Elecraft

Voltage drop in DX Power to K3

Classic

List

Threaded

78 messages Options

1234

N4ZR

Voltage drop in DX Power to K3

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.

______________________________________________________________
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
Message delivered to [hidden email]

David Herring

Re: Voltage drop in DX Power to K3

I’m late in coming to this thread, so sorry if I missed the answer to this question, but what is the voltage drop between the power supply and the 4005i?

73, David N5DCH

> On Apr 26, 2020, at 8:46 AM, N4ZR <[hidden email]> 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.
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Leroy Buller

Re: Voltage drop in DX Power to K3

In reply to this post by N4ZR

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 <[hidden email]> 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.
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: Voltage drop in DX Power to K3

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 <[hidden email]> 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.
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

N4ZR

Re: Voltage drop in DX Power to K3

In reply to this post by David Herring

Approximately .3 volts with a cable about a foot long.

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.

On 4/26/2020 11:08 AM, David Herring wrote:

> I’m late in coming to this thread, so sorry if I missed the answer to this question, but what is the voltage drop between the power supply and the 4005i?
>
> 73, David N5DCH
>
>> On Apr 26, 2020, at 8:46 AM, N4ZR <[hidden email]> 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.
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]

Adrian-3

Re: Voltage drop in DX Power to K3

In reply to this post by Bob McGraw - K4TAX

I got a good chuckle out of that one Bob, happens to me often

take 2 >
The calculation is simple: E = I x R current multiplied by
resistance equals the voltage.

>
> The calculation is simple: E = I x R current multiplied by
> amps equal voltage.
>
> 73
>
> Bob, K4TAX
>
>
______________________________________________________________
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
Message delivered to [hidden email]

Elecraft mailing list

Re: Voltage drop in DX Power to K3

In reply to this post by Bob McGraw - K4TAX

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 <[hidden email]> 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 <[hidden email]> 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.
>>>
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

George Danner-2

Re: Voltage drop in DX Power to K3

In reply to this post by David Herring

A couple of solutions used in TV Broadcasting, especially in ENG & Satellite
mobile units.

1) Use a short jumper from the large conductor the the connector. I solder
the 2 wires together (inline) and cover the connection with shrink tubing.
This helps when you want flexibility between the large connector and the
equipment (think mobile vibration).
2)If the large conductor is stranded then remove strands until it fits the
connector.

Another solutions would be to keep what you have and remote the power supply
sense to the destination.
The advantage of this solution is that you have a large voltage swing with a
varying load.
The disadvantage is the power supply has to be capable of supplying all the
current needed at maximum load and the time constant has to be considerable
shorter than the load variation time constant.
Another disadvantage is that any other equipment on the power supply line
will "see" a varying power supply.
This solution is used in many different pieces of equipment in broadcasting.

73
George AI4VZ

-----Original Message-----
From: David Herring
Sent: Sunday, April 26, 2020 11:08 AM
To: N4ZR
Cc: Elecraft List
Subject: Re: [Elecraft] Voltage drop in DX Power to K3

I’m late in coming to this thread, so sorry if I missed the answer to this
question, but what is the voltage drop between the power supply and the
4005i?

73, David N5DCH

> On Apr 26, 2020, at 8:46 AM, N4ZR <[hidden email]> 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.
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

______________________________________________________________
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
Message delivered to [hidden email]

______________________________________________________________
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
Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: Voltage drop in DX Power to K3

In reply to this post by Adrian-3

Oh well, I need another cup of coffee.    I'll try to do better proof
reading. Can't blame that one on auto-correct!

Cutting to the chase........., measure from the power supply POS
terminal to the ACC 12V on the K3 radio.    That is the total voltage
drop in the POS DC path. Then do the same for the NEG terminal of the
power supply to the ground terminal on the radio. That is the voltage
drop on the NEG DC path. Add those two together and one has the total
voltage drop. Now, step by step, isolate where each amount of voltage
drop occurs.

Anytime over 0.5 volts total voltage drop occurs, something needs
attention.   Thus DC Pos should be less than 0.25 volt drop and DC Neg
should be less than 0.25 volts. For a total of 0.5 volts drop at the
radio.

