Pages: [1] 2   Go Down

Author Topic: Weird grounding issue...  (Read 653 times)

KT0DD

  • Member
  • Posts: 568
Weird grounding issue...
« on: January 29, 2023, 01:59:26 PM »

I just disconnected the negative wire from a battery I am running my backup TS450S radio with and it stayed ON! I have another radio (FT891) hooked to the same battery and connect the 2 antenna outputs to one antenna via a good Diawa switch. Could the ground path be following the antenna connections thru the other radio?

Todd - KT0DD
Logged

VK3KTO

  • Member
  • Posts: 18
Re: Weird grounding issue...
« Reply #1 on: January 29, 2023, 02:29:13 PM »

Current can take strange paths, as I once found. I was testing a club radio, I think a TS450 and although it would receive OK, every time I tried to transmit, no matter what I did with antennas and tuners, the SWR just went off the scale. Then I noticed there was a fuse in both power leads and sure enough the negative fuse was blown, replaced it and everything worked fine!
73 de Mike VK3KTO       
Logged

W7CXC

  • Member
  • Posts: 335
Re: Weird grounding issue...
« Reply #2 on: January 29, 2023, 02:46:20 PM »

yes ;)
Logged

WA8NVW

  • Member
  • Posts: 367
Re: Weird grounding issue...
« Reply #3 on: January 29, 2023, 02:53:40 PM »

Remember one of the basics you were taught while getting your ham license: Draw yourself the schematic. It will make the question more clear.  The answer is yes, just as you suspected.
Logged

AI5BC

  • Posts: 456
    • HomeURL
Re: Weird grounding issue...
« Reply #4 on: January 29, 2023, 04:51:00 PM »

So, what is the question? Of course, it stays on. It is a problem only ham radio operators suffer from, and the problem is in your DC power supply and using a radio designed for a car in your house.

The problem lies in your DC power Supply, your Astron. It is outdate still using 1960's grounding topology. Your DC Negative output terminal is bonded to the chassis of the DC power supply. That does two nasty thing hams love because it gives them problems to fix.

First, you lose AC and DC electrical isolation required by all electrical codes placing your radio in a nasty daisy-chained ground loop. Now any noise flowing in the AC ground system is now flowing through your DC ground system (your radio). The two mix together, have an orgy, and produce noise. One big party with both the front and back doors wide open for anything to come inside and look around. You're in a Ground Loop!

The second thing it does is it turns your whole ground system into a DC negative circuit conductor. You no longer have a ground. Your car radio power and ground topology are two-wire vs modern 3-wire systems. Inside your radio, the DC negative is bonded to the chassis of the radio. A huge no-no in the modern world. Compounding the problem is your DC power supply with the chassis bonded to DC Negative again. This places Ground in parallel with your DC negative return conductor. By doing that, you no longer have Ground, you have a DC circuit conductor you call Ground.

So, when you lift the DC wire from you power supply, your coax shield and station ground are there to take up the slack Stupid simple to fix, so simple most hams have not figured it out in 50 years when the electrical world changed and went to 3-wire topology. Open that antiquated Astron and remove the jumper that bonds DC negative output terminal to the Chassis. Do that and all the problems go away. Problem is, it can eliminate a lot of noise problems you guys like to waste a lot of money and time fixing with band aids rather than addressing the real problem. Gives you something to do, I guess.   



Logged

AI5BC

  • Posts: 456
    • HomeURL
Re: Weird grounding issue...
« Reply #5 on: January 29, 2023, 06:18:16 PM »

Interesting post, but I reread all the posts and saw no mention of an Astron power supply
Wanna bet it is an Astron? You will lose the bet. Hams are creatures of habits.

Regardless of if it is an Astron or not, the problem is in the DC power supply. Older designs bonded the negative to the chassis. That all changed in the 60/70's when electrical codes changed when your homes wiring changed from 2-wire to 3-wire. Hams never caught on and never changed.

Ask yourself why commercial radios do not bond either battery polarity to the equipment chassis. Same reason all electrical codes do not permit either circuit conductor polarity to be bonded to the chassis. If it were permitted forces normal load currents on your ground conductors. Ground conductors are not permitted to have normal operating currents on them. That is dangerous and can cause equipment malfunction in sensitive electronics, your reference is full of noise.  You can deal with it, but you need to understand it to integrate it properly. A good start point is fixing your DC power supply, and if you have an Astron likely have the problem.

FWIW commercial operators do bond the Positive Battery Terminal to Ground to facilitate breaker operation just like an AC circuit. Telephone companies discovered one hundred years ago if you bond negative to ground corrodes and destroys ground electrodes by galvanic corrosion. By using positive protects the ground electrode system. Ironic huh?
« Last Edit: January 29, 2023, 06:32:37 PM by AI5BC »
Logged

KC6RWI

  • Member
  • Posts: 901
Re: Weird grounding issue...
« Reply #6 on: January 29, 2023, 06:25:29 PM »

Understood, I am going to check my Astron power supply, it must be 30 yrs old, I'll see if the negative terminal is the same potential as the third pin on the plug.
Logged

AI5BC

  • Posts: 456
    • HomeURL
Re: Weird grounding issue...
« Reply #7 on: January 29, 2023, 06:45:43 PM »

Understood, I am going to check my Astron power supply, it must be 30 yrs old
I guarantee you will see negative and chassis bonded together on a 30-year old unit. Pretty easy to track down. Astron has a few methods used over the years. Look over any green wires around the output terminals or regulator board. 

