Rick:
See interposed comments.
73
Steve Kercel
AA4AK
At 05:00 PM 4/16/2008, Rick Dettinger wrote:
If I remember correctly, the base K2 came without the ground screw.
Its been a long time. I think the ground screw came with the ATU.
*******************
I have a K2/100 with no ATU. It came with a ground screw.
*******************
The K1 doesn't have a ground screw, even with the ATU. I am confused
about the use of an RF ground with a balanced antenna.
******************
If the antenna were perfectly balanced there would be zero RF ground
current, and the RF ground impedance would not matter. In many
dipole/doubet installations the antenna is sort of balanced, and the
ground current is not exactly zero, but close enough that it causes
no noticeable problems.
*******************
One of the
advantages of a balanced antenna, verses an antenna that works with a
ground such as a vertical, is efficiency.
*********************
Do not confuse these two different kinds of grounds. The RF ground
provides a path to remote earth for those pesky unbalanced currents.
A radial system on a ground mounted vertical is an integral part of
the antenna, that just happens to be slightly under ground.
The reason that a dipole is more efficient than a ground mounted
vertical is that for the ground mounted vertical, half the antenna is
immersed in a lossy medium.
*********************
If I use an RF ground with
a balanced antenna, am I losing efficiency.
*****************
No, your balanced doublet is located some distance away from the
lossy medium. The RF ground is keeping things from going wrong (such
as smoke detectors going off in step with your keying), but has
little influence on the efficiency of your balanced antenna.
*****************
Especially if the ground
is mediocre? I don't want to put down 60 radials for my center fed
doublet.
*******************
You are correct. That would be an absolute waste.
*******************
When I used my K1 or K2 with a battery and a balanced
antenna, I had confidence that most of the power was getting
radiated. Now I have a K3-100 with an Astron 35 M power supply and I
am wondering if that has changed.
*****************
It is very unlikely anything has changed. Remember, it is extremely
poor practice to use your house ground as an RF ground, and wise
practice to put some ferrites on your power supply leads just to be
sure that no RF sneaks into hour house ground via the power supply.
If you are worried about RF getting into your house ground via the
power supply put six MFJ-701 ferrites on your power supply lead.
Simply run both the positive and negative wires through the hole in
the ferrite.
*****************
The 35 M schematic shows that the
13.8v DC terminal is connected to the 120v AC supply system ground.
This is continuous, overhead and underground, to the substation ground
mat. This doesn't sound too bad for a 160 M vertical, however, I
can't decide what effect this has on my CF doublet.
******************
The effect is that somewhere in your house ground wiring, part of it
might resonate at your operating frequency and cause you all sorts of
problems, as manifested by bizarre behavior in other household
electronics such as digital clocks and telephones.
You'll never see the substation ground; the very large inductive
reactance of the intervening wires will effectively isolate you from it.
******************
Am I sending RF
all over the neighborhood on the power lines?
**************
Unlikely, see above.
*************
Is this why a BALUN is
needed?
*****************
RF in the shack is a problem sometimes (a lot less often than the
people selling them would have you think) mitigated by baluns. A
bigger problem is that radiation from the feedline (which baluns
minimize) can perturb the radiation pattern of a directional antenna.
That is why most beam antennas include a balun in the package.
*****************
Is my antenna efficiency and pattern different than when I
used battery power?
****************
Extremely unlikely
***************
If I use the doublet and a BALUN, what do I use
the ground screw for?
*****************
Unless you have "RF in the shack" or inexplicable EMI problems
somewhere in the house, leave it alone.
*****************
It would be redundant to attach it to the AC
ground as this is done thru the 13.0v supply cable.
***************
You will be a happier person if you avoid connecting the ground screw
of the radio to your house ground.
***************
73
Rck Dettinger K7MW
On Apr 16, 2008, at 11:50 AM, Roger Stein wrote:
Yes, good RF/safety practice, to the ground post on the back of the
K2 provided for that purpose.
Roger
WA7BOC
k2 755
k3 75
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Scott McDowell
Sent: Wednesday, April 16, 2008 11:19 AM
To: elecraft@mailman.qth.net
Subject: [Elecraft] grounding K2
Hello
Has anyone ever felt the need to ground their K2, and if so, where
did you
connect the ground wire to the K2?
Thanks
Scott
N5SM
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