Re: [Repeater-Builder] UHF Repeater Antenna Discussion
[EMAIL PROTECTED] wrote: My 2 cents worth. Many years ago I had a 200' run of LDF5-50 installed by a professional on a 900'tower (rptr at 700' antenna at 900') about a week later we noticed that the TR performance dropped considerably. Personal inspection revealed that water or condensate (about a teaspoon full) had drained down the cable insde the hollow center conductor and had seeped around the inside of the bottom connector. The solution was to completely remove the connector and center pin, drain the cable and let it thoroughly dry then reinstall the connector. I never had another problem with it after that. I suggest you take a look at yours. An issue I've heard come up-if the connector/antenna was installed on a hot, humid day, there will be more water vapor in the air trapped inside. When it cools down, that water will condense out, making it look like it wasn't sealed properly, and of course causing high VSWR. Sometimes putting an antenna up on a hot, humid, sunny day is as bad as putting it up in the rain.
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort Buffington wrote: For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. You're correct. At 100', you won't have a problem. Now if you were up 1000', you might want some downtilt. As far as spacing in a side-mount situation, if you want an omni pattern, you will want to be about one-wavelength out from the tower leg. That gets fairly close to an omni pattern. Spacing of 1/4-wave will put a notch in the pattern through the tower, a half-wave will give you 2 lobes perpendicular to the tower, and 3/4 wave will give you 3 lobes arranged away from the tower in a kind of 'clover-leaf' pattern.
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, It sounds like a mechanical problem somewhere, as others have mentioned. If you can get your hands on a TDR or similar device to sweep the new antenna and feedline on top (using calibrated 50 ohm load on the feedline, and then adding the antenna on for the next test), you'll probably find the problem. If you can't borrow that kind of gear, perhaps a jumper from the bottom feedline to the top antenna to see if it changes the performance would help you figure out if the problem is the new Telewave antenna, or the feedline going to it. Remember, the wattmeter at the transmitter will show good SWR if something is eating the RF but not radiating it. You may also want to consider sending someone up the tower with the wattmeter and seeing what's going on right at the input to the antenna, if all you have is the wattmeter for test gear. The key thing to remember is that the numbers should match theory, or be real close to it. If you're putting in X amount of power at the transmitter, and you know the feedline loss numbers, you can calculate for what you should see at the base of the antenna measurement. If the RF isn't getting there, you know it's a problem in the hardline. If it is getting there but you have high SWR at the antenna base, something is physically wrong with the new antenna, a connector, something... I think from this text and the replies of others, you can come up with a plan that will eliminate a section at a time... if you have jumpers inside the building to the outside, test those (a high power dummy load is nice here, if you have one that you know is a solid 50 ohm load, and not a hunk of junk that's reactive or cheap -- I like the big Bird dummy loads for this part of the job), test just beyond the Polyphaser (a friend had one show up bad from the factory lately), etc... all depending on how much stuff you have between the TX and the antenna... test at every point. Somewhere you'll find it all falls apart according to the numbers... or... if you don't, the antenna's got problems. At that point, jumper over to the other antenna with a nice solid piece of LMR-400 or better, and see if it behaves normally -- you'll find it! There's an art to finding this type of problem, but it's all based in feedline and antenna theory... if you know what the numbers SHOULD be at each test point, you're WAY ahead of the game. Make up a diagram and calculate feedline losses to each point, etc... it'll make it pretty obvious where the RF is disappearing if there's a mechanical/connection problem or a bad antenna. I'm no RF pro, but the pros I've learned from over the years would all tackle this problem this way... find the place where the theoretical RF behavior falls apart, and you've found the problem, most likely. It's better than just shotgunning in new gear until the problem is fixed. Nate WY0X
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
