RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas
If i read your post correctly, you are trying to achieve omni coverage and downtilt while maintaining a high level of antenna gain. I think that you will only achieve what you want by using electrical downtilting in the antenna. Otherwise you are going to have to trade off something. I might try using a lower gain omni antenna since the concept of antenna gain is basically squashing the doughnut (if you have seen the illustration of a doughnut on it's side as representative of the pattern of the antenna radiation pattern for an omni antenna) in that as antenna gain increases, vertical beamwidth decreases. Try a 6dB or 3dB omni (if available for your frequency range) and see if that improves the closer coverage. It might also have the benefit of reducing interference from distant stations. In re-reading you original post I see that you have 2-120 degree sector antennas spaced 60 degrees apart. While this is an area that I don't have practical experience in, I recall that overlapping antenna patterns can be additive or subtractive. I would change the spacing so that the antennas are 120 degrees apart and see if that doesn't improve the overall performance. Milt N3LTQ Quoting Matthew kc7...@hotmail.com: I am trying to achieve an almost 360 pattern with some gain and down tilt. Right now I have a vertical antenna at 11 dBi with no down tilt, so most of my gain is shot out in the horizon. So the area I am trying to get my maximum gain is from under my antenna (Red in attached pic) to 7 to 15 miles out which requires either electrical down tilt of the antenna or a mechanical one. I drew a very crude picture to show what I am trying to do. See attached or embedded. Thanks 73 Matthew KC7EQO PS the null is not critical, just trying to focus the energy to the area I am trying to serve. _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Barry Sent: Friday, October 09, 2009 8:04 PM To: repeater-builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas How about some indication of what you hope to achieve I use a skelol slot I made on .70cm with great success and have used a refletor with good gain on a vertical in the past for a null B fyi http://www.patentstorm.us/patents/5477224/claims.html _ To: Repeater-Builder@yahoogroups.com From: kc7...@hotmail.com Date: Fri, 9 Oct 2009 23:25:31 + Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas LOL thanks for your honesty. I am sure someone here can help with my questions. Oh BTW I have have not slept at a Holiday Inn Express either :) those are funny and creative commercials too. 73 Matthew KC7EQO --- In Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com, Chuck Kelsey wb2...@... wrote: Actually Jeff Depolo is much better versed to explain this than I am. Hopefully he can enter into this thread. I don't have an engineering background, and don't play an engineer on TV. I haven't even stayed at a Holiday Inn Express :-) Chuck WB2EDV - Original Message - From: Matt kc7...@... To: Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com Sent: Friday, October 09, 2009 6:55 PM Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas Thanks for replying Chuck. The antennas are not perfectly back to back. More like 60 degrees from each other. I would have thought I'd have a null in one direction. Is there a better way to do this? I want close to the 11 dB gain my omni has, but with more down tilt. Thanks, 73 Matthew KC7EQO --- In Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com, Chuck Kelsey wb2edv@ wrote: Are the two antennas pointed the same direction? If they are back to back, I'd guess that your results are what I'd expect. Chuck WB2EDV - Original Message - From: Matt kc7eqo@ To: Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com yahoogroups.com Sent: Friday, October 09, 2009 2:29 PM Subject: [Repeater-Builder] feeding two 120 degree sector antennas I am experimenting with some 3 Ghz antennas. I have a 2 way power divider feeding two 120 degree sector antennas rated at 15 dBi each. I have a 11 dBi omni that I am comparing it too. It seems the omni is getting better performance then the array is. I am seeing more than a 4 dB difference, loss. My goal is to get more down tilt in my antenna pattern, as the sectors offer a mechanical down tilt. Am I doing something wrong? I am feeding the antennas with LMR400 and feed is short as possible. Each feed from the divider is 15 inches long to the antenna. The insertion loss in the divider is 0.4 dBi according to the spec sheet. Thanks in advance, Matthew
RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas
Milt, You gave an excellent description of the problem, and I agree that a lower gain antenna is called for. However, there is a dirty little secret regarding fiberglass vertical antennas with electrical downtilt: Their vertical patterns are quite spoky, meaning that there are many peaks and nulls. For example, one of the local radio clubs has a Celwave Super Stationmaster antenna with electrical downtilt on a nearby mountaintop repeater. The downtilt was chosen in good faith to provide close-in coverage of users living near the base of the mountain. Over time, we found that there were many areas where you had line-of-sight to the repeater but could not get into it from a handheld. But, you could move closer or further away and then get in, full-quieting. This phenomenon was repeated at intervals. Bottom line: Electrical downtilt is not as simple as it sounds, and it should be employed only after careful study of the antenna radiation patterns and the desired coverage areas. