Re: Topband: Antenna terminations
Well, those GE silicone sealants are designed to have pretty high resistivity and are designed to be insulators as well as for protection. Main thing, I expect is that the highest temperature that you reach is the curing temperature of the silicone compound. No heat guns! :) I wouldn't hesitate to apply it over the termination resistors on my receiving loops, but I haven't bothered Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Don Kirk Sent: Thursday, March 14, 2013 6:41 AM To: Jim Monahan Cc: topband Subject: Re: Topband: Antenna terminations K1PX said, I've covered my resistors and solder joints with GE Silicone II sealant and have never had a problem. I do the same thing with my pennant termination resistors (just cover them with GE Silicone II sealant). 73's Don (wd8dsb) _ Topband Reflector _ Topband Reflector
Topband: Antenna terminations
I've covered my resistors and solder joints with GE Silicone II sealant and have never had a problem. The curing does not impact solder joints and I've used this product for some 20+ years. I can't measure any resistance using it. It cures in several hours similar to a rubbery type substance. And, it is easily peeled back when needed. Around here in CT, it is available in 2.8 oz. tubes in most hardware stores. Jim, K1PX K1PX at msn.com _ Topband Reflector
Re: Topband: Antenna terminations
Same here, Frank I can't do Beverages on my city lot, but I do use carbon comps exposed to the weather in my terminated KAZ receiving loops, with no apparent detrimental effects after years in the weather. Perhaps we shouldn't abuse electronic components (even resistors) with heat guns? Regards, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Wednesday, March 13, 2013 1:55 AM To: topband@contesting.com Subject: Re: Topband: Antenna terminations Like Tom, I install my carbon composition Beverage termination resistors fully exposed to the weather. I measure them annually and over a 20 year period just a few have changed resistance outside of their marked tolerance band. I'm sure there are better ways to protect them, but open air has been very reliable for me. 73 Frank W3LPL Original message Date: Tue, 12 Mar 2013 14:01:51 -0400 From: Tom W8JI w...@w8ji.com Subject: Re: Topband: Antenna terminations To: topband@contesting.com Depends on the method used to provide the conductivity. If it's carbon black filled, the shrinking is goin g to push the molecules of the carbon black closer together and that results in a net decrease in volume resistivity. It may not matter however, as carbon filled stuff is going to be in the K-ohms range in the lowest case. Other fillers may have lower values. This is of interest to me, because I use carbon resistors and heat shrink so often. I just measured several carbon composition and film resistors, and none changed value with pressure (in a table vice) until they fractured. I can't find any conductive heatshrink, either. This potential issue really should concern all of us, because it is a serious hazard if we heatshrink power line leads or HV cables. I'm not doubting the results, but the only resistors that I've seen change value outside of age or abuse are large carbon bar resistors when submerged in a liquid. For dummy loads, like a Cantenna, the resistor has to be specially treated before spending any time submerged. I routinely mount Allen Bradley carbon composition and Ohmite metal composition termination resistors right out in the open air, directly exposed to weather, and they stay good for years! They can look really ugly and still test good. This isn't saying that is a good practice, just that I haven't ever seen an issue outside of direct lightning hits. I have some pretty ugly resistors retrieved when redoing antenna end connections (the fence wire rusts with age), and they still are good! If there is a certain brand of materials that is sensitive, it would be helpful to learn what it is. I do not use metal or carbon films outside, or in high overload applications. BTW, some carbon films look **exactly** like carbon composition resistors!! 73 Tom _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Antenna terminations
K1PX said, I've covered my resistors and solder joints with GE Silicone II sealant and have never had a problem. I do the same thing with my pennant termination resistors (just cover them with GE Silicone II sealant). 73's Don (wd8dsb) _ Topband Reflector
Re: Topband: Antenna terminations
Like Tom, I install my carbon composition Beverage termination resistors fully exposed to the weather. I measure them annually and over a 20 year period just a few have changed resistance outside of their marked tolerance band. I'm sure there are better ways to protect them, but open air has been very reliable for me. 73 Frank W3LPL Original message Date: Tue, 12 Mar 2013 14:01:51 -0400 From: Tom W8JI w...