I'll keep the list posted on what we find. I'm playing it all by the numbers, and I don't have access to a TDR. Calculate and measure, one step at a time is my plan. Sooner or later if we don't find a problem, we plan to replace the Telewave F10 with another DB420 we have and if that works well, consider a problem with the F10. I'm now wise to looking very closely at hardline fittings, and have realized the DC grounded antenna trick, etc. All of the responses here have added additional emphasis or new tricks to try -- Please keep them coming, but I'm probably going to keep them filed and wait for some more testing for a reply on the list. Now the thing I do want to emphasize is that Telewave has been incredibly responsive to us and has not put unreasonable burden on us to prove the F10 is bad before taking it back -- I have no proof of this yet, or reason to think it's the F10, I just want everyone to know that Telewave has been a real class act when I've called them. I was immediately put in touch with John Hilmer, the director of their antenna division, and he has been keeping in touch via e-mail. It is clear that even just one pair of hams buying one antenna is important to them. 73 for now! Cort (N0MJS) On Oct 17, 2008, at 12:26 PM, Nate Duehr wrote: Cort, It sounds like a mechanical problem somewhere, as others have mentioned. If you can get your hands on a TDR or similar device to sweep the new antenna and feedline on top (using calibrated 50 ohm load on the feedline, and then adding the antenna on for the next test), you'll probably find the problem. If you can't borrow that kind of gear, perhaps a jumper from the bottom feedline to the top antenna to see if it changes the performance would help you figure out if the problem is the new Telewave antenna, or the feedline going to it. Remember, the wattmeter at the transmitter will show good SWR if something is eating the RF but not radiating it. You may also want to consider sending someone up the tower with the wattmeter and seeing what's going on right at the input to the antenna, if all you have is the wattmeter for test gear. The key thing to remember is that the numbers should match theory, or be real close to it. If you're putting in X amount of power at the transmitter, and you know the feedline loss numbers, you can calculate for what you should see at the base of the antenna measurement. If the RF isn't getting there, you know it's a problem in the hardline. If it is getting there but you have high SWR at the antenna base, something is physically wrong with the new antenna, a connector, something... I think from this text and the replies of others, you can come up with a plan that will eliminate a section at a time... if you have jumpers inside the building to the outside, test those (a high power dummy load is nice here, if you have one that you know is a solid 50 ohm load, and not a hunk of junk that's reactive or cheap -- I like the big Bird dummy loads for this part of the job), test just beyond the Polyphaser (a friend had one show up bad from the factory lately), etc... all depending on how much stuff you have between the TX and the antenna... test at every point. Somewhere you'll find it all falls apart according to the numbers... or... if you don't, the antenna's got problems. At that point, jumper over to the other antenna with a nice solid piece of LMR-400 or better, and see if it behaves normally -- you'll find it! There's an art to finding this type of problem, but it's all based in feedline and antenna theory... if you know what the numbers SHOULD be at each test point, you're WAY ahead of the game. Make up a diagram and calculate feedline losses to each point, etc... it'll make it pretty obvious where the RF is disappearing if there's a mechanical/connection problem or a bad antenna. I'm no RF pro, but the pros I've learned from over the years would all tackle this problem this way... find the place where the theoretical RF behavior falls apart, and you've found the problem, most likely. It's better than just shotgunning in new gear until the problem is fixed. Nate WY0X -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206 Yahoo! Groups Links * To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ * Your email settings: Individual Email | Traditional * To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) * To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] * To unsubscribe from this group, send an email to: [EMAIL PROTECTED] * Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
[Repeater-Builder] UHF Repeater Antenna Discussion
Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
RE: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, Do you really have 5/8 ? Here are the part numbers for the coax LDF4-50A 1/2 50 ohms - loss at 450MHz ~1.447 LDF5-50A 7/8 50 ohms - loss at 450MHz ~ .808 LDF6-50A 1 1/4 50 ohms LDF7-50A 1 5/8 50 ohms So if you have the real deal feed line loss doesn't look like your problem If you have something else all bets are off send me what number is on the cable. The Telewave antenna (actuality ANY Telewave antenna) is problematic. We tried using several in the paging business most likely for the same reason you did they are cheap. They never performed as well as advertised. If you want a cheap antenna the best for the money is and ASP705K by Decibel Products (or whatever they are this week) They work well have a nice round