senao/Engenius EOC-3610S-EXT. http://tinyurl.com/2efrmf and http://tinyurl.com/28qx4n You will also need a high gain, omni-directional antenna and a "Type N to RP-SMA" cable adapter: http://tinyurl.com/38mwak and http://tinyurl.com/2j6p29 Of the two bridges, I prefer the EOC-3610S-EXT because of its somewhat greater power and receive sensitivity. The 3220 is slightly easier to configure however. You will need a source of 110 volt power for the POE adapter, best bet is a small sine wave inverter which can also power your laptop. |
wi-fi antenna
On Wed, 02 Apr 2008 06:41:59 +0000, Larry wrote:
BIG money is being poured into Xohm's WiMax now.... Maybe in 2 or 3 years. Meanwhile WiFi and/or Aircards are the way to go. With the right equipment WiFi is operable up to 3 or 4 miles over water. |
wi-fi antenna
I use a marinized version of: http://www.radiolabs.com/products/wireless/waverv.php
Over water I can 'hit' at 2+ miles |
wi-fi antenna
Amen to all the respondents about how wifi can work, and how long it
will be before the newer technology is available. To shorten the learning curve, while I didn't do this (those here for a while, and those visiting alt.internet.wireless, I think it was, will recall I went through the tortures of the damned to get to where I am today), my equivalent is available in 12V, plug-and-play, from islandtimepc.com. Those interested can see all the installation details, as well, in my photo gallery. Bob Stewart, the owner, who's also, now, sold me the 12V replacement to my rapaciously hungry (over 10A) "laptop", was extremely helpful in assisting my way through the minefields that a senao rep had created for me by selling me something which patently wouldn't work. The end result was essentially what he sells, but I'd already done the 110VAC POE, so didn't replace it. I heartily recommend him, unless you're a geek like me and like tinkering, and would rather recreate the wheel. In the end, I would have been far better served to have bought it there, immediately, and I'd have had more than 2 additional years of use, rather than the first two years of agony (and failure, along with constantly having to defend my time to Lydia, who wanted everything else to be done first - but, now, having internet phone and her own, separate, wifi signal aboard, loves it and forgives me) I did... As to strength and utility, it's now a very rare event that I don't have a usable signal at anchor, anywhere, and frequently can pick up a usable signal under way if I'm near (1-3 miles) shore... L8R Skip Morgan 461 #2 SV Flying Pig KI4MPC See our galleries at www.justpickone.org/skip/gallery ! Follow us at and "Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." - Mark Twain |
wi-fi antenna
"Wayne.B" wrote in message ... The potential problem is the long run of cable up the mast which will create a lot of signal loss even with the very best LMR400 cable. That cable has a loss of about 6 dB/100 ft at WiFi frequencies. A colinear antenna can have gain way in excess of the loss and maintain an isotropic pattern in the horizontal plane. Figure 50' of cable with 3 dB of loss added to a 9 dB gain antenna is a net gain of 6 dB. It could work out quite well. One has to consider the entire system, not just isolated elements. This is a much cheaper and more reliable solution than an active bridge up on the mast head. Glory! |
wi-fi antenna
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wi-fi antenna
On Wed, 2 Apr 2008 09:32:14 -0600, "Bob Crantz"
wrote: This is a much cheaper and more reliable solution than an active bridge up on the mast head. Believe it or not my bridges have been very reliable. I know others who are using similar configurations without any issues. Of course in the event of a nearby lightning strike, all bets are off regardless of bridge location. I already have a 9 db antenna and would not want an extra 3 db of loss in my system if I could avoid it. It can make all the difference on a distant access point. |
wi-fi antenna
"Bob Crantz" wrote in message ... "Wayne.B" wrote in message ... The potential problem is the long run of cable up the mast which will create a lot of signal loss even with the very best LMR400 cable. That cable has a loss of about 6 dB/100 ft at WiFi frequencies. A colinear antenna can have gain way in excess of the loss and maintain an isotropic pattern in the horizontal plane. Figure 50' of cable with 3 dB of loss added to a 9 dB gain antenna is a net gain of 6 dB. It could work out quite well. One has to consider the entire system, not just isolated elements. This is a much cheaper and more reliable solution than an active bridge up on the mast head. Glory! I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard |
wi-fi antenna
"Wilbur Hubbard" wrote in message anews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. This is explained by the theory of images, which in effect doubles the antenna gain toward the horizon. If the antenna is horizontally polarized the radiation pattern become directed more skyward and there is an associated decrease in gain toward the horizon. Wilbur, you have a keen sense of observation. |
