Grounding - a subject near and dear to my heart.
Here's what I have learned, specifically about chassis, from long
experience:
* If you want your case to act as a shield, do NOT put RF current
through it.
If you want your VFO to be stable and not shift when you touch the
case, do NOT put RF current through the case.
* If you don't want your tube radio to hum, do NOT put AC filament
current through the chassis or case!
Once upon a time, I built a linear with 4 sweep tubes in an ARC-5
cabinet. There was a hum
on the HV - no amount of filtering would cure it. It turned out that
the hum was caused by sharing a single ground return for the HV and the
filaments. IIRC those filaments pulled 10A of ac current, which caused
an ac voltage drop on the ground return. The fix was to use a separate
ground for the AC filament current. And I had to lift all the
individual filament pins off the
chassis.
Somebody gave me a Heathkit OM-1 oscilloscope. There was a hum on the
trace. It went away if you shorted the input. No amount of filtering
would cure it. The cause was - again - AC current being passed through
the chassis. And the chassis was aluminum, held together with
self-tapping sheetmetal screws. Dissimilar-metal corrosion caused
resistance which the AC current turned into AC voltage.
Whups, gotta go. Mailman just delivered my K2!
- Jerry KF6VB
On 2021-06-24 12:49, Hal Massey wrote:
Fixing a common misconception about grounding…
Grounding does not get all the devices at the same potential. It just
minimizes the potential difference among them. “Where there is metal
there is resistance and if there is any current there will be a
voltage (period).
This is one of the biggest urban myths around and the source of many
difficulties for lay folks trying to understand grounding. -BSEE and
MSEE here.
A practical application of this for hams is to keep the runs short and
low inductance too!
73
On Jun 24, 2021, at 06:27, John Oppenheimer <[email protected]> wrote:
Hi Peder,
K3s grounding post is also one of the board ground plane to enclosure
connections. See Assembly manual, Page 68, Figure 97.
John KN5L
On 6/23/21 9:58 PM, Peder Kittelson wrote:
I have been following the Pin 1 grounding discussions with interest.
I
have one of the last Elecraft K3s Transceivers built at the factory
and
love using it.
I wonder if the grounding post on the back of the K3s attaches
directly to
the case or runs to the motherboard ground?
I currently have the grounding post attached to an RF grounding strap
running as a single point ground between all my devices to keep from
voltage differences.
Should I be concerned?
73 to all,
Peder, W7RPK
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