pattern. And will generally out perform a DB-420 because of less pattern distortion. The statement The DB420 is spaced correctly from the tower concerns me as there is no correct way to side mount an antenna. You must take in to account the desired v. undesired coverage areas and optimize the mount and elements to achieve the desired coverage. On that antenna with an 18 face tower mounted 16 off the point of the tower set in an omni configuration You will see peaks of around 10.5dBd and nulls of around 5dBd. I see nothing here that would indicate that the Telewave system is performing correctly. Remember to take into the feed line loss when calculating SWR. That is if you are putting a 100 watts into the feed line and get 50 watts back That indicates a fault at the top as you have 100 watts and 2.894dB loss (1.447*2 up and down) that would be half power of 50 watts. Do some more looking before you call the antenna bad. Robert / KD4PBC -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 9:17 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
LDF4.5-50A http://www.tessco.com/products/displayProductInfo.do?sku=466137eventGroup=4eventPage=1 1.05dB loss at 450MHz @ 100' DB420 spacing -- spacing and mounting per DB Products/Andrew/ComScope, etc. :) instructions, I agree, it's never perfect, just wanted to be clear that it is all by the book. Will keep looking -- measuring power at the feedline-antenna connection is my next step. Thanks for the input Robert -- this helps! On Oct 16, 2008, at 9:18 PM, KD4PBC wrote: Cort, Do you really have 5/8 ? Here are the part numbers for the coax LDF4-50A 1/2 50 ohms - loss at 450MHz ~1.447 LDF5-50A 7/8 50 ohms - loss at 450MHz ~ .808 LDF6-50A 1 1/4 50 ohms LDF7-50A 1 5/8 50 ohms So if you have the real deal feed line loss doesn't look like your problem If you have something else all bets are off send me what number is on the cable. The Telewave antenna (actuality ANY Telewave antenna) is problematic. We tried using several in the paging business most likely for the same reason you did they are cheap. They never performed as well as advertised. If you want a cheap antenna the best for the money is and ASP705K by Decibel Products (or whatever they are this week) They work well have a nice round pattern. And will generally out perform a DB-420 because of less pattern distortion. The statement The DB420 is spaced correctly from the tower concerns me as there is no correct way to side mount an antenna. You must take in to account the desired v. undesired coverage areas and optimize the mount and elements to achieve the desired coverage. On that antenna with an 18 face tower mounted 16 off the point of the tower set in an omni configuration You will see peaks of around 10.5dBd and nulls of around 5dBd. I see nothing here that would indicate that the Telewave system is performing correctly. Remember to take into the feed line loss when calculating SWR. That is if you are putting a 100 watts into the feed line and get 50 watts back That indicates a fault at the top as you have 100 watts and 2.894dB loss (1.447*2 up and down) that would be half power of 50 watts. Do some more looking before you call the antenna bad. Robert / KD4PBC -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 9:17 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Could be a bad-out-of-the-box antenna. I've heard of this happening with fiberglass antennas. It could be broken near the bottom and still show good VSWR but give you no gain. Chuck WB2EDV - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 9:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew 5/8 heliax. We also side-mounted an old DB420 with the top a few feet down from the top of the tower with about 85' of old 7/8 Andrew heliax. So, we put smokin' new gear on top, and smokin old below it. The DB420 is spaced correctly from the tower and is set up with each half 90 degrees rotated. The tower is on relatively high pasture land (for NE Kansas anyway) with a nice clear view all around. I'll not say we're on a hill, but on relatively high ground. We are attempting to cover two towns approximately 25 miles apart. We are 1/3 of the way from town 1 to town 2 and about 3 miles N of the highway that pretty much is a straight shot connecting them. The Telewave setup on top performs poorly. The DB420 on the side is working great. By this difference, I mean signals that are getting in full quieting on the DB420 are very noisy on the Telewave. Transmit differences mirror receive. S9 reception on the DB420, switch to the Telewave and it's S1-S3. We experience this phenomenon in all directions. Wattmeter (yes, it is a real one -- Telewave 44) says that things look good as far as loading both antennas -- DB420 is 1.43:1, F10 is 1.39:1. We are about to climb and take readings at the top to make sure there is no feed problem with the Telewave 'F10, and I admit that has not been done yet. We did have a discussion with Telewave, who advised that vertical alignment of the F10 (as they refer to it) is critical. We have