wi-fi antenna
I think it would be wise to learn something about 2.4ghz wave propagation
and the Fresnel effect before you make that statement. If you just want a couple of hundred yards range deck mounting is fine but for 2 miles plus you need to be UP. By far the best solution is a waterproof wifi bridge at the masthead connected by Ethernet with POE to a hub. Long range because there is minimal coax loss and a wide Fresnel zone. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Wilbur Hubbard" wrote in message anews.com... "Bob Crantz" wrote in message ... "Wayne.B" wrote in message ... The potential problem is the long run of cable up the mast which will create a lot of signal loss even with the very best LMR400 cable. That cable has a loss of about 6 dB/100 ft at WiFi frequencies. A colinear antenna can have gain way in excess of the loss and maintain an isotropic pattern in the horizontal plane. Figure 50' of cable with 3 dB of loss added to a 9 dB gain antenna is a net gain of 6 dB. It could work out quite well. One has to consider the entire system, not just isolated elements. This is a much cheaper and more reliable solution than an active bridge up on the mast head. Glory! I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard |
wi-fi antenna
"Bob Crantz" wrote in message ... "Wilbur Hubbard" wrote in message anews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. This is explained by the theory of images, which in effect doubles the antenna gain toward the horizon. If the antenna is horizontally polarized the radiation pattern become directed more skyward and there is an associated decrease in gain toward the horizon. Wilbur, you have a keen sense of observation. Thanks. I can't help but be brilliant. From the spec sheet: http://www.radiolabs.com/downloads/WaveRV.pdf vertical beamwidth - 35 degrees horizontal beamwidth - 360 degrees. Wilbur Hubbard |
wi-fi antenna
"Glenn Ashmore" wrote in message ... I think it would be wise to learn something about 2.4ghz wave propagation and the Fresnel effect before you make that statement. If you just want a couple of hundred yards range deck mounting is fine but for 2 miles plus you need to be UP. Bullocks. I happen to know by personal experience that low is better. Even the manufacturer recommends deck top mounting. By far the best solution is a waterproof wifi bridge at the masthead connected by Ethernet with POE to a hub. Long range because there is minimal coax loss and a wide Fresnel zone. Bullocks again. KISS! Keep it simple, stupid. The more complicated it gets the more failure prone it is. What happens to any antenna at the masthead at anchor and even moreso under way? You have wind shaking it around, You have the roll and pitch of the boat swaying it around. You have the heel pointing it in all the wrong directions. You have static electricity going on at the mast head. And watch out for any nearby lightning strike. WIPEOUT! I am a sailor. I've been a sailor most of my life. I know what works and your ideas won't! For lubbers maybe but for sailors, forget all about it. And, BTW. What's with the top-posting? If you can't even learn how to post correctly why is it you think people should take you seriously about anything else? Wilbur Hubbard |
wi-fi antenna
"Glenn Ashmore" wrote in message ... I think it would be wise to learn something about 2.4ghz wave propagation and the Fresnel effect before you make that statement. If you just want a couple of hundred yards range deck mounting is fine but for 2 miles plus you need to be UP. By far the best solution is a waterproof wifi bridge at the masthead connected by Ethernet with POE to a hub. Long range because there is minimal coax loss and a wide Fresnel zone. The pattern of coverage from the antenna is crucial. Something with a high gain might work great when you're a mile or two offshore, but will work horribly when you're in a marina. The pattern from most omnidirectional antenna resembles a 'donut'. The higher the gain the 'wider' the donut will be, but it'll be more compressed vertically. When you compress it this way you become more susceptible to signal loss from wave motion. You're tipping the pattern away from the intended source. I'm no RF-weenie so forgive my use of layman's terms. The other downside to picking up distant signals is picking up TOO MANY distant signals. Being able to grab a signal from a mile offshore is one thing. But using that same setup while in an anchorage that has several wireless networks will result in poorer network throughput. Higher power sucks too, not just for you but for the other networks you're interferring with. After dealing with these issues for two seasons I decided it was a lot less hassle to just get a cellular network data card. I pop the card into the router and it's DONE. No fiddling, no leeching a wifi signal from someone's unsecured network, etc. It "just works". I still have the wifi gear and in the unlikely event I'm in an area not covered I'll certainly use it as a fallback. -Bill Kearney |
wi-fi antenna
