On 5/10/2013 1:17 PM, Jim Brown wrote:
On 5/10/2013 9:29 AM, George Dubovsky wrote:
3. "RF ground system" is a perfectly good term and is accepted and
understood in the rf design community.
I strongly disagree -- it has led to HUGE misunderstandings and TERRIBLE
errors in the construction of equipment that are so widespread that they
are accepted as the only way to do it, and are a major cause of hum,
buzz, and RFI. It causes people to think that ground rods are a desired
part of an antenna system.
It's like hearing a ham say he's using a 150 deep well for a fround on
his vertical and really gets out. He has no idea that the antenna
probably sees no more than a foot or two of that well.
I believe in Europe the terms "Earth" and ground are well defined.
When we look at today's rigs it is very common to see shields connected
to PC boards when they should go to a real ground/earth not a circuit
ground. Icom even uses the shield for the mik as a control return that
if grounded will lose functionality.it will actually pick up enough AC
in my den to key the vox.
It also causes people to think that separate grounds for RF, audio, and
power are somehow a good idea. And it causes people to view a connection
to earth as a cure for all ills, including, but not limited to, RFI,
TVI, and antenna performance. And that the earth is somehow a sink into
which noise and RFI can be poured.
Don't I wish.<:-))
What REALLY matters to the RF design community is keeping track of where
the current flows, and that means ALL the current -- DC, audio, and RF
-- on every cable. Henry Ott says this quite poetically when he speaks
of "the half of the schematic hidden behind the ground symbol." Is the
reference PCB layer under microstrip complete, or is it broken for a
extra trace that wouldn't fit (or was forgotten) on the main layer? Does
the cable shield go directly to the shielding enclosure, or does it go
to a circuit trace to create a "Pin One Problem" YOU may not have made
these errors, but the vast majority of equipment is built with these
faults.
I've not seen the new Kenwood, but the Icoms do this as I mentioned
above. I haven't found the schematic for the FTDX5000 yet
73
Roger (K8RI)
If you re-read my post, you will see that I wasn't objecting to the
connection of the common point of a radial system to a ground rod.
73, Jim K9YC
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