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Author Topic: grounding question  (Read 775 times)

W9IQ

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Re: grounding question
« Reply #15 on: June 12, 2020, 04:51:44 PM »

The balun near the shack helps keep local RFI off of the shield and helps to keep any residual transmit common mode current out of the shack.

- 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.

N6MST

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Re: grounding question
« Reply #16 on: June 13, 2020, 12:36:37 AM »

The balun near the shack helps keep local RFI off of the shield and helps to keep any residual transmit common mode current out of the shack.

- Glenn W9IQ

Ok, so where is the balanced line at that location?
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W9IQ

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Re: grounding question
« Reply #17 on: June 13, 2020, 03:50:46 AM »

The objective is to have the current balanced. Since the balun thwarts current flowing on the outside of the shield, the remaining current on/in the coax is balanced. This prevents the coaxial transmission line from acting as an antenna - i.e. radiating or receiving.

A balun placed near the shack end also effectively removes the RF ground reference for the exterior of the coaxial shield. Ground in this case being relative to the chassis/earth connection of the coaxial shield.

- 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.

N6MST

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Re: grounding question
« Reply #18 on: June 13, 2020, 06:19:23 AM »

The objective is to have the current balanced. Since the balun thwarts current flowing on the outside of the shield, the remaining current on/in the coax is balanced. This prevents the coaxial transmission line from acting as an antenna - i.e. radiating or receiving.

A balun placed near the shack end also effectively removes the RF ground reference for the exterior of the coaxial shield. Ground in this case being relative to the chassis/earth connection of the coaxial shield.

- Glenn W9IQ

Obviously you don't understand the question. Oh well.
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W9IQ

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Re: grounding question
« Reply #19 on: June 13, 2020, 06:51:32 AM »

Feel free to restate the question. Perhaps better yet, explain your reason for the question since there obviously is not a balanced feed line in the mix.

- 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.

N6MST

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Re: grounding question
« Reply #20 on: June 13, 2020, 07:51:48 AM »

...explain your reason for the question since there obviously is not a balanced feed line in the mix.

You suggest a balun at the shack. BAL-UN. Balanced to unbalanced. There is no balanced line at the shack by this time as you already took care of that at the feedpoint. You do not use a balun at the shack. A choke, sure. Not a balun.
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W9IQ

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Re: grounding question
« Reply #21 on: June 13, 2020, 08:03:12 AM »

A choke and a current balun perform exactly the same function. They cannot be distinguished in a black box test. So don't get hung up on the acronym. Look at the function that it performs.

As an aside, the only construction difference between what many people consider to be a 1:1 current balun and a choke is simply the type of transmission line used. The 1:1 current balun is generally shown with a parallel style transmission line while the choke is shown with a coaxial transmission line. The mechanism of its function is exactly the same. The terminology is also interchangeable. There is no difference.

- 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.

N6MST

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Re: grounding question
« Reply #22 on: June 13, 2020, 08:48:48 AM »

I know nobody really cares but "balun" isn't an acronym, it's a portmanteau. But I digress...

And I disagree with your statement that the words are interchangeable. "Balun" specifically indicates there is a balanced line on one side and an unbalanced on the other. Regardless of similar function, suggesting someone use a balun when there is no balanced line to work with is misleading at best, disingenuous at worst. I don't think you meant to mislead anyone but I have seen it happen with my own eyes more than once and people (always new hams who don't know better) wasted time and money buying or building baluns that were ultimately NOT what they really needed.

The terminology is not interchangeable, even though it seems the majority of hams think it is. Most of them are lucky enough to know what is really going on, but an outsider or a new ham may not and we owe it to them to use the right words. RF is confusing enough without knowledgeable folks mucking it up even further.
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W9IQ

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Re: grounding question
« Reply #23 on: June 13, 2020, 09:41:10 AM »

If a current balun and a choking balun are not the same, then please make your case for how they function differently - not how they are applied. Or are you making a case to use different terminology for the same device depending upon application?

There was nothing disingenuous about my statements - solid engineering facts. But I am willing to hear your case.

- 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.

AA4PB

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Re: grounding question
« Reply #24 on: June 13, 2020, 11:14:59 AM »

It seems to me that if a device is balanced on one side and unbalanced on the other then it's a BALUN. If it's unbalance on both sides then it's an UNUN or a CHOKE. The term BALUN means "balanced to unbalanced".

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Bob  AA4PB
Garrisonville, VA

W9IQ

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Re: grounding question
« Reply #25 on: June 13, 2020, 11:23:53 AM »

It seems to me that if a device is balanced on one side and unbalanced on the other then it's a BALUN. If it's unbalance on both sides then it's an UNUN or a CHOKE. The term BALUN means "balanced to unbalanced".