checked alignment and even implemented a little down- tilt in the most important direction (just a few degrees). We see not real appreciable difference. For you repeater elmers out there: If we don't find a problem with the feedline on the Telewave antenna, does this make any sense? Telewave also HIGHLY recommended that the F10 isn't a good fit for this installation due to its extremely narrow vertical beamwidth, and recommended that a 4-bay dipole of theirs would be MUCH better because of the ability to tune the pattern to our desired coverage area and the increased vertical beamwidth. I always thought I wanted NARROW vertical beamwidth to keep the RF on the horizon. I would have thought that 100' up on relatively high ground (this is Kansas, after all) wouldn't have a real problem shooting over the top 10 - 30 miles away. In any event I seek advice and wisdom, and yes, we are planning to check the coax for loss at the earliest convenience. I would like to take advantage of the top slot on the tower for improved performance rather than stay on the lower spot, and will try another antenna if necessary. I'm just having a hard time imagining that the F10 has appreciably narrower vertical beam as a 9.something dBd antenna than the F10 as a 10dBd antenna, etc. etc. And it also seems counter intuitive that a taller vertical beamwidth and less gain on the horizon in this application would be better. I trust the experience and knowledge of Telewave, but I also trust the wisdom from this list, which has saved me many times. Your thoughts gentlemen? -- Cort Buffington H: +1-785-838-3034 M: +1-785-865-7206
RE: [Repeater-Builder] UHF Repeater Antenna Discussion
Cort, One problem that I don't think has been mentioned, is the possibility that the center conductor of the feedline to the top antenna has somehow disconnected from the center pin at the top end. This doesn't happen very often with foam dielectric Heliax, but it does happen often with air dielectric feedline. When the sun beats on the black exterior of the feedline, it expands longitudinally, but more on the outside than on the inside. After many cycles, the center conductor pulls out of the back of the center pin. On captive-pin Heliax connectors, it looks like the center pin is fine when viewed from the top, but there may be no connection to the cable's center conductor. One quick way to check this is to measure the DC resistance between the center conductor and shield at the bottom end of the feedline, where it connects to the duplexer. When a DC-grounded is properly connected at the top, you should measure close to zero ohms plus the loop resistance of the feedline. Incidentally, this quick and simple measurement is a good one to make on any new installation, right after it is certain that everything is working properly. The measured resistance value should be posted somewhere in the shack so that it can be verified from time to time, or when there is a suspected problem with the antenna or feedline. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 7:38 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Repeater Antenna Discussion Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] mailto:cort%40lawrence-ks.org To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
Eric! That's a really, really fantastic idea. That's TOP on the list. On Oct 16, 2008, at 10:16 PM, Eric Lemmon wrote: Cort, One problem that I don't think has been mentioned, is the possibility that the center conductor of the feedline to the top antenna has somehow disconnected from the center pin at the top end. This doesn't happen very often with foam dielectric Heliax, but it does happen often with air dielectric feedline. When the sun beats on the black exterior of the feedline, it expands longitudinally, but more on the outside than on the inside. After many cycles, the center conductor pulls out of the back of the center pin. On captive-pin Heliax connectors, it looks like the center pin is fine when viewed from the top, but there may be no connection to the cable's center conductor. One quick way to check this is to measure the DC resistance between the center conductor and shield at the bottom end of the feedline, where it connects to the duplexer. When a DC-grounded is properly connected at the top, you should measure close to zero ohms plus the loop resistance of the feedline. Incidentally, this quick and simple measurement is a good one to make on any new installation, right after it is certain that everything is working properly. The measured resistance value should be posted somewhere in the shack so that it can be verified from time to time, or when there is a suspected problem with the antenna or feedline. 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Cort Buffington Sent: Thursday, October 16, 2008 7:38 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] UHF Repeater Antenna Discussion Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] mailto:cort%40lawrence-ks.org To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna Discussion Folks, My repeater partner and I have recently placed our new 440 machine. We have realized some odd issues. We bought a new Telewave ANT450F10 to put on top of the 100' tower, fed with a new piece of Andrew
