Re: [Elecraft] K3 Voltage on TX

[Bob McGraw - K4TAX]

In general, it would be ideal if there were zero voltage drop. This just 
won't be the case in the real world.The VFO-B voltage indication is 
reliable in terms of the voltage in receive vs. the voltage in 
transmit.  I think it reasonable to accept < 0.5 volt drop or less 
between RX and TX at 100 watts output.  Do consider the regulation of 
the supply.  Measure that with a good DVM at the supply terminals.  And 
here, it is reasonable to expect less than 0.1 volt change between RX 
and TX at 100 watts.  Many of the better supplies will be in the < 0.01 
volt range under this condition.


If one finds more voltage drop than expected, then further investigation 
is suggested.  Are the terminals properly crimped and soldered on both 
ends?  Are the terminals tight fitting?  Is the wire gauge correct for 
the current demand and length?   Are there other devices between the 
supply and radio that will contribute to voltage drop?   These are a few 
questions to be answered.


Better regulation and maintaining a voltage at the radio between 13.5 
and 14.5 will make for a cleaner transmitter in respect to transmitted 
IMD.   And that topic was "beat to death" in a previous discussion.  If 
the supply is not well regulated, be sure the voltage at the radio will 
never exceed 15.0 volts.


73
Bob, K4TAX

On 11/5/2015 7:36 AM, ok1rp wrote:

Hi Jeff,

many thanks for your post regarding the soldering Anderson Plug leads
connections.
It seems that I should check it too as I have 0.7V drop RX/TX on VFO-B line
measurement.
(even although I never had any problem regarding the low voltage...)

It is good hint for my old timer K3 (#778) although it work like champ now.



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Re: [Elecraft] K3 Voltage on TX

[ok1rp]

Hi Jeff,

many thanks for your post regarding the soldering Anderson Plug leads
connections.
It seems that I should check it too as I have 0.7V drop RX/TX on VFO-B line
measurement.
(even although I never had any problem regarding the low voltage...)

It is good hint for my old timer K3 (#778) although it work like champ now.

73 - Petr, OK1RP




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Re: [Elecraft] K3 Voltage on TX

[Jeff Cochrane - VK4XA]

Rich,
The first K3 I owned always showed a large voltage drop on TX that was
pretty much incurable (as well as other issues), much to my (and others)
consternation.
I tried (In no particular order)
Heavy gauge power cables, No fuses, Upping the power supply voltage, Re
soldering the 30 Amp Anderson plugs on the power cable [s] and numerous
different power leads, all to no avail.
So, I learnt to live with it sort of. (The issue was always in the back of
my mind however.)
After some time though, financial circumstances forced me to sell my beloved
K - Line.
The new owner of the K3 also had concerns about the voltage drop, but, as he
knew that I had already tried all the common things listed above he gave the
radio the 'once over'.
imagine his surprise when he discovered that there was NO SOLDER AT ALL on
the Anderson Plug leads where they connect to the mainboard of the radio!
So, he soldered the connections and as a result, that K3 now works perfectly
all the time and with minimal voltage drop.
(Which is probably just as well as the owner is a gold miner and lives in
bush camps in Tropical Far North Queensland, Australia using nothing but
solar power and batteries.)

So, it may just be an idea to open the radio and check the solder joints in
and around the Anderson Plugs, you never know, your rig may have a dry joint
there too.

(And yes, I still own a K3, they ARE the best Amateur Radio transceiver on
the planet after all) :)

73 de
Jeff Cochrane - VK4XA (Ex VK4BOF, VK4VHF)
Proud owner of Elecraft K3 #4767


Folks,

I am not sure if I have some sort of issues or not.  My K3 shows 13.7VDC 
on RX. When I TX that reading drops to 10.9VDC.  Is that a normal drop?  
I do not believe this is a K3 issue, but I was wondering if others see 
that much drop before I dig into my 12VDC supply system.

Thanks
Rich
__




-
Jeff Cochrane - VK4XA
Innisfail, QLD, Australia.
K3 #4767

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Re: [Elecraft] K3 Voltage on TX

[Bill Frantz]

I gave up running my K3 through a RigRunner for just that 
reason. I put in a short lead directly to the battery bank APP 
junction strip and things got a lot better. They got even better 
with a N8XJK Boost Regulator between the K3 and the junction. 
(Tested with 100W into a dummy load.)


