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Author Topic: DC Power supply grounding question  (Read 780 times)

K6UJ

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DC Power supply grounding question
« on: November 15, 2021, 10:37:30 PM »

I saw a You Tube video on grounding for ham stations.  Common grounds with a buss at the operating desk and avoiding ground loops was discussed.  The usual stuff we all do and my station has been set this way.   One thing however was brought up that isn't clear to me.  It was said that we should inspect  our DC power supply for a bonding jumper between the chassis and DC negative.  If found remove it. 
Does this make sense ?  Am I watching too many You Tube videos ?    ;D

Bob
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NA4IT

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Re: DC Power supply grounding question
« Reply #1 on: November 16, 2021, 03:41:18 AM »

I'd leave well enough alone in the power supply.
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K4KRW

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Re: DC Power supply grounding question
« Reply #2 on: November 16, 2021, 04:04:30 AM »

Bob,

Look up 'The Pin 1 Problem'.

Here is one document I found that talks about it.
 
http://audiosystemsgroup.com/GroundingAndAudio.pdf

Richard
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SWMAN

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Re: DC Power supply grounding question
« Reply #3 on: November 16, 2021, 05:02:25 AM »

Richard,
 Nice write up about bonding and grounding. 282 pages of interesting facts. Thanks for sending.
Jim. W5JJG
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W9IQ

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Re: DC Power supply grounding question
« Reply #4 on: November 16, 2021, 05:45:39 AM »

If the power supply is in the SPG zone, you don't want the household AC safety ground connected to the SPG through a second path - the chassis of the supply. So separating the grounds is the correct practice in this case.

A second justification for isolating the grounds is to reduce noise on the DC ground.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

WA9AFM

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Re: DC Power supply grounding question
« Reply #5 on: November 16, 2021, 06:22:11 AM »

You might want to get a copy of "Grounding and Bonding For The Radio Amateur" by Ward Silver, N0AX.  It covers this very situation.  The book also covers RF management, lightning protections, and electrical safety.
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K6AER

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Re: DC Power supply grounding question
« Reply #6 on: November 16, 2021, 07:18:51 AM »

Most transceivers have the negative battery lead grounded to the radio chassis. At this point bonding ground and battery ground are the same.
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K6UJ

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Re: DC Power supply grounding question
« Reply #7 on: November 16, 2021, 10:40:38 AM »

If the power supply is in the SPG zone, you don't want the household AC safety ground connected to the SPG through a second path - the chassis of the supply. So separating the grounds is the correct practice in this case.

A second justification for isolating the grounds is to reduce noise on the DC ground.

- Glenn W9IQ


Thanks for the info Glenn. The power is an Astron 60M.   I will investigate further and start with the schematic and see what I find.

Bob
K6UJ
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K6UJ

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Re: DC Power supply grounding question
« Reply #8 on: November 16, 2021, 04:37:59 PM »

Thanks everyone for the info and resources for learning more so I can be well grounded on grounding, hihi   (sorry couldn't help it hihi)

I checked my Astron 60M and it does indeed have a jumper connecting the negative output to the chassis.
I will work on improving my understanding on this. 

tnx  es 73,
Bob
K6UJ
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AA4PB

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Re: DC Power supply grounding question
« Reply #9 on: November 23, 2021, 03:09:36 PM »

The possible problem with the internal negative power to case bond is the voltage drop across the minus DC wire between the radio and the power supply (especially if you have a fuse and connectors in that line). My solution is to run a 1-inch wide flexible strap between the grounding screw on the radio and the grounding screw on the Astron. That reduces the voltage drop in the line to a small fraction of a volt and minimizes the current flowing in any ground loops through the AC power ground.
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Bob  AA4PB
Garrisonville, VA

WB4SPT

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Re: DC Power supply grounding question
« Reply #10 on: December 21, 2021, 08:51:25 AM »

If the power supply is in the SPG zone, you don't want the household AC safety ground connected to the SPG through a second path - the chassis of the supply. So separating the grounds is the correct practice in this case.

A second justification for isolating the grounds is to reduce noise on the DC ground.

- Glenn W9IQ

This is rather a tricky one.  I had an industrial device keep failing surge testing.  (The waveform that attempts to simulate lightning.)  Lots of 3.3V stuff was failing.  Turns out, the SMPS fed thru about 10% of the surge waveform.  We had floated the output 12V from Earth.   Tying the NEG to GND shunted the waveform, and the unit now passed surge testing.   So, the Common Mode Voltage went to about zero, and the Normal Mode noise was dealt with by the built in Caps across the 12v out. 
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W9WQA

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Re: DC Power supply grounding question
« Reply #11 on: December 21, 2021, 01:26:31 PM »

i added a dc ground to my astron.
a primary to secondary short/leak would put line volts on your radio.
not good !!!
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WB4SPT

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Re: DC Power supply grounding question
« Reply #12 on: December 22, 2021, 06:09:29 AM »

i added a dc ground to my astron.
a primary to secondary short/leak would put line volts on your radio.
not good !!!

Yes, a good example of a supreme common mode issue!
Also the reason for the utility power earthing/grounding of the neutral. 
Note, however, this grounding scheme is not always desirable.   There can be other factors at work.
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N8FVJ

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Re: DC Power supply grounding question
« Reply #13 on: December 22, 2021, 03:47:29 PM »

The power supply negative is grounded thru the transceiver.
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W9WQA

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Re: DC Power supply grounding question
« Reply #14 on: December 22, 2021, 09:32:56 PM »

The power supply negative is grounded thru the transceiver.

assuming the radio is grounded.

if radio is connected to the supply with line volts on dc and you touch the radio as you connect the ground, you get shocked.
ground the dc to chassis ground...
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