[Elecraft] Terminal resistance

[Bob McGraw K4TAX]

The company for which I previously worked designed and built recording 
studio consoles.   In order to eek out every bit of noise, that is 
achieve the lowest noise floor, it was necessary to crimp and then 
solder the lugs on the power supply cables on both ends.  Crimping was 
only OK and was done until it was discovered that also soldering the 
lugs did lower noise floor a few dB. This leads me to conclude that 
crimping AND soldering is preferred, leading to a lower resistance 
connection.

For lightning grounding, joints and terminations, soldering alone is not 
permitted.  Crimping is required.

Yes, lugs can not be soldered alone.  They must be crimped first and 
THEN soldered.    At the same time, some installations of aeronautical 
equipment, along with NASA procedure, I do understand does indicate 
sweating solder into the lug and it thereby wicking up into the stranded 
wires makes for a "stiff" connection.   This connection is reported to 
break under vibration conditions.   I've personally never experienced 
such with ham equipment, although I've never carried any into space.  I 
suppose there is merit to this directive.    Perhaps you FAA and NASA 
types can expand this thought.

I am also aware with power distribution systems, a.k.a TVA,  it is quite 
common to use a crimp method to join wires.   These conductors  are 
several thousand circular mills in size and are of many layers of 
stranded conductors.  When properly and completely crimped by a 
hydraulic crimp machine, the joint is void of space. If fact, having cut 
one of these in half just to see for myself, it appeared as a solid rod 
with no voids observed.  Thus the strands were compressed to that 
degree.    The center strand was steel as the messenger and the five 
outer layers of aluminum were alternating in direction of rotation, 
clockwise wound and counterclockwise wound.

In most cases, crimping connectors with a crimping tool which has the 
correct die for the connector is noted to be satisfactory.  On the other 
hand, I've seen many cables in various ham applications which were 
installed using what ever was handy to mash the sleeve.   That is NOT 
crimping.  Crimping does not distort the tubular diameter nor round 
shape of the sleeve as the correct size die prevents distortion of the 
sleeve.   A correct crimping tool puts a dimple in one side of the sleeve.

And now you know the rest of the story.

73

Bob, K4TAX

On 6/16/2019 7:27 PM, Nate Bargmann wrote:
> * On 2019 16 Jun 18:50 -0500, Kidder, George wrote:
>> 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!
> For what it is worth, the company I worked for prohibited the use of
> soldered connectors for terminating bonding or power wiring.  Especially
> with regard to bonding, dissipating any lightning strike energy through
> a soldered connector could cause it to enough to melt the solder.  In
> doing some microwave site upgrades I did pull out a previous generation
> of bonding wiring that was soldered and some connectors had signs of
> being heated since installation.
>
> In my shack I use crimp connectors and a quality crimping tool with no
> problems.
>
> 73, Nate, N0NB
>