AeroElectric-List Digest Archive

Thu 12/20/18


Total Messages Posted: 7



Today's Message Index:
----------------------
 
     1. 07:01 AM - Re: what is the truth about gps antennas? (user9253)
     2. 08:56 AM - Re: what is the truth about gps antennas? (Robert L. Nuckolls, III)
     3. 11:23 AM - Fuse-able link (John Morgensen)
     4. 01:15 PM - Re: Fuse-able link (Robert L. Nuckolls, III)
     5. 02:10 PM - Re: Fuse-able link (Charlie England)
     6. 04:00 PM - Re: Fuse-able link (John Morgensen)
     7. 04:05 PM - Re: Fuse-able link (John Morgensen)
 
 
 


Message 1


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    Time: 07:01:06 AM PST US
    Subject: Re: what is the truth about gps antennas?
    From: "user9253" <fransew@gmail.com>
    Read this thread: http://forum.matronics.com/viewtopic.php?t=16766060&start=0&postdays=0&postorder=asc&highlight=&sid=4eec20ad70d380aa54524dd467494a91 While none of the postings were by engineers, their replies are based on experience. Stein owns an avionics company. He is the expert. Follow his recommendations. If shorter cable must be used, consider RG-58. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=486456#486456


    Message 2


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    Time: 08:56:49 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: what is the truth about gps antennas?
    At 09:23 PM 12/19/2018, you wrote: > >I'm interested in hearing from an engineer who >might know about what really goes on with my >stratus esg gps antenna. they say to use RG400 >cable, 10' minimum, and never paint the antenna. >they also told me the strength ratings should >run in the 30's. I have 3' of RG400 with a >mechanical 90=C2=B0 elbow, I spray painted the >antenna flat black and mounted it on the >glareshield of my RV. my readings are all in the >40's. they told me this shows an overdriven condition. >so why use low impedance cable then need 10'? my >iFly740 and Lowrance 1000 gps's have antennas >with much smaller cables. the iFly shows WAAS >grade accuracy, using an antenna 1/4 the size of the stratus RAMI antenna. >when does being overdriven prove to be a >problem? is this a situation where I could add >more mechanical connectors to increase impedance >rather than more cable length? >I get the feeling things get written and then >forever repeated, such as never paint an >antenna, without asking any questions. could I >use a different antenna than the RAMI brand? >should I not worry about any of this and just go fly? Paint MIGHT degrade antenna performance but without laboratory grade testing, you don't know about YOUR paint. Hence, easiest way to deal with it is never paint. Now, if you have a painted antenna and the receiver is still got good signal numbers, then the 99% sure THAT paint is not an issue. OVER-DRIVEN? Never heard of such a thing in GPS receivers. RG400 has an attenuation figure on the order of 16db typical to 20 db maximum PER 100 FEET at GPS frequencies. Assume worst at 20db/100' for a 10' feeder cable, shortening it to ZERO feet would raise the signal by 2db Maximum, probably less. This is trivial. Color be skeptical . . . Antenna dimensions are only loosely related to performance. Physical and electrical things INSIDE make the difference . . . and the technology is now so old that manufacturing a good antenna is child's play. You certainly want to minimize connections but don't loose any sleep over it if you've added one for enhanced maintenance. I've got a GPS cable on my bench signal generator that is 20' long and RG174 style (relatively high attenuation) that drives the GPS disciplined reference oscillator . . . it gets stood up in less than 2 minutes even after being off for weeks. There's been a lot of hangar-lore floating around the aviation environs concerning things technical for over a century. Sadly, many 'field representatives' of major suppliers are not all that cognizant of foundations in physics for the products they sell. Stories not backed up by measurement and/or demonstration are suspect. GPS is no exception. If anyone encounters a 'factory representative' who offers less than comfortable advice, shoot me their name and phone number. The proof of the pudding is in the flying. You'll be getting error messages when an if the receiver is being improperly serviced by what's coming down the coax. Bob . . .


    Message 3


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    Time: 11:23:58 AM PST US
    From: John Morgensen <john@morgensen.com>
    Subject: Fuse-able link
    Two years ago I had an over-voltage event and the crowbar protection behaved as expected. It popped the 5amp breaker. I had the alternator (Plane Power 60amp internal) repaired and it has behaved normally since then. The alternator stopped working this Sunday. The crimp had failed on the 18ga to 22ga fuse-link. Closer inspection revealed that the insulation under the heat shield on the fuse-link was almost completely gone. Questions: 1. Should I have inspected the fuse-link after the over-voltage incident before putting the plane back in service? 2. Is it acceptable to solder the joint between the 18ga and the 22ga or is a crimp connector required? Thanks, john


    Message 4


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    Time: 01:15:18 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Fuse-able link
    At 01:23 PM 12/20/2018, you wrote: > >Two years ago I had an over-voltage event and the crowbar protection >behaved as expected. It popped the 5amp breaker. I had the >alternator (Plane Power 60amp internal) repaired and it has behaved >normally since then. The alternator stopped working this Sunday. The >crimp had failed on the 18ga to 22ga fuse-link. Closer inspection >revealed that the insulation under the heat shield on the fuse-link >was almost completely gone. > >Questions: > >1. Should I have inspected the fuse-link after the over-voltage >incident before putting the plane back in service? > >2. Is it acceptable to solder the joint between the 18ga and the >22ga or is a crimp connector required? I would really like to have that fusible link assembly. Can you cut it out and fabricate a new one? When you say "gone" . . . is it melted, charred, evaporated? Was it Tefzel wire? That link normally carries 3A or less. I've demonstrated that 22AWG Tefzel will carry 20A indefinitely in the open air. Some combination of factors stacked up to cause this particular link to suffer damage. A good place to start is careful examination of the link. Bob . . .