On Wed, 2 Apr 2008 15:25:43 -0400, "Glenn Ashmore"
wrote: By far the best solution is a waterproof wifi bridge at the masthead connected by Ethernet with POE to a hub. I thought I said that. :-) I know it works for me. |
wi-fi antenna
On Wed, 2 Apr 2008 15:37:08 -0400, "Wilbur Hubbard"
wrote: "Glenn Ashmore" wrote in message ... I think it would be wise to learn something about 2.4ghz wave propagation and the Fresnel effect before you make that statement. If you just want a couple of hundred yards range deck mounting is fine but for 2 miles plus you need to be UP. Bullocks. I happen to know by personal experience that low is better. Even the manufacturer recommends deck top mounting. All worked out for you he http://www.cisco.com/en/US/products/...ence_list.html |
wi-fi antenna
I use the WaveRV marine antenna. Near metro, etc. areas I can get
adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on the stern rail ... seems to work better there. |
wi-fi antenna
"RichH" wrote in message ... I use the WaveRV marine antenna. Near metro, etc. areas I can get adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on the stern rail ... seems to work better there. Thank you for telling it like it is. Experience under actual sailing conditions trumps armchair bull**** every time. Wilbur Hubbard |
wi-fi antenna
(Eliminating a lot of BS)
Are you sure you are not related to Jax? I am a sailor too. Been sailing for 40 odd years now but I specify and install long distance WIFI links as part of the job I do to pay for my sailing. A bit over 60 systems to date including an island wide network of anchorage hot spots for a pay for use operation in the Caribbean and a private 9.5 mile link between Red Hook, St. Thomas and Little Thatch Island .. I get paid well and I don't get many complaints. I have some idea what I am talking about and, after monitoring a number of your posts, I have concluded that you sir have a mouth in dire need of a good treatment of Preparation H. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com |
wi-fi antenna
An 8or 9db antenna is about the best compromise to get both close in and the
longest possible range on a sailboat. You might go a little higher on a trawler. The cellular cards are great if you are primarily coastal but if you venture down to the Caribbean the WIFI route is by far the most economical. When you get into Cable & Wireless or Carricom territory the roaming fees can eat you a new one even with an international roaming agreement with your carrier. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
wi-fi antenna
On Wed, 2 Apr 2008 13:16:17 -0700 (PDT), RichH
wrote: I use the WaveRV marine antenna. Near metro, etc. areas I can get adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on the stern rail ... seems to work better there. You are height limited by the 15 ft USB cable are you not ? There are obviously situations in a marina where height may be a disadvantage but I've found that the higher the better if you are trying to get above the nearby clutter and achieve some real distance. My record is about 5 miles while actually underway, with the antenna about 30 feet above the water. Last November I was solidly connected for a month to an access point in Nags Head, NC while docked at a marina 3 miles away on Roanoke Island. |
wi-fi antenna
"Glenn Ashmore" wrote in message ... I think it would be wise to learn something about 2.4ghz wave propagation and the Fresnel effect before you make that statement. If you just want a couple of hundred yards range deck mounting is fine but for 2 miles plus you need to be UP. The maximum radius of the first Fresnel zone for 2 miles is 33 feet. So if the tower is at 66 feet, the path is clear. Even if there was a large reflection in the first zone, the maximum phase deviation would be 90 degrees, a phase quadrature signal, which would make the link even more immune to fading and could increase the recieved signal strength as Wilbur has reported. By far the best solution is a waterproof wifi bridge at the masthead connected by Ethernet with POE to a hub. Long range because there is minimal coax loss and a wide Fresnel zone. The Fresnel zone does not become any wider with that mounting installation, it is just that there are less object to protrude into it. The concept of a Fresnel zone is just a crude rule of thumb calculation to prevent multipath. It doesn't take into account antenna beamwidth or any of the physical properties of the in-path scatterers. It's great for determining cell phone tower sites but is completely meaningless for actually estimating what signals arrive at the antenna. You can place a vertical aligned metal grid directly in the path of a horizontally polarized signal and see virtually no effect yet the Fresnel rule of thumb would say otherwise. The Fresnel rule of thumb sees no difference between vegetation and buildings, it provides no insight into wave propagation at all. -- Glenn Ashmore |
wi-fi antenna
In article s.com,