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of men...@pa.net Sent: Saturday, October 10, 2009 6:20 AM To: Repeater-Builder@yahoogroups.com Subject: RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas If i read your post correctly, you are trying to achieve omni coverage and downtilt while maintaining a high level of antenna gain. I think that you will only achieve what you want by using electrical downtilting in the antenna. Otherwise you are going to have to trade off something. I might try using a lower gain omni antenna since the concept of antenna gain is basically squashing the doughnut (if you have seen the illustration of a doughnut on it's side as representative of the pattern of the antenna radiation pattern for an omni antenna) in that as antenna gain increases, vertical beamwidth decreases. Try a 6dB or 3dB omni (if available for your frequency range) and see if that improves the closer coverage. It might also have the benefit of reducing interference from distant stations. In re-reading you original post I see that you have 2-120 degree sector antennas spaced 60 degrees apart. While this is an area that I don't have practical experience in, I recall that overlapping antenna patterns can be additive or subtractive. I would change the spacing so that the antennas are 120 degrees apart and see if that doesn't improve the overall performance. Milt N3LTQ Quoting Matthew kc7...@hotmail.com mailto:kc7eqo%40hotmail.com : I am trying to achieve an almost 360 pattern with some gain and down tilt. Right now I have a vertical antenna at 11 dBi with no down tilt, so most of my gain is shot out in the horizon. So the area I am trying to get my maximum gain is from under my antenna (Red in attached pic) to 7 to 15 miles out which requires either electrical down tilt of the antenna or a mechanical one. I drew a very crude picture to show what I am trying to do. See attached or embedded. Thanks 73 Matthew KC7EQO PS the null is not critical, just trying to focus the energy to the area I am trying to serve. _ From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of Barry Sent: Friday, October 09, 2009 8:04 PM To: repeater-builder@yahoogroups.com mailto:repeater-builder%40yahoogroups.com Subject: RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas How about some indication of what you hope to achieve I use a skelol slot I made on .70cm with great success and have used a refletor with good gain on a vertical in the past for a null B fyi http://www.patentstorm.us/patents/5477224/claims.html http://www.patentstorm.us/patents/5477224/claims.html _ To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com From: kc7...@hotmail.com mailto:kc7eqo%40hotmail.com Date: Fri, 9 Oct 2009 23:25:31 + Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas LOL thanks for your honesty. I am sure someone here can help with my questions. Oh BTW I have have not slept at a Holiday Inn Express either :) those are funny and creative commercials too. 73 Matthew KC7EQO --- In Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com, Chuck Kelsey wb2...@... wrote: Actually Jeff Depolo is much better versed to explain this than I am. Hopefully he can enter into this thread. I don't have an engineering background, and don't play an engineer on TV. I haven't even stayed at a Holiday Inn Express :-) Chuck WB2EDV - Original Message - From: Matt kc7...@... To: Repeater-Builder@ mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com yahoogroups.com Sent
RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas
At 10/10/2009 07:13, you wrote: Milt, You gave an excellent description of the problem, and I agree that a lower gain antenna is called for. However, there is a dirty little secret regarding fiberglass vertical antennas with electrical downtilt: Their vertical patterns are quite spoky, meaning that there are many peaks and nulls. For example, one of the local radio clubs has a Celwave Super Stationmaster antenna with electrical downtilt on a nearby mountaintop repeater. The downtilt was chosen in good faith to provide close-in coverage of users living near the base of the mountain. Over time, we found that there were many areas where you had line-of-sight to the repeater but could not get into it from a handheld. But, you could move closer or further away and then get in, full-quieting. This phenomenon was repeated at intervals. Bottom line: Electrical downtilt is not as simple as it sounds, and it should be employed only after careful study of the antenna radiation patterns and the desired coverage areas. 73, Eric Lemmon WB6FLY A long time ago I remember seeing ads in a trade mag. for antennas with Null Fill made by Bogner. The idea was to wash out the nulls below the horizon so users close to the system but behind some local minor obstruction wouldn't lose coverage. Not sure what happened to the company. I do see some other manufacturers use that term, but only for antennas above 700 MHz. Bob NO6B
Re: [Repeater-Builder] Re: feeding two 120 degree sector antennas
