Elecraft

RE: In Shack Radials and Ground

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JIMMY D HARRIS

RE: In Shack Radials and Ground

Don,

Maybe my thinking is too simple. But here goes. I believe that we both
have indicated that quarter wavelength can eliminate RF in the shack among
other RF problems caused by less than a perfect antenna system. I believe
that we also agree that a half wavelength does not do that. Therefore, a
half wavelength ground wire has no positive influence on RF problems. That
indicates to me that I should avoid half wavelength ground runs as they have
no positive influence on RF problems. I would guess in the world of amateur
radio there are RF problems that are not recognized. Half wavelength
grounds runs do nothing to clear up those problems. Of course, the real
solution is to have an adequate antenna system. You can bet that in
commercial systems a proper antenna system is used.

Jim, AB0UK

>From: "Don Wilhelm" <[hidden email]>
>Reply-To: <[hidden email]>
>To: "JIMMY D HARRIS" <[hidden email]>
>Subject: RE: In Shack Radials and Ground
>Date: Mon, 22 Jan 2007 23:23:09 -0500
>
>Jim,
>
>The way I read your post was that half wave lengths of wire to the ground
>rod are things to stay away from. Perhaps I mis-understood your intent -
>but you did say to stay away from ground rod runs that are a half wave or a
>multiple thereof, and that is the incorrect part.
>
>Yes, the run to the ground rod can radiate - but that is not necessarily a
>bad thing.
>
>The really best place to create the RF Ground is at the antenna (or its
>feedpoint), but not all folks are blessed with a controllable situation and
>must resort to other 'cures' like tuned counterpoise wires.
>
>I have no RF in the shack problems here, all my antennas have an effective
>RF ground as an integral part of their design (no OCF antennas here), and I
>have to suffer with a 150 foot run of coax before I get to the distribution
>point going to the antenna field. It keeps the RF out of the shack, but
>requires low loss coax runs.
>
>73,
>Don W3FPR
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]]On Behalf Of JIMMY D HARRIS
> > Sent: Monday, January 22, 2007 10:46 PM
> > To: [hidden email]; [hidden email]
> > Subject: RE: [Elecraft] In Shack Radials and Ground
> >
> >
> > Don,
> >
> > I'm not sure we disagree. I seems like we are both are agreeing to stay
> > away from quarter wavelength ground runs (wires) and use half
> > wavelength.
> > That is what I intended to say. Usually ground systems are not
> > effective RF
> > grounds. The connecting wire may be a relatively effective
> > radiator or an
> > element in tuning an antenna system.
> >
> > Jim, AB0UK
> > k2/100 S/N 4787
> >
> >
> > >From: "Don Wilhelm" <[hidden email]>
> > >Reply-To: <[hidden email]>
> > >To: "JIMMY D HARRIS" <[hidden email]>,<[hidden email]>
> > >Subject: RE: [Elecraft] In Shack Radials and Ground
> > >Date: Mon, 22 Jan 2007 22:27:08 -0500
> > >
> > >Jim,
> > >
> > >Sorry to disagree - consider what happens on a quarterwave wire:
> > It has a
> > >low impedance at one end and a high impedance at the other end. Think
> > >about
> > >what will happen if you connect the far end of a quarter wave wire to a
> > >good
> > >ground (low impedance) - the other (near) end will have a high
> > impedance at
> > >that frequency, and will not serve as an RF ground at all (in fact
>quite
> > >the
> > >opposite).
> > >
> > >A halfwave wire however can have a low impedance at each end, so
> > grounding
> > >the far end of a half wave wire will make the near end at a similarly
>low
> > >impedance.
> > >
> > >A grounded radial and a counterpoise wire are two different things -
>the
> > >counterpoise wire creates a low impedance (about 35 ohms) by nature of
> > >having the far end ungrounded, whereas a grounded (or buried)
> > radial forms
> > >a
> > >screen or reflector - yes, the counterpoise will radiate because
> > it becomes
> > >a part of the antenna system. The counterpoise controls the radiation
> > >instead of having it wander willy-nilly around the shack and other
>places
> > >where it should not be present.
> > >
> > >I do understand that this is not intuitive - we have to think in terms
>of
> > >antenna theory when dealing with RF grounds - what works fine at
> > DC and low
> > >frequency AC does not necessarily work at RF.
> > >
> > >Ground rods can be a good RF ground, but the wire connecting the
> > ground rod
> > >to the shack may not behave as expected - a 16 foot connection to the
> > >ground
> > >rod will present a high impedance to 14 MHz RF at the shack end - but
> > >should
> > >be a good RF ground for 10 meters since it is a halfwavelength away
>from
> > >the
> > >low impedance ground rod.
> > >
> > >73,
> > >Don W3FPR
> > >
> > > > -----Original Message-----
> > > >
> > > > There was mention about ground rods not being a good RF
> > ground. For the
> > > > most part I agree with that. However, the wiring to the
> > ground rod is
> > >in
> > > > fact a radial that is some part of a wavelength long. As we know
> > >quarter
> > > > wavelength radials can tune out RF. By the same token other
> > fraction
> > >of
> > > > wavelength ground runs (radials) can create RF in the shack
> > when used in
> > > > conjunction with a poorly designed antenna system. Stay away from
> > >ground
> > > > runs that are halfwave wavelength (or near) or multiples thereof of
> > > > frequencies your antenna system is designed for.
> > > >
> > > > 'nough said......
> > > >
> > > > Jim, AB0UK
> > > > K2/100 S/N 4787
> > > >
> > >--
> > >No virus found in this outgoing message.
> > >Checked by AVG Free Edition.
> > >Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date:
>1/22/2007
> > >7:30 AM
> > >
> >
> >
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> > http://mailman.qth.net/mailman/listinfo/elecraft
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date:
> > 1/22/2007 7:30 AM
> >
>--
>No virus found in this outgoing message.
>Checked by AVG Free Edition.
>Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date: 1/22/2007
>7:30 AM
>

