Connecting Transceivers in Vehicles - Change of Recommended Practice - OT
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Thought I'd pass this on, may not be so OT. I've seen many posts here on mobile installation and the use of 2 fuses, in fact I've posted on that and I use two fuses. The below came from a tutors reflector in the UK and affects our training.
Connecting Transceivers in Vehicles - Change of Recommended Practice Guidance for vehicle installation was originally contained in MPT1362 issued by the Radiocommunications Agency after consultation with industry. That role has now passed to the Federation of Communication Services and re-issued as the UK Code of Practice FCS1362. http://www.fcs.org.uk/my%20files/fcs_pdfs/codesofpractice/08-05-12%20fcs%201362%20final.pdf. There is a significant change in the guidance, section which will affect the UK Advanced examination and the UK Advanced course book. The advice in MPT1362 and all copies of Advance! up to and including the 2009 reprint was to connect the transceiver directly to the vehicle battery with appropriate fuses in both the positive and negative leads. Often there is an incidental DC route from the vehicle chassis via the antenna mount, coaxial cable outer, rig and negative power lead to the battery terminal. Some vehicle load current will take that route and if the battery negative to chassis strap fails then all vehicle loads including starting current (100A plus) could. Clearly a fire risk especially for the super thin coax intended to fit round a door or boot seal. New advice. The new guidance is to connect the transceiver negative directly to the vehicle chassis and no fuse in the negative. (Assumes negative earth.) The positive lead should still be fused and connected to the battery or in accordance with the vehicle manufactures specific recommendation. Remember that transceivers should be specified for vehicle use and the manufacturer’s guidance on RF power limits, antenna placement and DC supplies must be followed. Failure to do so might affect your insurance cover and questions on this point must be directed to your insurance provider. 73 de M0XDF, K3 #174 -- The bamboo that bends is stronger than the oak that resists. -Japanese proverb ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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<<<New advice.
The new guidance is to connect the transceiver negative directly to the vehicle chassis and no fuse in the negative. (Assumes negative earth.) The positive lead should still be fused and connected to the battery or in accordance with the vehicle manufactures specific recommendation. Remember that transceivers should be specified for vehicle use and the manufacturer’s guidance on RF power limits, antenna placement and DC supplies must be followed. Failure to do so might affect your insurance cover and questions on this point must be directed to your insurance provider.>>> It's about time everyone had common sense about this. If the device has a floating negative power supply buss, like the old Motorola land mobile radios designed for positive or negative supply vehicles, that ground loop is not present. Fusing the negative made some sense, or at least did not hurt. Now a negative line fuse is a horrible idea. If you lose the negative path from the radio to the battery or from the battery to the engine block, it can cause all sorts of damage inside and outside the radio. We'll see how long it takes the rest of the world to pull its head out of the sand on this! Tom ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by M0XDF
I should have said "going to the negative post and fusing
the negative lead" is a bad idea. The radio negative needs to go to the vehicle chassis near but not on the battery chassis ground connection. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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strikes me that is a bad idea, it the battery ground connection becomes disconnected, your rig carries all the current, including the starter - fuse or no fuse!
73 de M0XDF -- Extraordinary claims require extraordinary evidence. -Carl Sagan, astronomer and author (1934-1996) On 17 Mar 2010, at 14:33, Tom W8JI wrote: > I should have said "going to the negative post and fusing the negative lead" is a bad idea. The radio negative needs to go to the vehicle chassis near but not on the battery chassis ground connection. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Connecting Transceivers in Vehicles - Change ofRecommended Practice - OT
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Dave,
The chassis of the radio is usually connected to the vehicle chassis through the coax shield anyway. The negative terminal on the radio is also connected to the radio chassis ground. The problem comes from the common practice of connecting the negative power to the radio directly to the *battery*. It should go the the vehicle chassis - with no fuse. 73, Don W3FPR David Ferrington, M0XDF wrote: > strikes me that is a bad idea, it the battery ground connection becomes disconnected, your rig carries all the current, including the starter - fuse or no fuse! > 73 de M0XDF > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by M0XDF
This becomes a problem ONLY when the radio is connected to the negative terminal of the
battery. In that case, you should use the negative fuse. But if you connect the radio to the chassis as W8JI recommended, then you should not use a negative fuse. > strikes me that is a bad idea, it the battery ground connection becomes disconnected, your > rig carries all the current, including the starter - fuse or no fuse! > 73 de M0XDF > > Tom W8JI wrote: >> I should have said "going to the negative post and fusing the negative >> lead" is a bad idea. The radio negative needs to go to the vehicle chassis near but not >> on the battery chassis ground connection. -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Connecting Transceivers in Vehicles - Change ofRecommended Practice - OT
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> This becomes a problem ONLY when the radio is connected to the negative
> terminal of the > battery. In that case, you should use the negative fuse... But consider that case where a rig is powered through a pair of fuses home-run to the battery posts. If the negative fuse blows and the positive fuse remains closed -- and *if* the radio chassis is common to negative power with grounded connectors (e.g., SO-239) via a ground return through the vehicle chassis, then the coax braid and other supplemental grounded leads on the radio chassis will carry the full rig current. Seems like in all cases where the rig chassis is common to the negative power lead, the negative lead wiring should go un-fused at or very close to the negative battery post. Paul, W9AC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Don Wilhelm-4
Ok, thanks Don, I think I understand why now - looks like I'll have to do a bit of rewiring!
