Re: Topband: Insulator problems- Notr og caution
Using grommets to create additional leakage/creepage distance is clever! I never would have thought of that! Best is to turn the material on a lathe, but in a pinch you can use a bolt as a mandrel in a drill press and do it that way. Not as nice, but lots more people have drill presses than lathes. -Bill That problem can be cured with rubber ribs, or by using a larger insulator and turning ribs or skirts in it. Next time, just find rubber panel grommets that fit tight and string them over the rod. They make shrink to fit sealing grommets that are 5 OD. They make dandy skirts, or you can improvise with other materials like you did. They put polymer ribs over fiberglass rod insulators for good reason. :-) http://www.victorinsulators.com/polymerindex.htm 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Using grommets to create additional leakage/creepage distance is clever! I never would have thought of that! I'm cheap and lazy, not clever. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Try here Herb, http://www.surplussales.com/antennas/antennas-6.html http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx I have not purchased from either of these 2 places... Doug - K1ZO - Original Message - From: Herb Schoenbohm he...@vitelcom.net To: topband@contesting.com Sent: Tuesday, December 17, 2013 2:19 PM Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Herb, Try Fair Radio Sales in Lima, OH The catalog I have shows a 5-1/4in diameter thru panel insulator. Ron N9AU -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Herb Schoenbohm Sent: Tuesday, December 17, 2013 1:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Thanks Tim. I might try one of these if I can get them to send them in single unit quantities. The one I currently use is a bowl type but about 3 inches on the flange. I guess for a 160 ATU I should be able to punch a new hole through the metal box and get it to work. The one presently there was all that was left of a motorized 2-30 Mhz automatic ATU for which I just retained the Vacuum Cap and put in my own 6 inch flat wound AM coil. It was made in Ft. Lauderdale, FL over 40 years ago but the beehive feed through was made from some glazed bead like material which must soak up water like a sponge although so far has not failed in my tower's wire cage feed tuning box at the base. I had even considered replacing it with a small necked rum bottle glued into the original hole. But the idea of a large porcelain replacement would look so much better. 73, Herb Schoenbohm, KV4FZ On 12/17/2013 3:30 PM, Shoppa, Tim wrote: Some of the old-school ham radio suppliers sell/stock Daburn porcelain insulators, or you can get them direct from Daburn. e.g. Daburn 10-52: http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx Tim N3QE From: Topband [topband-boun...@contesting.com] on behalf of Herb Schoenbohm [he...@vitelcom.net] Sent: Tuesday, December 17, 2013 2:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Some of the old-school ham radio suppliers sell/stock Daburn porcelain insulators, or you can get them direct from Daburn. e.g. Daburn 10-52: http://www.daburn.com/10-58ceramicfeed-thruinsulators.aspx Tim N3QE From: Topband [topband-boun...@contesting.com] on behalf of Herb Schoenbohm [he...@vitelcom.net] Sent: Tuesday, December 17, 2013 2:19 PM To: topband@contesting.com Subject: Re: Topband: Insulator problems My 160 meter ATU uses an old military box with the original behive feed thru insulator that is starting to crumble. I haven't been able to find a pocelin feed thu of that size (about 3'') and the ones on e bay are very small. Any suggestions for a source? Herb Schoenbohm, KV4FZ On 12/17/2013 3:09 PM, w9...@aol.com wrote: When I lost my last set of monster buss bar ceramic insulators to breakage due to a broken guy line on the tower, I replaced them with artificial wood. I used 4 X 4's. It machines easily and works flawlessly wet or dry with full power even in very high voltage conditions. The material is actually made from recycled milk containers, so the factory told me. Anyone who wants a picture, I'll send it to you. 73, Barry W9UCW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Not sure what your replacing if it is a round insulator piece for 2 pipes or stand off type insulator for matching section or what? Try fiberglass rod material or Teflon blocks depends on application. Teflon blocks were used on heavy industrial equipment when shipped so the equipment can be slide over the floor. Bird poop will short things out no matter what you use!! -- Jim K9TF _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
You might consider polycarbonate. (GE calls it Lexan) It's very strong both mechanically and electrically, and it's machinable. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim GM Sent: Monday, December 16, 2013 10:58 AM To: topband Subject: Re: Topband: Insulator problems Not sure what your replacing if it is a round insulator piece for 2 pipes or stand off type insulator for matching section or what? Try fiberglass rod material or Teflon blocks depends on application. Teflon blocks were used on heavy industrial equipment when shipped so the equipment can be slide over the floor. Bird poop will short things out no matter what you use!! -- Jim K9TF _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Because of a current/voltage node I was toasting SO-239's (FORGET Type N's) I went to Amphenol Type HN connectors in the 160 tuning box at the base of the tower. It NEVER arcs now, ever. http://www.amphenolrf.com/products/hn.asp?N=0sid=52AE42803C4E617F; They are not cheap, but they work great... 73, John, W4NU On 12/16/2013 11:16 AM, Charlie Cunningham wrote: You might consider polycarbonate. (GE calls it Lexan) It's very strong both mechanically and electrically, and it's machinable. