RE: [Repeater-Builder] Re: Antenna on the side of a water tower
The water tank is a convex surface (at least on the side you can get to) not a concave surface. However offhand I don't think that you will be able to get far enough away from the surface of the tank to illuminate it properly and the curvature will most likely not be anywhere near optimum for the desired pattern. I would just mount the antenna on the rail and see what it does. As to a second antenna on the opposite side of the tank there is no need to have the two cables from the power splitter to be the same length. The two antennas are not going to see one another and they are not part of a phased array so cable lengths will be immaterial. There will be some nulls (and peaks) in directions where both antennas happen to be in view but moving a few feet one way or the other by the unit in view will change the phase relationship between the two antennas anyway. Nothing you can do about it. Regards Gary K4FMX _ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of allan crites Sent: Wednesday, January 31, 2007 12:39 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Antenna on the side of a water tower I'd suggest you consider the water tank as a reflector of the type called Gregorian after James Gregory of England who devised it about 1660, and the operation of which is described in the book Antennas for all applications by John Kraus 3rd edition on pp. 680-684. Illumination of the (water tank as a) reflector (called a concave ellipsoidal surface) with a point source ( a yagi or other such similar directional type of antenna pointed at the reflector ) will yield a wide distribution of RF energy in the desired area of operation (close to 180 degrees) without the multi-lobes and nulls which can and do occur with the use of an omni-directional antenna regardless what ever the spacing from the antenna to the reflector (water tank surface). Since the reflector (water tank) is not a flat sheet, determination of the appropriate spacing from an omni-directional antenna to a spherical reflector is a compromise at best, if one hopes to achieve an optimum radiation pattern in the area of desired operation with-out undesirable nulls. One thing is for sure, you cannot expect more than 180 degrees of operation from the side of the water tank on which the antenna is mounted. Any signal found on the opposite side of the tank is the result of multi-path reflections, and will not and can not be dependable or predictable for use. You may want to mount another directional antenna on the opposite side of the tank to improve the coverage in the opposite area. This obviously would require a splitter ( power divider) to couple the two antennas and /or an additional length of transmission line from the xmtr to the 2nd antenna. Both lines feeding the antennas from the power splitter should be of the same length. And there may be nulls at the 90 degree and 270 degree locations around the tank with two antennas mounted at 0 and 180 degrees. Good Luck! 73, Allan Crites, WA9ZZU Jim B. [EMAIL PROTECTED] wrote: Dave VanHorn wrote: I would suggest 1/2 wave away from the surrounding metal as a minimum, but try and get as far away as you can. Yes, but what's bugging me is that I'm sure there are BAD distances, especially up close within 1-2 wavelengths Normally for side-mounting on a normal tower, one wavelength will get you close to an omni pattern, but something as big as a water tower, I don't know. I don't think you'll be able to mount it far enough away, practically speaking. I'd still mount it facing towards the most important area to cover from that site, and vote it. -- Jim Barbour WD8CHL
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
I'd suggest you consider the water tank as a reflector of the type called Gregorian after James Gregory of England who devised it about 1660, and the operation of which is described in the book Antennas for all applications by John Kraus 3rd edition on pp. 680-684. Illumination of the (water tank as a) reflector (called a concave ellipsoidal surface) with a point source ( a yagi or other such similar directional type of antenna pointed at the reflector ) will yield a wide distribution of RF energy in the desired area of operation (close to 180 degrees) without the multi-lobes and nulls which can and do occur with the use of an omni-directional antenna regardless what ever the spacing from the antenna to the reflector (water tank surface). Since the reflector (water tank) is not a flat sheet, determination of the appropriate spacing from an omni-directional antenna to a spherical reflector is a compromise at best, if one hopes to achieve an optimum radiation pattern in the area of desired operation with-out undesirable nulls. One thing is for sure, you cannot expect more than 180 degrees of operation from the side of the water tank on which the antenna is mounted. Any signal found on the opposite side of the tank is the result of multi-path reflections, and will not and can not be dependable or predictable for use. You may want to mount another directional antenna on the opposite side of the tank to improve the coverage in the opposite area. This obviously would require a splitter ( power divider) to couple the two antennas and /or an additional length of transmission line from the xmtr to the 2nd antenna. Both lines feeding the