Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Paul - Were the U-bolts that attach each element arm to the mast stainless or hot dip galvanized? I do know of one (UHF) Sinclair array that used plated U-bolts and they rusted. Chuck WB2EDV Several weeks ago I posted about my ongoing battle with duplex noise on a 2 meter repeater. I have now found a big piece of the problem (maybe all of it) but I'm a little surprised. I am wondering if others have had similar experiences. Two years ago I put up a new (well... NOS, actually) Sinclair SD2352 antenna (8 dipoles, bidirectional pattern). I had no noise for several months after that, but then it started coming back. By this Spring the repeater had become all but unusable.
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Chuck, They are hot dip galvanized and there is no sign of rust (yet). When I took this apart I checked every bit of hardware for looseness and rust, found nothing suspect. One thing I did notice when I got the antenna was the factory Y splices and heat shrink over the 1/4 wave 35 ohm matching section were anything but water tight. I added waterproofing (butyl rubber and tape) in which I had total confidence but now paranoia is making me doubt myself. :-) I will rip into it today. Paul N1BUG Chuck Kelsey wrote: Paul - Were the U-bolts that attach each element arm to the mast stainless or hot dip galvanized? I do know of one (UHF) Sinclair array that used plated U-bolts and they rusted. Chuck WB2EDV Several weeks ago I posted about my ongoing battle with duplex noise on a 2 meter repeater. I have now found a big piece of the problem (maybe all of it) but I'm a little surprised. I am wondering if others have had similar experiences. Two years ago I put up a new (well... NOS, actually) Sinclair SD2352 antenna (8 dipoles, bidirectional pattern). I had no noise for several months after that, but then it started coming back. By this Spring the repeater had become all but unusable.
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Thanks Burt! Great info there. If all the dipoles seem to be OK (not noisy) I am thinking of making my own harness to use 4 of them. I've constructed several multiple-antenna EME arrays so I understand the concepts and the importance of equal lengths, etc. My only concern with making my own harness is that the length of coax attached to each dipole is not long enough to reach a tee connector on the mast and allow sufficient vertical spacing between dipoles. (The original configuration had four bays of two side by side dipoles, so the shorter length was appropriate there.) It will be easy enough to add on some coax but since the impedance at my 147 MHz frequency is not exactly 50 ohms and somewhat reactive it will vary somewhat with the coax length. I don't think it will be enough to cause major issues. I see that I will need to use some odd multiple of a quarter wavelength for the 50 ohm coax sections from the array center tee to each of the outer tees feeding pairs of dipoles. I need to see if I can figure out what failed and why in the original configuration before I go investing time and money into a rebuild though. Its useful service life before becoming too noisy was less than a year! Paul N1BUG Burt Lang wrote: The matching section inside the loop is a 1/4 wavelength of RG-63B 125 ohm coax. The overall outside diameter is the same as RG-214 but the dielectric is semi-air (like a large version of RG-62 93 ohm coax) and the center conductor is quite small, like RG-59. I have a few hundred feet of RG-63B if you want to experiment. The actual length of the matching section in the commercial loop is not however a 1/4 wavelength at the center freq of the dipole but rather on the high side. A Sinclair loop I dismantled had a matching section that was 1/4 wave at 182 MHz. I believe that this is the secret to the extra wide bandwidth of the dipole. Using a matching section that is 1/4 wave at the center freq of the dipole (156 MHz) gives a much better return loss at 156 MHz but is at least 20% narrower bandwidth. I have made a number of clones with both the dipole and the matching section tuned to 146MHz. The return loss was very good at 2m (SWR very close to 1:1 vs the commercial antenna that was 1.2:1 at its lowest point over the 138-174 MHz bandwidth.) I also used the same design in several 4 bay 220MHz versions that have been in service for up to 15 years. Check the following URL for a diagram of my clone design: http://www.gorum.ca/fdipolev.gif One point of warning: It is very hard to insert the coax into the loop. You have to make as short a splice as possible since it must slide past the 180 deg bend in the loop. Avoid messing with this coax unless absolutely necessary. As for the harness, the key point is that the electrical length of the RG-213 from each dipole must be identical. The actual electrical length is unimportant, it just has to be the same for all dipoles. The actual configuration of the harness depends on the number of dipoles. One and 4 dipoles can be made entirely with RG-213 whereas 2 and 8 dipoles require a 1/4 wave section of RG-83 35 ohm coax. The one mystery I have is how Sinclair inserts the harness into the mast for the fully enclosed model. The matching section parts of the harness are completely inside the mast and is beyond the means of us amateurs. However an external harness is very practical. Burt Lang VE2BMQ
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