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Ron D'Eau Claire-2

RE: RE: In Shack Radials and Ground

Perhaps you are being a bit "hard" on the poor half wavelength, Jim!
Actually, the "villain" in your scenario is the 1/4 wavelength wire, not the
1/2 wavelength wire. But they are both really good "guys" around the shack!

A wire that has RF flowing along it with show a range of impedances from
high to low, depending upon its length in wavelengths. The earth shows a low
impedance to RF. A wire connected to the earth will show an impedance of,
essentially, the resistance of the connection to the earth. At HF and using
a simple ground rod, you can expect this resistance to be several hundred
ohms, typically.

If you connect a wire to that ground and feed RF into the other end of the
wire, current will flow into the ground provided the wire is very short in
terms of wavelengths - say less than 0.1 wavelength long. That's about 40
feet on 160 meters, 20 feet on 80 meters, but only 5 feet on 20 meters and
2.5 feet on 10 meters. Those are *maximum* practical lengths for a ground
wire if you don't want the length to play a significant role in the circuit.
As the wire is made longer, you must consider the length to understand what
to expect.

With one end of the wire grounded, 1/4 wave away from the ground the
impedance, and RF voltage, will be very high. At the highest it can be under
the circumstances, actually. One quarter wave further along - 1/2 wave from
the ground connection - the impedance and the RF voltage will be the same as
it is at the ground connection! That is, whatever impedance is present at
one end of a half wave length of wire, it will be "repeated" every 1/2 wave
along the wire. So a 1/2 wave "ground wire" would be perfect! But only
where the wire is 1/2 wave long. If that were the case, say, we used a
32-foot ground wire on 20 meters, it would be an effective ground
connection, but on 40 meters the 32-foot wire is 1/4 wave long. Remember,
the impedance will be very high 1/4 wave from the ground, so now the rig
would be at a high RF voltage because of that same 'ground' wire that worked
so well on 20.