73 Bill AE6JV

On 10/26/15 at 12:50 PM, j...@audiosystemsgroup.com (Jim Brown) wrote:


On Mon,10/26/2015 12:37 PM, Bob McGraw - K4TAX wrote:
In fact, anything in line between the power supply and radio 
can contribute to this.  Even fuses, switches, power 
connectors and such.  Any connection that is loose or terminal 
that is loose will be a voltage drop point.  They just add up.


Yes. I've been told that the DC bus in popular DC distribution 
strips is quite small considering the rated current. They're 
fine for accessories that don't draw much current, but don't 
run your rig through them (unless it's QRP)!


---
Bill Frantz| If the site is supported by  | Periwinkle
(408)356-8506  | ads, you are the product.| 16345 
Englewood Ave
www.pwpconsult.com |  | Los Gatos, 
CA 95032


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Re: [Elecraft] K3 Voltage on TX

[Richard Fjeld]

It would be nice to have test point type jacks on the back of the K3 to 
test the voltage drop from the PS through the APP's entering the K3.
This would check the accuracy of the K3 volt-meter as well.  I don't 
remember what it looks like in the vicinity of the APP's.


The next best thing we have is the 12V jack, but I think that has two 
diodes in series to it.


Dick, n0ce


On 10/26/2015 12:05 PM, Rich wrote:
Thanks to all.  I have check my PS and it does not fluctuate even a 
tenth of a volt on TX.With the radio connected directly to the PS. 
I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer 
at the wire gauge and connectors.  That is still about 2VDC drop.


Thanks for the help

rich



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Re: [Elecraft] K3 Voltage on TX

[Jim Miller]

Forgot to mention: the RR runs everything else that needs 14v.

On Mon, Oct 26, 2015 at 5:08 PM, Jim Miller  wrote:

> I was having too much drop with RR as well. I switched to a 1ft line
> directly to my Samlex 1235M which has been jacked to 14.4v no load. It only
> moves a few mV when loaded to 20A.
>
> IIRC, the cable is now AWG12.
>
> jim ab3cv
>
>
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Re: [Elecraft] K3 Voltage on TX

[Bob McGraw - K4TAX]

You don't happen to have anything else in line between the power supply 
and the K3 do you?  I've found those DC distribution panels sold by 
certain companies are contributors to significant voltage drop.  Your 
statement " With the radio connected directly to the PS.  I am now 
seeing 14.1 VDC and 12.0 VDC on TX." is a clue that the way you have 
things configured is not optimum. In fact, anything in line between 
the power supply and radio can contribute to this.  Even fuses, 
switches, power connectors and such.  Any connection that is loose or 
terminal that is loose will be a voltage drop point.  They just add up.


My rule:  the radio connects direct to the power supply.  No exception.  
If you need DC for something else, connect it direct to the power supply 
as well.  I also use a dedicated ground conductor between the radio and 
DC supply ground.  The DC Negative is not considered to be adequate ground.


73
Bob, K4TAX
K3S s/n 10163

 


On 10/26/2015 12:05 PM, Rich wrote:
Thanks to all.  I have check my PS and it does not fluctuate even a 
tenth of a volt on TX.With the radio connected directly to the PS. 
I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer 
at the wire gauge and connectors.  That is still about 2VDC drop.


Thanks for the help

rich

On 10/26/2015 12:09 PM, Phil Wheeler wrote:
If the wire gauge is OK and the supply regulation is not at fault, 
give some attention to the connectors at each end of the cable, too. 
A drop of 2.8 Volts points to some sort of issue.


73, Phil W7OX



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Re: [Elecraft] K3 Voltage on TX

[Bob McGraw - K4TAX]

I just checked my radio.  Receive shows 13.7 volts.  At 100 watts CW key 
down transmit it shows 13.3 volts.  The current indicated on the power 
supply is 18 amps.   Power leads are about 2 ft in length being #10 
stranded with connectors crimped and soldered at both ends.  Also a #10 
AWG ground is in place between the radio and power supply


73
Bob, K4TAX
K3S  s/n 10163

On 10/26/2015 2:37 PM, Bob McGraw - K4TAX wrote:
You don't happen to have anything else in line between the power 
supply and the K3 do you?  I've found those DC distribution panels 
sold by certain companies are contributors to significant voltage 
drop.  Your statement " With the radio connected directly to the PS.  
I am now seeing 14.1 VDC and 12.0 VDC on TX." is a clue that the way 
you have things configured is not optimum. In fact, anything in 
line between the power supply and radio can contribute to this.  Even 
fuses, switches, power connectors and such.  Any connection that is 
loose or terminal that is loose will be a voltage drop point.  They 
just add up.