73

Bob, K4TAX

On 4/26/2020 11:22 AM, Adrian wrote:

> I got a good chuckle out of that one Bob, happens to me often
>
>
> take 2 >
> The calculation is simple: E = I x R current multiplied by
> resistance equals the voltage.
>
>
>>
>> The calculation is simple: E = I x R current multiplied by
>> amps equal voltage.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>
>

N4ZR

Re: Voltage drop in DX Power to K3

In reply to this post by Bob McGraw - K4TAX

Aside from my decimal point problems.... The cable measured 0.3 ohms,
with my DMM, but in retrospect, its measurement could not have been
correct. However, the measurement on the 4005i is about right, because
that was done by comparing the voltages at its input and output, and was
at 100 watts key-down. The 4005i's *voltage drop* at 100 watts was 0.08
*volts*, which strikes me as not bad at all.

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.

On 4/26/2020 12:11 PM, Bob McGraw K4TAX 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 <[hidden email]> 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.
>>>
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
>>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: Voltage drop in DX Power to K3

Pete: Sorry I read some of your numbers incorrectly. A cable with 0.3
ohms resistance and 20 amps of current will have a voltage drop of 20 x
0.3 for 6 volts. This can't be correct. More like 20 x 0.03 for 1.2
volts. Still too much.

Don't try to measure resistance with a DVM, as point contact and lead
resistance will be too great. Just measure voltage drop across the
various components which will be more accurate. That's what is important
anyway.

73

Bob, K4TAX

On 4/26/2020 11:34 AM, N4ZR wrote:

> Aside from my decimal point problems.... The cable measured 0.3
> ohms, with my DMM, but in retrospect, its measurement could not have
> been correct. However, the measurement on the 4005i is about right,
> because that was done by comparing the voltages at its input and
> output, and was at 100 watts key-down. The 4005i's *voltage drop* at
> 100 watts was 0.08 *volts*, which strikes me as not bad at all.
>
> 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.
>
> On 4/26/2020 12:11 PM, Bob McGraw K4TAX 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 <[hidden email]> 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.
>>>>
>>>> ______________________________________________________________
>>>> 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
>>>> Message delivered to [hidden email]
>>> ______________________________________________________________
>>> 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
>>> Message delivered to [hidden email]
>>>
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

N4ZR

Re: Voltage drop in DX Power to K3

In reply to this post by Bob McGraw - K4TAX

Thanks, Bob - I had forgotten about being able to measure at the acc 12v
output. In any case, though, the front-panel display provides a pretty
good number. It says that the RX-only voltage at the K3 is 13.7 volts.
My worst-case at 100 watts key down is 12.6 - I don't know where the 11
volts came from. As someone suggested, it could be as simple as my
having plugged and unplugged the various powerpoles a few times.

But here's the real bottom line - depending on band, I only need at most
40 watts to drive my KPA-1500 to full output. At that level, voltage
only drops to 13.1, which is plenty good enough.

Thanks everyone for putting up with me - at least, I'm leaving this
exercise a little smarter than I went in...

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.

On 4/26/2020 12:32 PM, Bob McGraw K4TAX wrote:

> Oh well, I need another cup of coffee.    I'll try to do better proof
> reading. Can't blame that one on auto-correct!
>
> Cutting to the chase........., measure from the power supply POS
> terminal to the ACC 12V on the K3 radio.    That is the total voltage
> drop in the POS DC path. Then do the same for the NEG terminal of the
> power supply to the ground terminal on the radio. That is the voltage
> drop on the NEG DC path. Add those two together and one has the total
> voltage drop. Now, step by step, isolate where each amount of voltage
> drop occurs.
>
> Anytime over 0.5 volts total voltage drop occurs, something needs
> attention.   Thus DC Pos should be less than 0.25 volt drop and DC Neg
> should be less than 0.25 volts. For a total of 0.5 volts drop at the
> radio.
>
> 73
>
> Bob, K4TAX
>
>
> On 4/26/2020 11:22 AM, Adrian wrote:
>> I got a good chuckle out of that one Bob, happens to me often
>>
>>
>> take 2 >
>> The calculation is simple:    E = I x R      current multiplied by
>> resistance equals the voltage.
>>
>>
>>>
>>> The calculation is simple:    E = I x R      current multiplied by
>>> amps equal voltage.
>>>
>>> 73
>>>
>>> Bob, K4TAX
>>>
>>>
>>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Pete Lascell-2