antennas from the power splitter should be of the same length. And there may be nulls at the 90 degree and 270 degree locations around the tank with two antennas mounted at 0 and 180 degrees. Good Luck! 73, Allan Crites, WA9ZZU Jim B. [EMAIL PROTECTED] wrote: Dave VanHorn wrote: I would suggest 1/2 wave away from the surrounding metal as a minimum, but try and get as far away as you can. Yes, but what's bugging me is that I'm sure there are BAD distances, especially up close within 1-2 wavelengths Normally for side-mounting on a normal tower, one wavelength will get you close to an omni pattern, but something as big as a water tower, I don't know. I don't think you'll be able to mount it far enough away, practically speaking. I'd still mount it facing towards the most important area to cover from that site, and vote it. -- Jim Barbour WD8CHL
RE: [Repeater-Builder] Re: Antenna on the side of a water tower
_ From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Dave VanHorn Sent: Monday, January 29, 2007 4:26 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Antenna on the side of a water tower --- In Repeater-Builder@ mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com, Iszak, Mike [EMAIL PROTECTED] wrote: Dave; Are you able to choose where on the side of the tank (IE, facing a particular direction) or are you stuck with a specific spot? I haven't seen the details yet, but as far as I know we can pick the spot. I would suggest 1/2 wave away from the surrounding metal as a minimum, but try and get as far away as you can. Yes, but what's bugging me is that I'm sure there are BAD distances, especially up close within 1-2 wavelengths It is going to be very similar to mounting on the side of a tower except that the back side will be completely shielded. 73 Gary K4FMX
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
skipp025 wrote: Which reminds me that I should have mentioned the available scan of club using a series of yagi antennas around a wide tower to obtain a quasi omni pattern. You can probably find the info on the repeater builder antenna page along with the mounting offset paper I mentioned earlier. skipp An agency we work with uses VHF corner reflectors pointed opposite directions, with a power splitter, to cover a freeway... -- Jim Barbour WD8CHL
[Repeater-Builder] Re: Antenna on the side of a water tower
Ok, the sector thing is interesting, but we've drifted FAR away from the question I was trying to answer. Can anyone direct me to information, or modeling software (preferrably free) that can predict the pattern of an omni antenna, at various distances from a large cylindrical water tower? I'm looking to end up with an .ant file that I can use in radio mobile, but whatever the output form might be, I'm sure I can translate it one way or another.
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
Dave VanHorn wrote: I would suggest 1/2 wave away from the surrounding metal as a minimum, but try and get as far away as you can. Yes, but what's bugging me is that I'm sure there are BAD distances, especially up close within 1-2 wavelengths Normally for side-mounting on a normal tower, one wavelength will get you close to an omni pattern, but something as big as a water tower, I don't know. I don't think you'll be able to mount it far enough away, practically speaking. I'd still mount it facing towards the most important area to cover from that site, and vote it. -- Jim Barbour WD8CHL
[Repeater-Builder] Re: Antenna on the side of a water tower
Normally for side-mounting on a normal tower, one wavelength will get you close to an omni pattern, I'm not trying to get to an omni pattern, I know that's impossible. What I want to do is approximate the pattern that I will get, and look at that (using RM) against the terrain, and see what distances work out best.. I'd still mount it facing towards the most important area to cover from that site, and vote it. Voting's not an option at this point.
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
Laryn Lohman wrote: Now that I think about it, with all the wireless stuff (cell antennas) that I have seen mounted around a water tower single legs (the modern towers), on buildings at each face, etc. , I bet there is info out there that you can tailor for your needs using the phased antenna approach. Roger W5RD Except don't forget that cell antennas usually are not used and phased in the way we may be discussing here. Laryn K8TVZ In fact, it's normal these days that when you see banks of cell antennas on each side of a structure, each bank feeds a different bank of tx/rx; in other words, each bank is a different cell site. -- Jim Barbour WD8CHL
[Repeater-Builder] Re: Antenna on the side of a water tower.
--- In Repeater-Builder@yahoogroups.com, gervais fillion [EMAIL PROTECTED] wrote: Dave gave us the model of your antenna,is it the 4 loops on a 20 feets mast antenna? The VHF is a Telewave ANT150D9, and UHF is a DB-404 (unless I find something better before then)
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, Steve Peg [EMAIL PROTECTED] wrote: It is what you get when the county takes a free site, when better ones existed. Cheap, free is always better to people who know nothing and dollars count. Well, in my case, we've been looking for two years, and the only one that really responded was $2000/month. BIT steep for a ham repeater, in my opinion.