That is interesting Gran. The noise did not change with weather conditions, be it wet or dry, dead calm or gale force winds. I didn't try spraying with water while testing, but did tap on all the dipoles and wiggle as much coax as I could reach. It didn't seem to react to any of that. It was very noisy during all this testing, but not much more or less so than at any other time. Paul N1BUG Gran Clark wrote: Paul I have recently had to deal with the same problem. Note if the noise goes away when the antenna is wet for frozen. If this is the case try selectively spraying elements with water while whacking the antenna with a rubber hammer. I will leave the mechanics of doing this up to youHI.Feed line noise due to flexing could be eliminated as a cause with this test also. Tightening hardware helped in my case but the final answer was going to all welded construction. Gran K6RIF
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Hi Paul The info I gave you applied to the SD214 series antennas (old SRL210A4 oe 210C4). I am guessing that it would also apply to the cheaper SD2352 series. Let's hope you don't need to get inside the dipole itself. BTW what is the diameter of the aluminum tubing used on the SD2352? The SD214 uses 3/4in OD. Paul Kelley N1BUG wrote: Thanks Burt! If all the dipoles seem to be OK (not noisy) I am thinking of making my own harness to use 4 of them. I've constructed several multiple-antenna EME arrays so I understand the concepts and the importance of equal lengths, etc. I used an old HP RF impedance bridge to match the harness sections on the antennas I built. It allowed me to match actual electrical lengths to within .01 wavelength. My only concern with making my own harness is that the length of coax attached to each dipole is not long enough to reach a tee connector on the mast and allow sufficient vertical spacing between dipoles. (The original configuration had four bays of two side by side dipoles, so the shorter length was appropriate there.) It will be easy enough to add on some coax but since the impedance at my 147 MHz frequency is not exactly 50 ohms and somewhat reactive it will vary somewhat with the coax length. I don't think it will be enough to cause major issues. You could try using 3/4 wavelength matching pieces to get the extra length. That should be equivalent to 1/4 wave but will be more sensitive to frequency changes. I see that I will need to use some odd multiple of a quarter wavelength for the 50 ohm coax sections from the array center tee to each of the outer tees feeding pairs of dipoles. Never having seen one of those antennas (the SD2352) up close, I am not sure of the harness configuration and how it would compare to the SD214 that I am familiar with. I need to see if I can figure out what failed and why in the original configuration before I go investing time and money into a rebuild though. Its useful service life before becoming too noisy was less than a year! Figuring out the failure mode is the most important first step. Then you can go from there to possible solutions whether it is harness replacement, repair or dig into the dipoles. Good luck Burt Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Hi Burt, Let's hope you don't need to get inside the dipole itself. BTW what is the diameter of the aluminum tubing used on the SD2352? The SD214 uses 3/4in OD. I *am* hoping! They use 3/4 in. OD on these also. The width of the folded dipole is 4.25 inches and the tip to tip (outer radius of bend to outer radius of bend) length is 34.5 inches. You could try using 3/4 wavelength matching pieces to get the extra length. That should be equivalent to 1/4 wave but will be more sensitive to frequency changes. I only need to extend them by about a foot to get ideal spacing between dipoles, so 1/4 wavelength with .66 VF would be enough. Never having seen one of those antennas (the SD2352) up close, I am not sure of the harness configuration and how it would compare to the SD214 that I am familiar with. Total of 8 dipoles. Impedance at end of coax coming from each dipole approximately 50 ohms. Two dipoles connect to a type N tee, so at the tee center should be about 25 ohms. From there, 1/4 wavelength RG-213 to a a factory harness 'Y' splice, coax should transform the impedance to about 100 ohms, divided by 2 at the Y so we're back to 50 ohms coming out of there. From there, approximately 66 inches RG-213 to the center Y splice of the overall harness. This coax should maintain 50 ohms, divided by two at the center Y splice = 25 ohms. There is a 1/4 wavelength of some coax coming out of there, spliced to a length of RG213 running down to the bottom of the mast. I'm assuming the 1/4 wavelength matching section is 35 ohm coax, but cannot confirm that. This description may be clear as mud... I can make a diagram of it later if you want. Figuring out the failure mode is the most important first step. Then you can go from there to possible solutions whether it is harness replacement, repair or dig into the dipoles. I have decided no matter what I'm not putting it back up as an 8 dipole bidirectional array so I will take apart the original harness for inspection. I will also test each of the dipoles on the repeater individually to check for noise. If I do not find any problems in either of these processes, then I will have no clue what caused the problem! Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Paul Kelley N1BUG wrote: Hi Burt, snip You could try using 3/4 wavelength matching pieces to get the extra length. That should be equivalent to 1/4 wave but will be more sensitive to frequency changes. I only need to extend them by about a foot to get ideal spacing between dipoles, so 1/4 wavelength with .66 VF would be enough. Be careful how you splice. I normally used short pieces of thin wall brass tubing of appropriate size to splice the center conductor. You can get this tubing in various sizes (increments of 1/32in diameter up to 9/16 OD) (KS brand) at most hobby shops. You can also use a piece of larger tubing to splice the shields. The most important step is the use of heavy adhesive lined shrink tubing to seal and waterproof the joint. Never having seen one of those antennas (the SD2352) up close, I am not sure of the harness configuration and how it would compare to the SD214 that I am familiar with. Total of 8 dipoles. Impedance at end of coax coming from each dipole approximately 50 ohms. Two dipoles connect to a type N tee, so at the tee center should be about 25 ohms. From there, 1/4 wavelength RG-213 to a a factory harness 'Y' splice, coax should transform the impedance to about 100 ohms, divided by 2 at the Y so we're back to 50 ohms coming out of there. From there, approximately 66 inches RG-213 to the center Y splice of the overall harness. This coax should maintain 50 ohms, divided by two at the center Y splice = 25 ohms. There is a 1/4 wavelength of some coax coming out of there, spliced to a length of RG213 running down to the bottom of the mast. I'm assuming the 1/4 wavelength matching section is 35 ohm coax, but cannot confirm that. This description may be clear as mud... I can make a diagram of it later if you want. That is exactly what I would have expected ie same as the SRL210 series. BTW the Wireman may have RG-83 35 ohm coax available - at least he had many years ago when I inquired. When I got my stock of RG-63B I had to buy a 500 ft roll at many , which was only practical since I intended to make many antennas. I probably only used 175 ft of the roll. The high cost is due to the fact that the cable was true Mil-Spec (complete with compliance records) and small demand/production runs. The same would apply to RG-83. Figuring out the failure mode is the most important first step. Then you can go from there to possible solutions whether it is harness replacement, repair or dig into the dipoles. I have decided no matter what I'm not putting it back up as an 8 dipole bidirectional array so I will take apart the original harness for inspection. I will also test each of the dipoles on the repeater individually to check for noise. If I do not find any problems in either of these processes, then I will have no clue what caused the problem! Consider the possibility that water has got into the RG-213 and corroded the shield. This would likely give noise when RF is applied but not be particularly sensitive to vibration. Look for green copper shields, it is not environmentally friendly :-) Burt Paul N1BUG Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Or the white, powder residue. That's just as bad as the green stuff. Chuck WB2EDV - Original Message - From: Burt Lang b...@gorum.ca To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 10:00 AM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) Consider the possibility that water has got into the RG-213 and corroded the shield. This would likely give noise when RF is applied but not be particularly sensitive to vibration. Look for green copper shields, it is not environmentally friendly :-) Burt
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Update... the entire harness looks pristine. No sign of any problem. That goo they put inside the plastic clam shells around the factory Y splices is rather interesting stuff! I hope I find one or more noisy dipoles when I test 'em... otherwise I'll be left with a mystery and have no idea what was wrong. Meanwhile the repeater continues to be 100% perfectly free of noise on the single dipole from this array. It was never this good with the whole SD2352 up there... not even on day one. Paul N1BUG Chuck Kelsey wrote: Or the white, powder residue. That's just as bad as the green stuff. From: Burt Lang Consider the possibility that water has got into the RG-213 and corroded the shield. This would likely give noise when RF is applied but not be particularly sensitive to vibration. Look for green copper shields, it is not environmentally friendly :-)
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
On Tue, 19 May 2009 09:03:51 -0400, Paul Kelley N1BUG paul.kelley.n1...@gmail.com said: I have decided no matter what I'm not putting it back up as an 8 dipole bidirectional array so I will take apart the original harness for inspection. I will also test each of the dipoles on the repeater individually to check for noise. If I do not find any problems in either of these processes, then I will have no clue what caused the problem! Paul N1BUG Paul, You didn't say, but are you running on some other antenna right now. (I'm looking here for how you know it was the Sinclair making the noise, and not some nearby rusty joint problem in a high RF field environment. (Are you in a high RF field environment? Any new transmitters right on top of your new Sinclair antenna?) Just thinking through it and wanting to make sure you didn't do anything drastic to the antenna before you KNOW it was the antenna and not something else nearby... Just a precautionary comment... maybe useful, maybe not... Nate WY0X -- Nate Duehr n...@natetech.com
