Re: Topband: K3 some interesting noise lessons in the ARRL 160.
Why would the NB null be frequency dependent? Why does it change? Why would a different antenna make any difference unless you pick up different noise sources with the two different antennas? 73, Greg-N4CC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: Sunday, December 15, 2013 8:59 PM To: Richard (Rick) Karlquist Cc: TopBand List Subject: Re: Topband: K3 some interesting noise lessons in the ARRL 160. I am confused about 1831.5 being occupied. That's 1831 was UNoccupied, so I used it as a run frequency. No one else was using it as a run frequency. The noise blanker, at that time, with aforementioned settings, was producing a very effective null in the noise at 1831-1833. There were vacant frequencies in that range, vacant at various times, and I used them, in the process breaking the dx window rule. The combination of NB settings and the 250 Hz width (with 250 8 pole filter) on the K3 was NOT being falsed by nearby frequencies, nor was it mushing the noise over weak signals, that discovered by a few hours messing with settings. If I turned OFF the K3 NB, the buzz noise at 1831-1833 drowned out all but loud signals. Tonight the noise null using the NB on the TX antenna is around 1826. On the TX antenna the noise goes up over 16 dB when I turn the NB off. On the RX ant the null is at 1838 and the noise goes up 17 dB when I turn NB off. These are less pronounced than on the contest night when the diffs were in the low 20's, and the noise was S9. 73, Guy 1. The NB works well on the noise, but gets falsed by nearby signals on a crowded band in the contest. IOW, the NB would have worked fine during non-contest times. The NB on my FT-1000 is like this (I have the W8JI NB mod). or 2. The local noise was lower on 1831.5, but you still needed the NB. QRM from other stations was not an issue. I don't own a K3, but an considering buying one. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: RUSSIAN 160 METER CONTEST
International 160m contest named RUSSIAN 160 METER CONTEST are sponsored jointly by the Radio Magazine and the Top Band DX Club. In general, new rules of the contest are close to the RUSSIAN DX CONTEST rules (exchange, scoring, QSO points, mults). Results are scored separately for the three groups: European Russia, Asiatic Russia (see WAC rules for continent definition), and the rest of the world. This year, the contest will take place on December 20, 2013 , from 20 to 24 UTC, CW and SSB. There will be only MIX entries for both SO and MS (one TX) entrants. Dupes are allowed in different modes. Foreign hams send RS(T) and QSO serial number starting 001. Russian hams send RS(T) and oblast ID. Points for Russian stations: QSO with a Russian station in your own continent is 2 points; QSO with a Russian station from another continent is 5 points. Points for foreign stations: QSO with a Russian station (any continent) is 10 points; QSO with your own territory is 2 points; QSO with another territory in your own continent is 3 points; QSO with another continent is 5 points. See DXCC rules for entity definition. Kaliningrad (UA2F) counts as separate DXCC entity and separate oblast for multiplier, and as EU Russia for QSO points. Total multiplier for all entrants is a sum of entities (DXCC list), plus Russian oblast number. Each entity and oblast count once only, regardless mode. Logs shall be sent in Cabrillo format. Log-file shall be named as YOUR_CALL.log, or YOUR_CALL.cbr. Your call shall be shown in subject line of the message. Log shall be attached to the message and sent to cont...@radio.ru or downloaded via WEB interface at http://ua9qcq.com/contests/robot.php . Paper logs will still be accepted in 2012. These shall be sent to: Radio Magazine, Seliverstov Pereulok 10, Moscow, 107045, Russia. You can use RDXC logging program in this contest; just replace contest name in the log file with RADIO-160. Logs shall be sent until December 30, 2012 (including). Winners in groups shall be awarded with commemorative prizes. 2nd and 3rd winners will be awarded with RADIO Magazine Contest certificates. Complete rules of the contest may be found at ftp://ftp.radio.ru/pub/2012/11/55.pdf See English version at http://www.radio.ru/cq/contest/rule-results/index2012.shtml Everybody is welcome for the Contest! 73! -- С уважением, Vlad/ R7LV mailto:r...@dx.ruua...@dx.ru ua...@mail.ru _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: K3 some interesting noise lessons in the ARRL 160.