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, Iszak, Mike [EMAIL PROTECTED] wrote: Dave; Are you able to choose where on the side of the tank (IE, facing a particular direction) or are you stuck with a specific spot? I haven't seen the details yet, but as far as I know we can pick the spot. I would suggest 1/2 wave away from the surrounding metal as a minimum, but try and get as far away as you can. Yes, but what's bugging me is that I'm sure there are BAD distances, especially up close within 1-2 wavelengths
RE: [Repeater-Builder] Re: Antenna on the side of a water tower.
hummm goggle dont find this antenna,,, Original Message Follows From: Dave VanHorn [EMAIL PROTECTED] Reply-To: Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Re: Antenna on the side of a water tower. Date: Mon, 29 Jan 2007 20:30:27 - --- In Repeater-Builder@yahoogroups.com, gervais fillion [EMAIL PROTECTED] wrote: Dave gave us the model of your antenna,is it the 4 loops on a 20 feets mast antenna? The VHF is a Telewave ANT150D9, and UHF is a DB-404 (unless I find something better before then) _ Essayez Windows Live Messenger: le futur de MSN Messenger! http://imagine-msn.com/messenger/launch80/default.aspx?locale=fr-ca
[Repeater-Builder] Re: Antenna on the side of a water tower
In fact, it's normal these days that when you see banks of cell antennas on each side of a structure, each bank feeds a different bank of tx/rx; in other words, each bank is a different cell site. They are called sectors. Out here in LA, sites consist of 2, 3 or 4 sectors. On PCS 1950, each sector has 2 antennas. They use both for diversity receive. Only one is used for transmit at a time. The new ones are dual polarity, slant left and slant right. And I have seen several postings about taking a 6 dB hit in receiver sensitivity when combining antennas into a common receiver. Not true. The 6dB figure only works when splitting, not combining. Assuming the phase angles are close, you only get resistive losses through the device. td wb6mie _ Get live scores and news about your team: Add the Live.com Football Page http://www.live.com/?addtemplate=football
RE: [Repeater-Builder] Re: Antenna on the side of a water tower
They are combined. Nextel does this and calls it a Quasi-Omni site. There are some drawbacks to it, but it actually works quite well. Most panel antennas used are 90 or 65 degree antennas. The biggest drawback is the 6dB hit that you take on receive and some strange nulls between the sectors. The 3-diversity receive scheme they use seems to help in these areas. As you stated, a voter would be the best solution to the water tank site. But. what would you do about transmit? Switching the transmit would eliminate the omnidirectional coverage that you need for mobile-to-mobile communications. This would start to get to be a very complex system. I was trying to keep it simple a affordable. Joe -- Original message -- From: Eric Lemmon [EMAIL PROTECTED] Joe, I don't think those three panel antennas are combined at all. Most cellular and PCS providers are using 120-degree panel antennas to cover three 120-degree sectors, each with its own base station, effectively tripling their capacity. The older omnidirectional antenna cell sites- usually a cluster of fiberglass vertical pairs, one pointing up and one pointing down- are being retrofitted with panel antennas. Panel antennas are much easier to camouflage, and they can be physically tilted for better close-in coverage. One solution to obtaining omnidirectional coverage around a water tank- assuming your site owner will allow you to put up three antennas- is to use a voter to select the best signal from three low-gain Yagi antennas, and switch the transmitter output to that antenna. I suppose combining would work, but I wonder if destructive cancellation will rear its ugly head. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Joe Sent: Saturday, January 27, 2007 3:17 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Antenna on the side of a water tower snip One of the carriers does something similar. They put panel antennas on each of the 3 faces, then combine them into one omni-directional antenna system. It does work. I know of several water tank installations that are just like this. Joe ---BeginMessage--- Joe, I don't think those three panel antennas are combined at all. Most cellular and PCS providers are using 120-degree panel antennas to cover three 120-degree sectors, each with its own base station, effectively tripling their capacity. The older omnidirectional antenna cell sites- usually a cluster of fiberglass vertical pairs, one pointing up and one pointing down- are being retrofitted with panel antennas. Panel antennas are much easier to camouflage, and they can be physically tilted for better close-in coverage. One solution to obtaining omnidirectional coverage around a water tank- assuming your site owner will allow you to put up three antennas- is to use a voter to select the best signal from three low-gain Yagi antennas, and switch the transmitter output to that antenna. I suppose combining would work, but I wonder if destructive cancellation will rear its ugly head. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com] On Behalf Of Joe Sent: Saturday, January 27, 2007 3:17 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Antenna on the side of a water tower snip One of the carriers does something similar. They put panel antennas on each of the 3 faces, then combine them into one omni-directional antenna system. It does work. I know of several water tank installations that are just like this. Joe ---End Message---
