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K3 - Power cable voltage drop

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Karin Johnson

K3 - Power cable voltage drop

Why hasn't anyone used remote sensing at the radio voltage input?
As far as I know all of the Astron supplies don't have external sense
wiring. Many so called professional grade high current supplies provide
For external connection of the voltage sense back to the regulator chip.
I've toyed with this idea a bit but haven't had the time dig in to the
Astron supply I have. If this were implemented then one could maintain
13.8 volts or whatever you desired at the radio power supply inputs,
Regardless of the current draw.

Karin Anne Johnson K3UU

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Rose

Re: K3 - Power cable voltage drop

First, it would require some basic technical skill ... (;-)

73

K0PP

On Tue, Dec 24, 2019, 13:20 Karin Johnson <[hidden email]> wrote:

> Why hasn't anyone used remote sensing at the radio voltage input?
> As far as I know all of the Astron supplies don't have external sense
> wiring. Many so called professional grade high current supplies provide
> For external connection of the voltage sense back to the regulator chip.
> I've toyed with this idea a bit but haven't had the time dig in to the
> Astron supply I have. If this were implemented then one could maintain
> 13.8 volts or whatever you desired at the radio power supply inputs,
> Regardless of the current draw.
>
> Karin Anne Johnson K3UU
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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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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Jim Rhodes-2

Re: K3 - Power cable voltage drop

I have thought about doing that. Just requires a 2 wire hookup with small
gauge wire. But I run all of my small items like the remoterig box, LP-pan
box, VHF/UHF rig and so forth off of the main supply and if I have a larger
than anticipated voltage drop on rig power cable the voltage on the other
tings could go fairly high. The power supply is a HB thing with at least a
50 amp capacity and plenty of voltage overhead before pass transistors.
(Used to run 2 HF rigs before downsizing.)

On Tue, Dec 24, 2019 at 2:25 PM Rose <[hidden email]> wrote:

> First, it would require some basic technical skill ... (;-)
>
> 73
>
> K0PP
>
> On Tue, Dec 24, 2019, 13:20 Karin Johnson <[hidden email]>
> wrote:
>
> > Why hasn't anyone used remote sensing at the radio voltage input?
> > As far as I know all of the Astron supplies don't have external sense
> > wiring. Many so called professional grade high current supplies provide
> > For external connection of the voltage sense back to the regulator chip.
> > I've toyed with this idea a bit but haven't had the time dig in to the
> > Astron supply I have. If this were implemented then one could maintain
> > 13.8 volts or whatever you desired at the radio power supply inputs,
> > Regardless of the current draw.
> >
> > Karin Anne Johnson K3UU
> >
> >
> > ______________________________________________________________
> > 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]
> >
> ______________________________________________________________
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> Help: http://mailman.qth.net/mmfaq.htm
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>
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> Message delivered to [hidden email]
>

--
Jim K0XU
[hidden email]
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Elecraft mailing list

Re: K3 - Power cable voltage drop

In reply to this post by Karin Johnson

I do use voltage sensing at the rear of the radio. Astron supplies can be
modified easily to do this - they already have sense wires tied to the
voltage output terminals. Basically you disconnect them there and run leads
(keep em short) to the radio. On transmit, my K3s drops less than 1/10 a
volt.

There are a few write ups floating around on how to do this. I installed a
switch (make before break type) on my RS-50M so I can return to "normal"
sensing. ***WARNING*** If the external sense wires are not connected to
anything the crowbar circuit will fire!!!

Hank
K4HYJ

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Karin Johnson
Sent: Tuesday, December 24, 2019 3:20 PM
To: [hidden email]
Subject: [Elecraft] K3 - Power cable voltage drop

Why hasn't anyone used remote sensing at the radio voltage input?
As far as I know all of the Astron supplies don't have external sense
wiring. Many so called professional grade high current supplies provide For
external connection of the voltage sense back to the regulator chip.
I've toyed with this idea a bit but haven't had the time dig in to the
Astron supply I have. If this were implemented then one could maintain
13.8 volts or whatever you desired at the radio power supply inputs,
Regardless of the current draw.

Karin Anne Johnson K3UU

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Don Wilhelm

Re: K3 - Power cable voltage drop

That would be a neat thing to do, but DO NOT do that on a power supply
that is connected to anything other than the rig you are sensing from.

The voltage on other devices connected to the power supply will increase
when you transmit on the rig to which the sense wires are connected.

Use a separate power supply for accessories.

If you need to use the same supply, you can adjust the voltage upward -
the SS30 sold by Elecraft already has an output voltage of 14.1 volts.
Still use a separate power cable to the transceiver and another cable to
any distribution box that you use for accessories for best results
(lowest voltage drop when transmitting).

73,
Don W3FPR

On 12/24/2019 4:23 PM, K4HYJ via Elecraft wrote:

> I do use voltage sensing at the rear of the radio. Astron supplies can be
> modified easily to do this - they already have sense wires tied to the
> voltage output terminals. Basically you disconnect them there and run leads
> (keep em short) to the radio. On transmit, my K3s drops less than 1/10 a
> volt.
>
> There are a few write ups floating around on how to do this. I installed a
> switch (make before break type) on my RS-50M so I can return to "normal"
> sensing. ***WARNING*** If the external sense wires are not connected to
> anything the crowbar circuit will fire!!!