My rule:  the radio connects direct to the power supply.  No 
exception.  If you need DC for something else, connect it direct to 
the power supply as well.  I also use a dedicated ground conductor 
between the radio and DC supply ground.  The DC Negative is not 
considered to be adequate ground.


73
Bob, K4TAX
K3S s/n 10163



On 10/26/2015 12:05 PM, Rich wrote:
Thanks to all.  I have check my PS and it does not fluctuate even a 
tenth of a volt on TX.With the radio connected directly to the 
PS. I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look 
closer at the wire gauge and connectors.  That is still about 2VDC drop.


Thanks for the help

rich 



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Re: [Elecraft] K3 Voltage on TX

[Bob McGraw - K4TAX]

Well my take.ANYTHING between the power source and radio has 
resistance, regardless of how small.  Resistance with any amount of 
current equals voltage drop.  Thus E = IR   Where E is the voltage drop, 
I is the current and R is the resistance.


I'm not sure what some of those thing are nor why they are needed but I 
do know least is best.  As to operating from batteries, floating AGM 
batteries at 13.8 should not produce any voltage drop other than the 
resistance of the power cable.Of course a fuse or switch in line 
does have R so there goes the regulation as current changes.  Nothing is 
better than a good regulated supply and hopefully one with remote 
voltage sensing.   Of course those are more expensive and more of a 
challenge to install and then have operate correctly in the presence of 
a RF field.


73
Bob, K4TAX
K3S s.n. 10163
 


On 10/26/2015 3:55 PM, Bill Frantz wrote:
I gave up running my K3 through a RigRunner for just that reason. I 
put in a short lead directly to the battery bank APP junction strip 
and things got a lot better. They got even better with a N8XJK Boost 
Regulator between the K3 and the junction. (Tested with 100W into a 
dummy load.)


73 Bill AE6JV

On 10/26/15 at 12:50 PM, j...@audiosystemsgroup.com (Jim Brown) wrote:


On Mon,10/26/2015 12:37 PM, Bob McGraw - K4TAX wrote:
In fact, anything in line between the power supply and radio can 
contribute to this.  Even fuses, switches, power connectors and 
such.  Any connection that is loose or terminal that is loose will 
be a voltage drop point.  They just add up.


Yes. I've been told that the DC bus in popular DC distribution strips 
is quite small considering the rated current. They're fine for 
accessories that don't draw much current, but don't run your rig 
through them (unless it's QRP)!



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Re: [Elecraft] K3 Voltage on TX

[Jim Brown]

On Mon,10/26/2015 12:37 PM, Bob McGraw - K4TAX wrote:
In fact, anything in line between the power supply and radio can 
contribute to this.  Even fuses, switches, power connectors and such.  
Any connection that is loose or terminal that is loose will be a 
voltage drop point.  They just add up. 


Yes. I've been told that the DC bus in popular DC distribution strips is 
quite small considering the rated current. They're fine for accessories 
that don't draw much current, but don't run your rig through them 
(unless it's QRP)!


73, Jim K9YC
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Re: [Elecraft] K3 Voltage on TX

[Jim Miller]

I was having too much drop with RR as well. I switched to a 1ft line
directly to my Samlex 1235M which has been jacked to 14.4v no load. It only
moves a few mV when loaded to 20A.

IIRC, the cable is now AWG12.

jim ab3cv
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Re: [Elecraft] K3 Voltage on TX

[Bill Frantz]

Perhaps it's vanity, but I like running my rig off solar power 
and batteries. Since I also take the rig out in the field 
somewhat frequently, battery power avoids noisy generators. 
(Besides, I own the panels and batteries, but don't own a generator.)


In any case, floating batteries requires a power source during 
operations which doesn't work really well with solar power at 
night. The WVARA operation discovered during the last California 
QSO Party that tired batteries and K3s are a recipe for 
transmitter distortion and local interference in a multi-radio 
operation. The N8XJK Battery Booster is an attempt to get more 
life from tired batteries into the just before dawn hours.


