Discussion in 'General Technical Questions and Answers' started by AI5DH, Oct 29, 2019.
You either cant read, or dont understand Ohms Law.
You are the one who does not understand and demonstrating it. If you leave the jumper in the power supply you are creating one nasty ground loop. If you understood Ohm's Law and where current should and should not go, you would understand it. It matters where you bond the circuit conductor. If you bond inside the Power Supply you are bonding the Input Ground ACEG to the Output Center Tap or Circuit Ground you call RF Ground. The Transformer electrically isolates the two sides so what happens on one side does not effect the other side.fundamentals of transformers is eliminating common mode noise.
The Output side SHOULD NOT be bonded, Astron is the only manufacture that does that. When you bond it inside the power supply you are connecting the input and output grounds together and completing a electrical circuit which now forces normal operating current on your ground circuit. You created a parallel conductors between Ground and Neg 12-Volt.You will have both DC and AC Current flowing on ground conductors where there should be none.
Your RADIO is what should be bonding Ground and 12-Volt Negative which does NOT create a LOOP, input and output are isolated and the only common bond between them is the Ground Electrode System which both your AC Service uses and your RF Ground circuit where you bond the coax as it enters the shack. If you leave the Bonding Jumper in the PS, you complete the LOOP.
Like I said if you seen the circuit drawn out you can clearly see the problem and the nasty loop it forms. So maybe this will help. You want to get rid of the bonding jumper inside the Astron Power Supply if present. Then it will be like all other DC power Supplies with the output FLOATING and not referenced to ground as seen below in first picture. Second picture is what some of you might find waiting for you. Check with an Ohm Meter between Neg and Chassis. If you see any continuity open it up and locate the short or resistor. Note disconnect all wiring from power supply before you test.
It makes a huge difference where Ground and 12 Volt Negative are bonded together. When done at the Radio as shown there is no problem as that does not put ground in parallel with negative. It is only when you bond them together in the Power Supply puts them in parallel. You joined the two grounds together, thus loosing the Isolation the Transformer gave you inside the power supply.All that hard work you did providing a Ground outside the shack for your coax and RF ground is lost and gone. You can get it back, remove the jumper if present. Might get rid of annoying common mode noise. That is what transformers do if you let them and apply them correctly.
Draw the rest of the diagram with the amplifier and all the other station accessories too.
How? Describe exactly which current paths comprise the "loop'" and why it matters?
So you think that "floating" the Astron's requlator by not strapping its 0V terminal to the Astron chassis (normally done at the terminal strip on the rear of the supply) is going to prevent RF common-mode current (that arrives at the Astron via the black wire coming from a ham rig) from flowing out the green wire in the Astron's Line cord?
You believe that a 60HZ big-iron transformer has sufficiently low capacitance between its windings to block RF common-mode current. Not even close!
Just like hundreds of industrial power supply makers, my Astron supply is totally floating on the output side. I can tie its +12V terminal to chassis (green wire) ground, or tie the 0V terminal to chassis ground, or leave the off the jumper. I did not install the jumper, however, that makes zero difference because the 0V end of the Astron supply is tied to earth ground just inches away.
But only along the black wire that runs from the Astron to the ham rig chassis. That wire is about 2ft long (in my case). At worst, that wire carries DC current to the radio, and possibly some RF common mode current if your antenna/feedline system is poorly designed.
First off, my Astron is floating, but it would not matter one iota if I installed the jumper. The two foot loop between the rig and the Astron is immaterial.
What you seem to miss completely is that it is impossible to isolate the rig/Power Supply/Tuner/computer/etc from the in-wall house wiring ground path, especially for RF currents. If you comply with the Code, then you add a second ground path from the rig/Power Supply/Tuner/computer/etc to outside ground rod(s) that are part of the antenna tower or entry panel. These two ground paths are effectively in parallel, as viewed from the chassis of the ham rig.
Now add the (Code required) conductor that cross-ties the antenna ground rod(s) to the one under the electric service entry panel. Now you have created a huge loop. You want to discuss this one? This is the one that matters!
making a big issue out of a non issue, unbelievable!!!
Incorrect and that is what you are missing. If you have the bonding jumper installed in the power supply, the radio now receives battery return current from two paths. One the normal Path you want on the Black Neg wire between PS and Radio. The second path or Loop, is through the Jumper in the Power Supply > AC Ground Wire > AC Main Breaker Panel > AC Service Ground > Ground Electrode> and returns finally via the Coax Shield to Radio. That is a Ground Loop, almost as bad as connecting a mobile radio directly to battery neg term post.
Sure lets talk about it.I showed it clearly in the drawing, you cannot have isolated Ground Electrodes like most hams interpret incorrectly including yourself from the sounds of it. Your RF Ground and AC Ground must use a common Ground Electrode System as I have clearly shown. The Transformer in the DC power supply is where the Two Grounds come in close Proximity. The Chassis is bonded to the AC Ground Conductor, and Negative is Bonded to Ground inside the Radio via the Coax connection required by code to be bonded to a common electrode when the coax enters the shack. When there is a bonding jumper inside the PS connected to the Tap of the secondary side of transformer, connects the two grounds together to form a loop and completely defeats the purpose of a clean RF Ground is now corrupted with both DC and AC Currents.
So you are right, the electrode bonding jumper connecting grounding rods is very important, and where you bond to it and how makes a huge difference. Unfortunately ham operators are not blessed to have the AC service and coaxes entering the same point and take advantage of Single Point Grounding. Thus are forced to have two appearances of Ground, one from the AC Service on one side of the house, and the shack on the other side. That forces you to use multi-point grounding. In other words two different reference points. If you are not careful you can unintentionally bond the two ground points inside the building creating a Ground Loop, A house is not a vehicle where ground and negative are the same conductor. In a vehicle is a ground plane with extremely low impedance. Not so in a building using only inductive wire. You intentionally inject DC and AC current into your ground circuit used as 0-Volt signal reference. That produces small voltage difference between points of the ground wire. Noise is any unwanted current or voltage.
Telephone and wireless operators go great length to avoid those loops as it has two nasty consequences of noise and lightning damage. The issue with Astron inconsistency is well documented anyone can look up. Personally I do not care what you do, I don't have to live next door to you and out up with it. But to fail to understand what is happening might be worth some of the members time to investigate. Really simple circuit to understand. There is no problem bonding the battery return conductor to ground or even the positive as done in telecom 48 volt systems. Every operator bonds one of the polarities to round in a battery plant. It is not done at the rectifiers where the AC circuit is contained. It is at an external location centrally at one point only so no current can flow in ground. Exact same thing you want to do. All it requires is for you to make your Astron like all other power supplies with Floating output.
I got a little problem with the drawings as shown in reply #12.
Look at the AC signal symbol.
If the lower connection is to ground or the Neutral side, you cannot ground the upper side, ( in the lower drawing) to ground and short out the AC supply source.
Nah you are just reading more into it than intended. Just a quick stencil I used to designate AC Service. No Neutral conductor is implied or shown. Just showing the Ground Electrode to AC Equipment Ground Conductor ran with L and N not shown.. The neutral if shown would be on the primary winding of the transformer with Line conductor on opposite tap.