[Elecraft] KPA-1500 Power Supply Cable Size

[Charlie T]

Be VERY cautious of unknown Red/White wire, either twisted or mesh shielded.  That is the industry standard color code for Iron/Constantan, Type J Thermocouple wire.   It has MUCH higher resistance than the same size copper wire.  


73, Charlie k3ICH




-----Original Message-----
From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On Behalf Of Jim Brown
Sent: Monday, July 30, 2018 3:32 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KPA-1500 Power Supply Cable Size

On 7/30/2018 6:43 AM, K8ZCT wrote:
> Speaker wire is made for speaker systems. Although it may look like "lamp cord" it is not listed for use to wire up a lamp.

Right -- it has to do with voltage breakdown of the insulation, which must be 3kV on the AC power line (in the case of a lightning spike).

It is my understanding that the KPA1500 operates at about 60VDC, and that cable is carrying 50-60A. There are no lightning spikes to contend with. All that matters is DC resistance, sufficiently robust physical construction, and voltage breakdown.

In large sound systems, power amps often produce voltage peaks in the range of 150V.

FWIW, the Red/White zip cord sold as speaker cable is often pretty lousy quality. Insulation is made very thick as a marketing measure -- to make it look "beefier" than it really is, and therefore worth more money. :) When I've measured some hamfest cables like this with a micrometer I've found that they're actually smaller than labeled!  In other words, we're getting cheated. :)

73, Jim K9YC

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