73 Bill AE6JV

On 10/26/15 at 2:18 PM, rmcg...@blomand.net (Bob McGraw - K4TAX) wrote:

Well my take.ANYTHING between the power source and radio 
has resistance, regardless of how small.  Resistance with any 
amount of current equals voltage drop.  Thus E = IR   Where E 
is the voltage drop, I is the current and R is the resistance.


I'm not sure what some of those thing are nor why they are 
needed but I do know least is best.  As to operating from 
batteries, floating AGM batteries at 13.8 should not produce 
any voltage drop other than the resistance of the power 
cable.Of course a fuse or switch in line does have R so 
there goes the regulation as current changes.  Nothing is 
better than a good regulated supply and hopefully one with 
remote voltage sensing.   Of course those are more expensive 
and more of a challenge to install and then have operate 
correctly in the presence of a RF field.


73
Bob, K4TAX
K3S s.n. 10163

On 10/26/2015 3:55 PM, Bill Frantz wrote:
I gave up running my K3 through a RigRunner for just that 
reason. I put in a short lead directly to the battery bank APP 
junction strip and things got a lot better. They got even 
better with a N8XJK Boost Regulator between the K3 and the 
junction. (Tested with 100W into a dummy load.)


73 Bill AE6JV

---
Bill Frantz|The nice thing about standards| Periwinkle
(408)356-8506  |is there are so many to choose| 16345 
Englewood Ave
www.pwpconsult.com |from.   - Andrew Tanenbaum| Los Gatos, 
CA 95032


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Re: [Elecraft] K3 Voltage on TX

[Gary]

This discussion has got me confused.
If a power supply fails, it is pretty easy to fault find.
If you use the correct size cable for the length you require, then it WILL work.
Discussions on APP and test points seem to me to be a little pedantic as apart 
from from a power supply failure I have not had voltage drop issues other than 
killing a large battery bank while exuberantly working a field day operation 
some years ago. I blame Eric for chatting to me too long on that occasion 
From memory the only other fault I have seen was a disconnected APP on the 
board. The owner told me had no idea how that came about. I re-soldered the 
connection and the K3 came back to life.
Caveat emptor..i have always used a heavier DC power lead.

Gary 


-Original Message-
From: "Richard Fjeld" <rpfj...@outlook.com>
Sent: ‎27/‎10/‎2015 9:30 AM
To: "elecraft@mailman.qth.net" <elecraft@mailman.qth.net>
Subject: Re: [Elecraft] K3 Voltage on TX

It would be nice to have test point type jacks on the back of the K3 to 
test the voltage drop from the PS through the APP's entering the K3.
This would check the accuracy of the K3 volt-meter as well.  I don't 
remember what it looks like in the vicinity of the APP's.

The next best thing we have is the 12V jack, but I think that has two 
diodes in series to it.

Dick, n0ce


On 10/26/2015 12:05 PM, Rich wrote:
> Thanks to all.  I have check my PS and it does not fluctuate even a 
> tenth of a volt on TX.With the radio connected directly to the PS. 
> I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer 
> at the wire gauge and connectors.  That is still about 2VDC drop.
>
> Thanks for the help
>
> rich
>

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Re: [Elecraft] K3 Voltage on TX

[ac5p]

If voltage is being checked via the K3 display, I believe there is a series 
diode before the internal metering that adds a 0.6V drop in TX?   
73, Mike  AC5P 


 On Monday, October 26, 2015 5:08 PM, Bill Frantz  
wrote:
   

 Perhaps it's vanity, but I like running my rig off solar power 
and batteries. Since I also take the rig out in the field 
somewhat frequently, battery power avoids noisy generators. 
(Besides, I own the panels and batteries, but don't own a generator.)

In any case, floating batteries requires a power source during 
operations which doesn't work really well with solar power at 
night. The WVARA operation discovered during the last California 
QSO Party that tired batteries and K3s are a recipe for 
transmitter distortion and local interference in a multi-radio 
operation. The N8XJK Battery Booster is an attempt to get more 
life from tired batteries into the just before dawn hours.