Actually Jeff Depolo is much better versed to explain this than I am. Hopefully he can enter into this thread. I don't have an engineering background, and don't play an engineer on TV. I haven't even stayed at a Holiday Inn Express :-) Chuck WB2EDV - Original Message - From: Matt kc7...@hotmail.com To: Repeater-Builder@yahoogroups.com Sent: Friday, October 09, 2009 6:55 PM Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas Thanks for replying Chuck. The antennas are not perfectly back to back. More like 60 degrees from each other. I would have thought I'd have a null in one direction. Is there a better way to do this? I want close to the 11 dB gain my omni has, but with more down tilt. Thanks, 73 Matthew KC7EQO --- In Repeater-Builder@yahoogroups.com, Chuck Kelsey wb2...@... wrote: Are the two antennas pointed the same direction? If they are back to back, I'd guess that your results are what I'd expect. Chuck WB2EDV - Original Message - From: Matt kc7...@... To: Repeater-Builder@yahoogroups.com Sent: Friday, October 09, 2009 2:29 PM Subject: [Repeater-Builder] feeding two 120 degree sector antennas I am experimenting with some 3 Ghz antennas. I have a 2 way power divider feeding two 120 degree sector antennas rated at 15 dBi each. I have a 11 dBi omni that I am comparing it too. It seems the omni is getting better performance then the array is. I am seeing more than a 4 dB difference, loss. My goal is to get more down tilt in my antenna pattern, as the sectors offer a mechanical down tilt. Am I doing something wrong? I am feeding the antennas with LMR400 and feed is short as possible. Each feed from the divider is 15 inches long to the antenna. The insertion loss in the divider is 0.4 dBi according to the spec sheet. Thanks in advance, Matthew Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas
Have you considered a passive reflector ? it might offer the direction and tilt your looking for ( plus a couple of db) To: Repeater-Builder@yahoogroups.com From: kc7...@hotmail.com Date: Fri, 9 Oct 2009 22:55:18 + Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas Thanks for replying Chuck. The antennas are not perfectly back to back. More like 60 degrees from each other. I would have thought I'd have a null in one direction. Is there a better way to do this? I want close to the 11 dB gain my omni has, but with more down tilt. Thanks, 73 Matthew KC7EQO --- In Repeater-Builder@yahoogroups.com, Chuck Kelsey wb2...@... wrote: Are the two antennas pointed the same direction? If they are back to back, I'd guess that your results are what I'd expect. Chuck WB2EDV - Original Message - From: Matt kc7...@... To: Repeater-Builder@yahoogroups.com Sent: Friday, October 09, 2009 2:29 PM Subject: [Repeater-Builder] feeding two 120 degree sector antennas I am experimenting with some 3 Ghz antennas. I have a 2 way power divider feeding two 120 degree sector antennas rated at 15 dBi each. I have a 11 dBi omni that I am comparing it too. It seems the omni is getting better performance then the array is. I am seeing more than a 4 dB difference, loss. My goal is to get more down tilt in my antenna pattern, as the sectors offer a mechanical down tilt. Am I doing something wrong? I am feeding the antennas with LMR400 and feed is short as possible. Each feed from the divider is 15 inches long to the antenna. The insertion loss in the divider is 0.4 dBi according to the spec sheet. Thanks in advance, Matthew Yahoo! Groups Links _ Take a peek at other people's pay and perks Check out The Great Australian Pay Check http://clk.atdmt.com/NMN/go/157639755/direct/01/
RE: [Repeater-Builder] Re: feeding two 120 degree sector antennas
How about some indication of what you hope to achieve I use a skelol slot I made on .70cm with great success and have used a refletor with good gain on a vertical in the past for a null B fyi http://www.patentstorm.us/patents/5477224/claims.html To: Repeater-Builder@yahoogroups.com From: kc7...@hotmail.com Date: Fri, 9 Oct 2009 23:25:31 + Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas LOL thanks for your honesty. I am sure someone here can help with my questions. Oh BTW I have have not slept at a Holiday Inn Express either :) those are funny and creative commercials too. 73 Matthew KC7EQO --- In Repeater-Builder@yahoogroups.com, Chuck Kelsey wb2...@... wrote: Actually Jeff Depolo is much better versed to explain this than I am. Hopefully he can enter into this thread. I don't have an engineering background, and don't play an engineer on TV. I haven't even stayed at a Holiday Inn Express :-) Chuck WB2EDV - Original Message - From: Matt kc7...@... To: Repeater-Builder@yahoogroups.com Sent: Friday, October 09, 2009 6:55 PM Subject: [Repeater-Builder] Re: feeding two 120 degree sector antennas Thanks for replying Chuck. The antennas are not perfectly back to back. More like 60 degrees from each other. I would have thought I'd have a null in one direction. Is there a better way to do this? I want close to the 11 dB gain my omni has, but with more down tilt. Thanks, 73 Matthew KC7EQO --- In Repeater-Builder@yahoogroups.com, Chuck Kelsey wb2edv@ wrote: Are the two antennas pointed the same direction? If they are back to back, I'd guess that your results are what I'd expect. Chuck WB2EDV - Original Message - From: Matt kc7eqo@ To: Repeater-Builder@yahoogroups.com Sent: Friday, October 09, 2009 2:29 PM Subject: [Repeater-Builder] feeding two 120 degree sector antennas I am experimenting with some 3 Ghz antennas. I have a 2 way power divider feeding two 120 degree sector antennas rated at 15 dBi each. I have a 11 dBi omni that I am comparing it too. It seems the omni is getting better performance then the array is. I am seeing more than a 4 dB difference, loss. My goal is to get more down tilt in my antenna pattern, as the sectors offer a mechanical down tilt. Am I doing something wrong? I am feeding the antennas with LMR400 and feed is short as possible. Each feed from the divider is 15 inches long to the antenna. The insertion loss in the divider is 0.4 dBi according to the spec sheet. Thanks in advance, Matthew Yahoo! Groups Links Yahoo! Groups Links _ Take a peek at other people's pay and perks Check out The Great Australian Pay Check http://clk.atdmt.com/NMN/go/157639755/direct/01/