Suppose we disconnect that 32-foot wire from the ground stake when we're on
40 meters and isolate the far end. Isolating (insulating) the far end forces
it to be at a high impedance instead of the low impedance it saw connected
to the earth. If the impedance at the far end is high, then the impedance at
the rig *must* be low! Now that wire provides a rather good RF ground for
the rig!

For most of us, it's easier to arrange a 1/4 wave ground for each band that
is isolated at the far end than it is to arrange 1/2 wave length wires on
each band that are connected to the earth, but either one will work equally
well.

Remember, the impedance repeats every half wave along the line: what you
find at one end repeats at the other end. That's why both ends of a half
wave antenna are at a high-impedance point and the center, 1/4 wave from
each end, is at a low(er) impedance point.

The impedance of a 1/4 wave wire inverts. That is, if it's high at one end
(insulated) it will be low at the other end.

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of JIMMY D HARRIS
Sent: Tuesday, January 23, 2007 4:40 PM
To: [hidden email]; [hidden email]
Subject: [Elecraft] RE: In Shack Radials and Ground

Don,

Maybe my thinking is too simple. But here goes. I believe that we both
have indicated that quarter wavelength can eliminate RF in the shack among
other RF problems caused by less than a perfect antenna system. I believe
that we also agree that a half wavelength does not do that. Therefore, a
half wavelength ground wire has no positive influence on RF problems. That
indicates to me that I should avoid half wavelength ground runs as they have

no positive influence on RF problems. I would guess in the world of amateur

radio there are RF problems that are not recognized. Half wavelength
grounds runs do nothing to clear up those problems. Of course, the real
solution is to have an adequate antenna system. You can bet that in
commercial systems a proper antenna system is used.

Jim, AB0UK

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Don Wilhelm-3

RE: In Shack Radials and Ground

In reply to this post by JIMMY D HARRIS

Jim,

Actually a half wavelength run to a ground rod will produce a low impedance
at the shack end - if the ground rod is truly a good RF ground (sometimes it
is and sometimes not). So yes, it can have a positive influence, but it
will not guarantee it (the effectiveness depends on the ground
characteristics at the grounded far end) - the half wave wire only repeats
what it has on the other end.

Yes, we agree that a proper antenna system is the ideal solution, and that
quarterwave counterpoises can help (as long as the user remembers that the
quarter wave starts at the antenna tuner or transceiver - it seems that
subtle fact is often overlooked or ignored).