Re: Voltage drop in DC Power to K3

In reply to this post by Leroy Buller

Consider using larger stranded wire. When making connections unravel a few outside strands and cut off so the remaining strands will fit the terminals being used correctly. The smaller (higher resistance) section of cable will be only part of an inch. Heatshrink tubing will cover the unsightly chop job.

Depending on the exact stranding configuration of the cable, going from #10 stranded, #8 stranded is 56-64%, and #6 stranded is 37-43% the resistance of the larger #10 cable. If going from #10 with individual strands of #26 wire to #6 cable with individual strands of #36 wire, the resistance can be as little as 35% of the larger #10 cable.

Pete W4WWQ

----- Original Message -----
From: Leroy Buller <[hidden email]>
To: N4ZR <[hidden email]>
Cc: Elecraft List <[hidden email]>
Sent: 4/26/2020 11:53:28 AM
Subject: Re: [Elecraft] Voltage drop in DX Power to K3
________________________________________________________________________________

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 <[hidden email]> wrote:

______________________________________________________________
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
Message delivered to [hidden email]
______________________________________________________________
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
Message delivered to [hidden email]

rcbenedict1545

Re: Voltage drop in DC Power to K3

Or use bigger connectors, like 45 amp power poles.
Ray
W8LYJ

Sent from my iPad

> On Apr 26, 2020, at 11:19, Pete Lascell <[hidden email]> wrote:
>
> Consider using larger stranded wire. When making connections unravel a few outside strands and cut off so the remaining strands will fit the terminals being used correctly. The smaller (higher resistance) section of cable will be only part of an inch. Heatshrink tubing will cover the unsightly chop job.
>
> Depending on the exact stranding configuration of the cable, going from #10 stranded, #8 stranded is 56-64%, and #6 stranded is 37-43% the resistance of the larger #10 cable. If going from #10 with individual strands of #26 wire to #6 cable with individual strands of #36 wire, the resistance can be as little as 35% of the larger #10 cable.
>
> Pete W4WWQ
>
>
> ----- Original Message -----
> From: Leroy Buller <[hidden email]>
> To: N4ZR <[hidden email]>
> Cc: Elecraft List <[hidden email]>
> Sent: 4/26/2020 11:53:28 AM
> Subject: Re: [Elecraft] Voltage drop in DX Power to K3
> ________________________________________________________________________________
>
> 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 <[hidden email]> 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.
>>
>> ______________________________________________________________
>> 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
>> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

NK7Z

Re: Voltage drop in DC Power to K3

Voltage drop the easy way:

1. Press the DISP button on the K3.
2. Adjust VFO B for voltage.
3. Go into transmit at full power.
4. Write down the voltage you see.
5. Meter the power supply.
6. Go into full power transmit.
7. Write down the Power Supply voltage.

Subtract the number you got in step 4, form teh number you got in step
7. You have now calculated the total voltage drop across your 12 V
power system.

If you want to know the individual item drops, replace an item with a
jumper, goto step 1.

According to WMR, each mating surface adds .0006 ohm on a 35 Amp PP
connector.

73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist
ARRL Asst. Director, NW Division, Technical Resources
______________________________________________________________
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
Message delivered to [hidden email]

Jim Brown-10

Re: Voltage drop in DX Power to K3

In reply to this post by N4ZR

I wouldn't expect useful accuracy from anything but a lab instrument for
such low resistances as a few feet of #12. Far better to look up the
resistance of copper wire from a wire table. An unknown "black box" like
a power strip is not so easy. :) As for the protection diode, that's
pretty easy too -- look up the junction voltage for that type of diode,
and you're within 0.1 volt of reality.

The thing I find baffling (or depressing) here is that we all had to
understand Ohm's Law to pass the exam for our license, and it's REAL
simple. Take resistance values from a wire table, multiply by the
length, then by two for the two conductors, then by the current. I dunno
what the exam is like nowadays -- my experience was 1955 with the Novice
test and a year later with the General -- but surely there must be
something about how diodes work!