K9MA

Re: K3 - Power cable voltage drop

There can be stability issues with remote sensing. Also RF susceptibility. Take care!

73,
Scott K9MA

----------

Scott Ellington

--- via iPad

> On Dec 24, 2019, at 4:03 PM, Don Wilhelm <[hidden email]> wrote:
>
> That would be a neat thing to do, but DO NOT do that on a power supply that is connected to anything other than the rig you are sensing from.
>
> The voltage on other devices connected to the power supply will increase when you transmit on the rig to which the sense wires are connected.
>
> Use a separate power supply for accessories.
>
> If you need to use the same supply, you can adjust the voltage upward - the SS30 sold by Elecraft already has an output voltage of 14.1 volts.
> Still use a separate power cable to the transceiver and another cable to any distribution box that you use for accessories for best results (lowest voltage drop when transmitting).
>
> 73,
> Don W3FPR
>
>> On 12/24/2019 4:23 PM, K4HYJ via Elecraft wrote:
>> I do use voltage sensing at the rear of the radio. Astron supplies can be
>> modified easily to do this - they already have sense wires tied to the
>> voltage output terminals. Basically you disconnect them there and run leads
>> (keep em short) to the radio. On transmit, my K3s drops less than 1/10 a
>> volt.
>> There are a few write ups floating around on how to do this. I installed a
>> switch (make before break type) on my RS-50M so I can return to "normal"
>> sensing. ***WARNING*** If the external sense wires are not connected to
>> anything the crowbar circuit will fire!!!
> ______________________________________________________________
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Bob McGraw - K4TAX

Re: K3 - Power cable voltage drop

In reply to this post by Karin Johnson

With the Astron supplies, the 723 regulator does have provision for
remote sensing. And with a bit of work and some extra wiring and
components one can have remote sensing.

I would suggest NOT doing so as remote sensing become "inputs" to the
723 regulator chip and any noise or RF on the remote sensing lines can
be very problematic.   Proper filtering and time constants will be
required to prevent oscillations.

My suggestion is to use good quality #10 AWG wire, such as auto primary
wire fitted with correct terminals on the ends. Be sure to correctly
crimp and solder as needed.   Suggested length is something less than 10
ft.    Also be sure to have a dedicated ground between the ground screw
on the back of the radio to the ground on the power supply.

In the end, if you desire to have remote sensing, purchase a suitable
supply that provides remote sensing.   Life will be much easier.

73

Bob, K4TAX

On 12/24/2019 2:20 PM, Karin Johnson wrote:

Bob McGraw - K4TAX

Re: K3 - Power cable voltage drop

In reply to this post by Jim Rhodes-2

Yes, but one screw-up on the remote sensing system and it will take
advantage of the voltage overhead on the pass transistors and likely
wipe out every piece of equipment. I strongly do not advise it.
And you make a valid point for NOT using remote sensing.

73

Bob, K4TAX

On 12/24/2019 3:22 PM, Jim Rhodes wrote:

> I have thought about doing that. Just requires a 2 wire hookup with small
> gauge wire. But I run all of my small items like the remoterig box, LP-pan
> box, VHF/UHF rig and so forth off of the main supply and if I have a larger
> than anticipated voltage drop on rig power cable the voltage on the other
> tings could go fairly high. The power supply is a HB thing with at least a
> 50 amp capacity and plenty of voltage overhead before pass transistors.
> (Used to run 2 HF rigs before downsizing.)
>
>
> On Tue, Dec 24, 2019 at 2:25 PM Rose <[hidden email]> wrote:
>
>> First, it would require some basic technical skill ... (;-)
>>
>> 73
>>
>> K0PP
>>
>> On Tue, Dec 24, 2019, 13:20 Karin Johnson <[hidden email]>
>> wrote:
>>
>>> Why hasn't anyone used remote sensing at the radio voltage input?
>>> As far as I know all of the Astron supplies don't have external sense
>>> wiring. Many so called professional grade high current supplies provide
>>> For external connection of the voltage sense back to the regulator chip.
>>> I've toyed with this idea a bit but haven't had the time dig in to the
>>> Astron supply I have. If this were implemented then one could maintain
>>> 13.8 volts or whatever you desired at the radio power supply inputs,
>>> Regardless of the current draw.
>>>
>>> Karin Anne Johnson K3UU
>>>
>>>
>>> ______________________________________________________________
>>> 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]
>>
>

K9MA

Re: K3 - Power cable voltage drop

Typically, there are small resistors at the power supply between the output and sense terminals to prevent the voltage from rising if a sense wire opens up.