73,
Don W3FPR

> -----Original Message-----
> From: JIMMY D HARRIS [mailto:[hidden email]]
> Sent: Tuesday, January 23, 2007 7:40 PM
> To: [hidden email]; [hidden email]
> Subject: RE: In Shack Radials and Ground
>
>
> Don,
>
> Maybe my thinking is too simple. But here goes. I believe that we both
> have indicated that quarter wavelength can eliminate RF in the
> shack among
> other RF problems caused by less than a perfect antenna system.
> I believe
> that we also agree that a half wavelength does not do that. Therefore, a
> half wavelength ground wire has no positive influence on RF
> problems. That
> indicates to me that I should avoid half wavelength ground runs
> as they have
> no positive influence on RF problems. I would guess in the world
> of amateur
> radio there are RF problems that are not recognized. Half wavelength
> grounds runs do nothing to clear up those problems. Of course, the real
> solution is to have an adequate antenna system. You can bet that in
> commercial systems a proper antenna system is used.
>
> Jim, AB0UK
>
>
> >From: "Don Wilhelm" <[hidden email]>
> >Reply-To: <[hidden email]>
> >To: "JIMMY D HARRIS" <[hidden email]>
> >Subject: RE: In Shack Radials and Ground
> >Date: Mon, 22 Jan 2007 23:23:09 -0500
> >
> >Jim,
> >
> >The way I read your post was that half wave lengths of wire to the ground
> >rod are things to stay away from. Perhaps I mis-understood your intent -
> >but you did say to stay away from ground rod runs that are a
> half wave or a
> >multiple thereof, and that is the incorrect part.
> >
> >Yes, the run to the ground rod can radiate - but that is not
> necessarily a
> >bad thing.
> >
> >The really best place to create the RF Ground is at the antenna (or its
> >feedpoint), but not all folks are blessed with a controllable
> situation and
> >must resort to other 'cures' like tuned counterpoise wires.
> >
> >I have no RF in the shack problems here, all my antennas have an
> effective
> >RF ground as an integral part of their design (no OCF antennas
> here), and I
> >have to suffer with a 150 foot run of coax before I get to the
> distribution
> >point going to the antenna field. It keeps the RF out of the shack, but
> >requires low loss coax runs.
> >
> >73,
> >Don W3FPR
> >
> > > -----Original Message-----
> > > From: [hidden email]
> > > [mailto:[hidden email]]On Behalf Of JIMMY D HARRIS
> > > Sent: Monday, January 22, 2007 10:46 PM
> > > To: [hidden email]; [hidden email]
> > > Subject: RE: [Elecraft] In Shack Radials and Ground
> > >
> > >
> > > Don,
> > >
> > > I'm not sure we disagree. I seems like we are both are
> agreeing to stay
> > > away from quarter wavelength ground runs (wires) and use half
> > > wavelength.
> > > That is what I intended to say. Usually ground systems are not
> > > effective RF
> > > grounds. The connecting wire may be a relatively effective
> > > radiator or an
> > > element in tuning an antenna system.
> > >
> > > Jim, AB0UK
> > > k2/100 S/N 4787
> > >
> > >
> > > >From: "Don Wilhelm" <[hidden email]>
> > > >Reply-To: <[hidden email]>
> > > >To: "JIMMY D HARRIS" <[hidden email]>,<[hidden email]>
> > > >Subject: RE: [Elecraft] In Shack Radials and Ground
> > > >Date: Mon, 22 Jan 2007 22:27:08 -0500
> > > >
> > > >Jim,
> > > >
> > > >Sorry to disagree - consider what happens on a quarterwave wire:
> > > It has a
> > > >low impedance at one end and a high impedance at the other
> end. Think
> > > >about
> > > >what will happen if you connect the far end of a quarter
> wave wire to a
> > > >good
> > > >ground (low impedance) - the other (near) end will have a high
> > > impedance at
> > > >that frequency, and will not serve as an RF ground at all (in fact
> >quite
> > > >the
> > > >opposite).
> > > >
> > > >A halfwave wire however can have a low impedance at each end, so
> > > grounding
> > > >the far end of a half wave wire will make the near end at a
> similarly
> >low
> > > >impedance.
> > > >
> > > >A grounded radial and a counterpoise wire are two different things -
> >the
> > > >counterpoise wire creates a low impedance (about 35 ohms) by
> nature of
> > > >having the far end ungrounded, whereas a grounded (or buried)
> > > radial forms
> > > >a
> > > >screen or reflector - yes, the counterpoise will radiate because
> > > it becomes
> > > >a part of the antenna system. The counterpoise controls the
> radiation
> > > >instead of having it wander willy-nilly around the shack and other
> >places
> > > >where it should not be present.
> > > >
> > > >I do understand that this is not intuitive - we have to
> think in terms
> >of
> > > >antenna theory when dealing with RF grounds - what works fine at
> > > DC and low
> > > >frequency AC does not necessarily work at RF.
> > > >
> > > >Ground rods can be a good RF ground, but the wire connecting the
> > > ground rod
> > > >to the shack may not behave as expected - a 16 foot connection to the
> > > >ground
> > > >rod will present a high impedance to 14 MHz RF at the shack end - but
> > > >should
> > > >be a good RF ground for 10 meters since it is a halfwavelength away
> >from
> > > >the
> > > >low impedance ground rod.
> > > >
> > > >73,
> > > >Don W3FPR
> > > >
> > > > > -----Original Message-----
> > > > >
> > > > > There was mention about ground rods not being a good RF
> > > ground. For the
> > > > > most part I agree with that. However, the wiring to the
> > > ground rod is
> > > >in
> > > > > fact a radial that is some part of a wavelength long. As we know
> > > >quarter
> > > > > wavelength radials can tune out RF. By the same token other
> > > fraction
> > > >of
> > > > > wavelength ground runs (radials) can create RF in the shack
> > > when used in
> > > > > conjunction with a poorly designed antenna system. Stay away from
> > > >ground
> > > > > runs that are halfwave wavelength (or near) or multiples
> thereof of
> > > > > frequencies your antenna system is designed for.
> > > > >
> > > > > 'nough said......
> > > > >
> > > > > Jim, AB0UK
> > > > > K2/100 S/N 4787
> > > > >
> > > >--
> > > >No virus found in this outgoing message.
> > > >Checked by AVG Free Edition.
> > > >Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date:
> >1/22/2007
> > > >7:30 AM
> > > >
> > >
> > >
> > > _______________________________________________
> > > Elecraft mailing list
> > > Post to: [hidden email]
> > > You must be a subscriber to post to the list.
> > > Subscriber Info (Addr. Change, sub, unsub etc.):
> > > http://mailman.qth.net/mailman/listinfo/elecraft
> > >
> > > Help: http://mailman.qth.net/subscribers.htm
> > > Elecraft web page: http://www.elecraft.com
> > > --
> > > No virus found in this incoming message.
> > > Checked by AVG Free Edition.
> > > Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date:
> > > 1/22/2007 7:30 AM
> > >
> >--
> >No virus found in this outgoing message.
> >Checked by AVG Free Edition.
> >Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date: 1/22/2007
> >7:30 AM
> >
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.17.8/648 - Release Date:
> 1/23/2007 11:04 AM
>