"Wilbur Hubbard" wrote: "RichH" wrote in message ... I use the WaveRV marine antenna. Near metro, etc. areas I can get adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on the stern rail ... seems to work better there. Thank you for telling it like it is. Experience under actual sailing conditions trumps armchair bull**** every time. Wilbur Hubbard Willie, what you know about 2.4 Ghz RF Antenna Propagation and Path Design, is smaller than you IQ, which you amply demonstrate every time you post. Best you leave this to the folks, who actually have Professional Experience, in the field...... |
wi-fi antenna
"You" wrote in message ... In article s.com, "Wilbur Hubbard" wrote: "RichH" wrote in message ... I use the WaveRV marine antenna. Near metro, etc. areas I can get adequate 'signal' 2-3 miles off the NE US coast. I have it mounted on the stern rail ... seems to work better there. Thank you for telling it like it is. Experience under actual sailing conditions trumps armchair bull**** every time. Wilbur Hubbard Willie, what you know about 2.4 Ghz RF Antenna Propagation and Path Design, is smaller than you IQ, which you amply demonstrate every time you post. Best you leave this to the folks, who actually have Professional Experience, in the field...... All you armchair 'experts' can run off at the mouth till the cows come home but it proves nothing other than your heads are full of theoretical crap. What matters is how things work on a sailboat in the real work-a-day world. I sail. I've sailed most of my life and I know what works on a sailboat. I have actual practical experience with wi-fi on a sailboat. I know of which I speak. You theorists just spout lame ideas without ever having put them to the test. Wilbur Hubbard (sending this e-mail via a pirate signal through the wi-fi matrix and 1/2 mile offshore with wi-fi omni antenna stuck out the main salon hatch a mere four feet above the water. Signal strength 95%, Link Quality 97%) |
wi-fi antenna
"You" wrote in message ... Willie, what you know about 2.4 Ghz RF Antenna Propagation and Path Design, is smaller than you IQ, which you amply demonstrate every time you post. Best you leave this to the folks, who actually have Professional Experience, in the field...... You could start by using your Professional Experience and explaining what Wilbur has done wrong and why what he observes cannot be happening. As to any professed expertise on radio wave propagation all I've seen here are antenna installers. I'm sure they are competent at installing antennas but I really doubt they could make any accurate predictions of radio signal propagation based upon what knowledge is required for installing antennas. Thinking an antenna installer is expert on radio path propagation is like thinking the person who drains the bedpan in the hospital is a doctor. Even Wikipedia states: http://en.wikipedia.org/wiki/Fresnel_zone "If unobstructed, radio waves will travel in a straight line from the transmitter to the receiver. But if there are obstacles near the path, the radio waves reflecting off those objects may arrive out of phase with the signals that travel directly and reduce the power of the received signal. On the other hand, the reflection can enhance the power of the received signal if the reflection and the direct signals arrive in phase. Sometimes this results in the counterintuitive finding that reducing the height of an antenna increases the S+N/N ratio. Fresnel provided a means to calculate where the zones are where obstacles will cause mostly in phase and mostly out of phase reflections between the transmitter and the receiver. Obstacles in the first Fresnel will create signals that will be 0 to 90 degrees out of phase, in the second zone they will be 90 to 270 degrees out of phase, in third zone, they will be 270 to 450 degrees out of phase and so on. Odd numbered zones are constructive and even numbered zones are destructive.[2]" Please Note the following: "On the other hand, the reflection can enhance the power of the received signal if the reflection and the direct signals arrive in phase. Sometimes this results in the counterintuitive finding that reducing the height of an antenna increases the S+N/N ratio" Based upon your Professional Experience and all that you know about "2.4 Ghz RF Antenna Propagation and Path Design" can you refute the above statement? Did you get the part about "Odd numbered zones are constructive"? That means they increase the received signal. By lowering his antenna he has increased reflection in the first Fresnel Zone - "1" is an odd number the last time I looked and his signal should increase. If there is some new type of non-causal electromagnetics I'd love to hear about it, so fill me in. BTW "2.4 Ghz RF Antenna Propagation and Path Design" should be stated as "2.4 GHz Radio Wave Propagation and Path Analysis". Antennas don't propagate and paths are usually analyzed, not designed. Wilbur's observations are supported by proven science. |
wi-fi antenna
On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz"
