eHam
eHam Forums => Station Building => Topic started by: KT0DD on January 29, 2023, 01:59:26 PM
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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
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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
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yes ;)
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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.
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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.
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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?
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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.
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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.
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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.
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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.
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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 .....
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Break out the ohm meter and start testing! There appears to be a path, now find it!
-Mike.
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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
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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...
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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. ?
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draw a wire diagram, so simple... ac leakage can make radio hot/ dangerous without the ground.
some just cant see this...???toooo simple
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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.
Astron makes batteries?
OP explicitly stated he is powering his station from a battery.
And the answer is MUCH more likely that the radio has the chassis bonded to ground. Like every single 2SC2879 having radio has had that doesn't have a floating heat sink.
The emitter of the final output transistors is bonded to the case of the transistor. The emitter also has the ground lead attached to it.
As such, the chassis of the radio IS at negative DC potential.
What's funny is, CB radios typically have floating systems. Almost every single 100 watt or better ham radio produced in the last 30 years DOESN'T..... Even if you isolate the DC ground from the safety ground in the power supply it isn't going to make a difference because as soon as you hook up anything with a bipolar transistor in it with the emitter bonded to the case, you lose your DC and safety ground isolation.
Argue all you want about the rest, you aren't going to fix that problem without redesigning at least thermally, the radio(s) in question.
--Shane
WP2ASS / ex KD6VXI
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Well, I'm not going to worry about it. I'm not getting any kind of distortion, RF feedback or artifacts on my TX signal and RX seems just fine. I'll just have to be careful working on this equipment and disconnect everything from the battery completely and from each other if I work on anything. Nice thing is I no longer (Ok, RARELY and it has to be something simple) do any of my own work as I'm too shaky to solder Hi Hi. Thanks for all the info. 73.
Todd - KT0DD
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the reason for the jumper is to be sure the fuse blows if/when there is a short or leakage.
otherwise you can have ac line volts on the radio/ ant....its too simple
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the reason for the jumper is to be sure the fuse blows if/when there is a short or leakage.
otherwise you can have ac line volts on the radio/ ant....its too simple
I understand your point but a properly made transformer makes this a non-issue by UL standards. The metal chassis should be connected to the safety ground but the DC minus can be isolated.
The same concept applies to switching power supplies. The high frequency transformers can provide sufficient isolation for safety purposes.
- Glenn W9IQ
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the reason for the jumper is to be sure the fuse blows if/when there is a short or leakage.
otherwise you can have ac line volts on the radio/ ant....its too simple
I understand your point but a properly made transformer makes this a non-issue by UL standards. The metal chassis should be connected to the safety ground but the DC minus can be isolated.
The same concept applies to switching power supplies. The high frequency transformers can provide sufficient isolation for safety purposes.
- Glenn W9IQ
can be isolated.
can provide sufficient isolation
properly made transformer
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I've seen plenty of transformers , failed ones to. I'd say that most of the time the failure is between the wires of the primary with that thin varnish coat. The core of the transformer is further insulated with additional paper or card type paper, that would seem even harder to make some ac make it thru to the core. I think the user would be smelling some burnt smell before that happened.
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Forgot to mention, I'm running the factory power cord with fuses on both + & - leads. I'm making sure the negative stays connected to the battery, I'm not trying to short-cut (pun intended) anything. 73 and Thank you for the constructive comments.
Todd - KT0DD
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I've seen plenty of transformers , failed ones to. I'd say that most of the time the failure is between the wires of the primary with that thin varnish coat. The core of the transformer is further insulated with additional paper or card type paper, that would seem even harder to make some ac make it thru to the core. I think the user would be smelling some burnt smell before that happened.
sounds good, until you THINK,,,
THE CORE IS GROUNDED IRON,,,that blows the fuse as you want.
leakage from primary to secondary winding is the problem,,,but that will never happen !!! in a properly designed transformer,,,or parachute !!
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sounds good, until you THINK,,,THE CORE IS GROUNDED IRON,,,that blows the fuse as you want.
leakage from primary to secondary winding is the problem,,,but that will never happen !!! in a properly designed transformer,,,or parachute !!
All it takes is a lightning hit on the overhead power lines in your neighborhood. Then you've got Ltning HI on the service phase conductor, Ltning LO (ground) on the neutral of the ljne cord.and lots of inductance to make L di/dt. I don't recall the exact insulation standoff value that UL requires for the varnish winding layer, but the number 1 kV keeps jumping into my brain, so if the lightning strike potential exceeds 1 kV it can arc through the varnish and paper wrap. Now if you calculate the induced L di/dt voltage appearing across 25 feet of #6 ground conductor, it comes out to just over 18 kVAC. It's more than twice that for a typical 6 ft #16 ga line cord.
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If the core is grounded and the chassis is grounded then what you describe will have no effect on the secondary output.
UL has this very well thought out...
- Glenn W9IQ
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If the core is grounded and the chassis is grounded then what you describe will have no effect on the secondary output.
UL has this very well thought out...
- Glenn W9IQ
tell us once more,,,
"you cant have leakage from pri to sec"..???