Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/17/14, 11:09 AM, Lester Veenstra wrote: The classic DIY test of material for RF use is give it 60 seconds in a microwave oven. If it gets warm, it’s not a good candidate. that's fine if you're looking for a gross measure of suitability. If you're concerned about things like dielectric constant or tenths of a dB, that's probably not as good a test. That is, getting warm in a microwave is a sign of certainly not suitable, but not getting warm is not a sign of suitable. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
, I'd be very grateful. Thanks in advance and best regards Hag ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Message: 2 Date: Fri, 18 Apr 2014 06:09:14 -0700 From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Subject: Re: [time-nuts] GPS antenna in silicon/RTV encapsulation Message-ID: 535123fa.1030...@earthlink.net Content-Type: text/plain; charset=windows-1252; format=flowed On 4/17/14, 11:09 AM, Lester Veenstra wrote: The classic DIY test of material for RF use is give it 60 seconds in a microwave oven. If it gets warm, it?s not a good candidate. that's fine if you're looking for a gross measure of suitability. If you're concerned about things like dielectric constant or tenths of a dB, that's probably not as good a test. That is, getting warm in a microwave is a sign of certainly not suitable, but not getting warm is not a sign of suitable. -- Message: 3 Date: Fri, 18 Apr 2014 08:00:01 -0700 (PDT) From: Robert Roehrig k9...@yahoo.com To: timenuts time-nuts@febo.com Subject: [time-nuts] quartz clock/watch question Message-ID: 1397833201.64991.yahoomail...@web181002.mail.ne1.yahoo.com Content-Type: text/plain; charset=us-ascii When a quartz watch or clock is assembled, what method is used to get it as accurate as possible? -- Message: 4 Date: Fri, 18 Apr 2014 10:12:46 -0400 From: Bob Camp li...@rtty.us To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] time-nuts Digest, Vol 117, Issue 61 Message-ID: e7c598ed-8903-4c55-ab96-ed5875523...@rtty.us Content-Type: text/plain; charset=windows-1252 Hi The dividing line between wander and jitter is a ?legal one rather than a physics one. It?s a breakpoint in a spec where the treatment of the noise changes from ?do this? to ?do that?. In most cases you pass wander and you attenuate jitter. Different specs put the line at different points based on hoped for system performance. Bob On Apr 18, 2014, at 9:17 AM, HagaaarTheHorrible hagaaar587pl...@googlemail.com wrote: Hi Dave and thanks for the quick answer! My thesis is about a phase noise measurement device I developed, which primary use is to measure phase noise/jitter of audioband DACs. I probably won't be focussing on jitter too much but would like to know if there even is one accepted standard definition. For example, in the different definitions I found so far, the seperation between jitter and wander sometimes is given to be at 1Hz, 10Hz and sometimes just mushy definitions like very low frequencies... I doubt it is that important for my thesis anyway, but I'd really like to know for myself, so if anyone has a pointer for me it would be greatly appreciated! Von: Dave Brown tract...@ihug.co.nz Datum: 17. April 2014 11:21:25 MESZ An: Discussion of precise time and frequency measurement time-nuts@febo.com Betreff: Re: [time-nuts] Jitter Definition Antwort an: Discussion of precise time and frequency measurement time-nuts@febo.com It depends on what your thesis is all about- you could try some of the ITU documents for 'official' definitions but these may or may not be relevant to your thesis. DaveB, NZ - Original Message - From: HagaaarTheHorrible hagaaar587pl...@googlemail.com To: time-nuts@febo.com Sent: Thursday, April 17, 2014 2:54 PM Subject: [time-nuts] Jitter Definition Hello there, I tried searching the archives (and google, IEEE, NIST, ITU), but didn't really find a satisfying answer, so I thought I'd ask directly. In short: Is there any kind of standard definition for Jitter which is commonly accepted? I (think I) understood Jitter and phase noise by now, yet I need to give some references in my bachelor's thesis, so I'm looking for a definition. So far I haven't found a real definition of the different types (RMS,p2p,c2c,...) and components(RJ,DJ) of Jitter, but I guess there must be some kind of accepted standard!? If anyone could point me to some official sources which are accepted in the industry, I'd be very grateful. Thanks in advance and best regards Hag ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Message: 5 Date: Fri, 18 Apr 2014 08:43:53 -0700 From: Chris Albertson albertson.ch...@gmail.com To: Discussion of precise time
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Then again, if you home brew antenna rots due to a poor radome, this is all for naught. ;-) I hope you read the link I posted since it goes into rain drops on the radome. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