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
You could test the harness with dummy loads connected in place of each element, if you can round up enough dummy loads. And you could install the entire array at a different location and test it there. Two more options to think about. If the single element is mounted in the same location as where the array was, I'd not be terribly suspicious of a near-field noise maker - rusty bolt, guy wire, etc. Chuck WB2EDV - Original Message - From: Paul Kelley N1BUG paul.kelley.n1...@gmail.com To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 1:35 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) Update... the entire harness looks pristine. No sign of any problem. That goo they put inside the plastic clam shells around the factory Y splices is rather interesting stuff! I hope I find one or more noisy dipoles when I test 'em... otherwise I'll be left with a mystery and have no idea what was wrong. Meanwhile the repeater continues to be 100% perfectly free of noise on the single dipole from this array. It was never this good with the whole SD2352 up there... not even on day one. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
You didn't say, but are you running on some other antenna right now. (I'm looking here for how you know it was the Sinclair making the noise, and not some nearby rusty joint problem in a high RF field environment. (Are you in a high RF field environment? Any new transmitters right on top of your new Sinclair antenna?) Nate, I would call it a low RF environment. There are two cell towers, both about 500 feet away, neither has any VHF or UHF repeater tenants. The nearest broadcast station of any type is at least 15 miles away. There are one or two other VHF transmitters nearby but they are very rarely up and I had noise all the time. Right now I am running on one single dipole removed from the Sinclair array and it is working perfectly. Zero noise. Just thinking through it and wanting to make sure you didn't do anything drastic to the antenna before you KNOW it was the antenna and not something else nearby... I appreciate it! This problem has really had be baffled. In fact I DON'T KNOW it is the Sinclair. Here's the story: Two years ago my very old top-mounted PD220 failed (repeater signal dropped, lots of crackling noise). No surprise there, I had been wondering when that thing would die. I replaced it with the Sinclair but unfortunately I extended the tower at the same time so I introduced many new variables. I noticed right away there was some noise every time my transmitter came up but couldn't find any obvious cause and most of the time it wasn't enough to really be an issue. A year later the noise started increasing rapidly, sometimes some crackling but more often a highly variable white noise, basically just an unstable increase in receiver noise floor. It got worse and worse until at the end I had at least 10 dB noise increase every time my transmitter came up, varying to sometimes more than 30 dB. Ouch! Much testing and fooling around was done over a period of several months... dummy load at duplexer (no noise), at top of tower (no noise), swapped out the transmitter (no change), swapped out receiver (no change), tried using two antennas (that helped especially when the Sinclair was NOT the transmit antenna, but did not get rid of the noise entirely). Shook, wiggled, prodded and aggravated every metal and quasi-metal object within several hundred feet... nothing seemed to react. A week ago I pulled the Sinclair off the tower and stuck an old IsoPole up in the same spot. Zero noise! Huh? I increased transmitter power by several dB, still no noise whatsoever. I now have one dipole removed from the Sinclair on the tower, and there is no noise at all with that arrangement. My gut tells me this is a rusty bolt / bad connection kind of thing, but it goes away when the Sinclair isn't on the tower. I know that doesn't prove anything, but I have no idea where else to look other than the Sinclair antenna. I'm open to suggestions. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.) -- Nate Duehr n...@natetech.com
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
There's nothing crazy about that idea Nate! I get creative thoughts when sleep deprived too. :) I had been thinking the transmitter might be doing something funny. I don't have easy access to a spectrum analyzer, but I think I've ruled out spurs as the primary cause? Correct me if my logic is flawed. I did some tests before I pulled the Sinclair off the tower. With the Sinclair and another antenna on the tower, here is what I found: RX TX on Sinclair SEVERE noise, 10 to 40+ dB RX on other ant, TX on Sinclair moderate noise, peaks to 10+ dB RX on Sinclair, TX on other ant... mild noise, nil to maybe 5 dB RX and TX on other ant... maybe traces of noise??, barely detectable RX and TX on other ant, Sinclair removed from tower... no noise detected... dead quiet I think this suggests something in the Sinclair is generating noise, and that even when transmitting into another antenna it picks up enough RF to make some noise? You wouldn't believe how many pages of notes I have on various tests and experiments over the last year or so... I don't even know what's in there any more! I was hoping to get up to the site today to do a brief test duplexed into each of the other dipoles pulled from the Sinclair, but no go. Maybe tomorrow. Paul N1BUG Nate Duehr wrote: A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.)