wrote: "Wilbur Hubbard" wrote in message tanews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. 6dB. Principle of superposition. No power splitting required for the image. No change in antenna radiation impedance if the distance from antenna to ground plane is large in terms of wavelengths, as is likely to be the case in this situation. |
wi-fi antenna
On Thu, 3 Apr 2008 12:45:43 -0600, "Bob Crantz"
wrote: "You" wrote in message ... Willie, what you know about 2.4 Ghz RF Antenna Propagation and Path Design, is smaller than you IQ, which you amply demonstrate every time you post. Best you leave this to the folks, who actually have Professional Experience, in the field...... You could start by using your Professional Experience and explaining what Wilbur has done wrong and why what he observes cannot be happening. As to any professed expertise on radio wave propagation all I've seen here are antenna installers. I'm sure they are competent at installing antennas but I really doubt they could make any accurate predictions of radio signal propagation based upon what knowledge is required for installing antennas. Thinking an antenna installer is expert on radio path propagation is like thinking the person who drains the bedpan in the hospital is a doctor. Even Wikipedia states: http://en.wikipedia.org/wiki/Fresnel_zone "If unobstructed, radio waves will travel in a straight line from the transmitter to the receiver. But if there are obstacles near the path, the radio waves reflecting off those objects may arrive out of phase with the signals that travel directly and reduce the power of the received signal. On the other hand, the reflection can enhance the power of the received signal if the reflection and the direct signals arrive in phase. Sometimes this results in the counterintuitive finding that reducing the height of an antenna increases the S+N/N ratio. Fresnel provided a means to calculate where the zones are where obstacles will cause mostly in phase and mostly out of phase reflections between the transmitter and the receiver. Obstacles in the first Fresnel will create signals that will be 0 to 90 degrees out of phase, in the second zone they will be 90 to 270 degrees out of phase, in third zone, they will be 270 to 450 degrees out of phase and so on. Odd numbered zones are constructive and even numbered zones are destructive.[2]" Please Note the following: "On the other hand, the reflection can enhance the power of the received signal if the reflection and the direct signals arrive in phase. Sometimes this results in the counterintuitive finding that reducing the height of an antenna increases the S+N/N ratio" Based upon your Professional Experience and all that you know about "2.4 Ghz RF Antenna Propagation and Path Design" can you refute the above statement? Did you get the part about "Odd numbered zones are constructive"? That means they increase the received signal. By lowering his antenna he has increased reflection in the first Fresnel Zone - "1" is an odd number the last time I looked and his signal should increase. If there is some new type of non-causal electromagnetics I'd love to hear about it, so fill me in. BTW "2.4 Ghz RF Antenna Propagation and Path Design" should be stated as "2.4 GHz Radio Wave Propagation and Path Analysis". Antennas don't propagate and paths are usually analyzed, not designed. Wilbur's observations are supported by proven science. That certainly soils Glen Ashmore's credibility. One would begin to wonder if his success is built more on luck than knowledge. Here's another website offering the same arguments: http://www.zytrax.com/tech/wireless/fresnel.htm It is really sad to see someone attempt to sully another's reputation with misrepresentations and wind up ruining their own. JT |
wi-fi antenna
"Goofball_star_dot_etal" wrote in message ... On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz" wrote: "Wilbur Hubbard" wrote in message ctanews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. 6dB. Principle of superposition. No power splitting required for the image. No change in antenna radiation impedance if the distance from antenna to ground plane is large in terms of wavelengths, as is likely to be the case in this situation. It's 3 dB in power and it's the Principle of Images that is used to remove the ground plane and locate a virtual mirror image of the antenna. The Principle of Superposition is used after the Principle of Images to calculate the field. One would tend to say it's 6 dB in voltage but that is misleading as the input impedance varies between the real and image and it is power (actually energy) that is conserved. You're right about the spacing being important. Glory! |
wi-fi antenna
"James Taggart" wrote