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim GM Sent: Monday, December 16, 2013 10:58 AM To: topband Subject: Re: Topband: Insulator problems Not sure what your replacing if it is a round insulator piece for 2 pipes or stand off type insulator for matching section or what? Try fiberglass rod material or Teflon blocks depends on application. Teflon blocks were used on heavy industrial equipment when shipped so the equipment can be slide over the floor. Bird poop will short things out no matter what you use!! _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Delrin is a trademark for acetal. Acetal is the generic name so you'll have a lot better time finding acetal most likely. My recommendation is to get the *black* acetal as it will hold up much better in UV outdoors. It machines easily, but it's a lot harder (and stronger) than nylon. Acetal can be comparable to some mild metals in terms of strength so it's great for bearings and clamps where you need a non-conductive material. Also, someone mentioned using polycarbonate (lexan). There's been a lot of interest in that material since QST ran an article about it a while ago but it's not always the best material to use for everything, and it's not the only machinable plastic. If you do use it outdoors you should try to find a UV-stabilized variant. For most other plastics just try to get them in black since the black pigment commonly used will also generally provide improved UV resistance to the material. My personal recommendation for most outdoor insulators that will be subjected to any amount of mechanical stress/strain is to use black acetal. It's readily available in sheet and rod stock, and the rod is a good starting point for most insulators. You can find small pieces on ebay or you can get it from most commercial plastic supply houses. Teflon, BTW, is probably not a good choice since it is not very durable mechanically. -Bill -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Greg - ZL3IX Sent: Saturday, December 14, 2013 12:10 PM To: Topband Reflector Subject: Re: Topband: Insulator problems Many thanks to everyone who commented on the above. The consensus is that nylon is a particularly bad choice of insulator for high field environments, even on Topband. Tomorrow I will be looking for an alternative that is available here in ZL. I think Delrin will be the choice, if available. 73, Greg ZL3IX _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Many black plastics are blackened by the addition of carbon black that can make them rather lossy at RF! Been there, done that in my work - at 900 MHz. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Wichers Sent: Monday, December 16, 2013 2:06 PM To: Greg - ZL3IX; Topband Reflector Subject: Re: Topband: Insulator problems Delrin is a trademark for acetal. Acetal is the generic name so you'll have a lot better time finding acetal most likely. My recommendation is to get the *black* acetal as it will hold up much better in UV outdoors. It machines easily, but it's a lot harder (and stronger) than nylon. Acetal can be comparable to some mild metals in terms of strength so it's great for bearings and clamps where you need a non-conductive material. Also, someone mentioned using polycarbonate (lexan). There's been a lot of interest in that material since QST ran an article about it a while ago but it's not always the best material to use for everything, and it's not the only machinable plastic. If you do use it outdoors you should try to find a UV-stabilized variant. For most other plastics just try to get them in black since the black pigment commonly used will also generally provide improved UV resistance to the material. My personal recommendation for most outdoor insulators that will be subjected to any amount of mechanical stress/strain is to use black acetal. It's readily available in sheet and rod stock, and the rod is a good starting point for most insulators. You can find small pieces on ebay or you can get it from most commercial plastic supply houses. Teflon, BTW, is probably not a good choice since it is not very durable mechanically. -Bill -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Greg - ZL3IX Sent: Saturday, December 14, 2013 12:10 PM To: Topband Reflector Subject: Re: Topband: Insulator problems Many thanks to everyone who commented on the above. The consensus is that nylon is a particularly bad choice of insulator for high field environments, even on Topband. Tomorrow I will be looking for an alternative that is available here in ZL. I think Delrin will be the choice, if available. 73, Greg ZL3IX _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Yep, that's the black pigment commonly used that I refer to. It's used in the PE jacks of coax too! I can't say I've tested black - vs - white materials in the microwave region, but I've never seen a problem with them down in the HF (or 2m/6m) range. Regarding acetal itself, I have a white bearing block on a boat lift that (was) in the sun pretty much all day, all summer, every year, and it lasted about 15 years. It gets chalky after that time and starts to fracture. It would be a problem in tension, and it was a problem in constant used as a rotary bearing. The black material I replaced it with is about 5 years old now and still like new. -Bill -Original Message- From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Monday, December 16, 2013 2:33 PM To: Bill Wichers; 'Greg - ZL3IX'; 'Topband Reflector' Subject: RE: Topband: Insulator problems- Notr og caution Many black plastics are blackened by the addition of carbon black that can make them rather lossy at RF! Been there, done that in my work - at 900 MHz. 73, Charlie, K4OTV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
