[Elecraft] Voltage drop in DX Power to K3

[Jack Brindle]

There is one more item that has been forgotten. The K3 has an SB530 Schottky diode in the power input circuit between the input fuse and the main 12V bus (but not the 100 watt 12V PA bus). This will account for about a half of a volt drop. If you are using the front panel voltage reading, this must be added into the equation. In other words, the voltage at the power pole is about a half volt higher than the front panel reading.

It might be worth while to take a look at the schematics for the K3 - they are available at the Elecraft web site.

Now back to the discussion…

73!
Jack, W6FB
ps.  DX Power?

> On Apr 26, 2020, at 9:11 AM, Bob McGraw K4TAX <rmcgraw at blomand.net> wrote:
> 
> The power cable at 0.03 ohms on each side,  a total of 0.06 ohms resistance.  The 4005i, per his measurements, has 0.08 ohms resistance.   The power distribution strip contributes more than 50% of the voltage drop.   Actually more than the power cables.
> 
> The power cable contributes  1.2 volts of drop.   The 4005i contributes an added 1.6 volts of drop for a total of 2.8 volts.
> 
> The calculation is simple:    E = I x R      current multiplied by amps equal voltage.
> 
> 73
> 
> Bob, K4TAX
> 
> 
> 
> On 4/26/2020 10:53 AM, Leroy Buller wrote:
>> 40 inches of power cable.  In my experiences,  that could be an issue
>> depending on the gauge of the wire.  I used a long cable 12 gauge and had
>> issues.  Went to 24 inches number 10 gauge and voltage drop significantly
>> improved.  The resustace does not have to be large to cause a voltage  drop
>> 
>> Lee
>> 
>> On Sun, Apr 26, 2020, 9:47 AM N4ZR <n4zr at comcast.net> wrote:
>> 
>>> I've had an e-mail exchange with West Mountain Radio.  Measured the
>>> voltage drop inside the 4005i at only .08 volts at 100 watts key down.
>>> My power cable from the 4500i to the K3 measures 0.3 ohms on each
>>> conductor, which at 20 amps should only yield a 1.2 volt drop, right?  I
>>> don't know where the other volt plus of drop is coming from.  The cable
>>> is 40 inches long, and only minor shortening is possible.  It is about
>>> the largest wire that will fit in the Powerpoles on both the K3 and the
>>> 4005i.
>>> 
>>> Suggestions welcome
>>> 
>>> --
>>> 73, Pete N4ZR
>>> Check out the Reverse Beacon Network
>>> at <http://reversebeacon.net>, now
>>> spotting RTTY activity worldwide.
>>> For spots, please use your favorite
>>> "retail" DX cluster.
>>> 
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