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
I'd agree with your observation Paul. It looks like something with the Sinclair. Now you've just got to try each element individually and rule more out. Chuck WB2EDV - Original Message - From: Paul Kelley N1BUG paul.kelley.n1...@gmail.com To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 5:49 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) There's nothing crazy about that idea Nate! I get creative thoughts when sleep deprived too. :) I had been thinking the transmitter might be doing something funny. I don't have easy access to a spectrum analyzer, but I think I've ruled out spurs as the primary cause? Correct me if my logic is flawed. I did some tests before I pulled the Sinclair off the tower. With the Sinclair and another antenna on the tower, here is what I found: RX TX on Sinclair SEVERE noise, 10 to 40+ dB RX on other ant, TX on Sinclair moderate noise, peaks to 10+ dB RX on Sinclair, TX on other ant... mild noise, nil to maybe 5 dB RX and TX on other ant... maybe traces of noise??, barely detectable RX and TX on other ant, Sinclair removed from tower... no noise detected... dead quiet I think this suggests something in the Sinclair is generating noise, and that even when transmitting into another antenna it picks up enough RF to make some noise? You wouldn't believe how many pages of notes I have on various tests and experiments over the last year or so... I don't even know what's in there any more! I was hoping to get up to the site today to do a brief test duplexed into each of the other dipoles pulled from the Sinclair, but no go. Maybe tomorrow. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Paul, One test I have not noticed listed is if you've tried the Sinclair while it was not attached to the tower (and a reasonable distance away from anything that could affect it). Ed Yoho W6YJ Paul Kelley N1BUG wrote: There's nothing crazy about that idea Nate! I get creative thoughts when sleep deprived too. :) I had been thinking the transmitter might be doing something funny. I don't have easy access to a spectrum analyzer, but I think I've ruled out spurs as the primary cause? Correct me if my logic is flawed. I did some tests before I pulled the Sinclair off the tower. With the Sinclair and another antenna on the tower, here is what I found: RX TX on Sinclair SEVERE noise, 10 to 40+ dB RX on other ant, TX on Sinclair moderate noise, peaks to 10+ dB RX on Sinclair, TX on other ant... mild noise, nil to maybe 5 dB RX and TX on other ant... maybe traces of noise??, barely detectable RX and TX on other ant, Sinclair removed from tower... no noise detected... dead quiet I think this suggests something in the Sinclair is generating noise, and that even when transmitting into another antenna it picks up enough RF to make some noise? You wouldn't believe how many pages of notes I have on various tests and experiments over the last year or so... I don't even know what's in there any more! I was hoping to get up to the site today to do a brief test duplexed into each of the other dipoles pulled from the Sinclair, but no go. Maybe tomorrow. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
humm maybe o/t sinclair antenna has not be solded to comprod antenna sometime ago 73/s all gervais ve2ckn -- From: Nate Duehr n...@natetech.com Sent: Tuesday, May 19, 2009 5:04 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.) -- Nate Duehr n...@natetech.com Yahoo! Groups Links
RE: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
I did see Paul's reply also Nate,, I'm betting if he had some of those spurious products with the numbers he has given, they would be too small to see with even the best gear. I had a similar noise level issue that turned out to be an amp and I couldn't see squat with my HP8921a, (weak S/A) but I was warned by elmers it may not be measurable. Your suggestion is a good one. Paul, the lesson I learned on that event was that just because the problem went away on the dummy load, don't assume all the tested good on a dummy load parts are eliminated. Don Kirchner W5DK -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Nate Duehr Sent: Tuesday, May 19, 2009 4:05 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.) -- Nate Duehr n...@natetech.com Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Ed, That is true. I stupidly neglected to do that after removing it from the tower and have been kicking myself ever since! I will probably end up re-assembling it to try that... but of course now everything has been disturbed so it may or may not act as it did before. I did do a brief test on it before it went up the tower two years ago and noted a couple dB of noise. I dismissed it as probably somehow related to the antenna being too close to the repeater equipment etc. but had about the same observed noise after mounting it on the tower. It held that way for months and then started getting worse. Paul N1BUG Ed Yoho wrote: Paul, One test I have not noticed listed is if you've tried the Sinclair while it was not attached to the tower (and a reasonable distance away from anything that could affect it). Ed Yoho W6YJ
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
No, Comprod is a separate company. Yes, the products look like Sinclair clones. Chuck WB2EDV - Original Message - From: gervais ve2...@hotmail.com To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 6:04 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) humm maybe o/t sinclair antenna has not be solded to comprod antenna sometime ago 73/s all gervais ve2ckn -- From: Nate Duehr n...@natetech.com Sent: Tuesday, May 19, 2009 5:04 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.) -- Nate Duehr n...@natetech.com Yahoo! Groups Links Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Chuck Kelsey wrote: You could test the harness with dummy loads connected in place of each element, if you can round up enough dummy loads. I like that idea. I would have to buy a bunch of loads though, not much chance of borrowing that many around here. And you could install the entire array at a different location and test it there. I wish I had at least checked it at ground level after pulling it off the tower... I goofed there! If the single element is mounted in the same location as where the array was, I'd not be terribly suspicious of a near-field noise maker - rusty bolt, guy wire, etc. It is at the same location, but is not mounted with the same hardware. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