But is there a functional difference between the two devices - no! So you wish to use different terms for the same device depending upon how it is applied? Should the manufacturers list it twice in their catalog under different names and part numbers?

An unun and choke are two different devices with different behaviors. They are not interchangeable.

- Glenn W9IQ
« Last Edit: June 13, 2020, 11:26:55 AM by 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.

KD2HPQ

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Re: grounding question
« Reply #26 on: June 16, 2020, 10:40:41 AM »

Thanks for all the suggestions. To answer an early responder, I have an antenna ground. I'm looking for (I guess) an RF ground. Something to connect to the terminals on the back of all my equipment designated as "GND". Sorry if that is the incorrect name.
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KD2HPQ

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Re: grounding question
« Reply #27 on: June 16, 2020, 10:52:32 AM »

I have the grounding/bonding book. This is a very important topic obviously, but the average (or in my case below average) ham should not have to read an entire book to employ best practices for those little pieces of metal protruding from the backs of equipment with "GND" above or below in big lettering. Seems like a problem that should have a fairly easy answer. Of course becoming a "grounding and bonding expert" does and should require study. I promise I'll get to it. Right now I have an IC7300, 60 feet of coax leading to a "matchbox" type un-un that is grounded via a rod right under the tree in which it is located, with 117' of wire coming out the end.

I currently have a 23-24-foot length of heavy gauge wire running from the 7300 to a copper rod no more than one foot deep, two stories below. I cannot get the rod any deeper. Hence my interest in exploiting the presence of an exposed cable which I know terminates deep underground.

Sorry if I didn't explain myself correctly the first time.
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KC0W

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Re: grounding question
« Reply #28 on: June 29, 2020, 03:03:02 AM »


There was nothing disingenuous about my statements - solid engineering facts. But I am willing to hear your case.

- Glenn W9IQ

 A true gentleman, first class..........Unfortunately this kind of mild mannered & open minded response is a rarity on eHam.

                                                             Tom KH0/KC0W   
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K6BRN

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Re: grounding question
« Reply #29 on: June 29, 2020, 07:01:27 AM »

Michael (N6MST):

Glenn is correct and is a very competent engineer and ham.  I've never known him to mislead anyone on the forums or claim technical supremacy at the expense of someone else (as some do).  He does have an obsession with spelling and capitalization though.  :)

Regarding grounding and bonding...  This is more of a religious topic on the forums and I hesitate to start another humorous dispute on the issue.  Needless to say, Angelo's (KD2HPQ) suggestion to pick up the ARRL handbook on bonding and grounding is a good one.

With regard to your situation, a primary goal should be to "keep RF out of the shack", so that it does not interfere with computer interfaces, analog (mic) interfaces, radio operation, etc.  Generally, an RF choke or Balun (both common terms for the same thing, just as Glenn mentioned) on the coax before entrance to your home and operating area OR a coax grounding block attached directly to a solid grounding rod system, just before entrance to your home, will help control this. 

In the latter case, you will have established an alternate ground path (other than the AC plug SAFETY ground) for your radio, via the coax shield, to EARTH ground, which under some circumstances can lead to small currents (noise) through the radio from the house safety ground.  The best way to handle this is to have a dedicated power/ground line run directly from your entrance panel to the shack, and then use a ground bar as a single-point ground for all equipment in the shack, with the power panel ground and shack ground tied together per code OUTSIDE your home.  The  "ground loop" this creates is short and folds back on itself without any external noise-makers in the circuit, hence works well.  This is more complex and expensive than a Balun and is what CAN be used in a high man-made noise (inverter driven ashers, A/C, solar installs, etc.) - it's what I do at QTH#1 and has solved all sorts or noise and RF problems.

But a Choke/Balun is a good solution, too, and creates no complex grounding issues to think through.  I use this approach as a 2nd QTH. 

So - reading the ARRL grounding and bonding book is very worthwhile.  Note that in a grounding system, high frequency components will see higher impedances, causing the EARTH ground part of the function to work poorly, very rapidly as frequency rises and distance to "EARTH" grows.  For that reason, your shack ground should be viewed mainly as a LOCAL ground reference at RF and as a noise free safety ground at AC.  AC noise, even low frequency noise, can be so large on some home safety grounds that it will generate higher frequency products in your radio and even by a process called PIMs, within the house wiring.  Inverter driven appliances and solar installations are both chief drivers of this noise.

That said, get the book, read it, think about it and then develop your own concept for a station ground.  If you really need it.  A balun works well.

Best Regards,

Brian - K6BRN

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