The classic DIY test of material for RF use is give it 60 seconds in a microwave oven. If it gets warm, its not a good candidate. The other more typical concern with RTV type materials are the ones using acetic acid to cure. This outgases, condenses with water vapor to form an corrosive material on the electronics inside a sealed environment. When the unit mails, and you look inside, you find lots of green corrosion inside, to the point interconnects fail. There are electronic friendly forms of the sealant that do not have the vinegar odor. Lester B Veenstra MØYCM K1YCM W8YCM les...@veenstras.com US Postal Address: 5 Shrine Club Drive HC84 Box 89C Keyser WV 26726 GPS: 39.336826 N 78.982287 W (Google) GPS: 39.33682 N 78.9823741 W (GPSDO) Telephones: Home: +1-304-289-6057 US cell +1-304-790-9192 UK cell +44-(0)7849-248-749 Guam Cell: +1-671-929-8141 Jamaica: +1-876-456-8898 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Lux Sent: Monday, April 14, 2014 11:32 PM To: time-nuts@febo.com Subject: Re: [time-nuts] GPS antenna in silicon/RTV encapsulation On 4/14/14, 12:11 PM, ewkeh...@aol.com wrote: Am experimenting with small low cost GPS antennas and am considering as an alternative RTV/silicon. Any information on RF attenuation of RTV/silicon at 1.6 GHz ? Are you potting the antenna in a solid mass of silicone? Or using it to seal an enclosure or what? pure silicone is very low loss, and it probably has an epsilon around 3. It can be loaded with silica (which is also low loss) to adjust the mechanical properties and electrical properties. It can also be loaded with other things (TiO2) which will increase the epsilon, but also the loss. the plastics that are notorious for loss are ones that have metal or carbon loading or that are hygroscopic so they pick up water. In the clear plastics world, Polypropylene, polyethylene and polystrene are pretty good. Polycarbonate isn't as good, neither are various acetals (Delrin) and acetates Here's a chart http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.h tm or another chart http://www.eccosorb.com/Collateral/Documents/English-US/dielectric-chart.pdf here's a whole report from Dow on silcone rubbers as dielectrics http://www.dtic.mil/dtic/tr/fulltext/u2/656331.pdf They give quite low loss tangents at 10^9 cps (which I looked up on my cps to Hz conversion chart.. That's in your frequency range) 0.0059 loss tangent for Silastic 80. The trick for you will be knowing what else is in your particular silicone resin, and controlling the water content. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/15/14, 8:16 PM, nuts wrote: I don't use the surf board resin. I use http://www.tapplastics.com/product/fiberglass/polyester_resins/tap_marine_vinyl_ester_resin/34 I don't have specifics on what Tap sells, but vinyl ester resins have a dielectic coeficient around 4 and dissipation of at least 0.00x. The resin is actually better than the S-2 glass.I suppose I can ask who makes their resin, but I don't know if anyone at a store has that answer. ah, but this is time nuts and we obsess about the 14th decimal pointgrin It kind of depends on what you're looking for. For instance, I don't recall what the big radome over the fancy Leica multiband artichoke antennas is like. I think it's just plastic (some UV inhibited plastic), but it might have glass or nomex in it. The one over the actual elements (inside the choke ring) is some fairly exotic filled plastic in a carefully designed shape to keep the phase center in the same place regardless of incidence angle. 1mm phase center shift is 0.005 wavelength (about 2 degrees) of carrier phase. Over a 8 hour pass (4.3E13 cycles) that's in the 1 part in 1E15 range. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
I'd be inclined to look at radome construction. http://www.mpdigest.com/issue/articles/2008/may/mfg/default.asp The E-3 AWACS is mostly S-2 glass, but they need the strength. For a radome sitting outside, you might be able to do better. The advantage to S-2 glass is you can buy it easily, especially if you have a Tap Plastics handy. It works well with the Marine Resin they sell, so you know it will last a long time outdoors. You need to cure the resin in a vacuum, though not a particularly good vacuum. There are probably guides on the internet, but here is the basic scheme to make a fiberglass composite structure. Make a form of the final product. Cover the form in mylar. Tap Plastics sells the mylar too. The resin won't stick to the mylar. Cut the cloth to cover the form. Where you overlap, leave at least an inch. You need both the S-2 glass and the thin fiberglass mat. The mat is a very loose weave that can hold more resin than the glass. The basic construction is a sandwich of cloth, mat, then cloth. You can add more layers, but you always want mat between the cloth, and cloth on the outside. You will need more mylar to cover the last layer of cloth. This is to keep the air out. It helps to have this cut ahead of time because the resin will be