K3 voltage indicator

[G4FNL]

Folks

I suspect that may have been asked before, so forgive me if it has, but I
need to know what the typical voltage readings are observed (on the K3
voltage indicator) when
a) On receive?
b) With say 10w TX power?
c)  With 100W TX power?

Using a DMM, I can see that my 13.8volt linear PSU seems to drop 0.1volt
when going from receive to the 100W TX level - yet the  display indicator on
the K3 goes from 13.7v (receive) to 13.3v (10W) to 12.9v (100W) Is this
typical?

73 Graham G4FNL

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[Joe Subich, W4TV-4]

On 2015-03-07 5:27 AM, G4FNL wrote:
> Using a DMM, I can see that my 13.8volt linear PSU seems to drop
> 0.1volt when going from receive to the 100W TX level - yet the
> display indicator on the K3 goes from 13.7v (receive) to 13.3v (10W)
> to 12.9v (100W) Is this typical?

Where are you measuring the 13.8V in your PSU - at the output
terminals?

The behavior you see is to be expected as the K3 has V/I metering
points on both the main board and on the KPA3 amplifier.  If there
is 0.05 Ohms of total resistance (power lead, PowerPole connectors,
connections to the PSU, etc.) between the PSU and metering points
and your K3 draws 18A at 100W TX power, the voltage as measured in
the KPA3 will drop 0.9V (I * R -> 18 * 0.05 = 0.9V) between RX and
TX.

Since the KPA3 contains a 15V zener for overvoltage protection, many
prefer to adjust the PSU's no load voltage to 14.8V to accommodate the
~ 1V drop due to connection losses in transmit.  This permits the KPA3
to operate at nominal voltage and improves transmit IMD somewhat.

73,

    ... Joe, W4TV



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[Elecraft mailing list]

What are you using for a Power Supply?


      From: G4FNL <[hidden email]>
 To: Elecraft Reflector <[hidden email]>
 Sent: Saturday, March 7, 2015 5:27 AM
 Subject: [Elecraft] K3 voltage indicator
   
Folks

I suspect that may have been asked before, so forgive me if it has, but I
need to know what the typical voltage readings are observed (on the K3
voltage indicator) when
a) On receive?
b) With say 10w TX power?
c)  With 100W TX power?

Using a DMM, I can see that my 13.8volt linear PSU seems to drop 0.1volt
when going from receive to the 100W TX level - yet the  display indicator on
the K3 goes from 13.7v (receive) to 13.3v (10W) to 12.9v (100W) Is this
typical?

73 Graham G4FNL

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[Robin Moseley]

Measure the voltage inside the K3,   at the powerpole..   you may need
thicker DC lead or clean the fuse contacts.

G1MHU

-----Original Message-----
From: Harry Yingst via Elecraft
Sent: Sunday, March 08, 2015 12:47 AM
To: [hidden email] ; Elecraft Reflector
Subject: Re: [Elecraft] K3 voltage indicator

What are you using for a Power Supply?


      From: G4FNL <[hidden email]>
To: Elecraft Reflector <[hidden email]>
Sent: Saturday, March 7, 2015 5:27 AM
Subject: [Elecraft] K3 voltage indicator

Folks

I suspect that may have been asked before, so forgive me if it has, but I
need to know what the typical voltage readings are observed (on the K3
voltage indicator) when
a) On receive?
b) With say 10w TX power?
c)  With 100W TX power?

Using a DMM, I can see that my 13.8volt linear PSU seems to drop 0.1volt
when going from receive to the 100W TX level - yet the  display indicator on
the K3 goes from 13.7v (receive) to 13.3v (10W) to 12.9v (100W) Is this
typical?

73 Graham G4FNL

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[G4FNL]

Guys

I may need to re-enforce my power lead and connections - but they appear OK.


What I was asking was what does the voltage display indicator show on your
K3 - when compared to mine?  I have since understood that the voltage drop
that I see (at the 3 power settings mentioned) is about normal......

73 Graham G4FNL

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Robin
Moseley
Sent: 08 March 2015 02:17
To: Elecraft Reflector
Subject: Re: [Elecraft] K3 voltage indicator

Measure the voltage inside the K3,   at the powerpole..   you may need
thicker DC lead or clean the fuse contacts.

G1MHU

-----Original Message-----
From: Harry Yingst via Elecraft
Sent: Sunday, March 08, 2015 12:47 AM
To: [hidden email] ; Elecraft Reflector
Subject: Re: [Elecraft] K3 voltage indicator

What are you using for a Power Supply?