--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.432 / Virus Database: 268.17.8/648 - Release Date: 1/23/2007
11:04 AM

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
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JIMMY D HARRIS

RE: In Shack Radials and Ground

Don,

Seems we are in basic agreement. I agree that the equipment termination
point of the ground wire can be a subtle thing. My preference would be at
the actual point of generating the RF, i.e. the transceiver usually. Here I
go again, but my way of thinking is an antenna tuner is only an impedence
matching device and has no direct relation to the length of ground wires.

Jim, AB0UK

>From: "Don Wilhelm" <[hidden email]>
>Reply-To: <[hidden email]>
>To: "Elecraft reflector" <[hidden email]>,"JIMMY D HARRIS"
><[hidden email]>
>Subject: RE: In Shack Radials and Ground
>Date: Tue, 23 Jan 2007 22:49:00 -0500
>
>Jim,
>
>Actually a half wavelength run to a ground rod will produce a low impedance
>at the shack end - if the ground rod is truly a good RF ground (sometimes
>it
>is and sometimes not). So yes, it can have a positive influence, but it
>will not guarantee it (the effectiveness depends on the ground
>characteristics at the grounded far end) - the half wave wire only repeats
>what it has on the other end.
>
>Yes, we agree that a proper antenna system is the ideal solution, and that
>quarterwave counterpoises can help (as long as the user remembers that the
>quarter wave starts at the antenna tuner or transceiver - it seems that
>subtle fact is often overlooked or ignored).
>
>73,
>Don W3FPR
>
> > -----Original Message-----
> > From: JIMMY D HARRIS [mailto:[hidden email]]
> > Sent: Tuesday, January 23, 2007 7:40 PM
> > To: [hidden email]; [hidden email]
> > Subject: RE: In Shack Radials and Ground
> >
> >
> > Don,
> >
> > Maybe my thinking is too simple. But here goes. I believe that we both
> > have indicated that quarter wavelength can eliminate RF in the
> > shack among
> > other RF problems caused by less than a perfect antenna system.
> > I believe
> > that we also agree that a half wavelength does not do that. Therefore,
>a
> > half wavelength ground wire has no positive influence on RF
> > problems. That
> > indicates to me that I should avoid half wavelength ground runs
> > as they have
> > no positive influence on RF problems. I would guess in the world
> > of amateur
> > radio there are RF problems that are not recognized. Half wavelength
> > grounds runs do nothing to clear up those problems. Of course, the real
> > solution is to have an adequate antenna system. You can bet that in
> > commercial systems a proper antenna system is used.
> >
> > Jim, AB0UK
> >
> >
> > >From: "Don Wilhelm" <[hidden email]>
> > >Reply-To: <[hidden email]>
> > >To: "JIMMY D HARRIS" <[hidden email]>
> > >Subject: RE: In Shack Radials and Ground
> > >Date: Mon, 22 Jan 2007 23:23:09 -0500
> > >
> > >Jim,
> > >
> > >The way I read your post was that half wave lengths of wire to the
>ground
> > >rod are things to stay away from. Perhaps I mis-understood your intent
>-
> > >but you did say to stay away from ground rod runs that are a
> > half wave or a
> > >multiple thereof, and that is the incorrect part.
> > >
> > >Yes, the run to the ground rod can radiate - but that is not
> > necessarily a
> > >bad thing.
> > >
> > >The really best place to create the RF Ground is at the antenna (or its
> > >feedpoint), but not all folks are blessed with a controllable
> > situation and
> > >must resort to other 'cures' like tuned counterpoise wires.
> > >
> > >I have no RF in the shack problems here, all my antennas have an
> > effective
> > >RF ground as an integral part of their design (no OCF antennas
> > here), and I
> > >have to suffer with a 150 foot run of coax before I get to the
> > distribution
> > >point going to the antenna field. It keeps the RF out of the shack,
>but
> > >requires low loss coax runs.
> > >
> > >73,
> > >Don W3FPR
> > >
> > > > -----Original Message-----
> > > > From: [hidden email]
> > > > [mailto:[hidden email]]On Behalf Of JIMMY D HARRIS
> > > > Sent: Monday, January 22, 2007 10:46 PM
> > > > To: [hidden email]; [hidden email]