hardening as you work. Mix the resin with hardener. Brush the mylar on the form with resin. The resin on the form is needed to hold the cloth onto it. Place the cloth on the form. Brush on resin. Cover with mat. Brush on more resin. Cover with the final layer. Apply more resin. Apply the mylar. Use masking tape to keep it attached. Wait two days. Note that the form has to be destructible, that is you need to pull it away from the radome. Generally you use cardboard. An alternative scheme, though I don't suggest it for a radome, is to use a foam core. You can bush directly onto the form. You need to at least a layer of mat then cloth on both sides of the form. Apply the mylar and wait two days. The form is part of the final structure, so there is nothing to remove. Generally for antennas in radome, all you do is have a weep hole at the bottom the antenna to allow air exchange. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/15/14, 1:53 AM, nuts wrote: I'd be inclined to look at radome construction. http://www.mpdigest.com/issue/articles/2008/may/mfg/default.asp The E-3 AWACS is mostly S-2 glass, but they need the strength. For a radome sitting outside, you might be able to do better. Radome design is considerably more complex than just putting something over an antenna. Typically, they make them as two face sheets separated by a honeycomb, but the dimensions and materials are chosen to minimize the reflection losses (e.g. the spacing might not be constant in the radome, depending on the angle of incidence of the radiation). A very thin face sheet is a tiny fraction of a wavelength, so the reflections from the two surfaces are almost in the same phase. For folks like time-nuts interested in parts in 1E15, this kind of thing makes a difference; not so much because of the attenuation, but because the reflected waves can cause a small phase shift in the apparent carrier phase; e.g. a 20dB reflection at 90 degrees shifts the apparent phase by about arctan(0.9)= 25 degrees. Typically in a radome, you shoot not only for low loss, but also low epsilon, so the reflection effects will be less. The advantage to S-2 glass is you can buy it easily, especially if you have a Tap Plastics handy. It works well with the Marine Resin they sell, so you know it will last a long time outdoors. What are the dielectric properties of such a composite? There's a reason why we don't build microwave circuits (in general) on G-10 or FR-4 material and use more exotic Rogers or Taconic substrates. (there's other reasons too..) Typical fiberglass uses an acrylic resin and acrylic has the spectacularly high loss tangent of 0.02 at only 1 MHz. The glass would help bring the loss down (since glass has a somewhat lower tangent, and if you have a fairly dry mix with small resin fraction, that helps) FR-4 has an epsilon of about 5 at low frequencies falling to a bit more than 4 at GHz frequencies, depending on the glass/epoxy ratio, and a loss tangent of around 0.01 at 1-2 GHz. This is quite high compared to sheet plastic of one sort or another. Take home message: I wouldn't fabricate a radome out of surfboard/boat building fiberglass unless you are very careful with the EM design. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Bert, I don't know about 1.6 GHz but I can tell you with some authority that before RTV/silicone is fully cured it is highly conductive to energy at 60 Hz. ... Martin VE3OAT Bert wrote : Am experimenting with small low cost GPS antennas and am considering as an alternative RTV/silicon. Any information on RF attenuation of RTV/silicon at 1.6 GHz ? Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/15/14, 8:13 AM, ewkeh...@aol.com wrote: Working off list on a super high performance GPSDO but low cost thanks to a time nut (sorry forgot his name) he directed me to DX.com which have ublox with antenna for lwss than $ 23. Super performance and though they are out of the one with 1 pps all you have to do is solder directly to the module. Have both versions. Attached you see what I did with the antenna but found out the hard way that when it rains the concave bottom fills with water, still works but not as good. So last night I made it flat with 3M Marine 5200 slow cure that I have extensive experience with from boating. Will take a full week to cure but if it does not work I can always remove it and start over There is a similar approach using a small display dome which is basically a round bottom beaker kind of shape designed to go on a wooden base. It can just as easily go on a big cork or stopper, or a disk cut out of a HDPE cutting board. Googling display dome will show you copious choices. or somewhere like glassdomes.com Of course, if you have a supply of canning jars or babyfood jars, then you can use those. Nothing says the jar has to be mounted with the axis vertical. You could do it sideways (like a ship in a bottle) to help solve the rain in the punt problem. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