73 Bill AE6JV

On 10/26/15 at 2:18 PM, rmcg...@blomand.net (Bob McGraw - K4TAX) wrote:

>Well my take.ANYTHING between the power source and radio 
>has resistance, regardless of how small.  Resistance with any 
>amount of current equals voltage drop.  Thus E = IR  Where E 
>is the voltage drop, I is the current and R is the resistance.
>
>I'm not sure what some of those thing are nor why they are 
>needed but I do know least is best.  As to operating from 
>batteries, floating AGM batteries at 13.8 should not produce 
>any voltage drop other than the resistance of the power 
>cable.    Of course a fuse or switch in line does have R so 
>there goes the regulation as current changes.  Nothing is 
>better than a good regulated supply and hopefully one with 
>remote voltage sensing.  Of course those are more expensive 
>and more of a challenge to install and then have operate 
>correctly in the presence of a RF field.
>
>73
>Bob, K4TAX
>K3S s.n. 10163
>
>On 10/26/2015 3:55 PM, Bill Frantz wrote:
>>I gave up running my K3 through a RigRunner for just that 
>>reason. I put in a short lead directly to the battery bank APP 
>>junction strip and things got a lot better. They got even 
>>better with a N8XJK Boost Regulator between the K3 and the 
>>junction. (Tested with 100W into a dummy load.)
>>
>>73 Bill AE6JV
---
Bill Frantz        |The nice thing about standards| Periwinkle
(408)356-8506      |is there are so many to choose| 16345 
Englewood Ave
www.pwpconsult.com |from.  - Andrew Tanenbaum    | Los Gatos, 
CA 95032

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Re: [Elecraft] K3 Voltage on TX

[efortner]

I am using the same SamLex supply with the K3s Elecraft power cord that came
with the kit. At 100 Watts key down I can just see the voltmeter move maybe
the width of the needle. The readout on the radio does not dim.
Earl, K4KAY

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim
Miller
Sent: Monday, October 26, 2015 5:09 PM
To: Bill Frantz
Cc: Elecraft Reflector
Subject: Re: [Elecraft] K3 Voltage on TX

I was having too much drop with RR as well. I switched to a 1ft line
directly to my Samlex 1235M which has been jacked to 14.4v no load. It only
moves a few mV when loaded to 20A.

IIRC, the cable is now AWG12.

jim ab3cv
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Re: [Elecraft] K3 Voltage on TX

[Don Wilhelm]

Dick,

If the main interest is the drop in voltage, the 12V jack will work 
fine, no matter how many diodes are in series with it.
So you get 10 volts during RX and 9 volts during TX, that is a 1 volt 
drop (OK, that is extreme, but hopefully makes the point).
If you are instead looking for the absolute voltage delivered to the K3, 
use the VFO B voltage display.


73,
Don W3FPR

On 10/26/2015 7:29 PM, Richard Fjeld wrote:
It would be nice to have test point type jacks on the back of the K3 
to test the voltage drop from the PS through the APP's entering the K3.
This would check the accuracy of the K3 volt-meter as well.  I don't 
remember what it looks like in the vicinity of the APP's.


The next best thing we have is the 12V jack, but I think that has two 
diodes in series to it.




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Re: [Elecraft] K3 Voltage on TX

[Bob McGraw - K4TAX]

Seems to me the display on VFO B is accurate enough for this purpose.  
Now to make sure of the accuracy along with voltage drop, measure the 
voltage at the power supply terminals.  I would expect the voltage at 
the power supply terminals and the VFO B display in receive mode to be 
identical, +/- meter accuracy.


As Don said, diodes or no diodes, the objective is voltage drop at the 
radio between RX and TX full power.  I would perceive anything greater 
than 0.5 volts as shown on the VFO B display is reason for one to  
investigate the station DC power distribution.


73
Bob, K4TAX
K3S s/n 10163

On 10/26/2015 8:02 PM, Don Wilhelm wrote:

Dick,

If the main interest is the drop in voltage, the 12V jack will work 
fine, no matter how many diodes are in series with it.
So you get 10 volts during RX and 9 volts during TX, that is a 1 volt 
drop (OK, that is extreme, but hopefully makes the point).
If you are instead looking for the absolute voltage delivered to the 
K3, use the VFO B voltage display.