[Repeater-Builder] Re: Antenna on the side of a water tower
Which reminds me that I should have mentioned the available scan of club using a series of yagi antennas around a wide tower to obtain a quasi omni pattern. You can probably find the info on the repeater builder antenna page along with the mounting offset paper I mentioned earlier. skipp [EMAIL PROTECTED] wrote: For a water tower, I would imagine the backside null is rather substantial. A club I was associated with more than 20 years ago tried the side mounting of an 2 meter antenna on the railing of a old style water tower (four legs supporting the Ball. It performed as expected with deep, very noticeable (on the air) nulls off the back. However, if that is all you can get, then go for it. I have seen guys mount a Rohn 25 type tower on the platform where the railing is, mount the antenna on top of the tower section(s) and then the top of the antenna will see over the top of the water tower. I guess it should work. However. I bet there is a mechanical situation that has to be worked out to insure mechanical integrity during high winds. If you can bolt the tower top to the ball, that would help. I have seen that also. Roger W5RD From: Dave VanHorn [EMAIL PROTECTED] Date: 2007/01/26 Fri PM 12:16:39 CST To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Antenna on the side of a water tower Can anyone point me to something that will show me the antenna pattern for a VHF and UHF antenna mounted on the side of a water tank at different distances from the tank? I've been offered a site, but I can't have top mount, I have to go on the side. I have the mfgr's docs showing pattern with different distances between the loops and the mast, but I don't have any info on how the big metal tank reflection will disturb the pattern. I'm sure there's an optimal distance, but I don't know what it would be. Roger White Murphy, Texas
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, skipp025 [EMAIL PROTECTED] wrote: Which reminds me that I should have mentioned the available scan of club using a series of yagi antennas around a wide tower to obtain a quasi omni pattern. You can probably find the info on the repeater builder antenna page along with the mounting offset paper I mentioned earlier. Somehow, I don't think the paper pointed to earlier is the one you are talking about.
[Repeater-Builder] Re: Antenna on the side of a water tower
However, if that is all you can get, then go for it. I have seen guys mount a Rohn 25 type tower on the platform where the railing is, mount the antenna on top of the tower section(s) and then the top of the antenna will see over the top of the water tower. Problem is, there's a fire repeater on the top, and they want us on the side, specificially NOT above the side. I'm just looking for a way to predict the pattern(s) so I can plug that into RM, and see if it's worth spending a bucket of money to change to this site.
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
Dave VanHorn [EMAIL PROTECTED] wrote: Can anyone point me to something that will show me the antenna pattern for a VHF and UHF antenna mounted on the side of a water tank at different distances from the tank? I've been offered a site, but I can't have top mount, I have to go on the side. I have the mfgr's docs showing pattern with different distances between the loops and the mast, but I don't have any info on how the big metal tank reflection will disturb the pattern. I'm sure there's an optimal distance, but I don't know what it would be. More information would be helpful , when you say side is that same level as the tank or looking above it with side diplacement ? _ Advertisement: Fresh jobs daily. Stop waiting for the newspaper. Search Now! www.seek.com.au http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fninemsn%2Eseek%2Ecom%2Eau_t=757263760_r=Hotmail_EndText_Dec06_m=EXT
[Repeater-Builder] Re: Antenna on the side of a water tower
More information would be helpful , when you say side is that same level as the tank or looking above it with side diplacement ? The first case, besittin' beside of it as Andy Griffith would say.
[Repeater-Builder] Re: Antenna on the side of a water tower
More information would be helpful , when you say side is that same level as the tank or looking above it with side diplacement ? The first case, besittin' beside of it as Andy Griffith would say.