> > > > Subject: RE: [Elecraft] In Shack Radials and Ground
> > > >
> > > >
> > > > Don,
> > > >
> > > > I'm not sure we disagree. I seems like we are both are
> > agreeing to stay
> > > > away from quarter wavelength ground runs (wires) and use half
> > > > wavelength.
> > > > That is what I intended to say. Usually ground systems are not
> > > > effective RF
> > > > grounds. The connecting wire may be a relatively effective
> > > > radiator or an
> > > > element in tuning an antenna system.
> > > >
> > > > Jim, AB0UK
> > > > k2/100 S/N 4787
> > > >
> > > >
> > > > >From: "Don Wilhelm" <[hidden email]>
> > > > >Reply-To: <[hidden email]>
> > > > >To: "JIMMY D HARRIS" <[hidden email]>,<[hidden email]>
> > > > >Subject: RE: [Elecraft] In Shack Radials and Ground
> > > > >Date: Mon, 22 Jan 2007 22:27:08 -0500
> > > > >
> > > > >Jim,
> > > > >
> > > > >Sorry to disagree - consider what happens on a quarterwave wire:
> > > > It has a
> > > > >low impedance at one end and a high impedance at the other
> > end. Think
> > > > >about
> > > > >what will happen if you connect the far end of a quarter
> > wave wire to a
> > > > >good
> > > > >ground (low impedance) - the other (near) end will have a high
> > > > impedance at
> > > > >that frequency, and will not serve as an RF ground at all (in fact
> > >quite
> > > > >the
> > > > >opposite).
> > > > >
> > > > >A halfwave wire however can have a low impedance at each end, so
> > > > grounding
> > > > >the far end of a half wave wire will make the near end at a
> > similarly
> > >low
> > > > >impedance.
> > > > >
> > > > >A grounded radial and a counterpoise wire are two different things
>-
> > >the
> > > > >counterpoise wire creates a low impedance (about 35 ohms) by
> > nature of
> > > > >having the far end ungrounded, whereas a grounded (or buried)
> > > > radial forms
> > > > >a
> > > > >screen or reflector - yes, the counterpoise will radiate because
> > > > it becomes
> > > > >a part of the antenna system. The counterpoise controls the
> > radiation
> > > > >instead of having it wander willy-nilly around the shack and other
> > >places
> > > > >where it should not be present.
> > > > >
> > > > >I do understand that this is not intuitive - we have to
> > think in terms
> > >of
> > > > >antenna theory when dealing with RF grounds - what works fine at
> > > > DC and low
> > > > >frequency AC does not necessarily work at RF.
> > > > >
> > > > >Ground rods can be a good RF ground, but the wire connecting the
> > > > ground rod
> > > > >to the shack may not behave as expected - a 16 foot connection to
>the
> > > > >ground
> > > > >rod will present a high impedance to 14 MHz RF at the shack end -
>but
> > > > >should
> > > > >be a good RF ground for 10 meters since it is a halfwavelength away
> > >from
> > > > >the
> > > > >low impedance ground rod.
> > > > >
> > > > >73,
> > > > >Don W3FPR
> > > > >
> > > > > > -----Original Message-----
> > > > > >
> > > > > > There was mention about ground rods not being a good RF
> > > > ground. For the
> > > > > > most part I agree with that. However, the wiring to the
> > > > ground rod is
> > > > >in
> > > > > > fact a radial that is some part of a wavelength long. As we
>know
> > > > >quarter
> > > > > > wavelength radials can tune out RF. By the same token other
> > > > fraction
> > > > >of
> > > > > > wavelength ground runs (radials) can create RF in the shack
> > > > when used in
> > > > > > conjunction with a poorly designed antenna system. Stay away
>from
> > > > >ground
> > > > > > runs that are halfwave wavelength (or near) or multiples
> > thereof of
> > > > > > frequencies your antenna system is designed for.
> > > > > >
> > > > > > 'nough said......
> > > > > >
> > > > > > Jim, AB0UK
> > > > > > K2/100 S/N 4787
> > > > > >
> > > > >--
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> > > > >Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date:
> > >1/22/2007
> > > > >7:30 AM
> > > > >
> > > >
> > > >
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>1/22/2007
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> >
>--
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>11:04 AM
>

