[RFI] DigiKeyer II

Dale svetanoff at earthlink.net
Thu Dec 19 18:22:23 EST 2013


Good question.  Answer: it depends.  

If you can connect a DMM or VOM between the shack ground bus and the ground rod outside, TURN OFF ALL POWER to the connected equipment and take a reading.  If you get very close to ZERO ohms (as in 1 ohm or so), the braid is probably OK.  However, if it looks corroded, replace it even if it ohms out as "good".  As Eddie, K0IL, noted, corroded braids can lead  to lots of tiny self-rectifying connections that can spew harmonics all over the place.  

You should also be aware that there are special test instruments made just for the purpose of testing ground and grounding connections.  They are usually referred to as "Earth Ground Resistance Testers" or some such similar name.  They are a specialized ohmmeter, in that they test using AC (not DC) and they generate some "real" current (usually several amperes) to force thru the grounding path.  This is the tester to use if you want to find out how much actual earth resistance exists between your station ground rod and the ground on your house AC power panel (assuming that the AC power ground has not been bonded to your station grounding system).  Again, you have to turn off AC power so that stray currents in the house power system do not affect the reading and you then read between the ground rod and your power ground.  These meters are also used with auxiliary grounding probes to determine soil conductivity and related measurements.

73, Dale

-----Original Message-----
>From: Peter Laws <plaws at plaws.net>
>Sent: Dec 19, 2013 2:55 PM
>To: "rfi at contesting.com" <rfi at contesting.com>
>Subject: Re: [RFI] DigiKeyer II
>On Thu, Dec 19, 2013 at 2:42 PM, Dale <svetanoff at earthlink.net> wrote:
>> You mention use of braid to the ground rod outside.  That's OK if the braid is encased within some sort of weather-proof cover, such as shrink tubing.  The problem with braid that is exposed to the elements is that it corrodes, and unless you inspect it frequently (at least once per year), you could end with no connection (or a very high resistance one).  If you do not have covered braid available, replace that run of braid with insulated stranded (the kind used for electrical work - not welding cable) copper wire.  No. 6 or No. 4 AWG will be fine.
>Fair enough.  I'll add that to the to-do list ... because I haven't
>messed with it since I put it in ~7 years ago.
>Hey, so how would one measure whether or not a ground is good?  Is
>that doable?  With a regular multimeter?
>Peter Laws | N5UWY | plaws plaws net | Travel by Train!
>RFI mailing list
>RFI at contesting.com

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