Interesting data, Don. I wonder if there is any information about resistance variations between soldered and crimped terminals. One might think that, with stranded wire, even a good crimp connection might not solidly involve all of the strands, and might additionally deteriorate with time since oxygen could get between the strands. A good solder job should wet the wire through and (additionally) exclude oxygen. This wouldn't be easy to measure, for sure, but these engineers are cleaver people!
73 - George, W3HBM On 6/12/2019 7:55 PM, Don Wilhelm wrote: > [This message came from an external source. If suspicious, report to > ab...@ilstu.edu<mailto:ab...@ilstu.edu>] > > After consulting copper wire tables and typical connection resistances, > I can present the following analysis for a 20 amp load: > > Often hams power their 100 watt transceivers through DC distribution > devices such as a RigRunner which will contribute to the voltage drop. > Also in-line fuses will contribute to voltage drop. > > Connection resistance contributes .05 volt loss under a 20 amp load for > each contact point, you have 6 contact points in the path for a fused > RigRunner plus two in the APP connector at the transceiver, plus the > connection to the power supply for a total of 10 contact points. You > have to consider the negative path as well as the positive. So that is > a total of 0.5 volts of the total voltage drop. > > By contrast, a 5 foot length under a 20 amp load of #12 wire has 0.1588 > ohms (in both conductors) for a voltage drop of 0.3176 volts, and #10 > wire a drop of 0.1998 volts. > > So conclusion is that while increasing the wire size can reduce the > voltage drop, the main contributor is in the power distribution system. > > A path direct from the power supply terminals can be expected to have a > 0.5 volt drop with 5 feet of #12 wire to the inside of the K3. and #10 > wire can have a 0.4 volt drop - the difference is only slightly > significant. > > Conclusion - in a 5 foot power cable run, the difference between #10 and > #12 wire is only 0.1 volts (0.05 volts in each of the positive and > negative leads) - the major contributor is the number of contact points. > > So for those who choose to measure the voltage drop from the power > supply terminals to the APP connector on the outside of the K3, you > should measure about 0.2 volts in each conductor with #12 wire and 0.15 > volts with #10 wire. If it is much more than that, check your power > supply connection tightness and your crimp connections. > > Run the transceiver direct from a power supply using ring terminals > instead of routing through a power distribution accessory. > > 73, > Don W3FPR > > On 6/12/2019 6:29 PM, Bob McGraw K4TAX wrote: >> Regarding "heavy gauge wire", I suggest one measure the voltage drop >> using a DVM connected direct between the power supply Pos terminal and >> the radio Pos terminal. Likewise do the same for the Neg DC line. Put >> the radio in CW mode and close the key for rated output. If one finds >> more than 0.25 volts drop in either the Pos or Neg line, I'd say that >> attention to the power cable and connectors would be in order. Also >> measure between radio ground and power supply ground. Again a voltage >> value greater than 0.25 volts indicates attention to the power >> distribution system and station equipment grounding is needed. >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to gkid...@ilstu.edu ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