That certainly soils Glen Ashmore's credibility. One would begin to wonder if his success is built more on luck than knowledge. Here's another website offering the same arguments: http://www.zytrax.com/tech/wireless/fresnel.htm Did you actually READ that article? You probably stopped at the phrase "With apologies to Mr. Fresnel" thinking it was a refutation when actually the author was stating that he was vastly simplifying the principle. The article confirmed exactly what I said! "The strongest signals are the ones closest to the direct line between TX and RX and always lie in the 1st Fresnel Zone. The rule of thumb is that 60% of the 1st Fresnel zone must be clear of obstacles." With an omnidirectional 6 to 9db antenna (which is the only practical option for a boat moving around an anchor or mooring) on deck every hull and the water surface between you and the access point will be within zone one. As you get higher the less water and other boats are within zone one. The stronger you can get the signal in zone one the less the reflections from the other zones matter. In other words, for best long range performance Get Higher! D yourself a favor and learn something. Play around with the range calculator they link to. It is similar to the one I use. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
wi-fi antenna
On Thu, 03 Apr 2008 18:44:20 -0400, James Taggart
wrote: That certainly soils Glen Ashmore's credibility. One would begin to wonder if his success is built more on luck than knowledge. Here's another website offering the same arguments: http://www.zytrax.com/tech/wireless/fresnel.htm It is really sad to see someone attempt to sully another's reputation with misrepresentations and wind up ruining their own. The Fresnel effects are applicable in some circumstances, but in the real world, gaining an unobstructed path via antenna height almost always trumps everything else. |
wi-fi antenna
On Thu, 3 Apr 2008 19:00:47 -0400, "Bob Crantz"
wrote: "Goofball_star_dot_etal" wrote in message .. . On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz" wrote: "Wilbur Hubbard" wrote in message . octanews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. 6dB. Principle of superposition. No power splitting required for the image. No change in antenna radiation impedance if the distance from antenna to ground plane is large in terms of wavelengths, as is likely to be the case in this situation. It's 3 dB in power and it's the Principle of Images that is used to remove the ground plane and locate a virtual mirror image of the antenna. The Principle of Superposition is used after the Principle of Images to calculate the field. One would tend to say it's 6 dB in voltage but that is misleading as the input impedance varies between the real and image and it is power (actually energy) that is conserved. You're right about the spacing being important. Glory! It is not just a question of squeezing the energy from a sphere into a hemisphere. If the antenna and its image are separated by a number of wavelengths nulls occur in the polar plot, so that you cannot simply claim that a gain of more than 3dB violates the Conservation of Energy. Principle of Superposition rules. Amen! |
wi-fi antenna
"Goofball_star_dot_etal" wrote in message ... It is not just a question of squeezing the energy from a sphere into a hemisphere. If the antenna and its image are separated by a number of wavelengths nulls occur in the polar plot, so that you cannot simply claim that a gain of more than 3dB violates the Conservation of Energy. Principle of Superposition rules. Amen! Amen! Alright, you got me. Is that 6 dBi? If so, then I agree. Otherwise I don't see how. Do you have a reference, example or link showing this 6 dB(dipole) of gain for two end to end antenna separated by multiple wavelengths. The principle of superposition states the response of a linear system is the sum of the elements of the system. If each element is a dipole and both dipoles are in free space, the output can never be greater than the sum of the two dipoles acting independently. Maybe I don't understand what you're saying but I'm definitely missing something here. Thanks in advance for the help and insight. Bless you! BC |
wi-fi antenna
"James Taggart" wrote in message ... That certainly soils Glen Ashmore's credibility. One would begin to wonder if his success is built more on luck than knowledge. Here's another website offering the same arguments: http://www.zytrax.com/tech/wireless/fresnel.htm It is really sad to see someone attempt to sully another's reputation with misrepresentations and wind up ruining their own. JT Hey Jerk, Glen probably does a bang up job on putting in Wi-Fi. He uses his knowledge of the Fresnel effect to maximize performance. From installing tower systems how would he know about little known effects down near the earth? If anything, Glenn has a great reputation, his track record proves it. BC |
wi-fi antenna