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
Skipp, I sure would appreciate your sending to me the PDF file scan of the Sinclair paper. Thanks, 73, Allan Crites wa9zzu skipp025 [EMAIL PROTECTED] wrote: Depends a lot on the size of the water tank, then the type of antenna and its mounted distance from the tank. Not an easy guess unless you have a lot of math background with some serious extra time. Most people wing it' trying horizontal mount spacings from 1/4 to 1/2 wave (or multiples there of...) from the tower. It would not directly apply here but I have previously mentioned and passed out to group members a pdf file scan of a Sinclair Authored Paper showing basic antenna distance and space mounting. It's still available to anyone for just requesting it once again by email direct from me. cheers, skipp Dave VanHorn [EMAIL PROTECTED] wrote: Can anyone point me to something that will show me the antenna pattern for a VHF and UHF antenna mounted on the side of a water tank at different distances from the tank? I've been offered a site, but I can't have top mount, I have to go on the side. I have the mfgr's docs showing pattern with different distances between the loops and the mast, but I don't have any info on how the big metal tank reflection will disturb the pattern. I'm sure there's an optimal distance, but I don't know what it would be.
[Repeater-Builder] Re: Antenna on the side of a water tower
I don't think you are going to be able to model it to your satisfaction with any software you or I could afford. Perhaps you need to adopt an empirical approach, put up an antenna and see what you get. Drive test it, take field strength readings, plot and graph the real world data as much as you want. Then you can add in small tweaks in spacing, heading and gain. I would suggest starting with a low gain antenna, like maybe a 4 bay folded dipole array at the easiest to mount spacing from the tank. After you tweak that in for a while and have a feel for how it works, perhaps you could add a second antenna exactly 180 degrees on the other side of the tank. Try 0, 90, 180, 270 or totally random phase angles between the two antennas. Don't get bogged down in the math. Have fun with it. Last time I checked, ham radio is still a hobby. td, empiricist wb6mie It's hard to put into text. What I'd like to do, is get back to the more omni pattern if at all possible. The way everything is situated, if I put the antenna on the side of the tower facing through most of our coverage area, I think it will end up with too much gain in that direction, twoard another repeater to the northeast. Mostly, I'm just looking for a way to model what happens, ideally in something that radio mobile can digest, and I'll work it out from there. _ Search for grocery stores. Find gratitude. Turn a simple search into something more. http://click4thecause.live.com/search/charity/default.aspx?source=hmemtagline_gratitudeFORM=WLMTAG
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
This idea was in a ham magazine years ago, to solve a similar problem. It was on a very large tower, with a large face. This particular application used three sets of phased beams (two at each leg, fired tangentially to the tower). You have to start out with a bunch of gain at each leg, not just a dB224 or such. He used 2 five or so element beams on each leg. He fed them with a three way power divider made out of copper pipe to get the proper impedances. I wish I knew where the article was. I am thinking it was not in QST but maybe one of the ham technical mags that is still no longer around. I would search Google just in case a similar application is documented. He said it worked OK and gave him a somewhat circular pattern, albeit no more than 3-4 dB. Now that I think about it, with all the wireless stuff (cell antennas) that I have seen mounted around a water tower single legs (the modern towers), on buildings at each face, etc. , I bet there is info out there that you can tailor for your needs using the phased antenna approach. Roger W5RD - Original Message - From: tony dinkel To: Repeater-Builder@yahoogroups.com Sent: Saturday, January 27, 2007 12:45 PM Subject: [Repeater-Builder] Re: Antenna on the side of a water tower I don't think you are going to be able to model it to your satisfaction with any software you or I could afford. Perhaps you need to adopt an empirical approach, put up an antenna and see what you get. Drive test it, take field strength readings, plot and graph the real world data as much as you want. Then you can add in small tweaks in spacing, heading and gain. I would suggest starting with a low gain antenna, like maybe a 4 bay folded dipole array at the easiest to mount spacing from the tank. After you tweak that in for a while and have a feel for how it works, perhaps you could add a second antenna exactly 180 degrees on the other side of the tank. Try 0, 90, 180, 270 or totally random phase angles between the two antennas. Don't get bogged down in the math. Have fun with it. Last time I checked, ham radio is still a hobby. td, empiricist wb6mie It's hard to put into text. What I'd like to do, is get back to the more omni pattern if at all possible. The way everything is situated, if I put the antenna on the side of the tower facing through most of our coverage area, I think it will end up with too much gain in that direction, twoard another repeater to the northeast. Mostly, I'm just looking for a way to model what happens, ideally in something that radio mobile can digest, and I'll work it out from there. __ Search for grocery stores. Find gratitude. Turn a simple search into something more. http://click4thecause.live.com/search/charity/default.aspx?source=hmemtagline_gratitudeFORM=WLMTAG
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, Roger White [EMAIL PROTECTED] wrote: I am thinking it was not in QST but maybe one of the ham technical mags that is still no longer around. Seems like it was Ham Radio Magazine. Don't know which issue; early 80s, maybe? I may have it around here somewhere if y'all get desperate. Now that I think about it, with all the wireless stuff (cell antennas) that I have seen mounted around a water tower single legs (the modern towers), on buildings at each face, etc. , I bet there is info out there that you can tailor for your needs using the phased antenna approach. Roger W5RD Except don't forget that cell antennas usually are not used and phased in the way we may be discussing here. Laryn K8TVZ
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
Somehow I recollect that describing the 'extremely healty' Clarkston machine (near Detroit) ~ 3 TX yagis a single RX stik atop... Roger White wrote: This idea was in a ham magazine years ago, to solve a similar problem. It was on a very large tower, with a large face. This particular application used three sets of phased beams (two at each leg, fired tangentially to the tower).