I have been reading the mail and it occures to me that some of your repeater must need rack mount kits. I sell Motorola Dual Maxtrec radio size (2.04x7.04 inch) rack mounts, and just introduce our CDM 1250/1550 Dual rack mount. I sell these on eBay at $89.95, but discount $10 ($79.95) for direct sales. Units are in stock, can ship in a couple of business days. I accept PayPal, so ordering is ease. Also looking for the interest level for the Motorola CDM 750 size dual rack mounts. drop me an email with any questions. 73's and Thanks Dick K4EIH/6 San Diego, CA jazz...@san.rr.com - Original Message - From: Ed Yoho To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 3:00 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) Paul, One test I have not noticed listed is if you've tried the Sinclair while it was not attached to the tower (and a reasonable distance away from anything that could affect it). Ed Yoho W6YJ Paul Kelley N1BUG wrote: There's nothing crazy about that idea Nate! I get creative thoughts when sleep deprived too. :) I had been thinking the transmitter might be doing something funny. I don't have easy access to a spectrum analyzer, but I think I've ruled out spurs as the primary cause? Correct me if my logic is flawed. I did some tests before I pulled the Sinclair off the tower. With the Sinclair and another antenna on the tower, here is what I found: RX TX on Sinclair SEVERE noise, 10 to 40+ dB RX on other ant, TX on Sinclair moderate noise, peaks to 10+ dB RX on Sinclair, TX on other ant... mild noise, nil to maybe 5 dB RX and TX on other ant... maybe traces of noise??, barely detectable RX and TX on other ant, Sinclair removed from tower... no noise detected... dead quiet I think this suggests something in the Sinclair is generating noise, and that even when transmitting into another antenna it picks up enough RF to make some noise? You wouldn't believe how many pages of notes I have on various tests and experiments over the last year or so... I don't even know what's in there any more! I was hoping to get up to the site today to do a brief test duplexed into each of the other dipoles pulled from the Sinclair, but no go. Maybe tomorrow. Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
yes Chuck they are ex:engineer from Sinclair and they start thir company many years ago,i have done business with them,they are professionnal as Sinclair. 73/s gervais ve2ckn -- From: Chuck Kelsey wb2...@roadrunner.com Sent: Tuesday, May 19, 2009 6:23 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) No, Comprod is a separate company. Yes, the products look like Sinclair clones. Chuck WB2EDV - Original Message - From: gervais ve2...@hotmail.com To: Repeater-Builder@yahoogroups.com Sent: Tuesday, May 19, 2009 6:04 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) humm maybe o/t sinclair antenna has not be solded to comprod antenna sometime ago 73/s all gervais ve2ckn -- From: Nate Duehr n...@natetech.com Sent: Tuesday, May 19, 2009 5:04 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) A TOTALLY crazy idea Paul... Just going off of your comment that it gets better when you split antennas but is always there when the Sinclair is on the tower... Could the Sinclair be doing something funny to your transmitter and causing it to throw spurs? Things would be really bad when duplexed on it, and get better as you move the receive antenna away from it. Just a thought... would need to look at your output on a spectrum analyzer to see that one... preferably first on one of the antennas that works and then on the Sinclair. Nate WY0X (Sleep deprivation will lead to some creative thoughts, I'm finding today. It was a lng night last night.) -- Nate Duehr n...@natetech.com Yahoo! Groups Links Yahoo! Groups Links Yahoo! Groups Links
RE: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Paul, I have a question as to how you are mounting the antenna. If you are not top supporting the antenna and mounting it on top of the tower that would explain why as to you getting noise in your transmit signal. Same goes for DB antennas especially the DB224 being so long and not top supported you will eventually get noise in the signal as well. Mike Mike Mullarkey K7PFJ 6886 Sage Ave Firestone, Co 80504 303-954-9695 Home 303-954-9693 Home Office Fax 303-718-8052 Cellular _ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Kelley N1BUG Sent: Monday, May 18, 2009 1:01 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Sinclair dipole array premature failure (noisy) Several weeks ago I posted about my ongoing battle with duplex noise on a 2 meter repeater. I have now found a big piece of the problem (maybe all of it) but I'm a little surprised. I am wondering if others have had similar experiences. Two years ago I put up a new (well... NOS, actually) Sinclair SD2352 antenna (8 dipoles, bidirectional pattern). I had no noise for several months after that, but then it started coming back. By this Spring the repeater had become all but unusable. Recently I took down the Sinclair and installed a temporary antenna. Noise gone! Huh? I subsequently disassembled the Sinclair to check for problems. Every piece of hardware was tight. I found no evidence of water in any of the N connectors on the harness, which I had wrapped with Scotch 23 rubber tape followed by Super 88 vinyl tape. The impedance of the complete array and of each individual dipole was still nominal, as it had been prior to being installed. I have now put one dipole from the array on the tower and it is running absolutely noise free. Moving it around on the tower doesn't have any affect... it is noise free wherever I put it. Lacking any other explanation it would seem something in the array became noisy after a short time. I don't know if it is a problem with one or more of the dipoles or perhaps something in the factory assembled portion of the harness. I have not yet attempted to do a post mortem on the factory harness assemblies. I am wondering if this is a unique experience or if this is a common failure mode in exposed dipole arrays? I don't recall hearing much about such arrays becoming noisy, at least in such a short time. Since these dipoles are 50 ohms, I think it would be easy enough to build two 4-dipole cardioid arrays from it, *if* the problem lies in the harness and not in one or more of the dipoles. I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Mike, Thanks. That is interesting. I don't recall hearing about this with dipole arrays before. What is the failure mechanism? Deterioration of the coax due to repeated slight flexing? The antenna was supported bottom and middle. Paul N1BUG Mike Mullarkey wrote: Paul, I have a question as to how you are mounting the antenna. If you are not top supporting the antenna and mounting it on top of the tower that would explain why as to you getting noise in your transmit signal. Same goes for DB antennas especially the DB224 being so long and not top supported you will eventually get noise in the signal as well.