"Glenn Ashmore" wrote in message ... "James Taggart" wrote That certainly soils Glen Ashmore's credibility. One would begin to wonder if his success is built more on luck than knowledge. Here's another website offering the same arguments: http://www.zytrax.com/tech/wireless/fresnel.htm Did you actually READ that article? You probably stopped at the phrase "With apologies to Mr. Fresnel" thinking it was a refutation when actually the author was stating that he was vastly simplifying the principle. The article confirmed exactly what I said! "The strongest signals are the ones closest to the direct line between TX and RX and always lie in the 1st Fresnel Zone. The rule of thumb is that 60% of the 1st Fresnel zone must be clear of obstacles." If you read further it says 60% of the radius. I don't think the link could tolerate obstructions on boresite that occupied less than 60% of the zone (ie a skinny tower in the way) With an omnidirectional 6 to 9db antenna (which is the only practical option for a boat moving around an anchor or mooring) on deck every hull and the water surface between you and the access point will be within zone one. Reflections from zone one are the strongest and additive - they increase the signal strength. This could very well explain what Wilbur has been experiencing. As you get higher the less water and other boats are within zone one. The stronger you can get the signal in zone one the less the reflections from the other zones matter. Wouldn't keeping the antenna low on the water eliminate any chance of getting anything in zones other than zone 1 and maximize the signal in zone 1? How can you get the signal "stronger" in zone 1? Aren't the antenna patterns and transmit power fixed? Keeping the antenna low keeps the power in Zone 1. In other words, for best long range performance Get Higher! For best long range performance get the longest unobstructed path and keep obstructions out of the even zone numbers. This does not necessarily maximize signal strength since there would be no additive reflections. D yourself a favor and learn something. Play around with the range calculator they link to. It is similar to the one I use. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
wi-fi antenna
In article ,
Goofball_star_dot_etal wrote: On Thu, 3 Apr 2008 19:00:47 -0400, "Bob Crantz" wrote: "Goofball_star_dot_etal" wrote in message .. . On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz" wrote: "Wilbur Hubbard" wrote in message . octanews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. 6dB. Principle of superposition. No power splitting required for the image. No change in antenna radiation impedance if the distance from antenna to ground plane is large in terms of wavelengths, as is likely to be the case in this situation. It's 3 dB in power and it's the Principle of Images that is used to remove the ground plane and locate a virtual mirror image of the antenna. The Principle of Superposition is used after the Principle of Images to calculate the field. One would tend to say it's 6 dB in voltage but that is misleading as the input impedance varies between the real and image and it is power (actually energy) that is conserved. You're right about the spacing being important. Glory! It is not just a question of squeezing the energy from a sphere into a hemisphere. If the antenna and its image are separated by a number of wavelengths nulls occur in the polar plot, so that you cannot simply claim that a gain of more than 3dB violates the Conservation of Energy. Principle of Superposition rules. Amen! It also really doesn't apply to the Original Question at hand, in that there is a Frequency Component , inherent in the Superposition Rule, and at 2.4 Ghz your Antenna would need to be a lot closer to the Conducting Groundplane than Wilbur's Sailboat Handrail, for this to have any effect....... |
wi-fi antenna
On Fri, 4 Apr 2008 09:57:55 -0600, "Bob Crantz"
wrote: "Goofball_star_dot_etal" wrote in message .. . It is not just a question of squeezing the energy from a sphere into a hemisphere. If the antenna and its image are separated by a number of wavelengths nulls occur in the polar plot, so that you cannot simply claim that a gain of more than 3dB violates the Conservation of Energy. Principle of Superposition rules. Amen! Amen! Alright, you got me. Is that 6 dBi? No, 'regular' common or garden dB. f so, then I agree. Otherwise I don't see how. Do you have a reference, example or link showing this 6 dB(dipole) of gain for two end to end antenna separated by multiple wavelengths. Does this help? http://books.google.co.uk/books?id=o...hbV18#PPA91,M1 (Foundations of Antenna Theory and Techniques By Vincent F. Fusco. page 91 ) " ....this leads to a 6dB power gain." If one transmitter gives 1mV into a receiver the addition of a second identical transmiter at the same distance and in phase, will give 2mV. This is a 4 x increase in power, 6dB. You have doubled the total tx power (3dB) so you have an antenna gain of 3dB. In the case of an image in a 'ground plane mirror', there is no extra tx power and still the same 6dB gain. The missing 3dB that came from the second transmitter comes from the power that would have gone into space, below the ground plane. |
wi-fi antenna
On Fri, 04 Apr 2008 19:17:00 GMT, You wrote:
