Re: Topband: Using GE silicone as antenna sealant.
On 2013-03-16, at 12:39 PM, wa3...@comcast.net wrote: Gents.. be very sure that if you pick GE silicone sealant.. (RTV or whatever you call it) DO NOT use the kind that has acetic acid in it.. Back in the early days of NASA rocket launches off Wallops Island NASA lost a rocket they launched. It failed because they had used RTV that had acetic acid and it had corroded the connections.. litterally. A friend of mine W3AUN was one of the people responsible for this launch.. Be sure to pick SILICONE II sealant (with emphasis on the II), no matter the brand...! It's true: the regular stuff exudes that vinegary-smelling stuff as it cures that is VERY corrosive. Back some 30+ years ago we used the bad stuff to secure a variable capacitor inside of a weather-proof box as part of the delta match tuning network for a 40-meter multi-element loop on Field Day---when we opened the box the next morning to see why our tuning had changed, all of the components in the cap that could rust did, in fact, do just that, on account of the locked-in vapours! So beware what you buy...! ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector
Re: Topband: Using GE silicone as antenna sealant.
WA3MEJ said : be very sure that if you pick GE silicone sealant.. (RTV or whatever you call it) DO NOT use the kind that has acetic acid in it. This is a very good point, and this is the reason I use GE Silicone Sealant II versus GE Silicone Sealant I. GE Silicone Sealant II is a neutral cure silicone whereas GE Silicone Sealant is an acid or acetoxy cure silicone. Neutral Cure silicone means no acids are released during the curing process (note this information was obtained from the GE website). 73's Don (wd8dsb) _ Topband Reflector
Re: Topband: Using GE silicone as antenna sealant.
After several less than satisfactory experiences with various outdoor sealed boxes and junctions etc. I have had my ladder line, transmit antenna, and all junctions completely exposed to the weather for the past 4 years with no problems. The problem was never as bad as the corrosion due to sealant, but I found out that what was happening was that I was sealing water in! Obviously I was doing something wrong but many of these containers had no lead-ins or holes in the top, only sealed lead-ins with drip loops at the bottom. I briefly had a NEMA rated junction box with watertight cover and seal over the spark gap, but after water started accumulating in there, I simply removed the cover. Every fall I go blow the leaves and bugs out. On the receive antenna side... My K9AY relay board and termination resistor are covered by a Tupperware dish but are exposed at the bottom. I had made a brief attempt at sealing them inside the Tupperware but despite drip loops and all the wires entering only at the bottom... I found water accumulating in the Tupperware even though I swear it hadn't rained since I had installed it. I don't have any fancy conformal coating or anything on the K9AY relay/transformer/termination board. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Don Kirk Sent: Monday, March 18, 2013 8:17 AM To: wa3...@comcast.net Cc: topband@contesting.com Subject: Re: Topband: Using GE silicone as antenna sealant. WA3MEJ said : be very sure that if you pick GE silicone sealant.. (RTV or whatever you call it) DO NOT use the kind that has acetic acid in it. This is a very good point, and this is the reason I use GE Silicone Sealant II versus GE Silicone Sealant I. GE Silicone Sealant II is a neutral cure silicone whereas GE Silicone Sealant is an acid or acetoxy cure silicone. Neutral Cure silicone means no acids are released during the curing process (note this information was obtained from the GE website). 73's Don (wd8dsb) _ Topband Reflector _ Topband Reflector
Re: Topband: Using GE silicone as antenna sealant.
Use the sensor safe variant to avoid that problem. Cecil K5DL Sent from my iPad On Mar 16, 2013, at 11:39 AM, wa3...@comcast.net wrote: Gents.. be very sure that if you pick GE silicone sealant.. (RTV or whatever you call it) DO NOT use the kind that has acetic acid in it.. Back in the early days of NASA rocket launches off Wallops Island NASA lost a rocket they launched. It failed because they had used RTV that had acetic acid and it had corroded the connections.. litterally. A friend of mine W3AUN was one of the people responsible for this launch.. Long Live Seal Team VI http://www.qsl.net/wa3mej/index.htm - Original Message - 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 _ Topband Reflector _ Topband Reflector
Topband: Reminder - WWROF Webinar to be given by W3LPL this evening
The first Top Band DX Contest - the 1921 Transatlantic Test 18-Mar-2013 9pm - 10pm EDT (19-Mar-2013 0100 - 0200 UTC) Frank Donovan, W3LPL, provides a very entertaining and informative look at the very first Topband DX contest, in 1921. For Webinar sign up details and other scheduled contest related WWROF Webinars, please visit: http://wwrof.org/webinars/ The Webinars are recorded and available for playback. You can view current WWROF Webinar archives here: http://wwrof.org/category/webinar-archive/ 73, Tim K3LR _ Topband Reflector
Re: Topband: Using GE silicone as antenna sealant.
I agree completely!! RTV will outgas acetic acid for a VERY LONG TIME - almost forever! You should try it in a high-vacuum chamber! Especially one that includes an ion pump to achieve very high vacuums! RTV will belch acetic acid in copious quantities virtually forever. Definitely need one of the newer gasless curing compounds that won't outgas corrosive gases! GOOD POINT! Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of wa3...@comcast.net Sent: Saturday, March 16, 2013 12:40 PM To: topband@contesting.com Subject: Topband: Using GE silicone as antenna sealant. Gents.. be very sure that if you pick GE silicone sealant.. (RTV or whatever you call it) DO NOT use the kind that has acetic acid in it.. Back in the early days of NASA rocket launches off Wallops Island NASA lost a rocket they launched. It failed because they had used RTV that had acetic acid and it had corroded the connections.. litterally. A friend of mine W3AUN was one of the people responsible for this launch.. Long Live Seal Team VI http://www.qsl.net/wa3mej/index.htm - Original Message - 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 _ Topband Reflector _ Topband Reflector