Don Wilhelm-3

RE: RE: In Shack Radials and Ground

Jim,

In an ideal world, the tuner is only an impedance transformation device -
but the name of this RF Ground game is the elimination of common mode
current from the transmission line and equipment in the shack so that all
devices, including the tuner can work as expected with no extra RF floating
around.

The RF ground needs to be associated with the antenna system, thus connect
to the tuner (or whatever is to be connected to the antenna system). The
transceiver does not need an RF Ground.

Most modern transceivers are designed to drive a 50 ohm coaxial load. Plus,
the transceiver itself will not put any common mode current on the coaxial
line - all its energy is inside the coax as a differential output between
the coax center conductor and the inside of the shield - there will be no RF
energy on the transceiver enclosure or the coax shield that is being
generated by the transceiver. So the bottom line is to keep the common mode
currents coming in from the antenna system from being coupled back onto the
coax shield between the tuner and transceiver.

The real proper place for the RF ground is at the antenna, so no common mode
energy is ever coupled back to the shack, but this is not a perfect world,
and in many cases, the RF ground must be placed at the shack end. If there
is a tuner, the RF ground should be placed at the tuner output - EXCEPT, if
chokes or baluns are placed between the tuner and the antenna, then the RF
ground should be placed at the choke or balun. In other words, looking from
the antenna toward the shack, place the RF Ground prior to any device that
attempts to eliminate common mode current from the remaining coaxial cables
and equipment chassis. There must be a path for that common mode current to
flow, and the RF Ground is a proper place for it to flow - it will find a
path if one is not provided, but the one found may not be desirable.

73,
Don W3FPR

> -----Original Message-----
>
> Don,
>
> Seems we are in basic agreement. I agree that the equipment termination
> point of the ground wire can be a subtle thing. My preference
> would be at
> the actual point of generating the RF, i.e. the transceiver
> usually. Here I
> go again, but my way of thinking is an antenna tuner is only an impedence
> matching device and has no direct relation to the length of ground wires.
>
> Jim, AB0UK
>