Confirm with Ohm Meter connected between the negative output terminal and the chassis. Don't trust using the ground pin on the power cord until you inspect the connection first. Astron is notorious for not removing the paint where the AC power cord ground wire terminates on the chassis. When you are done should have an open circuit between DC negative and chassis and AC ground pin.

When you disconnect the negative wire from the Astron wil work as planned, nothing will have power. Strange concept, disconnect one of the power leads, and the lights go out. Who would have ever thought of that?  ;D

I think when you are done might notice other improvements.
« Last Edit: January 29, 2023, 06:50:03 PM by AI5BC »
Logged

KC6RWI

  • Member
  • Posts: 901
Re: Weird grounding issue...
« Reply #8 on: January 29, 2023, 07:04:52 PM »

The ground pin is the first to make connection, thats why its a tiny bit longer, and I was taught that the metal box is grounded so any short or any failure will send the current to ground,
Now to belabor the point, if the case is grounded, then the negative terminal must be isolated like the postive.
Logged

WA2EIO

  • Member
  • Posts: 278
Re: Weird grounding issue...
« Reply #9 on: January 29, 2023, 07:10:47 PM »

Interesting post, but I reread all the posts and saw no mention of an Astron power supply
Wanna bet it is an Astron? You will lose the bet. Hams are creatures of habits.

Regardless of if it is an Astron or not, the problem is in the DC power supply. Older designs bonded the negative to the chassis. That all changed in the 60/70's when electrical codes changed when your homes wiring changed from 2-wire to 3-wire. Hams never caught on and never changed.

Ask yourself why commercial radios do not bond either battery polarity to the equipment chassis. Same reason all electrical codes do not permit either circuit conductor polarity to be bonded to the chassis. If it were permitted forces normal load currents on your ground conductors. Ground conductors are not permitted to have normal operating currents on them. That is dangerous and can cause equipment malfunction in sensitive electronics, your reference is full of noise.  You can deal with it, but you need to understand it to integrate it properly. A good start point is fixing your DC power supply, and if you have an Astron likely have the problem.

FWIW commercial operators do bond the Positive Battery Terminal to Ground to facilitate breaker operation just like an AC circuit. Telephone companies discovered one hundred years ago if you bond negative to ground corrodes and destroys ground electrodes by galvanic corrosion. By using positive protects the ground electrode system. Ironic huh?

OP said  "I just disconnected the negative wire from a battery I am running my backup TS450S radio with and it stayed ON! I have another radio (FT891) hooked to the same battery ..."  and  then "Could the ground path be following the antenna connections thru the other radio?"  No mention of a DC power supply, so it would appear that his analysis is correct in this situation using a battery for power.
« Last Edit: January 29, 2023, 07:13:36 PM by WA2EIO »
Logged

KF6QEX

  • Member
  • Posts: 788
Re: Weird grounding issue...
« Reply #10 on: January 29, 2023, 08:24:25 PM »

Quote
OP said  "I just disconnected the negative wire from a battery I am running my backup TS450S radio with and it stayed ON! I have another radio (FT891) hooked to the same battery ..."  and  then "Could the ground path be following the antenna connections thru the other radio?"  No mention of a DC power supply,

Shhhhh..... I was enjoying this .....
Logged
sdrawkcab daer tseb si txet sihT

WA3SKN

  • Member
  • Posts: 8124
Re: Weird grounding issue...
« Reply #11 on: January 30, 2023, 07:36:54 AM »

Break out the ohm meter and start testing!  There appears to be a path, now find it!

-Mike.
Logged

W9WQA

  • Member
  • Posts: 988
Re: Weird grounding issue...
« Reply #12 on: January 30, 2023, 12:09:22 PM »

astron/any supply,  transformer secondary and regulator are like a battery sitting on a metal chassis.  isolated from primary.

if primary ac volts leak or short to the secondary you can have line volts on the "battery",,,not good. it puts line volts on your radio.

in that case,the dc neg jumper should blow the supply main fuse for safety.

i added the jumper to my astron.

you guys have a convoluted concept of 3 wire systems.


think of a battery sitting on your wooden bench running your radio.
now touch an ac hot wire to the floating battery.
can you see ac volts on your radio/antenna?

batt neg needs grounding.

some will get this, others will refuse.
yes, draw a schematic
« Last Edit: January 30, 2023, 12:12:51 PM by W9WQA »
Logged

W9WQA

  • Member
  • Posts: 988
Re: Weird grounding issue...
« Reply #13 on: January 30, 2023, 12:13:49 PM »

Current can take strange paths, as I once found. I was testing a club radio, I think a TS450 and although it would receive OK, every time I tried to transmit, no matter what I did with antennas and tuners, the SWR just went off the scale. Then I noticed there was a fuse in both power leads and sure enough the negative fuse was blown, replaced it and everything worked fine!
73 de Mike VK3KTO   

eliminate the neg fuse...   
Logged

KC6RWI

  • Member
  • Posts: 901
Re: Weird grounding issue...
« Reply #14 on: January 31, 2023, 07:14:49 PM »

I am following these posts and rereading them to clarify to myself as I have an old astron.
I don't get you altogether, W9WQA, I'd like to know more, thanks,
I  know that current won't flow if ac hot wire to a battery floating no ground, there would be no path.
But then you say battery negative needs grounding, but that would give a path for an ac hot wire.
Also, if ac got from the prim to sec wouldn't the regulator fail or draw current down causing the main fuse to fail.
Why do you need a jumper. ?
Logged
Pages: [1] 2   Go Up