The Gerber Baby Food Jar at Wall Mart $ 0.49 In a message dated 4/15/2014 1:03:40 P.M. Eastern Daylight Time, jim...@earthlink.net writes: On 4/15/14, 8:13 AM, ewkeh...@aol.com wrote: Working off list on a super high performance GPSDO but low cost thanks to a time nut (sorry forgot his name) he directed me to DX.com which have ublox with antenna for lwss than $ 23. Super performance and though they are out of the one with 1 pps all you have to do is solder directly to the module. Have both versions. Attached you see what I did with the antenna but found out the hard way that when it rains the concave bottom fills with water, still works but not as good. So last night I made it flat with 3M Marine 5200 slow cure that I have extensive experience with from boating. Will take a full week to cure but if it does not work I can always remove it and start over There is a similar approach using a small display dome which is basically a round bottom beaker kind of shape designed to go on a wooden base. It can just as easily go on a big cork or stopper, or a disk cut out of a HDPE cutting board. Googling display dome will show you copious choices. or somewhere like glassdomes.com Of course, if you have a supply of canning jars or babyfood jars, then you can use those. Nothing says the jar has to be mounted with the axis vertical. You could do it sideways (like a ship in a bottle) to help solve the rain in the punt problem. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Radom for a GPS antenna. I used this for a while... Place your patch type antenna on a small round black of plastic foam packing material. Make a slit for the antenna cable so that the little antann lays flat on the disk of foam and the cable comes up from the bottom. Now find a suitable glass jar. Maybe you have finish some pickles or whatever. Clean the jar and turn it upside down then force the jar over the disk of foam. If you like to mount it to a pole or mast, cut a one inch hole in the jar lid turn the lid upside down and screw it to the a wood pole (2x4) The jar with thread onto the lid. Eventually the lib will rust and the flat bottom jar might not work in your location but is is completely weather proof for zero cost. I eventually bought a real timing GPS antenna and paced it on e 1 galvanized pipe mast. BTW I looked at some expensive GPS antenna mounting hardware intended to connect an antenna to a pipe and found it was functionally identical to a pipe flange.An inverted jar lid glued to a pipe flange would make a great radome, and then you lead the cable down the pipe. Spray paint it all white and it would even look good. On Tue, Apr 15, 2014 at 1:53 AM, nuts n...@lazygranch.com wrote: I'd be inclined to look at radome construction. http://www.mpdigest.com/issue/articles/2008/may/mfg/default.asp The E-3 AWACS is mostly S-2 glass, but they need the strength. For a radome sitting outside, you might be able to do better. The advantage to S-2 glass is you can buy it easily, especially if you have a Tap Plastics handy. It works well with the Marine Resin they sell, so you know it will last a long time outdoors. You need to cure the resin in a vacuum, though not a particularly good vacuum. There are probably guides on the internet, but here is the basic scheme to make a fiberglass composite structure. Make a form of the final product. Cover the form in mylar. Tap Plastics sells the mylar too. The resin won't stick to the mylar. Cut the cloth to cover the form. Where you overlap, leave at least an inch. You need both the S-2 glass and the thin fiberglass mat. The mat is a very loose weave that can hold more resin than the glass. The basic construction is a sandwich of cloth, mat, then cloth. You can add more layers, but you always want mat between the cloth, and cloth on the outside. You will need more mylar to cover the last layer of cloth. This is to keep the air out. It helps to have this cut ahead of time because the resin will be hardening as you work. Mix the resin with hardener. Brush the mylar on the form with resin. The resin on the form is needed to hold the cloth onto it. Place the cloth on the form. Brush on resin. Cover with mat. Brush on more resin. Cover with the final layer. Apply more resin. Apply the mylar. Use masking tape to keep it attached. Wait two days. Note that the form has to be destructible, that is you need to pull it away from the radome. Generally you use cardboard. An alternative scheme, though I don't suggest it for a radome, is to use a foam core. You can bush directly onto the form. You need to at least a layer of mat then cloth on both sides of the form. Apply the mylar and wait two days. The form is part of the final structure, so there is nothing to remove. Generally for antennas in radome, all you do is have a weep hole at the bottom the antenna to allow air exchange. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/15/14, 11:02 AM, ewkeh...