73,
Don W3FPR 



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Re: [Elecraft] K3 Voltage on TX

[Phil Wheeler]

If the wire gauge is OK and the supply regulation 
is not at fault, give some attention to the 
connectors at each end of the cable, too. A drop 
of 2.8 Volts points to some sort of issue.


73, Phil W7OX

On 10/26/15 9:02 AM, Jim Brown wrote:

On Mon,10/26/2015 8:48 AM, Rich wrote:
My K3 shows 13.7VDC on RX. When I TX that 
reading drops to 10.9VDC. Is that a normal drop? 


It's not good. Two possible reasons -- poor 
regulation of the power supply and IR drop in 
the power cable.


How long is the power cable between the K3 and 
power supply?  What wire gauge?  Do the 
arithmetic for Ohm's law for the IR drop in that 
length of that wire gauge. and remember to use 
the length of the cable x2 (for two conductors). 
Resistance per ft for various wire gauges is in 
the ARRL Handbook.


Put a voltmeter across the output terminals of 
the power supply and check the voltage. It's 
also possible that the power supply has poor 
regulation.


73, Jim K9YC


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Re: [Elecraft] K3 Voltage on TX

[Jim Brown]

On Mon,10/26/2015 8:48 AM, Rich wrote:
My K3 shows 13.7VDC on RX. When I TX that reading drops to 10.9VDC. Is 
that a normal drop? 


It's not good. Two possible reasons -- poor regulation of the power 
supply and IR drop in the power cable.


How long is the power cable between the K3 and power supply?  What wire 
gauge?  Do the arithmetic for Ohm's law for the IR drop in that length 
of that wire gauge. and remember to use the length of the cable x2 (for 
two conductors). Resistance per ft for various wire gauges is in the 
ARRL Handbook.


Put a voltmeter across the output terminals of the power supply and 
check the voltage. It's also possible that the power supply has poor 
regulation.


73, Jim K9YC


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Re: [Elecraft] K3 Voltage on TX

[Don Wilhelm]

Rich,

Yes, that is abnormal.
Either your power supply is sagging or there is too much voltage drop in 
the power cable.
To figure out which it is, measure the power supply voltage at its 
terminals during transmit.  If it is staying "right up there" as it 
should, then the problem is in the cable.  Check that the power supply 
terminals are tight, check that the fuseholders have good contact with 
the fuses (change the fuse(s) because they can develop a higher than 
normal resistance.  Make certain that the APP connector on the K3 end of 
the cable has its contacts fully inserted - the tip of the connector 
blade should be latched over the spring finger below it.  If you can see 
both the spring finger and the tip of the contact blade when you look 
from the front, the contact blade is not fully inserted.


73,
Don W3FPR

On 10/26/2015 11:48 AM, Rich wrote:

Folks,

I am not sure if I have some sort of issues or not.  My K3 shows 
13.7VDC on RX. When I TX that reading drops to 10.9VDC.  Is that a 
normal drop?  I do not believe this is a K3 issue, but I was wondering 
if others see that much drop before I dig into my 12VDC supply system.


Thanks
Rich
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Re: [Elecraft] K3 Voltage on TX

[Fred Jensen]

That's still too much.  Last time I measured my K3, the drop was 0.6 V 
on TX at 100W.  Cartridge type [AGC] fuses and the holders are common 
culprits.  I've replaced all of my fuses with the automotive fuses with 
the blade type contacts.  They present a large contact area, are very 
tight, and have a large wipe as you insert and remove them.


73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org

On 10/26/2015 10:05 AM, Rich wrote:

Thanks to all.  I have check my PS and it does not fluctuate even a
tenth of a volt on TX.With the radio connected directly to the PS. I
am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer at
the wire gauge and connectors.  That is still about 2VDC drop.


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Re: [Elecraft] K3 Voltage on TX

[Rich]

Thanks to all.  I have check my PS and it does not fluctuate even a 
tenth of a volt on TX.With the radio connected directly to the PS.  
I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer 
at the wire gauge and connectors.  That is still about 2VDC drop.


Thanks for the help

rich

On 10/26/2015 12:09 PM, Phil Wheeler wrote:
If the wire gauge is OK and the supply regulation is not at fault, 
give some attention to the connectors at each end of the cable, too. A 
drop of 2.8 Volts points to some sort of issue.