@w8ji.com Subject: Re: Topband: Antenna terminations To: topband@contesting.com Depends on the method used to provide the conductivity. If it's carbon black filled, the shrinking is goin g to push the molecules of the carbon black closer together and that results in a net decrease in volume resistivity. It may not matter however, as carbon filled stuff is going to be in the K-ohms range in the lowest case. Other fillers may have lower values. This is of interest to me, because I use carbon resistors and heat shrink so often. I just measured several carbon composition and film resistors, and none changed value with pressure (in a table vice) until they fractured. I can't find any conductive heatshrink, either. This potential issue really should concern all of us, because it is a serious hazard if we heatshrink power line leads or HV cables. I'm not doubting the results, but the only resistors that I've seen change value outside of age or abuse are large carbon bar resistors when submerged in a liquid. For dummy loads, like a Cantenna, the resistor has to be specially treated before spending any time submerged. I routinely mount Allen Bradley carbon composition and Ohmite metal composition termination resistors right out in the open air, directly exposed to weather, and they stay good for years! They can look really ugly and still test good. This isn't saying that is a good practice, just that I haven't ever seen an issue outside of direct lightning hits. I have some pretty ugly resistors retrieved when redoing antenna end connections (the fence wire rusts with age), and they still are good! If there is a certain brand of materials that is sensitive, it would be helpful to learn what it is. I do not use metal or carbon films outside, or in high overload applications. BTW, some carbon films look **exactly** like carbon composition resistors!! 73 Tom _ Topband Reflector _ Topband Reflector
Re: Topband: Antenna terminations
Depends on the method used to provide the conductivity. If it's carbon black filled, the shrinking is goin g to push the molecules of the carbon black closer together and that results in a net decrease in volume resistivity. It may not matter however, as carbon filled stuff is going to be in the K-ohms range in the lowest case. Other fillers may have lower values. 73/jeff/ac0c www.ac0c.com alpha-charlie-zero-charlie -Original Message- From: Bruce Sent: Tuesday, March 12, 2013 6:43 AM To: topband@contesting.com Subject: Re: Topband: Antenna terminations Anyone else found a lowering of resistance after heat shrinking terminations after cool down? 73 Bruce-K1FZ You may have some of that somewhat conductive heat shrink tubing. Good idea to check the glue for conductivity before use. www.qsl.net/k1fz/beveragenotes.html _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Antenna terminations
Heat shrink squeezes resistor. Squeezing a carbon composition resistor will decrease its resistance. Film and ceramic resistors much less affected. Remember when we were kids and played with telephone carbon microphone elements? Tim N3QE - Original Message - From: Bruce [mailto:k...@myfairpoint.net] Sent: Monday, March 11, 2013 06:43 PM To: topband@contesting.com topband@contesting.com Subject: Re: Topband: Antenna terminations Anyone else found a lowering of resistance after heat shrinking terminations after cool down? 73 Bruce-K1FZ You may have some of that somewhat conductive heat shrink tubing. Good idea to check the glue for conductivity before use. www.qsl.net/k1fz/beveragenotes.html _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: Antenna terminations
Depends on the method used to provide the conductivity. If it's carbon black filled, the shrinking is goin g to push the molecules of the carbon black closer together and that results in a net decrease in volume resistivity. It may not matter however, as carbon filled stuff is going to be in the K-ohms range in the lowest case. Other fillers may have lower values. This is of interest to me, because I use carbon resistors and heat shrink so often. I just measured several carbon composition and film resistors, and none changed value with pressure (in a table vice) until they fractured. I can't find any conductive heatshrink, either. This potential issue really should concern all of us, because it is a serious hazard if we heatshrink power line leads or HV cables. I'm not doubting the results, but the only resistors that I've seen change value outside of age or abuse are large carbon bar resistors when submerged in a liquid. For dummy loads, like a Cantenna, the resistor has to be specially treated before spending any time submerged. I routinely mount Allen Bradley carbon composition and Ohmite metal composition termination resistors right out in the open air, directly exposed to weather, and they stay good for years! They can look really ugly and still test good. This isn't saying that is a good practice, just that I haven't ever seen an issue outside of direct lightning hits. I have some pretty ugly resistors retrieved when redoing antenna end connections (the fence wire rusts with age), and they still are good! If there is a certain brand of materials that is sensitive, it would be helpful to learn what it is. I do not use metal or carbon films outside, or in high overload applications. BTW, some carbon films look **exactly** like carbon composition resistors!! 73 Tom _ Topband Reflector
Topband: Antenna terminations
Got a new Beverage antenna up and getting the termination resistor(s) ready. to install? The resistance is spot on, now to keep it dry, you put it in some heat shrink. There, now for a re-check of the resistance... it has gone down in resistance !!! . You may have some of that somewhat conductive heat shrink tubing. Good idea to check the glue for conductivity before use. I do not have a brand name as have purchased from multiple sources. It is more of a problem for higher resistance terminations like for Flag, Pennant, and Delta receiving antennas. 73 Bruce-K1FZ www.qsl.net/k1fz/beveragenotes.html _ Topband Reflector
Re: Topband: Antenna terminations
Anyone else found a lowering of resistance after heat shrinking terminations after cool down? 73 Bruce-K1FZ You may have some of that somewhat conductive heat shrink tubing. Good idea to check the glue for conductivity before use. www.qsl.net/k1fz/beveragenotes.html _ Topband Reflector _ Topband Reflector