Why would the NB null be frequency dependent? Why does it change? Why would a different antenna make any difference unless you pick up different noise sources with the two different antennas? 73, Greg-N4CC This is an anomaly with the particular noise he has, and the particular noise blanker and all related settings. Unique things like this occasionally occur with noise blankers and noise reduction systems, or with any local signal we are trying to locate or get rid of. It happens when the noise signal at the radio input is a mix of pulses arriving with various delays from multiple radiation points, such as when a single arcing source radiates from multiple points at greatly varying distances, all of which arrive at the receiver. As you change frequency the noise phase varies, because the distance in wavelengths for each path varies disproportionately. Say one radiation point is at a source, and another from the same source is 5 wavelengths further away (including velocity factor and the distance to and back from that point). If you change frequency 10%, you have changed 10% more (or 36 degrees in phase) for each wavelength between the radiation points. Also, time is a factor (although generally nearly constant with frequency change). At 5 wavelengths you have changed phase between the radiation points (of the same noise source) 180 degrees. This also happens when the noise source is not broad band, and does not have the same characteristics over a wide frequency range. You can occasionally find sweet and sour spots where the blanker system likes the particular waveshape or noise characteristics that appear at some frequency. After all that, the blanker comes into play. It would take a few pages to describe how blankers work and why they are sensitive to noise characteristics, and why that sensitivity causes a blanker system to work entirely different on two different noises. All we really need to remember is what happens at one place on one noise source and one receiving antenna for one blanker and one blanker setting isn't very likely to repeat at another station. It isn't going to repeat if one thing changes in the wrong way, let alone more than one thing changing. Since countless things can potentially change, what happens in one place with a blanker has little value elsewhere. The only thing ever repeatable is a wide bandwidth impulse noise from one source. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: K3 some interesting noise lessons in the ARRL 160.
I have used the K3 noise blanker in several different environments, sometimes with great success, sometimes with less success. I know the word null, which many will take to be a subtractive linear process, does not apply to the traditional impulse-noise blanker. The traditional noise blanker is in fact quite nonlinear and more accurately a multiply signal by zero during a noise pulse function. But it is not unusual to find a magic frequency where the NB settings and the noise phase characteristics and antenna characteristics all interact to yield good place on the band vs bad place on the band and that can be hugely important during a test. I'm not sure anyone needs to disqualify themselves for CQ'ing in a DX window in a contest, but discussions about the DX window and noise environments are very relevant to me and I like hearing them. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Greg Sent: Monday, December 16, 2013 6:30 AM To: 'TopBand List' Subject: Re: Topband: K3 some interesting noise lessons in the ARRL 160. Why would the NB null be frequency dependent? Why does it change? Why would a different antenna make any difference unless you pick up different noise sources with the two different antennas? 73, Greg-N4CC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: Sunday, December 15, 2013 8:59 PM To: Richard (Rick) Karlquist Cc: TopBand List Subject: Re: Topband: K3 some interesting noise lessons in the ARRL 160. I am confused about 1831.5 being occupied. That's 1831 was UNoccupied, so I used it as a run frequency. No one else was using it as a run frequency. The noise blanker, at that time, with aforementioned settings, was producing a very effective null in the noise at 1831-1833. There were vacant frequencies in that range, vacant at various times, and I used them, in the process breaking the dx window rule. The combination of NB settings and the 250 Hz width (with 250 8 pole filter) on the K3 was NOT being falsed by nearby frequencies, nor was it mushing the noise over weak signals, that discovered by a few hours messing with settings. If I turned OFF the K3 NB, the buzz noise at 1831-1833 drowned out all but loud signals. Tonight the noise null using the NB on the TX antenna is around 1826. On the TX antenna the noise goes up over 16 dB when I turn the NB off. On the RX ant the null is at 1838 and the noise goes up 17 dB when I turn NB off. These are less pronounced than on the contest night when the diffs were in the low 20's, and the noise was S9. 73, Guy 1. The NB works well on the noise, but gets falsed by nearby signals on a crowded band in the contest. IOW, the NB would have worked fine during non-contest times. The NB on my FT-1000 is like this (I have the W8JI NB mod). or 2. The local noise was lower on 1831.5, but you still needed the NB. QRM from other stations was not an issue. I don't own a K3, but an considering buying one. Rick N6RK _ 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: K3 some interesting noise lessons in the ARRL 160.