@aol.com wrote: The Gerber Baby Food Jar at Wall Mart $ 0.49 Is there a particular kind of food that works best? Perhaps strained prunes has the best regularity? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Actually I used a home canning type wide mouth mason jar.I thought about a fish bowl but there are not threads for mounting. Then I got smarter and spend $29 on a real timing antenna and it''s been on the roof for years. The jar on a stick works but has very poor WAF. On Tue, Apr 15, 2014 at 12:05 PM, Jim Lux jim...@earthlink.net wrote: On 4/15/14, 11:02 AM, ewkeh...@aol.com wrote: The Gerber Baby Food Jar at Wall Mart $ 0.49 Is there a particular kind of food that works best? Perhaps strained prunes has the best regularity? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Having five GPSDO's running and some for over 14 years I have a very sophisticated and expensive antenna system. This is part of a project that with the disappearance of Tbolts and other commercial GPSDO's to make available to time nuts state of the art performance at an affordable price, specifically those that have a hard time justifying large expenditures. To me the fun is in the challenge and maximum performance at minimum cost is fun. Stay tuned. Bert Kehren. In a message dated 4/15/2014 4:05:38 P.M. Eastern Daylight Time, albertson.ch...@gmail.com writes: Actually I used a home canning type wide mouth mason jar.I thought about a fish bowl but there are not threads for mounting. Then I got smarter and spend $29 on a real timing antenna and it''s been on the roof for years. The jar on a stick works but has very poor WAF. On Tue, Apr 15, 2014 at 12:05 PM, Jim Lux jim...@earthlink.net wrote: On 4/15/14, 11:02 AM, ewkeh...@aol.com wrote: The Gerber Baby Food Jar at Wall Mart $ 0.49 Is there a particular kind of food that works best? Perhaps strained prunes has the best regularity? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
Washed all three down the sink Bert Kehren In a message dated 4/15/2014 3:18:34 P.M. Eastern Daylight Time, jim...@earthlink.net writes: On 4/15/14, 11:02 AM, ewkeh...@aol.com wrote: The Gerber Baby Food Jar at Wall Mart $ 0.49 Is there a particular kind of food that works best? Perhaps strained prunes has the best regularity? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
I don't use the surf board resin. I use http://www.tapplastics.com/product/fiberglass/polyester_resins/tap_marine_vinyl_ester_resin/34 I don't have specifics on what Tap sells, but vinyl ester resins have a dielectic coeficient around 4 and dissipation of at least 0.00x. The resin is actually better than the S-2 glass.I suppose I can ask who makes their resin, but I don't know if anyone at a store has that answer. It works quite well on L-band. But to each his own. It is certainly better than the thick PVC pipe a lot of home brew antenna makers use. PVC degrades with UV unless you paint it, and if you paint it, who knows what the final result will be. The AWACS has a Al frame. Talk about reflections! The cheap arse test for a radome is you put it in the microwave with a bowl of water. See if the material gets hot. The S-2 with vinyl resin works great in that test. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS antenna in silicon/RTV encapsulation
Am experimenting with small low cost GPS antennas and am considering as an alternative RTV/silicon. Any information on RF attenuation of RTV/silicon at 1.6 GHz ? Bert Kehren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS antenna in silicon/RTV encapsulation
On 4/14/14, 12:11 PM, ewkeh...@aol.com wrote: Am experimenting with small low cost GPS antennas and am considering as an alternative RTV/silicon. Any information on RF attenuation of RTV/silicon at 1.6 GHz ? Are you potting the antenna in a solid mass of silicone? Or using it to seal an enclosure or what? pure silicone is very low loss, and it probably has an epsilon around 3. It can be loaded with silica (which is also low loss) to adjust the mechanical properties and electrical properties. It can also be loaded with other things (TiO2) which will increase the epsilon, but also the loss. the plastics that are notorious for loss are ones that have metal or carbon loading or that are hygroscopic so they pick up water. In the clear plastics world, Polypropylene, polyethylene and polystrene are pretty good. Polycarbonate isn't as good, neither are various acetals (Delrin) and acetates Here's a chart http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm or another chart http://www.eccosorb.com/Collateral/Documents/English-US/dielectric-chart.pdf here's a whole report from Dow on silcone rubbers as dielectrics http://www.dtic.mil/dtic/tr/fulltext/u2/656331.pdf They give quite low loss tangents at 10^9 cps (which I looked up on my cps to Hz conversion chart.. That's in your frequency range) 0.0059 loss tangent for Silastic 80. The trick for you will be knowing what else is in your particular silicone resin, and controlling the water content. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
