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K3 voltage reading

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Steve Ellington

K3 voltage reading

Can someone take a look at their voltage reading on their K3's DISP-V window and tell me what they get with key down, full power output into 50 ohms?
My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v. I'm just wondering if there is excessive voltage drop on the power leads. I'm using the factory cable. I'm not sure if the K3 is indicating the voltage at rig's connector or the voltage on the final amp. transistors.

Steve N4LQ
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K2QI

Re: K3 voltage reading

What band/frequency? I want to replicate your exact test variables and
revert with my results.

James K2QI

On Wed, Nov 17, 2010 at 10:02 AM, Steve Ellington <[hidden email]>wrote:

> Can someone take a look at their voltage reading on their K3's DISP-V
> window and tell me what they get with key down, full power output into 50
> ohms?
> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
> I'm just wondering if there is excessive voltage drop on the power leads.
> I'm using the factory cable. I'm not sure if the K3 is indicating the
> voltage at rig's connector or the voltage on the final amp. transistors.
>
> Steve N4LQ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

--
73 de James K2QI
President UNARC/4U1UN
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--... ...-- -.. . .--- .- -- . ...

N2TK

Re: K3 voltage reading

In reply to this post by Steve Ellington

Hi Steve,
Using the cable that came with my K3 I measure on the K3's meter display
13.6V key up and 12.4 - 12.6V key down at 100W out on 10-20M. Roughly 1.2A
in receive and 20A in transmit mode.

N2TK, Tony

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Steve Ellington
Sent: Wednesday, November 17, 2010 10:03 AM
To: [hidden email]
Subject: [Elecraft] K3 voltage reading

Can someone take a look at their voltage reading on their K3's DISP-V window
and tell me what they get with key down, full power output into 50 ohms?
My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
I'm just wondering if there is excessive voltage drop on the power leads.
I'm using the factory cable. I'm not sure if the K3 is indicating the
voltage at rig's connector or the voltage on the final amp. transistors.

Steve N4LQ
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Steve Ellington

Re: K3 voltage reading

In reply to this post by K2QI

Mine reads 13.1v on any band so it doesn't seem to matter.
Steve N4LQ

----- Original Message -----
From: James Sarte (K2QI)
To: Steve Ellington
Cc: [hidden email]
Sent: Wednesday, November 17, 2010 10:08 AM
Subject: Re: [Elecraft] K3 voltage reading

What band/frequency? I want to replicate your exact test variables and revert with my results.

James K2QI

On Wed, Nov 17, 2010 at 10:02 AM, Steve Ellington <[hidden email]> wrote:

Can someone take a look at their voltage reading on their K3's DISP-V window and tell me what they get with key down, full power output into 50 ohms?
My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v. I'm just wondering if there is excessive voltage drop on the power leads. I'm using the factory cable. I'm not sure if the K3 is indicating the voltage at rig's connector or the voltage on the final amp. transistors.

Steve N4LQ
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--

73 de James K2QI
President UNARC/4U1UN

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Steve Ellington

Re: K3 voltage reading

In reply to this post by N2TK

Wow...That's a lot more drop than I have so I feel pretty good now!
I still wonder where the K3 is actually measuring. If its reading comes
after a few chokes it would certainly make a difference.
N4LQ
Steve

----- Original Message -----
From: "N2TK, Tony" <[hidden email]>
To: "'Steve Ellington'" <[hidden email]>; <[hidden email]>
Sent: Wednesday, November 17, 2010 10:13 AM
Subject: RE: [Elecraft] K3 voltage reading

> Hi Steve,
> Using the cable that came with my K3 I measure on the K3's meter display
> 13.6V key up and 12.4 - 12.6V key down at 100W out on 10-20M. Roughly 1.2A
> in receive and 20A in transmit mode.
>
> N2TK, Tony
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Steve Ellington
> Sent: Wednesday, November 17, 2010 10:03 AM
> To: [hidden email]
> Subject: [Elecraft] K3 voltage reading
>
> Can someone take a look at their voltage reading on their K3's DISP-V
> window
> and tell me what they get with key down, full power output into 50 ohms?
> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
> I'm just wondering if there is excessive voltage drop on the power leads.
> I'm using the factory cable. I'm not sure if the K3 is indicating the
> voltage at rig's connector or the voltage on the final amp. transistors.
>
> Steve N4LQ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

