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Grounding question on remote tuner

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Randy Cook-2

Grounding question on remote tuner

Weather damage repair time. I am rewiring my ~84 foot inverted L antenna system, Up a SpiderPole about 31 feet, out about 53 additional feet. Still tuning length.
I have mounted a remote MFJ tuner on a post about 3 feet from the antenna base. Antenna wire goes down the pole, connects to 4:1 Unun input lug, then goes via coax to tuner. Out of the tuner to a long coax run to my shack. Choke at the rig end of the coax run.
Radials mount on ground connection lug on the Unun.
I was a bit confused with the tuner wiring. The manual says to connect ground lug to the ‘system ground’, I assume that means the radial collection point. But, isn’t the tuner already connected to the ‘system ground’ via the coax shield? Is it necessary to run another wire from the tuner ground to the radial connection ground?

Thanks in advance for any advice.

73
Randy - K6CRC

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Barry K3NDM

Re: Grounding question on remote tuner

Randy,
I would definitely ground the remote tuner. I infer that you are
feeding the inverted L at the base and working it against ground. In
this circumstance, the antenna tuner is a part of the system and should
be grounded to the remainder of your ground system. Think of it this
way. Your tuner in in series between the inverted L and your ground
which represents the other half of your antenna system.

I'm not sure I would use an 4:1 unum as you are. I would put an
isolator between the tuner and the run to your shack. You will be
feeding the antenna through the tuner which needs to see both the ground
half of your antenna system and the antenna itself. The unum will
attempt to isolate parts of the system that should not be isolated.
However, you do need to keep RF off the transmission line going to the
shack and an isolator will accomplish this.

73,
Barry
K3NDM

------ Original Message ------
From: "Randy Cook" <[hidden email]>
To: [hidden email]
Sent: 4/5/2017 2:19:30 PM
Subject: [Elecraft] Grounding question on remote tuner

>Weather damage repair time. I am rewiring my ~84 foot inverted L
>antenna system, Up a SpiderPole about 31 feet, out about 53 additional
>feet. Still tuning length.
>I have mounted a remote MFJ tuner on a post about 3 feet from the
>antenna base. Antenna wire goes down the pole, connects to 4:1 Unun
>input lug, then goes via coax to tuner. Out of the tuner to a long coax
>run to my shack. Choke at the rig end of the coax run.
>Radials mount on ground connection lug on the Unun.
>I was a bit confused with the tuner wiring. The manual says to connect
>ground lug to the ‘system ground’, I assume that means the radial
>collection point. But, isn’t the tuner already connected to the ‘system
>ground’ via the coax shield? Is it necessary to run another wire from
>the tuner ground to the radial connection ground?
>
>Thanks in advance for any advice.
>
>73
>Randy - K6CRC
>
>
>
>
>
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k6dgw

Re: Grounding question on remote tuner

In reply to this post by Randy Cook-2

Assuming I understand your configuration and that when you say "isn’t
the tuner already connected to the ‘system ground’ via the coax shield?"
you mean the 3 ft of coax from the 4:1 transformer to the tuner:

The 3 ft path from the transformer ["unun"] to the tuner is handled by
the coax. The "tuner ground" would then become a safety ground ...
which is a very large, long, and tedious subject involving the NEC,
UFER's, large conductors, a lot of work, and possibly $$.

If "long coax to the shack" means the tuner is a long way from the shack
and your service entrance, I'd drive a ground rod at the tuner and
connect the lug to that. I'm probably wrong, but that's what I'd do.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 4/5/2017 11:19 AM, Randy Cook wrote:

> Weather damage repair time. I am rewiring my ~84 foot inverted L antenna system, Up a SpiderPole about 31 feet, out about 53 additional feet. Still tuning length.
> I have mounted a remote MFJ tuner on a post about 3 feet from the antenna base. Antenna wire goes down the pole, connects to 4:1 Unun input lug, then goes via coax to tuner. Out of the tuner to a long coax run to my shack. Choke at the rig end of the coax run.
> Radials mount on ground connection lug on the Unun.
> I was a bit confused with the tuner wiring. The manual says to connect ground lug to the ‘system ground’, I assume that means the radial collection point. But, isn’t the tuner already connected to the ‘system ground’ via the coax shield? Is it necessary to run another wire from the tuner ground to the radial connection ground?
>
> Thanks in advance for any advice.
>
> 73
> Randy - K6CRC
>

Don Wilhelm

Re: Grounding question on remote tuner

In reply to this post by Randy Cook-2

Randy,

The RF does not need a ground other than the obvious connection to your
radial connection point.

I would dispense with the "unun" and connect the antenna wire and radial
connection point directly to your tuner. A few feet of wire from your
tuner to those points will not make a big difference since your antenna
is not resonant.

The only reason I can think of to connect your tuner to "station ground"
is for lightning protection. While that is a consideration not to be
taken lightly, be aware that *all* ground rods must be connected by
heavy wire to the utility entrance ground rod. That heavy wire is #6
bare copper but #4 is preferred. That connection is for AC mains
safety, not for lightning protection or anything having to do with RF.

The concept for lightning protection is to spread as much of the charge
as possible over as large an area of the earth as is possible. Your
radial system will help do that *if* the wires are large enough to
withstand the surge without evaporating the copper.

