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Re: [RFI] Daisy chain vs Common Ground in Shack

To: rfi@contesting.com
Subject: Re: [RFI] Daisy chain vs Common Ground in Shack
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Date: Thu, 8 Jun 2017 01:58:06 -0400
List-post: <mailto:rfi@contesting.com>
I downloaded your tutorials a while back, but haven't read the one on grounding. It makes sense to me as using a common ground is installing two grounds of different lengths. One being the ground line to the common point (Not CPG) and the other being the coax shields in a Daisy Chain. For more than two items, the ground currents / paths, can be quite complex, In the shack, why not leave the coax in tact. That way the braid is protected except at the very ends. I strip the ends just far enough back to be able to crimp the connectors on. I coat any exposed braid from the jacket onto the end of the crimp-on connector. I've used RG8X and 8X-LL for some years. This allowed me to have the ground line very close to the lengths of the coax cables. I do not solder into the crimp-on. That works well in aircraft where soldered connections are prohibited due to vibration except in specific connectors.

The recent common wisdom had me working on changing that, but now I'm going back to Daisy Chaining. Thanks for bringing it up, Sean and thanks Jim for the work on grounding.

73, Roger (K8RI)

On 6/7/2017 Wednesday 9:08 PM, Jim Brown wrote:
On Wed,6/7/2017 2:55 PM, Sean Waite wrote:
Hi Jim,

I was hoping you might respond. I've read a lot of your slides and papers and have started sharing them out (along with W1HIS's article on chokes) when people ask about RFI. I saw that book, but wasn't sure if there was much in there about RF grounding that wasn't already available on your site. I may have to pick up a copy, I have a few other grounding questions that it might answer.

Everything I've read of yours makes a lot of sense, the only reason I questioned it was because it strays directly against conventional wisdom. Considering how many hams consider RFI and grounding to be some sort of magic, it's not terribly surprising that there is bad information out there. Just today I saw a thread with someone recommending that when men have to answer the "call of nature" that they go out and periodically water the ground rod to increase the soil salinity and conductivity.

Is there ever a case where the star bond is the correct one?

There is FAR more to my tutorial (and to Ward's book) than how equipment is bonded in the shack. ALL of it is important.

Is there an evidence based counter to the methods you suggest?

Not that I know of. My recommendations, as well as Ward's, are based on the total picture -- power, lightning, fire and personal safety, audio, RFI, and all sorts of other systems.

Given the thoroughness of your research and the implied backing of the ARRL through NOAX's book, it seems like daisy chaining really is the right way to go though. If I'm reading your slides correctly, you recommend stripping the braid off of the coax linking devices like the transceiver, tuner, and switches? Does this remove the need for common mode chokes on the same pieces of coax?

I don't know where you got that idea. The answer is NO. What I DO recommend is using braid stripped from coax for indoor bonding. Ward does NOT recommend that, because he feels that the copper is more likely to oxidize when exposed to air (rather than remaining inside the insulation provided by the coax jacket). When I use braid in that manner, I usually enclose it in heat shrink to minimize that possibility.

It's taken me a few readthroughs of your material to digest it, and I had everything in the shack disconnected anyway so it was a good time to redo the ground.

73, Jim

The great part about this hobby is that there is always more learning to do. Thanks for the reply,
Sean WA1TE

On Wed, Jun 7, 2017 at 5:19 PM Jim Brown <jim@audiosystemsgroup.com <mailto:jim@audiosystemsgroup.com>> wrote:


    In the new ARRL book on Grounding and Bonding, you will find me
as a contributor, you will find my methods cited, and you will find a
    link to the slides for my tutorial on the topic. The book is by Ward
    Silver, N0AX, who also edits the ARRL Handbook and Antenna Book.

The primary my recommendation differs from prior "wisdom" on the topic is that the prior wisdom ignored the issue of leakage current from the AC power system, which is how power line "buzz" couples into equipment that is interconnected with other equipment. That prior wisdom depends on the fictional concept of a "ground loop" as the cause of that buzz,
    ignores the fact that the shield of audio cables between equipment
    creates a loop with a "star ground," and is ignorant of a widespread
    cause of both buzz and RFI called "The Pin One Problem."

    My method solves all of those problems, AND satisfies grounding and
    bonding requirements for RF and lightning protection.

FACT -- the ONLY way in which a LOOP affects a system is if it is in a
    magnetic field (from a poorly shielded power transformer, or in a
    with improper AC wiring). In both of those situations, the received
noise will be pure 60 Hz (hum) not buzz (triplen harmonics of 60 Hz --
    180, 360, 540, 720, etc).

    73, Jim K9YC

    On Wed,6/7/2017 12:50 PM, Sean Waite wrote:
    > Hi everyone,
    > I was reading through a lot of K9YC's articles on grounding and
    RFI. It
    > seems that he recommends daisy chaining ground together in the
    shack, and
    > then running a single cable from the last point out to the
    common house
> ground. His reasoning seems sound (combined with choking off coax to
    > eliminate ground loops), but it goes against everything you hear
    > station grounding.
    > Is this the correct thing to do? Am I just misreading what he's
    writing? A
    > lot of RFI topics seem to be borderline magic in the ham
    community and I'm
    > trying to unravel the myth from reality.
    > Thanks and 73,
    > Sean Waite, WA1TE
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