[Elecraft] K3/100 Voltage Drop when transmitting

[Harlan Sherriff]

Diode voltage drop is approximately 0.7v per diode

Sent from my iPhone

> On Feb 26, 2019, at 2:16 PM, Jack Brindle via Elecraft <elecraft at mailman.qth.net> wrote:
> 
> Be sure to use a DVM external to the K3 to measure the voltage at the K3. The input protection diode in the K3 will cause some drop (1/4 to 1/2 volt perhaps). What this means is that the K3 meter will always show less voltage than is really present at the transceiver supply input.
> 
> 
> 73!
> Jack, W6FB
> 
>> On Feb 26, 2019, at 9:37 AM, mjpilgrim <mpilgrim at bellsouth.net> wrote:
>> 
>> Well, i have received many helpful replies both publicly here and in private
>> emails.  Thanks to all for those ideas brought forward.
>> 
>> What I've gleaned to be most useful from your responses has been the
>> suggestions to investigate the power cord with power poles connecting the K3
>> to my switching power supply.  Per those inputs I've fabricated a shorter
>> (5') cable and insured that I used the crimp terminals rated at 30 AMPS. 
>> The initial result has been a reduction of about 30% of my measured voltage
>> drop (now 13.6 Volts in standby to 12.5V when key down 100W CW........
>> previously the drop was to 12.0)...............  Some background info. is
>> that the original observation of a voltage drop occurred as the K3 was
>> connected to my minimal-sized Solar Power supply.  After extensive
>> investigation, additional hardening in the wiring, and replacement of a
>> suspect imported power distribution strip, I was convinced there was no
>> voltage drop evidenced there.  The battery voltage measured at the input to
>> the referenced DC power distribution strip did not waver under key down
>> tests with the attached K3............. There remained however, the
>> above-mentioned voltage drop displayed in the K3 metering.
>> 
>> i plan to rebuild the afore-mentioned 5' power cable, this time soldering
>> the power pole lugs rather than trusting crimped connections.  My suspicion
>> that the power cable is suspect, so i plan to address those curiosities
>> before moving on to other possible cause.
>> 
>> Thanks again for your continued ideas and suggestions.
>> Regards,
>> Mike, K5MP
>> 
>> 
>> 
>> --
>> Sent from: http://elecraft.365791.n2.nabble.com/
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