[TowerTalk] There's 'ground', and then there's 'ground'

[Frank Donovan]

Hi Jim,

Here's another one to add to your list:

Discard all forms of "braided" cable. Braid is something a girl does to her
hair.
It is not a good RF ground and it's a terrible conductor for lightning
energy.

Use braid only for DC and audio applications, its just an inductor
for RF or lightning protection applications

Here's an excellent reference from the many industry sources on this topic:
http://members.cox.net/pc-usa/station/ground5.htm

73!
Frank
W3LPL
donovanf at erols.com



----- Original Message -----
From: Jim Jarvis <jimjarvis at comcast.net>
To: <towertalk at contesting.com>
Sent: Sunday, January 16, 2005 6:56 AM
Subject: [TowerTalk] There's 'ground', and then there's 'ground'


>
> 1)  I think you'll find that all unibody constructed cars
> have serious anti-corrosion coatings applied, after welding.
> Bolted-on components are almost never electrically connected,
> unless there is a reason for it, as it represents both extra
> work, and a breach of the corrosion protection.
>     As the owner of two Passat's which had an ic706-2 installed,
> I was careful to attach to the unibody when installing the
> antenna.  Cutting holes is painful, though...as was the bodyshop
> repair when I sold the vehicles.
>
> 2)  Most contemporary transceivers do not have a single point
> ground.  There is a logic ground, an RF ground, an audio
> ground, and a chassis ground.  They exist in different areas of
> the radio, on different boards, and may be deliberately
> separated from the chassis, for purposes of noise reduction.
>     Yes, chassis ground shows up on the back panel.  And yes,
> I would expect RF ground shows up at that point, too.  But
> the logic and audio circuits reside internal.
>     I think you'll find the mic 'ground' isn't the cable shield.
> You'll also find that the 'shield' side of the mic audio connects to
> chassis ground, on the PCB, via a resistor of 10 ohms or so.
> There is usually a 'single point ground' for audio, which references
> that circuit to chassis, and prevents ground loops. The mic element
> itself is usually floating within the housing.
>
> 3) External audio processing equipment requires particular care
> not to create ground loops.  As someone observed, pro-audio folks
> put real effort into that, in their equipment.
>
> 4) One could write a volume on proper grounding and shielding in
> the mixed signal environment presented by a hamshack.  And I won't.
> At least not here.  Just one sentence:
>
> SAFETY GROUND SHOULD BE TESTED.  SPEND 10 BUCKS ON A 'PLUG CHECKER',
> AND TEST ALL OUTLETS THROUGHOUT YOUR HOME.  YOU MAY BE SURPRISED,
> PARTICULARLY IF YOUR HOME WAS BUILT IN THE 60'S, OR HAS ALUMINUM WIRING.
>
>
> n2ea
> jimjarvis at ieee.org
>
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