Non-UV-rated clear 0.118 Polycarbonate is visibly yellowed and mildly brittle after 5 years in my outdoors environment in the sunshine and other weather. I think this is the plasticizers drying out but I'm sure a polymers chemist would correct me. Even though it's mildly brittle none of my insulators broke in service. They only broke when I flexed them with physical force. I would say the stuff was still way more flexible than similar new acrylic. I still have the original non-UV-rated polycarbonate up 80 feet in the sky, and last year I added some UV-rated polycarbonate spacers. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Bill Wichers Sent: Monday, December 16, 2013 2:36 PM To: Charlie Cunningham; 'Greg - ZL3IX'; 'Topband Reflector' Subject: Re: Topband: Insulator problems- Notr og caution Yep, that's the black pigment commonly used that I refer to. It's used in the PE jacks of coax too! I can't say I've tested black - vs - white materials in the microwave region, but I've never seen a problem with them down in the HF (or 2m/6m) range. Regarding acetal itself, I have a white bearing block on a boat lift that (was) in the sun pretty much all day, all summer, every year, and it lasted about 15 years. It gets chalky after that time and starts to fracture. It would be a problem in tension, and it was a problem in constant used as a rotary bearing. The black material I replaced it with is about 5 years old now and still like new. -Bill -Original Message- From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Monday, December 16, 2013 2:33 PM To: Bill Wichers; 'Greg - ZL3IX'; 'Topband Reflector' Subject: RE: Topband: Insulator problems- Notr og caution Many black plastics are blackened by the addition of carbon black that can make them rather lossy at RF! Been there, done that in my work - at 900 MHz. 73, Charlie, K4OTV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
I don't want to belabor this, because I think Greg was going to try Delrin, but Delrin homopolymer is slightly different than other acetal resin copolymers. They are similar, but not exactly the same. 1.) Black does not always mean poor insulating ability. It will be fine at HF 2.) Black also does not necessarily mean better UV resistance. It generally helps, but many white materials are good. I have white tower ropes that outlast black rope. It really depends a great deal on the UV inhibitors and the material. Most white nylon ropes contain UV inhibitors, for example. If he wants to get a special grade of Delrin, 527 UV would be most UV resistant. The little bit of carbon pigment won't hurt a thing at HF. Greg is in New Zealand, so he will probably have to buy what is available. Since nylon lasted a few years, the material doesn't have a high bar to jump. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
All good points. We have used gray UV-stabilized poly carbonate to mold covers for electricity watt-hour meters that had some rather stringent requirements fr with standing ambient sunlight. The problems that I encountered with black plastic that was blackened with carbon-black, the cheapest and most readily available material for blackening plastic, was in portable and water-meter pit devices whose transceivers operated io the 902-928 MHz ISM band, The black plastic, containing carbon-black would totally destroy the tuning and radiation efficiency of embedded antennas. There are other dyes and materials that can be used to blacken plastic, but one has to take care to specify the materials and or the electromagnetic properties of the plastic that is used! It's not so much an insulating problem, rather it has to do with the absorptive properties o ftne material at VHF and UHF. Not so sure about HF. But I've made lots of end and center insulators for antennas from polycarbonate sheet stock! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Monday, December 16, 2013 4:09 PM To: 'Topband Reflector' Subject: Re: Topband: Insulator problems- Notr og caution I don't want to belabor this, because I think Greg was going to try Delrin, but Delrin homopolymer is slightly different than other acetal resin copolymers. They are similar, but not exactly the same. 1.) Black does not always mean poor insulating ability. It will be fine at HF 2.) Black also does not necessarily mean better UV resistance. It generally helps, but many white materials are good. I have white tower ropes that outlast black rope. It really depends a great deal on the UV inhibitors and the material. Most white nylon ropes contain UV inhibitors, for example. If he wants to get a special grade of Delrin, 527 UV would be most UV resistant. The little bit of carbon pigment won't hurt a thing at HF. Greg is in New Zealand, so he will probably have to buy what is available. Since nylon lasted a few years, the material doesn't have a high bar to jump. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
On Mon, 16 Dec 2013 14:32:41 -0500 Charlie Cunningham charlie-cunning...@nc.rr.com wrote: Many black plastics are blackened by the addition of carbon black that can make them rather lossy at RF! Been there, done that in my work - at 900 MHz. I have been using 3 black Derlin (Acetal)insulators at the base of my 160 m vertical. Because the antenna is only 91 foot tall, there are substantial voltages on the insulators at legal limit. Indeed, one them caught fire just after a rain-shower, when water got between the insulator and the metal. I replaced the burned insulator with the a new one and covered all the insulators with high voltage putty. That was about two years ago and I had zero trouble with any of them since. George AA7JV _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