Re: [Repeater-Builder] UHF Repeater Antenna Discussion
My 2 cents worth. Many years ago I had a 200' run of LDF5-50 installed by a professional on a 900'tower (rptr at 700' antenna at 900') about a week later we noticed that the TR performance dropped considerably. Personal inspection revealed that water or condensate (about a teaspoon full) had drained down the cable insde the hollow center conductor and had seeped around the inside of the bottom connector. The solution was to completely remove the connector and center pin, drain the cable and let it thoroughly dry then reinstall the connector. I never had another problem with it after that. I suggest you take a look at yours. Years later I ordered 2 runs of LDF4-50 w/ connectors installed from DB and after receiving them checked them for continuitybefore installation. One cable showed a direct short between center conductor and ground. I removed both connectors and found one connector had been improperly installed at DB. Apparently the portion that has the spring fingers on it had been allowed to turn in the tightening process and it had grabbed the copper shield, shredded it and bent it inward to where it made contact with the center conductor. Needless to say ,but I then removed all the other connectors to verify their condition and reinstalled all of them properly. A third case similar to the one above (shredded shield ) but no physical contact (no continuity) showed a 1:1 SWR on Xmit but caused the RF to desense the rcvr. to the point where the perfomance of the rptr. was drastically reduced from what it should have been. Similar to what you are describing. While you might not see a direct short or even an indication of high reflected power when you test the system, if you have any contamination, moisture, or metallic debris in side the connector it can cause you the grief you are describing. Hope this helps some. -- Doug N3DAB/WPRX486/WPJL709 Cort Buffington [EMAIL PROTECTED] wrote: = Don, two completely different antenna and feedline systems. I swap them where each separate antenna/feedline system connects to the duplexer. The Telewave meter is new because I didn't trust my ham-type meters... (I've needed a real meter for years anyway) The Telewave shows a little less forward power and a little lower VSWR than the cheap comets. I did a quick check of the telewave by transmitting various signal levels into my IFR 1200S (currently in calibration from Aeroflex) I then transmitted the same signals into the telewave with a nice big DB load I've trusted for years on it. The Telewave was within a few % of the IFR. I know that's not a perfect method, but new meter, agrees with IFR in my limited testing format. I'm probably pretty confident of it. Problems before and after vertical alignment. If the feedline/ connector is damaged it was damaged when we put this system up -- from tower on the ground. I mean, we did it ALL three weeks ago. Saturday morning there was a pile of parts, by sundown it was all assembled and installed. No rain at all between erection and the first round of testing. After significant rains, no change. Thanks Don! Cort On Oct 16, 2008, at 9:24 PM, Don Kupferschmidt wrote: Cort, I need to understand if I have all the information correct from your post. One 440 machine. One duplexer. Two antennas connected to two feedlines which can either be terminated to the duplexer as you so desire? Only one feedline to one antenna, not coupled or combined in any way? One hardline / antenna works good (DB420) and one hardline / antenna (Telewave ANT450F10) works bad? The first step is to verify the Telewave wattmeter. I'd get a hold of a Bird 43 or equivalent and verify your readings. That's the easiest thing to do. If your forward / reverse numbers are accurate then I'd suspect the Telewave system or it's hardline, unless proven otherwise. You need to rule out either the antenna or the hardline by substitution, and one at a time. Possible issues could be bad connectors either at the antenna base or duplexer termination. How long ago was the antenna system put up? Was there some heavy rain in the area that water could have been introduced into the connector / hardline if they weren't properly water-proofed? Unless someone contradicts me here, I'm having a hard time believing that the vertical alignment of the Telewave is critical. In re-reading your post over a couple of times I'm wondering when you checked the alignment and then implemented a little down-tilt you may have done something wrong to cause the hardline / antenna system to react that way. Keep us posted and good luck with finding out the problem. Don, KD9PT - Original Message - From: Cort Buffington [EMAIL PROTECTED] To: Repeater-Builder@yahoogroups.com Sent: Thursday, October 16, 2008 8:16 PM Subject: [Repeater-Builder] UHF Repeater Antenna