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
There is a 1/4 wave impedance matching section of coax (125?) inside the element. The matching section is stagger tuned from the element itself. That's why it is more boadbanded and why you see two return loss dips. Chuck WB2EDV - Original Message - I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
That's what I thought Chuck. Thanks! I haven't yet decided whether I want to rip the heat shrink tubing off an element and disassemble it to see what coax is inside, which is why I asked. I was sort of contemplating whether it might be possible to replace all that coax with RG-214 in an attempt to build a noise free harness. But if there's a matching section, I'm sure the return loss without it would be really ugly. Paul N1BUG Chuck Kelsey wrote: There is a 1/4 wave impedance matching section of coax (125?) inside the element. The matching section is stagger tuned from the element itself. That's why it is more boadbanded and why you see two return loss dips. Chuck WB2EDV - Original Message - I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Sounds like something in the harness went intermittent. To get at the inner element connection, you'd need to cut the shrink tubing on the outside of the element. That should gave you access to the connection point of the 125-ohm matching section that is spliced to the RG-213. You could then pull that out. However, if each element plays alone with no noise, I'd leave the element wiring alone and check the harness that connects the elements together. All that said, I've never worked on a Sinclair. I'm going by info that I believe to be correct as to what is inside the element. Chuck WB2EDV - Original Message - From: Paul Kelley N1BUG paul.kelley.n1...@gmail.com To: Repeater-Builder@yahoogroups.com Sent: Monday, May 18, 2009 6:58 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) That's what I thought Chuck. Thanks! I haven't yet decided whether I want to rip the heat shrink tubing off an element and disassemble it to see what coax is inside, which is why I asked. I was sort of contemplating whether it might be possible to replace all that coax with RG-214 in an attempt to build a noise free harness. But if there's a matching section, I'm sure the return loss without it would be really ugly. Paul N1BUG Chuck Kelsey wrote: There is a 1/4 wave impedance matching section of coax (125?) inside the element. The matching section is stagger tuned from the element itself. That's why it is more boadbanded and why you see two return loss dips. Chuck WB2EDV - Original Message - I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
The matching section inside the loop is a 1/4 wavelength of RG-63B 125 ohm coax. The overall outside diameter is the same as RG-214 but the dielectric is semi-air (like a large version of RG-62 93 ohm coax) and the center conductor is quite small, like RG-59. I have a few hundred feet of RG-63B if you want to experiment. The actual length of the matching section in the commercial loop is not however a 1/4 wavelength at the center freq of the dipole but rather on the high side. A Sinclair loop I dismantled had a matching section that was 1/4 wave at 182 MHz. I believe that this is the secret to the extra wide bandwidth of the dipole. Using a matching section that is 1/4 wave at the center freq of the dipole (156 MHz) gives a much better return loss at 156 MHz but is at least 20% narrower bandwidth. I have made a number of clones with both the dipole and the matching section tuned to 146MHz. The return loss was very good at 2m (SWR very close to 1:1 vs the commercial antenna that was 1.2:1 at its lowest point over the 138-174 MHz bandwidth.) I also used the same design in several 4 bay 220MHz versions that have been in service for up to 15 years. Check the following URL for a diagram of my clone design: http://www.gorum.ca/fdipolev.gif One point of warning: It is very hard to insert the coax into the loop. You have to make as short a splice as possible since it must slide past the 180 deg bend in the loop. Avoid messing with this coax unless absolutely necessary. As for the harness, the key point is that the electrical length of the RG-213 from each dipole must be identical. The actual electrical length is unimportant, it just has to be the same for all dipoles. The actual configuration of the harness depends on the number of dipoles. One and 4 dipoles can be made entirely with RG-213 whereas 2 and 8 dipoles require a 1/4 wave section of RG-83 35 ohm coax. The one mystery I have is how Sinclair inserts the harness into the mast for the fully enclosed model. The matching section parts of the harness are completely inside the mast and is beyond the means of us amateurs. However an external harness is very practical. Burt Lang VE2BMQ Paul Kelley N1BUG wrote: That's what I thought Chuck. Thanks! I haven't yet decided whether I want to rip the heat shrink tubing off an element and disassemble it to see what coax is inside, which is why I asked. I was sort of contemplating whether it might be possible to replace all that coax with RG-214 in an attempt to build a noise free harness. But if there's a matching section, I'm sure the return loss without it would be really ugly. Paul N1BUG Chuck Kelsey wrote: There is a 1/4 wave impedance matching section of coax (125?) inside the element. The matching section is stagger tuned from the element itself. That's why it is more boadbanded and why you see two return loss dips. Chuck WB2EDV - Original Message - I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG Yahoo! Groups Links