In article , Goofball_star_dot_etal wrote: On Thu, 3 Apr 2008 19:00:47 -0400, "Bob Crantz" wrote: "Goofball_star_dot_etal" wrote in message .. . On Wed, 2 Apr 2008 13:10:05 -0600, "Bob Crantz" wrote: "Wilbur Hubbard" wrote in message . octanews.com... I have personal experience with respect to this topic. Putting a wi-fi antenna at the masthead is the WRONG thing to do. You don't want it high up. You want it low down. It gets better reception low. The signals seem to be stronger low. Mount a good amplified antenna at deck level for the best reception. No need to worry about long lengths of co-ax at all. Here's a good antenna that works well and is priced reasonably. http://www.radiolabs.com/products/wi...ne-antenna.php Wilbur Hubbard If your antenna is vertically polarized you could see a 3 dB increase in signal if it placed over a conducting ground plane such as salt water. 6dB. Principle of superposition. No power splitting required for the image. No change in antenna radiation impedance if the distance from antenna to ground plane is large in terms of wavelengths, as is likely to be the case in this situation. It's 3 dB in power and it's the Principle of Images that is used to remove the ground plane and locate a virtual mirror image of the antenna. The Principle of Superposition is used after the Principle of Images to calculate the field. One would tend to say it's 6 dB in voltage but that is misleading as the input impedance varies between the real and image and it is power (actually energy) that is conserved. You're right about the spacing being important. Glory! It is not just a question of squeezing the energy from a sphere into a hemisphere. If the antenna and its image are separated by a number of wavelengths nulls occur in the polar plot, so that you cannot simply claim that a gain of more than 3dB violates the Conservation of Energy. Principle of Superposition rules. Amen! It also really doesn't apply to the Original Question at hand, in that there is a Frequency Component , inherent in the Superposition Rule, It only means you can add things up, in this case vectors, provided there is no interaction eg. impedance change. It breaks down "closer" because impedance changes. and at 2.4 Ghz your Antenna would need to be a lot closer to the Conducting Groundplane than Wilbur's Sailboat Handrail, for this to have any effect....... See above. More to the point, the sea is very rough in terms of wavelength @ 2.4 GHz (in Wales, at least, Boyo) and not a mirror. One thing at a time.:-) |
wi-fi antenna
"Goofball_star_dot_etal" wrote in message ... Alright, you got me. Is that 6 dBi? No, 'regular' common or garden dB. dB is a relative measurement. Is it relative to isotropic or dipole? f so, then I agree. Otherwise I don't see how. Do you have a reference, example or link showing this 6 dB(dipole) of gain for two end to end antenna separated by multiple wavelengths. Does this help? http://books.google.co.uk/books?id=o...hbV18#PPA91,M1 (Foundations of Antenna Theory and Techniques By Vincent F. Fusco. page 91 ) " ....this leads to a 6dB power gain." If one transmitter gives 1mV into a receiver the addition of a second identical transmiter at the same distance and in phase, will give 2mV. This is a 4 x increase in power, 6dB. Let's say one transmitter is 1 watt. The second transmitter is 1 watt, both total 2 watts. The receiving antenna then sees a 4x increase in power by doubling the transmit power, by the law of superposition. Got it! So the Friis equation must be wrong: http://en.wikipedia.org/wiki/Friis_t...ssion_equation If the path, frequency etc are unchanged the Friis equation shows that doubling the transmit power only doubles the receive power. You have doubled the total tx power (3dB) so you have an antenna gain of 3dB. So, if the transmit power was quadrupled the receive power would go up by a factor of 16 and the antenna gain becomes 12 dB. I never realized antenna gain was determined by signal strength. In the case of an image in a 'ground plane mirror', there is no extra tx power and still the same 6dB gain. The missing 3dB that came from the second transmitter comes from the power that would have gone into space, below the ground plane. Your principles are correct but the numbers are wrong, unless you can state 3 dB relative to what? |
wi-fi antenna
"Goofball_star_dot_etal" wrote in message ... It only means you can add things up, in this case vectors, provided there is no interaction eg. impedance change. It breaks down "closer" because impedance changes. You can add vectors even if the impedance changes. 1. Solve the field for all space with just the source. 2. Replace reradiators with equivalent sources based upon the incident field from (1). 3. Using superposition, sum all the fields from (1) and (2) for the total field. and at 2.4 Ghz your Antenna would need to be a lot closer to the Conducting Groundplane than Wilbur's Sailboat Handrail, for this to have any effect....... The additional signal in Wilbur's antenna comes from reflections from the water. See above. More to the point, the sea is very rough in terms of wavelength @ 2.4 GHz (in Wales, at least, Boyo) and not a mirror. One thing at a time.:-) Yes, the rougher it gets the more reflections you see, just like a ship's radar. The reflections are in Fresnel zone 1 which add to the signal strength. The biggest time variations one would see in signal strength would be due to a slow, rolling sea surface. |
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