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
I remember that article and I was going to do something similar on a wide faced tower that I was trying to get space on. It was a CATV head-end tower that was full of log periodic antennas, the only available height was from 125 feet to the bottom. I almost got the project started when the cable company got bought out and I lost all my contacts with the owner. Anyway, if I had access to a water tank and had space available around the tank, I would mount 3 antennas equally spaced around the tank. If the antennas were shielded from each other by the water tank, I would probably try omni-directional antennas to keep it simple. I would then use a 3-way power splitter to combine the 3 antennas and just deal with the 6dB hit in signal for the ability to have omni-directional coverage. You can make up for the 6dB in the transmit path by raising the power output, but there isn't much you can do on the receive side except keep the receiver running a well as possible. These splitters are available, see: http://www.rfhamdesign.com/products/powersplitters/3waysplitter/index.html for an example of what I am talking about. Similar design units are available from a company in the Northeast, but I don't remember the name or location. One of the carriers does something similar. They put panel antennas on each of the 3 faces, then combine them into one omni-directional antenna system. It does work. I know of several water tank installations that are just like this. Joe At 03:00 PM 1/27/2007 -0600, you wrote: This idea was in a ham magazine years ago, to solve a similar problem. It was on a very large tower, with a large face. This particular application used three sets of phased beams (two at each leg, fired tangentially to the tower). You have to start out with a bunch of gain at each leg, not just a dB224 or such. He used 2 five or so element beams on each leg. He fed them with a three way power divider made out of copper pipe to get the proper impedances. I wish I knew where the article was. I am thinking it was not in QST but maybe one of the ham technical mags that is still no longer around. I would search Google just in case a similar application is documented. He said it worked OK and gave him a somewhat circular pattern, albeit no more than 3-4 dB. Now that I think about it, with all the wireless stuff (cell antennas) that I have seen mounted around a water tower single legs (the modern towers), on buildings at each face, etc. , I bet there is info out there that you can tailor for your needs using the phased antenna approach. Roger W5RD
RE: [Repeater-Builder] Re: Antenna on the side of a water tower
Joe, I don't think those three panel antennas are combined at all. Most cellular and PCS providers are using 120-degree panel antennas to cover three 120-degree sectors, each with its own base station, effectively tripling their capacity. The older omnidirectional antenna cell sites- usually a cluster of fiberglass vertical pairs, one pointing up and one pointing down- are being retrofitted with panel antennas. Panel antennas are much easier to camouflage, and they can be physically tilted for better close-in coverage. One solution to obtaining omnidirectional coverage around a water tank- assuming your site owner will allow you to put up three antennas- is to use a voter to select the best signal from three low-gain Yagi antennas, and switch the transmitter output to that antenna. I suppose combining would work, but I wonder if destructive cancellation will rear its ugly head. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Joe Sent: Saturday, January 27, 2007 3:17 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: Antenna on the side of a water tower snip One of the carriers does something similar. They put panel antennas on each of the 3 faces, then combine them into one omni-directional antenna system. It does work. I know of several water tank installations that are just like this. Joe
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
At 1/27/2007 10:45, you wrote: I don't think you are going to be able to model it to your satisfaction with any software you or I could afford. Perhaps you need to adopt an empirical approach, put up an antenna and see what you get. Drive test it, take field strength readings, plot and graph the real world data as much as you want. Then you can add in small tweaks in spacing, heading and gain. If the water tower face is sufficiently large compared to your wavelength (70 cm?), it will just look like an infinite vertical ground, in which case your pattern away from the tower will be 3 dB above the omni spec for your antenna, coverage behind will be 0. Bob NO6B
[Repeater-Builder] Re: Antenna on the side of a water tower
Depends a lot on the size of the water tank, then the type of antenna and its mounted distance from the tank. Not an easy guess unless you have a lot of math background with some serious extra time. Most people wing it' trying horizontal mount spacings from 1/4 to 1/2 wave (or multiples there of...) from the tower. It would not directly apply here but I have previously mentioned and passed out to group members a pdf file scan of a Sinclair Authored Paper showing basic antenna distance and space mounting. It's still available to anyone for just requesting it once again by email direct from me. cheers, skipp Dave VanHorn [EMAIL PROTECTED] wrote: Can anyone point me to something that will show me the antenna pattern for a VHF and UHF antenna mounted on the side of a water tank at different distances from the tank? I've been offered a site, but I can't have top mount, I have to go on the side. I have the mfgr's docs showing pattern with different distances between the loops and the mast, but I don't have any info on how the big metal tank reflection will disturb the pattern. I'm sure there's an optimal distance, but I don't know what it would be.