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K2QI

Re: K3 voltage reading

In reply to this post by Steve Ellington

OK, well mine drops from 13.6V to 12.8V on 40m. Amp draw is roughly around
17.88A

On 20m, it drops to 12.7V

HTH

James K2QI

On Wed, Nov 17, 2010 at 10:15 AM, Steve Ellington <[hidden email]>wrote:

> Mine reads 13.1v on any band so it doesn't seem to matter.
> Steve N4LQ
>
> ----- Original Message -----
> *From:* James Sarte (K2QI) <[hidden email]>
> *To:* Steve Ellington <[hidden email]>
> *Cc:* [hidden email]
> *Sent:* Wednesday, November 17, 2010 10:08 AM
> *Subject:* Re: [Elecraft] K3 voltage reading
>
> What band/frequency? I want to replicate your exact test variables and
> revert with my results.
>
> James K2QI
>
> On Wed, Nov 17, 2010 at 10:02 AM, Steve Ellington <[hidden email]>wrote:
>
>> Can someone take a look at their voltage reading on their K3's DISP-V
>> window and tell me what they get with key down, full power output into 50
>> ohms?
>> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
>> I'm just wondering if there is excessive voltage drop on the power leads.
>> I'm using the factory cable. I'm not sure if the K3 is indicating the
>> voltage at rig's connector or the voltage on the final amp. transistors.
>>
>> Steve N4LQ
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
>
> --
> 73 de James K2QI
> President UNARC/4U1UN
>
>

--... ...-- -.. . .--- .- -- . ...

K2QI

Re: K3 voltage reading

I'd like to add that on 10m, it only drops to 13.0V. Amp draw is around
15.5A.

James K2QI

On Wed, Nov 17, 2010 at 10:18 AM, James Sarte (K2QI) <[hidden email]>wrote:

> OK, well mine drops from 13.6V to 12.8V on 40m. Amp draw is roughly around
> 17.88A
>
> On 20m, it drops to 12.7V
>
> HTH
>
> James K2QI
>
> On Wed, Nov 17, 2010 at 10:15 AM, Steve Ellington <[hidden email]>wrote:
>
>> Mine reads 13.1v on any band so it doesn't seem to matter.
>> Steve N4LQ
>>
>> ----- Original Message -----
>> *From:* James Sarte (K2QI) <[hidden email]>
>> *To:* Steve Ellington <[hidden email]>
>> *Cc:* [hidden email]
>> *Sent:* Wednesday, November 17, 2010 10:08 AM
>> *Subject:* Re: [Elecraft] K3 voltage reading
>>
>> What band/frequency? I want to replicate your exact test variables and
>> revert with my results.
>>
>> James K2QI
>>
>> On Wed, Nov 17, 2010 at 10:02 AM, Steve Ellington <[hidden email]>wrote:
>>
>>> Can someone take a look at their voltage reading on their K3's DISP-V
>>> window and tell me what they get with key down, full power output into 50
>>> ohms?
>>> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
>>> I'm just wondering if there is excessive voltage drop on the power leads.
>>> I'm using the factory cable. I'm not sure if the K3 is indicating the
>>> voltage at rig's connector or the voltage on the final amp. transistors.
>>>
>>> Steve N4LQ
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>>
>>
>> --
>> 73 de James K2QI
>> President UNARC/4U1UN
>>
>>
>
>
> --
> 73 de James K2QI
> President UNARC/4U1UN
>
>

--... ...-- -.. . .--- .- -- . ...

Don Wilhelm-4

Re: K3 voltage reading

In reply to this post by Steve Ellington

Steve,

I don't think that is unusual. The K3 display reads the voltage after
the protective diode, so there you should consider a 0.3 volt drop due
to the diode, that leaves 0.4 volts of drop from the power supply to the
inside of the connector on the K3. If I assume 17 amps current draw,
that says the resistance is 0.023 ohms. You have 10 feet of #12
conductors (yes, one must count the return conductor too) for which the
resistance is 0.016 ohms, and add a few extra milliohms for each
connector - 2 at the power supply and 2 at the K3, so a 0.4 volt drop
across the cable is not unreasonable at 17 amps current draw.