73, Phil W7OX

On 10/26/15 9:02 AM, Jim Brown wrote:

On Mon,10/26/2015 8:48 AM, Rich wrote:
My K3 shows 13.7VDC on RX. When I TX that reading drops to 10.9VDC. 
Is that a normal drop? 


It's not good. Two possible reasons -- poor regulation of the power 
supply and IR drop in the power cable.


How long is the power cable between the K3 and power supply? What 
wire gauge?  Do the arithmetic for Ohm's law for the IR drop in that 
length of that wire gauge. and remember to use the length of the 
cable x2 (for two conductors). Resistance per ft for various wire 
gauges is in the ARRL Handbook.


Put a voltmeter across the output terminals of the power supply and 
check the voltage. It's also possible that the power supply has poor 
regulation.


73, Jim K9YC


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Re: [Elecraft] K3 Voltage on TX

[Fred Jensen]

That's way more drop than I experience with a 4S1P LiFePO4.  Things to 
check:


Length and gauge of wire [remember to double the length when calculating 
resistance, it's a round trip for the electrons].


Poor regulation in the power supply or depleted battery or battery at 
the end of useful life.


Voltage drop at connectors

Voltage drop at fuses.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the Cal QSO Party 1-2 Oct 2016
- www.cqp.org


On 10/26/2015 8:48 AM, Rich wrote:


I am not sure if I have some sort of issues or not.  My K3 shows 13.7VDC
on RX. When I TX that reading drops to 10.9VDC.  Is that a normal drop?
I do not believe this is a K3 issue, but I was wondering if others see
that much drop before I dig into my 12VDC supply system.


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Re: [Elecraft] K3 Voltage on TX

[Ron D'Eau Claire]

Guess I'm more empirically than theoretically oriented, but my first act
would be to touch and feel the cable and connectors after allowing the K3 to
draw full current for a minute or two. Even 2 volts at 10 amps is 20 watts.
That's enough to cause heating you should feel very quickly if it's
concentrated at a connector, fuse holder damaged point in the cable. 

73 Ron AC7AC


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Re: [Elecraft] K3 Voltage on TX

[Fred Townsend]

Hi Rich:
A couple of more things. First do the math. Assuming 20 amps of transmit
current (that's my rig @100 watts output) with a 2 volt drop is 40 watts of
lost energy (not my rig). That also happens to be the power rating of my
soldering iron. To point, something is likely to be getting warm. You should
be able to find your problem by touching your cables and connectors while
transmitting a 100 watts of RTTY,  AM, etc. 
Also, I hope you are not using a diode type power sharing device sold to
share power supply and battery. Think about it. Why do they need a big heat
sink? Big heat sinks mean lots of wasted power.
73
Fred, AE6QL 

-Original Message-
From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Rich
Sent: Monday, October 26, 2015 10:05 AM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] K3 Voltage on TX

Thanks to all.  I have check my PS and it does not fluctuate even a 
tenth of a volt on TX.With the radio connected directly to the PS.  
I am now seeing 14.1 VDC and 12.0 VDC on TX.  So I need to look closer at
the wire gauge and connectors.  That is still about 2VDC drop.

Thanks for the help

rich

On 10/26/2015 12:09 PM, Phil Wheeler wrote:
> If the wire gauge is OK and the supply regulation is not at fault, 
> give some attention to the connectors at each end of the cable, too. A 
> drop of 2.8 Volts points to some sort of issue.
>
> 73, Phil W7OX
>
> On 10/26/15 9:02 AM, Jim Brown wrote:
>> On Mon,10/26/2015 8:48 AM, Rich wrote:
>>> My K3 shows 13.7VDC on RX. When I TX that reading drops to 10.9VDC. 
>>> Is that a normal drop? 
>>
>> It's not good. Two possible reasons -- poor regulation of the power 
>> supply and IR drop in the power cable.
>>
>> How long is the power cable between the K3 and power supply? What 
>> wire gauge?  Do the arithmetic for Ohm's law for the IR drop in that 
>> length of that wire gauge. and remember to use the length of the 
>> cable x2 (for two conductors). Resistance per ft for various wire 
>> gauges is in the ARRL Handbook.
>>
>> Put a voltmeter across the output terminals of the power supply and 
>> check the voltage. It's also possible that the power supply has poor 
>> regulation.
>>
>> 73, Jim K9YC
>
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> rwnewbo...@comcast.net
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