On 12/16/2013 5:52 PM, GeorgeWallner wrote: On Mon, 16 Dec 2013 14:32:41 -0500 Charlie Cunningham charlie-cunning...@nc.rr.com wrote: Many black plastics are blackened by the addition of carbon black that can make them rather lossy at RF! Been there, done that in my work - at 900 MHz. I have been using 3 black Derlin (Acetal)insulators at the base of my 160 m vertical. Because the antenna is only 91 foot tall, there are substantial voltages on the insulators at legal limit. Indeed, one them caught fire just after a rain-shower, when water got between the insulator and the metal. I replaced the burned insulator with the a new one and covered all the insulators with high voltage putty. That was about two years ago and I had zero trouble with any of them since. George AA7JV Hi George, I had the same experience with black delrin insulators for one of my 160 meter vertical antennas. It was fine until it got wet, then forget it, it would breakdown. I kludged up a shroud to keep the rain off it. It's been fine ever since. BTW, I have never heard of high voltage putty. Where do you get it? 73, Mike W4EF. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems- Notr og caution
I have been using 3 black Derlin (Acetal)insulators at the base of my 160 m vertical. Because the antenna is only 91 foot tall, there are substantial voltages on the insulators at legal limit. Indeed, one them caught fire just after a rain-shower, when water got between the insulator and the metal. You are had that issue because you have no leakage path length. Aggravating that, you probably have contaminated water from the metal tower legs, although anything can tear up when wet unless it has a pretty long surface path. You can have Teflon or anything there and you will tear it up. That problem can be cured with rubber ribs, or by using a larger insulator and turning ribs or skirts in it. Next time, just find rubber panel grommets that fit tight and string them over the rod. They make shrink to fit sealing grommets that are 5 OD. They make dandy skirts, or you can improvise with other materials like you did. They put polymer ribs over fiberglass rod insulators for good reason. :-) http://www.victorinsulators.com/polymerindex.htm 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
2) I always thought that nylon was a pretty good dielectric, and did not expect problems, especially at 1.8 MHz. The gap in the insulator is 7.5mm, or about 0.3. I estimate that there will be around 2 kV across this gap. Is nylon perhaps not as good as I thought it was? Nylon is one of the worse dielectrics for RF. This shows when the electric field density is high, so it does not mean nylon won't work in some applications. For example, a nylon spacer in a typical linear amp with a screw protruding down in it will sometimes bubble and smell around the screw on the vacuum tube side of a tank circuit, but will be perfectly fine on the 50 ohm side where voltage is low. The 1 MHz dissipation factors are around: nylon = .022 or worse Delrin = most types .005 Teflon = less than .0002 3) If I replace the nylon with Teflon, will I lose anything in mechanical strength? Teflon is soft, but wear resistant and reasonable with compression loads. It has the least tendency to carbon track. Delrin is the best mechanically, unless it does not have to be rigid. I would think either Delrin or Teflon would be OK electrically, if you got years of service out of nylon. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Greg, One property you should look at when deciding the material to use for your insulator (especially if exposed to water) is a property called water absorption and normally it's listed as a weight percent. Some nylons are better than others, but nylon in general absorbs a lot of water and therefore probably not your best choice of material. 73, Don (wd8dsb) On Fri, Dec 13, 2013 at 9:19 PM, Greg - ZL3IX zl...@inet.net.nz wrote: The Tx antenna I have been using very successfully for the last 8+ years, is a top-fed vertical. This feed arrangement requires the yagi used for top loading to be insulated from the mast. I have been using a nylon insert between the two halves of the stub mast as my insulator. This morning I noticed high SWR, firstly only on high power, but then at any power level. Today I brought the mast down for inspection, and the only sign of trouble I can see is in the insulator, which has bubbled visibly. This may (or may not) be the problem, but I propose to change the insulator even if only to eliminate it as the culprit. I have a couple of questions for this group. 1) Does anyone know if I can upload a jpg file to contesting.com, so that guys can see what I am talking about? Tree, I guess I can't attach a photo to a post to the group? 2) I always thought that nylon was a pretty good dielectric, and did not expect problems, especially at 1.8 MHz. The gap in the insulator is 7.5mm, or about 0.3. I estimate that there will be around 2 kV across this gap. Is nylon perhaps not as good as I thought it was? 3) If I replace the nylon with Teflon, will I lose anything in mechanical strength? Unfortunately this problem means that I will not be able to enter the Stew. We are going away for a week for the festive season, next weekend, so won't have time to fix the issue. Comments welcome. 73, Greg, ZL3IX _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems
Many thanks to everyone who commented on the above. The consensus is that nylon is a particularly bad choice of insulator for high field environments, even on Topband. Tomorrow I will be looking for an alternative that is available here in ZL. I think Delrin will be the choice, if available. 73, Greg ZL3IX _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Insulator problems - attempt at attachment
_ Topband Reflector Archives - http://www.contesting.com/_topband