73,
Don W3FPR

On 4/5/2017 2:19 PM, Randy Cook wrote:
> Weather damage repair time. I am rewiring my ~84 foot inverted L antenna system, Up a SpiderPole about 31 feet, out about 53 additional feet. Still tuning length.
> I have mounted a remote MFJ tuner on a post about 3 feet from the antenna base. Antenna wire goes down the pole, connects to 4:1 Unun input lug, then goes via coax to tuner. Out of the tuner to a long coax run to my shack. Choke at the rig end of the coax run.
> Radials mount on ground connection lug on the Unun.
> I was a bit confused with the tuner wiring. The manual says to connect ground lug to the ‘system ground’, I assume that means the radial collection point. But, isn’t the tuner already connected to the ‘system ground’ via the coax shield? Is it necessary to run another wire from the tuner ground to the radial connection ground?
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k6dgw

Re: Grounding question on remote tuner

I believe Don is essentially correct regarding bonding all earth
terminals directly to the service entrance ground connection. This,
however, can be difficult and very costly in the case of an earth
terminal far from the service entrance. I believe that the NEC has
provisions for such cases [e.g. a barn or other outbuilding located some
distance from the service entrance].

200 ft sticks in my mind, but don't bet your paycheck on that.
Unfortunately, my copy of the NEC is located in an unknown box out of
many in the garage after our move. It is at least a decade old. It
will likely remain there.

Possibly someone who actually knows can enlighten the rest of us. It
*IS* a real issue.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 4/5/2017 2:05 PM, Don Wilhelm wrote:

> Randy,
>
> The RF does not need a ground other than the obvious connection to
> your radial connection point.
>
> I would dispense with the "unun" and connect the antenna wire and
> radial connection point directly to your tuner. A few feet of wire
> from your tuner to those points will not make a big difference since
> your antenna is not resonant.
>
> The only reason I can think of to connect your tuner to "station
> ground" is for lightning protection. While that is a consideration
> not to be taken lightly, be aware that *all* ground rods must be
> connected by heavy wire to the utility entrance ground rod. That
> heavy wire is #6 bare copper but #4 is preferred. That connection is
> for AC mains safety, not for lightning protection or anything having
> to do with RF.
>
> The concept for lightning protection is to spread as much of the
> charge as possible over as large an area of the earth as is possible.
> Your radial system will help do that *if* the wires are large enough
> to withstand the surge without evaporating the copper.
>
> 73,
> Don W3FPR
>
> On 4/5/2017 2:19 PM, Randy Cook wrote:
>> Weather damage repair time. I am rewiring my ~84 foot inverted L
>> antenna system, Up a SpiderPole about 31 feet, out about 53
>> additional feet. Still tuning length.
>> I have mounted a remote MFJ tuner on a post about 3 feet from the
>> antenna base. Antenna wire goes down the pole, connects to 4:1 Unun
>> input lug, then goes via coax to tuner. Out of the tuner to a long
>> coax run to my shack. Choke at the rig end of the coax run.
>> Radials mount on ground connection lug on the Unun.
>> I was a bit confused with the tuner wiring. The manual says to
>> connect ground lug to the ‘system ground’, I assume that means the
>> radial collection point. But, isn’t the tuner already connected to
>> the ‘system ground’ via the coax shield? Is it necessary to run
>> another wire from the tuner ground to the radial connection ground?
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Jim Brown-10

Re: Grounding question on remote tuner

In reply to this post by Randy Cook-2

On Wed,4/5/2017 11:19 AM, Randy Cook wrote:
> I have mounted a remote MFJ tuner on a post about 3 feet from the antenna base. Antenna wire goes down the pole, connects to 4:1 Unun input lug, then goes via coax to tuner. Out of the tuner to a long coax run to my shack.

HOW long is important here. Lightning is not a DC event, it is an RF
event, and any wire, whether coax or a #4 looks to lightning like a big
inductor. Rule of thumb is that if the distance from the tower to the
shack approaches 100 ft (some authorities say more than 60 ft), there's
no need to bond the tower base to the house. You don't have a tower, but
the physics is the same. At lightning frequencies, the impedance to
earth at the antenna is probably a lot less than the inductive reactance
of a bonding conductor back to the shack, and the choke adds more
inductance.

I would drive a couple of 8 ft rods at the antenna base spaced at least
a rod length apart, bond them together, and to the radials.
the sole function of the rods is lightning protection. So is bonding.
The radials are not a substitute for rods, but they will reduce the
impedance to earth by virtue of their capacitance to earth, which will
be in parallel with the rods. The choke should be at the tuner on the
coax going to the shack. There should also be a lightning arrestor there.

> Choke at the rig end of the coax run.

It's OK to have a choke at the rig end, but it's FAR more important to
have one at the antenna.

> Radials mount on ground connection lug on the Unun.

It's not clear to me whether your unun is step up or step down, and you
didn't say what band(s) you want this antenna to cover, but I would put
the radials on the antenna side of that unun.

> I was a bit confused with the tuner wiring. The manual says to connect ground lug to the ‘system ground’, I assume that means the radial collection point.

The instructions assume the tuner is in the shack.

73, Jim K9YC

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