73 de M0XDF, K3 #174 -- Natural ability without education has more often attained to glory and virtue than education without natural ability. -Cicero, statesman, orator, writer (106-43 BC) On 17 Mar 2010, at 15:28, Don Wilhelm wrote: > Dave, > > The chassis of the radio is usually connected to the vehicle chassis through the coax shield anyway. The negative terminal on the radio is also connected to the radio chassis ground. > The problem comes from the common practice of connecting the negative power to the radio directly to the *battery*. It should go the the vehicle chassis - with no fuse. > > 73, > Don W3FPR > > David Ferrington, M0XDF wrote: >> strikes me that is a bad idea, it the battery ground connection becomes disconnected, your rig carries all the current, including the starter - fuse or no fuse! >> 73 de M0XDF >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Connecting Transceivers in Vehicles - Change ofRecommended Practice - OT
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In reply to this post by W8JI
You need to carefully consider what is added to a vehicle, unless a
transceiver is "e" marked (in addition to CE marking) it cannot legally be fitted to most types of vehicle in Europe. See: http://www.vca.gov.uk/vehicletype/system-component-app.asp http://www3.hants.gov.uk/tradingstandards/tradingstandards-businessadvice/tradingstandards-automotive.htm 73 Dave, G4AON ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Major auto makers offer conflicting guidance on this subject.
In sum, Chrysler says negative lead to the body near the battery, not fused. Ford says both leads to the battery, but doesn't give clear guidance on fusing the negative lead. GM says it's best to connect the negative lead to the chassis, but IF you connect it to the battery terminal directly, then you should fuse it, in case the ground lead from the negative side of the battery to the chassis becomes disconnected (in which case your rig will be the car's only path to ground.) No wonder there's confusion. What makes the most sense to me is to attach the negative lead directly to the chassis, near the battery, and with no fuse. That's not what I have in my vehicle right now (currently have both leads to battery, both fused, but I will change it based on this thoughtful dialogue. Here are direct quotes from the documents available online provided by the "Big Three" US car makers: Daimler-Chrysler says: Special design considerations are incorporated into this vehicle's electronic system to provide immunity to radio frequency signals. Mobile two-way radio and telephone equipment must be installed properly by trained personnel. The following must be observed during installation. The positive power connection should be made directly to the battery and fused as close to the battery as possible. The negative power connection should be made to body sheet metal adjacent to the negative battery connection. This connection should not be fused. (and later in the same document) >DO NOT FUSE THE GROUND LEAD. If the ground-side fuse were to open, the entire supply current would be conducted by an alternate current return path, which could cause the feedline to overheat, with possible resulting damage. Ford Motor Company says: Transceiver power connections should be made directly to the battery and appropriately fused as close to the battery as possible. A weatherproof fuse holder is recommended. Twist the positive and negative power leads together to enhance noise immunity. (Ford is silent on the issue of whether to fuse the negative power lead or not, but implicit in their instruction (fuse holder is singular, not plural), is the notion that only the positive lead should be fused. GM says: 3.) Connect the positive lead to the auxiliary power terminal and connect the negative lead to the battery body connection point (identified by a short #10 AWG or larger wire running from the negative battery terminal to the body of the vehicle). If connections are made directly to the battery terminals, the GM approved methods of connecting auxiliary wiring include the adapter package illustrated in Figure 2, NAPA-Belden replacement battery bolts (part # 728198), or drilling and tapping the hex end of the original battery bolts 10-32 X 3/8" deep. NOTE: It is recommended that a fuse be placed in the transceiver negative lead to prevent possible transceiver damage in the event the battery to engine-block ground lead is inadvertently disconnected. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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