      From: G4FNL <[hidden email]>
To: Elecraft Reflector <[hidden email]>
Sent: Saturday, March 7, 2015 5:27 AM
Subject: [Elecraft] K3 voltage indicator

Folks

I suspect that may have been asked before, so forgive me if it has, but I
need to know what the typical voltage readings are observed (on the K3
voltage indicator) when
a) On receive?
b) With say 10w TX power?
c)  With 100W TX power?

Using a DMM, I can see that my 13.8volt linear PSU seems to drop 0.1volt
when going from receive to the 100W TX level - yet the  display indicator on
the K3 goes from 13.7v (receive) to 13.3v (10W) to 12.9v (100W) Is this
typical?

73 Graham G4FNL

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[ve3dvy]

13.8 RX
12.2 TX
voltage at distribution box drops to 13.3 on TX   key down CW  with 2 ft
10awg PSU to dc distribution box  with fuses.  3ft 12AWG to K3    still
well within specs and definitly still better IMD that any other rig I
have in the shack I am sure.  so no worries here.

David Moes
President: Peterborough Amateur Radio Club.
[hidden email]
VE3DVY,  VE3SD

On 3/8/2015 07:24, G4FNL wrote:

> Guys
>
> I may need to re-enforce my power lead and connections - but they appear OK.
>
>
> What I was asking was what does the voltage display indicator show on your
> K3 - when compared to mine?  I have since understood that the voltage drop
> that I see (at the 3 power settings mentioned) is about normal......
>
> 73 Graham G4FNL
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Robin
> Moseley
> Sent: 08 March 2015 02:17
> To: Elecraft Reflector
> Subject: Re: [Elecraft] K3 voltage indicator
>
> Measure the voltage inside the K3,   at the powerpole..   you may need
> thicker DC lead or clean the fuse contacts.
>
> G1MHU
>
> -----Original Message-----
> From: Harry Yingst via Elecraft
> Sent: Sunday, March 08, 2015 12:47 AM
> To: [hidden email] ; Elecraft Reflector
> Subject: Re: [Elecraft] K3 voltage indicator
>
> What are you using for a Power Supply?
>
>
>        From: G4FNL <[hidden email]>
> To: Elecraft Reflector <[hidden email]>
> Sent: Saturday, March 7, 2015 5:27 AM
> Subject: [Elecraft] K3 voltage indicator
>
> Folks
>
> I suspect that may have been asked before, so forgive me if it has, but I
> need to know what the typical voltage readings are observed (on the K3
> voltage indicator) when
> a) On receive?
> b) With say 10w TX power?
> c)  With 100W TX power?
>
> Using a DMM, I can see that my 13.8volt linear PSU seems to drop 0.1volt
> when going from receive to the 100W TX level - yet the  display indicator on
> the K3 goes from 13.7v (receive) to 13.3v (10W) to 12.9v (100W) Is this
> typical?
>
> 73 Graham G4FNL
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>
>
>
> ______________________________________________________________
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> delivered to [hidden email]
>
> ______________________________________________________________
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> delivered to [hidden email]
>
> ______________________________________________________________
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>
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>

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[Fred Townsend-2]

Graham:
I think what Joe and others have tried to tell you is your power lead
represents a variable and until you properly account for the variable
voltage drop in your power lead comparison is meaningless.
You say power lead appears to be OK. Appears??? How did you come to that
conclusion? If you placed your hand on the cable and said it is not hot and
therefore concluded the cable appears OK you have again missed the point. At
low voltages (and high currents) the quality of the cable (and connectors)
is determined by the voltage drop.
Additionally the voltage read on the front panel is read through a poly fuse
which has a voltage drop that is greater than the voltage seen by the 100
watt amplifier which is alternatively feed through a 22 amp circuit breaker.
The current that passes through the poly fuse is further regulated down to 5
volts so the voltage drop across the poly fuse is immaterial but it does
represent an insignificant error that the 100 watt amp does NOT see. Ergo
where you measure your voltages is all important to your pass/fail
calculations.

What to do? Measure the voltage at your power supply and then again at the
K3 circuit breaker. If the difference is more than 0.5 volts I would use a
heaver power lead.

73,
Fred, AE6QL

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of G4FNL
Sent: Sunday, March 08, 2015 4:24 AM
To: 'Robin Moseley'; 'Elecraft Reflector'
Subject: Re: [Elecraft] K3 voltage indicator

Guys

I may need to re-enforce my power lead and connections - but they appear OK.


What I was asking was what does the voltage display indicator show on your
K3 - when compared to mine?  I have since understood that the voltage drop
that I see (at the 3 power settings mentioned) is about normal......

73 Graham G4FNL


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