    Message 5


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    Time: 02:10:03 PM PST US
    Subject: Re: Fuse-able link
    From: Charlie England <ceengland7@gmail.com>
    On 12/20/2018 3:14 PM, Robert L. Nuckolls, III wrote: > At 01:23 PM 12/20/2018, you wrote: >> <john@morgensen.com> >> >> Two years ago I had an over-voltage event and the crowbar protection >> behaved as expected. It popped the 5amp breaker. I had the alternator >> (Plane Power 60amp internal) repaired and it has behaved normally >> since then. The alternator stopped working this Sunday. The crimp had >> failed on the 18ga to 22ga fuse-link. Closer inspection revealed that >> the insulation under the heat shield on the fuse-link was almost >> completely gone. >> >> Questions: >> >> 1. Should I have inspected the fuse-link after the over-voltage >> incident before putting the plane back in service? >> >> 2. Is it acceptable to solder the joint between the 18ga and the 22ga >> or is a crimp connector required? > > I would really like to have that fusible link > assembly. Can you cut it out and fabricate > a new one? > > When you say "gone" . . . is it melted, charred, > evaporated? Was it Tefzel wire? > > That link normally carries 3A or less. I've > demonstrated that 22AWG Tefzel will carry > 20A indefinitely in the open air. > > Some combination of factors stacked up to > cause this particular link to suffer > damage. A good place to start is careful > examination of the link. > > > Bob . . . > Sounds like the failure was in the joint, so... Less than perfect crimp, followed by years of increasing corrosion in the joint, causing resistance heating in the joint? I solder/heatshrink my fuselinks, but I trust my soldering skills (a couple of careers that required a decent skillset). Charlie --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus


    Message 6


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    Time: 04:00:18 PM PST US
    Subject: Re: Fuse-able link
    From: John Morgensen <john@morgensen.com>
    I'll fish it out of the trash and send it to you. john On 12/20/2018 2:14 PM, Robert L. Nuckolls, III wrote: > At 01:23 PM 12/20/2018, you wrote: >> <john@morgensen.com> >> >> Two years ago I had an over-voltage event and the crowbar protection >> behaved as expected. It popped the 5amp breaker. I had the alternator >> (Plane Power 60amp internal) repaired and it has behaved normally >> since then. The alternator stopped working this Sunday. The crimp had >> failed on the 18ga to 22ga fuse-link. Closer inspection revealed that >> the insulation under the heat shield on the fuse-link was almost >> completely gone. >> >> Questions: >> >> 1. Should I have inspected the fuse-link after the over-voltage >> incident before putting the plane back in service? >> >> 2. Is it acceptable to solder the joint between the 18ga and the 22ga >> or is a crimp connector required? > > I would really like to have that fusible link > assembly. Can you cut it out and fabricate > a new one? > > When you say "gone" . . . is it melted, charred, > evaporated? Was it Tefzel wire? > > That link normally carries 3A or less. I've > demonstrated that 22AWG Tefzel will carry > 20A indefinitely in the open air. > > Some combination of factors stacked up to > cause this particular link to suffer > damage. A good place to start is careful > examination of the link. > > > Bob . . . >


    Message 7


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    Time: 04:05:13 PM PST US
    Subject: Re: Fuse-able link
    From: John Morgensen <john@morgensen.com>
    I forgot to mention that this is a pretty faithful Z13/8 with dual pmags and an S700-2-10 for off/battery/alternator. john On 12/20/2018 3:11 PM, Charlie England wrote: > On 12/20/2018 3:14 PM, Robert L. Nuckolls, III wrote: >> At 01:23 PM 12/20/2018, you wrote: >>> <john@morgensen.com> >>> >>> Two years ago I had an over-voltage event and the crowbar protection >>> behaved as expected. It popped the 5amp breaker. I had the >>> alternator (Plane Power 60amp internal) repaired and it has behaved >>> normally since then. The alternator stopped working this Sunday. The >>> crimp had failed on the 18ga to 22ga fuse-link. Closer inspection >>> revealed that the insulation under the heat shield on the fuse-link >>> was almost completely gone. >>> >>> Questions: >>> >>> 1. Should I have inspected the fuse-link after the over-voltage >>> incident before putting the plane back in service? >>> >>> 2. Is it acceptable to solder the joint between the 18ga and the >>> 22ga or is a crimp connector required? >> >> I would really like to have that fusible link >> assembly. Can you cut it out and fabricate >> a new one? >> >> When you say "gone" . . . is it melted, charred, >> evaporated? Was it Tefzel wire? >> >> That link normally carries 3A or less. I've >> demonstrated that 22AWG Tefzel will carry >> 20A indefinitely in the open air. >> >> Some combination of factors stacked up to >> cause this particular link to suffer >> damage. A good place to start is careful >> examination of the link. >> >> >> Bob . . . >> > Sounds like the failure was in the joint, so... Less than perfect > crimp, followed by years of increasing corrosion in the joint, causing > resistance heating in the joint? > > I solder/heatshrink my fuselinks, but I trust my soldering skills (a > couple of careers that required a decent skillset). > > Charlie > > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> > Virus-free. www.avast.com > <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> > > > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>




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