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Well the 125 ohm quarter wave info sounds reasonable. That would imply the actual impedance of the folded dipole is in the vicinity of 300 ohms. I think my strategy at this point is to test each element by itself. I'll have to actually put each one on the repeater and check for noise as that's the only way I know to see if they are noisy in duplex operation or not. If all the elements test good, I will rip apart the factory interconnection harness to see if I can find anything wrong with the Y splices. Meanwhile if anyone else has any insight on exposed dipole arrays going noisy within a short time after installation, please chime in. I would really like to understand the issues with this. Paul N1BUG Chuck Kelsey wrote: Sounds like something in the harness went intermittent. To get at the inner element connection, you'd need to cut the shrink tubing on the outside of the element. That should gave you access to the connection point of the 125-ohm matching section that is spliced to the RG-213. You could then pull that out. However, if each element plays alone with no noise, I'd leave the element wiring alone and check the harness that connects the elements together. All that said, I've never worked on a Sinclair. I'm going by info that I believe to be correct as to what is inside the element. Chuck WB2EDV - Original Message - From: Paul Kelley N1BUG paul.kelley.n1...@gmail.com To: Repeater-Builder@yahoogroups.com Sent: Monday, May 18, 2009 6:58 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) That's what I thought Chuck. Thanks! I haven't yet decided whether I want to rip the heat shrink tubing off an element and disassemble it to see what coax is inside, which is why I asked. I was sort of contemplating whether it might be possible to replace all that coax with RG-214 in an attempt to build a noise free harness. But if there's a matching section, I'm sure the return loss without it would be really ugly. Paul N1BUG Chuck Kelsey wrote: There is a 1/4 wave impedance matching section of coax (125?) inside the element. The matching section is stagger tuned from the element itself. That's why it is more boadbanded and why you see two return loss dips. Chuck WB2EDV - Original Message - I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG Yahoo! Groups Links Yahoo! Groups Links -- Paul Kelley, N1BUG http://www.n1bug.com
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Hi Burt. I was hoping you'd jump in. Chuck WB2EDV - Original Message - From: Burt Lang b...@gorum.ca To: Repeater-Builder@yahoogroups.com Sent: Monday, May 18, 2009 8:15 PM Subject: Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy) The matching section inside the loop is a 1/4 wavelength of RG-63B 125 ohm coax. The overall outside diameter is the same as RG-214 but the dielectric is semi-air (like a large version of RG-62 93 ohm coax) and the center conductor is quite small, like RG-59. I have a few hundred feet of RG-63B if you want to experiment. SNIP
Re: [Repeater-Builder] Sinclair dipole array premature failure (noisy)
Paul I have recently had to deal with the same problem. Note if the noise goes away when the antenna is wet for frozen. If this is the case try selectively spraying elements with water while whacking the antenna with a rubber hammer. I will leave the mechanics of doing this up to youHI.Feed line noise due to flexing could be eliminated as a cause with this test also. Tightening hardware helped in my case but the final answer was going to all welded construction. Gran K6RIF At 12:00 PM 5/18/2009, you wrote: Several weeks ago I posted about my ongoing battle with duplex noise on a 2 meter repeater. I have now found a big piece of the problem (maybe all of it) but I'm a little surprised. I am wondering if others have had similar experiences. Two years ago I put up a new (well... NOS, actually) Sinclair SD2352 antenna (8 dipoles, bidirectional pattern). I had no noise for several months after that, but then it started coming back. By this Spring the repeater had become all but unusable. Recently I took down the Sinclair and installed a temporary antenna. Noise gone! Huh? I subsequently disassembled the Sinclair to check for problems. Every piece of hardware was tight. I found no evidence of water in any of the N connectors on the harness, which I had wrapped with Scotch 23 rubber tape followed by Super 88 vinyl tape. The impedance of the complete array and of each individual dipole was still nominal, as it had been prior to being installed. I have now put one dipole from the array on the tower and it is running absolutely noise free. Moving it around on the tower doesn't have any affect... it is noise free wherever I put it. Lacking any other explanation it would seem something in the array became noisy after a short time. I don't know if it is a problem with one or more of the dipoles or perhaps something in the factory assembled portion of the harness. I have not yet attempted to do a post mortem on the factory harness assemblies. I am wondering if this is a unique experience or if this is a common failure mode in exposed dipole arrays? I don't recall hearing much about such arrays becoming noisy, at least in such a short time. Since these dipoles are 50 ohms, I think it would be easy enough to build two 4-dipole cardioid arrays from it, *if* the problem lies in the harness and not in one or more of the dipoles. I wonder if anyone knows what (if any) gimmick Sinclair used to get such broad SWR bandwidth on these dipoles? The exposed portion of the coax on each dipole is RG-213, 50 ohms... but I'm wondering if they may use some quarter wavelength (or ???) of some other impedance on the part hidden inside the dipole, especially since these things exhibit a clear double dip SWR curve (one dip near the low end of the design range, 138 MHz, and another dip near the upper end, 174 MHz, with a somewhat reactive bump in between). 73, Paul N1BUG