On 2013-12-16 03:29, Greg wrote: Why would the NB null be frequency dependent? Why does it change? Why would a different antenna make any difference unless you pick up different noise sources with the two different antennas? 73, Greg-N4CC That's 1831 was UNoccupied, so I used it as a run frequency. No one else was using it as a run frequency. The noise blanker, at that time, with aforementioned settings, was producing a very effective null in the noise at 1831-1833. There were vacant frequencies in that range, vacant at various times, and I used them, in the process breaking the dx window rule. The combination of NB settings and the 250 Hz width (with 250 8 pole filter) on the K3 was NOT being falsed by nearby frequencies, nor was it mushing the noise over weak signals, that discovered by a few hours messing with settings. I'm still confused. Did you pick 1831 because the NB worked better there than elsewhere, or did it work the same, and you just wanted a clear run frequency? I'm trying to understand if the NB worked better on 1831 because of the lack of nearby signals that would cause false blanking, or if it worked as well anywhere in the band. My FT1000 would definitely work better in the lightly occupied DX window. Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Isolation of tower to antenna
hi ! for years i ran a shunt fed tower with a 6 el 20m yagi on top as a tx antenna for 160. I made sure that the antenna was well connected to the tower and nothing happened. Instead of trying to find a material that is electrically suficient as well as mechanical, i would simply change the feeding. I can see no reason to decouple the top yagi structure from the tower. At the same time this has hazards in lightning protection too. The extra capacity formed by the Yagi on top enhances the radiators efficiency even further ( if its not already at least a full quarter wave high ) All of this said without knowing all the detail of the installation. I´d go for a Gamma match , equalize potentials on the top, and be done with it and have no worries about insulation etc. 73 de wolfdf2py _ 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: Well, Duh... (Apology re: ARRL160)
It is always a good idea to read the rules, before beginning any contest/ Your opinion about the window is not the issue. There are many opinions, but only one set of rules. Allen - N2KW -- Original Message -- From: Jim Brown j...@audiosystemsgroup.com To: topband@contesting.com Subject: Re: Topband: Well, Duh... (Apology re: ARRL160) Date: Fri, 13 Dec 2013 19:07:38 -0800 This entire discussion strikes me as comical. I can recall several quite extensive discussions about the DX Window, and most of them have come to a consensus that that the DX window on topband was dead and buried. I haven't bothered to check the archives, but if I did, I'll bet that I've find that at least some of those speaking out so strongly in favor it it now said exactly the opposite back then. Another comical point -- everything written at HQ seems to be handed down from on high as chiseled into stone. How else to explain a rule for this contest that flies in the face of the CAC's recommendations from four years ago? Or does it mean that nothing that members say matters, and that nothing can ever change. 73, Jim K9YC On 12/13/2013 4:52 PM, Guy Olinger K2AV wrote: [1] Actually June, 2009, yes they did vote to drop it, and it was the ARRL Contest Advisory Committee. See: http://www.arrl.org/files/file/About%20ARRL/Committee%20Reports/July/29_Contest_Advisory_Committee.pdf An interesting read. Should note that the report phrases the current rule as a recommendation, as if to indicate they don't consider it a hard rule, and*nobody* voted to make it a requirement. They consider the rule unenforceable. From the report: 4. Vote: Rule 6.1 A. Delete (9) B. Make it a requirement (0) C. Leave it as a recommendation (7) _ Topband Reflector Archives - http://www.contesting.com/_topband Amazing Sleep Secret If you have trouble falling or staying asleep, try this weird trick. http://thirdpartyoffers.juno.com/TGL3131/52af7994a069799340d1st01duc _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: FW: Insulator problems- Notr og caution
-Original Message- From: Charlie Cunningham [mailto:charlie-cunning...@nc.rr.com] Sent: Monday, December 16, 2013 4:32 PM To: 'Tom W8JI'; 'Topband Reflector' Subject: 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