Re: [Repeater-Builder] Re: Antenna on the side of a water tower
It's also at the repeater-builder web site on the antenna systems page, or directly at http://www.repeater-builder.com/antenna/antenna-mounting-guidelines.pdf Mike WA6ILQ At 03:11 PM 01/26/07, you wrote: Depends a lot on the size of the water tank, then the type of antenna and its mounted distance from the tank. Not an easy guess unless you have a lot of math background with some serious extra time. Most people wing it' trying horizontal mount spacings from 1/4 to 1/2 wave (or multiples there of...) from the tower. It would not directly apply here but I have previously mentioned and passed out to group members a pdf file scan of a Sinclair Authored Paper showing basic antenna distance and space mounting. It's still available to anyone for just requesting it once again by email direct from me. cheers, skipp Dave VanHorn [EMAIL PROTECTED] wrote: Can anyone point me to something that will show me the antenna pattern for a VHF and UHF antenna mounted on the side of a water tank at different distances from the tank? I've been offered a site, but I can't have top mount, I have to go on the side. I have the mfgr's docs showing pattern with different distances between the loops and the mast, but I don't have any info on how the big metal tank reflection will disturb the pattern. I'm sure there's an optimal distance, but I don't know what it would be. Yahoo! Groups Links
[Repeater-Builder] Re: Antenna on the side of a water tower
It's hard to put into text. What I'd like to do, is get back to the more omni pattern if at all possible. The way everything is situated, if I put the antenna on the side of the tower facing through most of our coverage area, I think it will end up with too much gain in that direction, twoard another repeater to the northeast. Mostly, I'm just looking for a way to model what happens, ideally in something that radio mobile can digest, and I'll work it out from there.
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, skipp025 [EMAIL PROTECTED] wrote: Depends a lot on the size of the water tank, then the type of antenna and its mounted distance from the tank. Not an easy guess unless you have a lot of math background with some serious extra time. I can deal with that, I have Mathcad, and I wouldn't be opposed to crunching it in that, or other ways. I thought about simulating it with Pov-Ray, but POV deals with light in a particle manner, not as a wave, and pov objects are typically enormous on the scale of light wavelengths.. Most people wing it' trying horizontal mount spacings from 1/4 to 1/2 wave (or multiples there of...) from the tower. Yeah, that's what I'm trying to avoid. It would not directly apply here but I have previously mentioned and passed out to group members a pdf file scan of a Sinclair Authored Paper showing basic antenna distance and space mounting. I have the one from telwave that covers distance between the loops and the mast, but if this one is something closer to my situation, I'd like to see it. It's still available to anyone for just requesting it once again by email direct from me. As above, if you think it will help, please email it to me. Thanks
[Repeater-Builder] Re: Antenna on the side of a water tower
--- In Repeater-Builder@yahoogroups.com, Mike Morris [EMAIL PROTECTED] wrote: It's also at the repeater-builder web site on the antenna systems page, or directly at http://www.repeater-builder.com/antenna/antenna-mounting- guidelines.pdf Ok, no that dosen't really get me where I need to be. Thanks though.