73,
Scott K9MA

----------

Scott Ellington

--- via iPad

> On Dec 24, 2019, at 5:39 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>
> Yes, but one screw-up on the remote sensing system and it will take advantage of the voltage overhead on the pass transistors and likely wipe out every piece of equipment. I strongly do not advise it. And you make a valid point for NOT using remote sensing.
>
> 73
>
> Bob, K4TAX
>
>> On 12/24/2019 3:22 PM, Jim Rhodes wrote:
>> I have thought about doing that. Just requires a 2 wire hookup with small
>> gauge wire. But I run all of my small items like the remoterig box, LP-pan
>> box, VHF/UHF rig and so forth off of the main supply and if I have a larger
>> than anticipated voltage drop on rig power cable the voltage on the other
>> tings could go fairly high. The power supply is a HB thing with at least a
>> 50 amp capacity and plenty of voltage overhead before pass transistors.
>> (Used to run 2 HF rigs before downsizing.)
>>
>>
>>> On Tue, Dec 24, 2019 at 2:25 PM Rose <[hidden email]> wrote:
>>>
>>> First, it would require some basic technical skill ... (;-)
>>>
>>> 73
>>>
>>> K0PP
>>>
>>> On Tue, Dec 24, 2019, 13:20 Karin Johnson <[hidden email]>
>>> wrote:
>>>
>>>> Why hasn't anyone used remote sensing at the radio voltage input?
>>>> As far as I know all of the Astron supplies don't have external sense
>>>> wiring. Many so called professional grade high current supplies provide
>>>> For external connection of the voltage sense back to the regulator chip.
>>>> I've toyed with this idea a bit but haven't had the time dig in to the
>>>> Astron supply I have. If this were implemented then one could maintain
>>>> 13.8 volts or whatever you desired at the radio power supply inputs,
>>>> Regardless of the current draw.
>>>>
>>>> Karin Anne Johnson K3UU
>>>>
>>>>
>>>> ______________________________________________________________
>>>> 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]
>>>
>>
>
> ______________________________________________________________
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Bob McGraw - K4TAX

Re: K3 - Power cable voltage drop

Yes true.   However seeing they way some hams configure their stations,
building or modifying and implementing a power supply with voltage
sensing, is of serious questionable nature. Likewise, in conditions
where power supplies are buried under the desk. One needs to see the
volt meter when the supply is first turned on to assure the voltage is
correct. And that should be done before the radio is turned on. Oh
I know about crowbar circuits, but if that $2.50 part fails it will
likely take out a $3000 radio.   This just isn't smart.

Having worked with equipment that was supplied with 35 ft or 50 ft power
cables for loads of 20A to 30A at + & - 18 volts, I understand just a
wee bit about voltage sensing circuits and what makes them oscillate.

Just err on the safe side.    And for ham radio, it likely is not
necessary to have or implement remote voltage sensing. Wire and
connectors are cheap.   Use a shorter length of wire or larger gauge
wire.   There's no likely component failure with this approach.

73

Bob, K4TAX

On 12/24/2019 8:25 PM, K9MA wrote:

> Typically, there are small resistors at the power supply between the output and sense terminals to prevent the voltage from rising if a sense wire opens up.
>
> 73,
> Scott K9MA
>
> ----------
>
> Scott Ellington
>
> --- via iPad
>
>> On Dec 24, 2019, at 5:39 PM, Bob McGraw K4TAX <[hidden email]> wrote:
>>
>> Yes, but one screw-up on the remote sensing system and it will take advantage of the voltage overhead on the pass transistors and likely wipe out every piece of equipment. I strongly do not advise it. And you make a valid point for NOT using remote sensing.
>>
>> 73
>>
>> Bob, K4TAX
>>
>>> On 12/24/2019 3:22 PM, Jim Rhodes wrote:
>>> I have thought about doing that. Just requires a 2 wire hookup with small
>>> gauge wire. But I run all of my small items like the remoterig box, LP-pan
>>> box, VHF/UHF rig and so forth off of the main supply and if I have a larger
>>> than anticipated voltage drop on rig power cable the voltage on the other
>>> tings could go fairly high. The power supply is a HB thing with at least a
>>> 50 amp capacity and plenty of voltage overhead before pass transistors.
>>> (Used to run 2 HF rigs before downsizing.)
>>>
>>>
>>>> On Tue, Dec 24, 2019 at 2:25 PM Rose <[hidden email]> wrote:
>>>>
>>>> First, it would require some basic technical skill ... (;-)
>>>>
>>>> 73
>>>>
>>>> K0PP
>>>>
>>>> On Tue, Dec 24, 2019, 13:20 Karin Johnson <[hidden email]>
>>>> wrote:
>>>>
>>>>> Why hasn't anyone used remote sensing at the radio voltage input?
>>>>> As far as I know all of the Astron supplies don't have external sense
>>>>> wiring. Many so called professional grade high current supplies provide
>>>>> For external connection of the voltage sense back to the regulator chip.
>>>>> I've toyed with this idea a bit but haven't had the time dig in to the
>>>>> Astron supply I have. If this were implemented then one could maintain
>>>>> 13.8 volts or whatever you desired at the radio power supply inputs,
>>>>> Regardless of the current draw.
>>>>>
>>>>> Karin Anne Johnson K3UU
>>>>>
>>>>>
>>>>> ______________________________________________________________
>>>>> 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]
>>>>
>> ______________________________________________________________
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>