73, Jim K9YC

______________________________________________________________
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
Message delivered to [hidden email]

Jim Brown-10

Re: Voltage drop in DC Power to K3

In reply to this post by Pete Lascell-2

On 4/26/2020 10:18 AM, Pete Lascell wrote:
> When making connections unravel a few outside strands and cut off so the remaining strands will fit the terminals being used correctly. The smaller (higher resistance) section of cable will be only part of an inch. Heatshrink tubing will cover the unsightly chop job.

Yep.

And I've also used W1ZR's solution of two of the same size cables in
parallel.

73, Jim K9YC
______________________________________________________________
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
Message delivered to [hidden email]

N4ZR

Re: Voltage drop in DX Power to K3

In reply to this post by Jim Brown-10

Gee Jim, I didn't think I was *that* stupid. Yes, I didn't get the
decimal places right -that was a simple brain phart. As for the
licensing tests, did you have to draw a Colpitts oscillator? IIRC, that
was on my General exam in 1955.

With the power strip, what's wrong with measuring the voltage in and
out, knowing the current being drawn, and deriving the resistance from
that?

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.

On 4/26/2020 6:24 PM, Jim Brown wrote:

> I wouldn't expect useful accuracy from anything but a lab instrument
> for such low resistances as a few feet of #12. Far better to look up
> the resistance of copper wire from a wire table. An unknown "black
> box" like a power strip is not so easy. :) As for the protection
> diode, that's pretty easy too -- look up the junction voltage for that
> type of diode, and you're within 0.1 volt of reality.
>
> The thing I find baffling (or depressing) here is that we all had to
> understand Ohm's Law to pass the exam for our license, and it's REAL
> simple. Take resistance values from a wire table, multiply by the
> length, then by two for the two conductors, then by the current. I
> dunno what the exam is like nowadays -- my experience was 1955 with
> the Novice test and a year later with the General -- but surely there
> must be something about how diodes work!
>
> 73, Jim K9YC
>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Bill Frantz

Re: Voltage drop in DC Power to K3

In reply to this post by rcbenedict1545

If you really want better connections, try the 75 amp power
poles. Of course they are bigger, and not plug compatible with
the 15, 30, 45 amp connectors.

(And I always thought the only difference between the 15, 30,
and 45 amp connectors was the size of wire you could cram into them.)

73 Bill AE6JV

On 4/26/20 at 1:21 PM, [hidden email] (Gmail) wrote:

>Or use bigger connectors, like 45 amp power poles.
-----------------------------------------------------------------------
Bill Frantz | gets() remains as a monument | Periwinkle
(408)348-7900 | to C's continuing support of | 150
Rivermead Rd #235
www.pwpconsult.com | buffer overruns. |
Peterborough, NH 03458

______________________________________________________________
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
Message delivered to [hidden email]

Bill Frantz

Re: Voltage drop in DX Power to K3

In reply to this post by Jim Brown-10

Having helped teach a number of Tech level ham crams, Ohm's law
and diodes are both on the test. I'm not sure that all of the
nitty gritty of diodes -- voltage drop by type etc. are covered though.

I think you can pass not knowing either though. :-(

73 Bill AE6JV

On 4/26/20 at 6:24 PM, [hidden email] (Jim Brown) wrote:

>The thing I find baffling (or depressing) here is that we all
>had to understand Ohm's Law to pass the exam for our license,
>and it's REAL simple. Take resistance values from a wire
>table, multiply by the length, then by two for the two
>conductors, then by the current. I dunno what the exam is like
>nowadays -- my experience was 1955 with the Novice test and a
>year later with the General -- but surely there must be
>something about how diodes work!
-------------------------------------------------------------------------
Bill Frantz | The first thing you need when | Periwinkle
(408)348-7900 | using a perimeter defense is a | 150
Rivermead Rd #235
www.pwpconsult.com | perimeter. |
Peterborough, NH 03458

______________________________________________________________
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
Message delivered to [hidden email]

1234