The conclusion is that you can reduce the drop by shortening the power
cable - and make certain the connections at the power supply are tight.
With some power supplies, the loose connections are on the inside -
worthy of a check.

73,
Don W3FPR

On 11/17/2010 10:02 AM, Steve Ellington wrote:
> Can someone take a look at their voltage reading on their K3's DISP-V window and tell me what they get with key down, full power output into 50 ohms?
> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v. I'm just wondering if there is excessive voltage drop on the power leads. I'm using the factory cable. I'm not sure if the K3 is indicating the voltage at rig's connector or the voltage on the final amp. transistors.
>
> Steve N4LQ
>
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Scott Ellington

Re: K3 voltage reading

In reply to this post by Steve Ellington

My power supply is connected to the K3/100 through 6 feet of AWG 10 (pair, 12 feet total), plus a 30 A 3AG fuse in my overvoltage protector. Voltage reads 13.8 V in receive mode, 13.2 at full output, about 20 A. Without resorting to remote sensing, which few inexpensive power supplies support without modification, or welding cable, it will be very difficult to reduce the drop much below that 0.6 V. If I took out the OVP (NO!) and shortened the cable to 2 feet, I suppose the drop would be about 0.3 V. AWG 10 is very difficult to get into the Powerpole connectors without the special crimp tool. The welding cable would weigh more than the K3.

That said, I'm considering remote sensing, but I'll have to reverse-engineer part of the power supply to do it. If it works, I'll post the method and results, though it will only apply Samlex SEC-1235.

73,

Scott K9MA

Scott Ellington
Madison, Wisconsin
USA

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Scott Ellington

Re: K3 voltage reading

In reply to this post by Don Wilhelm-4

On Nov 17, 2010, at 9:26 AM, Don Wilhelm wrote:

> The K3 display reads the voltage after
> the protective diode,

I don't think so, but correct me if I'm wrong. The measured voltage appears to come from 12PA through a 4:1 voltage divider, which produces V12SPA, on the KPAI03 board. The only internal components I see between the 12 V power connector and the measurement point are the 0.005 Ohm shunt on KPAI03 (R3), and RFC6 on the RF board. The drop across R3 would be 0.1 V at 20 A. I don't know the resistance of RFC6, but I suppose it could account for another 0.1 V drop.

73,

Scott K9MA

Scott Ellington
Madison, Wisconsin
USA

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Jan Erik Holm

Re: K3 voltage reading

In reply to this post by K2QI

My radio has 14.9V at RX and 14.6V TX at 100W. I care about
my fellow hams and want to have as good IMD performance as
possible. I can clearly see that other hams aren´t like me.

/Jim SM2EKM
-------------------
On 2010-11-17 16:18, James Sarte (K2QI) wrote:

> OK, well mine drops from 13.6V to 12.8V on 40m. Amp draw is roughly around
> 17.88A
>
> On 20m, it drops to 12.7V
>
> HTH
>
> James K2QI
>
> On Wed, Nov 17, 2010 at 10:15 AM, Steve Ellington<[hidden email]>wrote:
>
>> Mine reads 13.1v on any band so it doesn't seem to matter.
>> Steve N4LQ
>>
>> ----- Original Message -----
>> *From:* James Sarte (K2QI)<[hidden email]>
>> *To:* Steve Ellington<[hidden email]>
>> *Cc:* [hidden email]
>> *Sent:* Wednesday, November 17, 2010 10:08 AM
>> *Subject:* Re: [Elecraft] K3 voltage reading
>>
>> What band/frequency? I want to replicate your exact test variables and
>> revert with my results.
>>
>> James K2QI
>>
>> On Wed, Nov 17, 2010 at 10:02 AM, Steve Ellington<[hidden email]>wrote:
>>
>>> Can someone take a look at their voltage reading on their K3's DISP-V
>>> window and tell me what they get with key down, full power output into 50
>>> ohms?
>>> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v.
>>> I'm just wondering if there is excessive voltage drop on the power leads.
>>> I'm using the factory cable. I'm not sure if the K3 is indicating the
>>> voltage at rig's connector or the voltage on the final amp. transistors.
>>>
>>> Steve N4LQ
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>
>>
>>
>> --
>> 73 de James K2QI
>> President UNARC/4U1UN
>>
>>
>
>