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KAT500 Antenna Grounding

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David Ahrendts

KAT500 Antenna Grounding

I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active? Do I need to mount an external antenna switch to ground the unused antenna, which is not desirable because of the KAT500’s ability to memorize frequencies and tuner corrections per antenna?

David A., KC0XT, Los Angeles

David Ahrendts [hidden email]

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Jack Brindle-2

Re: KAT500 Antenna Grounding

I can answer that. The KPA500 does not ground unselected antennas. Nor does it ground selected antennas. ;-)
(OK, it’s Friday. Even we Elecrafters let our hair down on Friday…)

- Jack Brindle, W6FB

> On May 8, 2015, at 5:18 PM, David Ahrendts <[hidden email]> wrote:
>
> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active? Do I need to mount an external antenna switch to ground the unused antenna, which is not desirable because of the KAT500’s ability to memorize frequencies and tuner corrections per antenna?
>
> David A., KC0XT, Los Angeles
>
>
>
> David Ahrendts [hidden email]
>
>
>
>
> ______________________________________________________________
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Cliff Frescura

Re: KAT500 Antenna Grounding

I'm in a similar situation. Love the KAT500 (especially with the KPA500 and Kenwood TS-940). Already have an Ameritron remote antenna switch, so not using the switching on the KAT500 (except for a switching in a dummy load).

The solution I've come up with is to have an Arduino monitor the radio frequency/band data and have it switch the antenna. However, I doubt that the Ameritron switch grounds the unused ports. The DX Engineering remote switches appear to have this as an option.

73,

Cliff K3LL/6

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Jack Brindle
Sent: Friday, May 08, 2015 5:42 PM
To: David Ahrendts
Cc: Elecraft List
Subject: Re: [Elecraft] KAT500 Antenna Grounding

I can answer that. The KPA500 does not ground unselected antennas. Nor does it ground selected antennas. ;-) (OK, it’s Friday. Even we Elecrafters let our hair down on Friday…)

- Jack Brindle, W6FB

> On May 8, 2015, at 5:18 PM, David Ahrendts <[hidden email]> wrote:
>
> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active? Do I need to mount an external antenna switch to ground the unused antenna, which is not desirable because of the KAT500’s ability to memorize frequencies and tuner corrections per antenna?
>
> David A., KC0XT, Los Angeles
>
>
>
> David Ahrendts [hidden email]
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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Jim Brown-10

Re: KAT500 Antenna Grounding

In reply to this post by David Ahrendts

On Fri,5/8/2015 5:18 PM, David Ahrendts wrote:
> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active?

Several MAJOR points of confusion here. First, what do you mean by
"grounding?" Do you mean shorting the coax? Second, because any
transmission line transforms the impedance by an amount determined
entirely by its electrical length, shorting the coax in the shack will
only short the antenna if the line is some multiple of half-waves long
AT THE FREQUENCY WHERE INTERACTION IS THE CONCERN. Not only that, an
OPEN in the shack would be transformed to a short at the antenna if the
line were some odd number of quarter-wavelengths.

So -- if you're going to implement that switch in the shack, you need to
MEASURE the electrical length of the transmission line to that MA5B to
pretty good accuracy. If you don't own a good VIA or VNA, find someone
who has an AIM or VNWA and have them measure it for you. With that
information, use TLW (comes on the ARRL Antenna Book CD) or SimSmith
(free Smith Chart program, runs in Java) to figure out how much coax to
add or subtract to put the short or open.

73, Jim K9YC
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Robert .

Re: KAT500 Antenna Grounding

In reply to this post by Cliff Frescura

Ameritron RcV-8V
The unused ports can be grounded but the solder jumper is not done at factory

I have found at times the RCV-8V that relay sticks and stays "connected" the mechanical "stuff" on top of the relay binds. or won't close (same issue) or coil relay burns out
removing the cover, can quickly fix mechanical jam. if the coil burns out - you got one less port or buy a new switch. Difficult to change relay out

on another grounding side: I use ports 4 & 5 to feed phased vertical array
have not figured out a way to ground those when not in use, one port is feed & other must float
73 Robert W5AJ

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Cliff Frescura
Sent: Saturday, May 09, 2015 1:19 PM
To: 'Jack Brindle'; 'David Ahrendts'
Cc: 'Elecraft List'
Subject: Re: [Elecraft] KAT500 Antenna Grounding

I'm in a similar situation. Love the KAT500 (especially with the KPA500 and Kenwood TS-940). Already have an Ameritron remote antenna switch, so not using the switching on the KAT500 (except for a switching in a dummy load).

The solution I've come up with is to have an Arduino monitor the radio frequency/band data and have it switch the antenna. However, I doubt that the Ameritron switch grounds the unused ports. The DX Engineering remote switches appear to have this as an option.

73,

Cliff K3LL/6

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Jack Brindle
Sent: Friday, May 08, 2015 5:42 PM
To: David Ahrendts
Cc: Elecraft List
Subject: Re: [Elecraft] KAT500 Antenna Grounding

I can answer that. The KPA500 does not ground unselected antennas. Nor does it ground selected antennas. ;-) (OK, it’s Friday. Even we Elecrafters let our hair down on Friday…)

- Jack Brindle, W6FB

> On May 8, 2015, at 5:18 PM, David Ahrendts <[hidden email]> wrote:
>
> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active? Do I need to mount an external antenna switch to ground the unused antenna, which is not desirable because of the KAT500’s ability to memorize frequencies and tuner corrections per antenna?
>
> David A., KC0XT, Los Angeles
>
>
>
> David Ahrendts [hidden email]
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> list: http://www.qsl.net/donate.html Message delivered to
> [hidden email]

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Elecraft mailing list

Re: KAT500 Antenna Grounding

In reply to this post by Jim Brown-10

Jim, I am afraid that you are ignoring the fact that RF ground and DC ground are not the same thing. Any thing that refers to wavelength of coax is talking about RF grounding. Anything that refers to lightning protection or personal protection refers to DC grounding. Anything that refers to antenna spacing refers primarily to interaction between the antennas. For interaction between the antennas a five foot mast is possibly enough. If you have an option for more, go ahead with more spacing. The widest spacing that I see is about 10 feet, but try what you think and see what you find. You can always extend the mast if you have to because a six meter beam is small and the extension can hold a lot on a 1 inch mast that is 5 or 10 feet long. It is easy enough to add a coax switch such as an MFJ-1702 Which has an alternate selection for a dummy load or second transceiver which you can install on each of your antennas. If the antenna is connected to your amplifier or transceiver there is surge protector which will protect your equipment to a certain extent if there is a strike when you are operating and a ground position when you are not operating or using a different antenna. You can also use the center position to ground your antenna to the station ground to check for interaction with the other antenna. If the SWR improves or your signal to the other station improves enough to consider, then you have a strong clue that you should ground that antenna when you are using the other antenna . Your path to the station ground must be low enough for the strike you are considering to bleed off without harming your equipment. The coax wave length property is a good one to use if you are having trouble withe SWR or Tuner settings. Personal protection is usually good enough from the power source if you have a DC bond to ground and watch what you touch because a direct strike will cause many amps of current in the ground path and only a few milliamps are needed to harm you or your equipment. Willis 'Cookie' Cooke,TDXS Contest Chairman K5EWJ & Trustee N5BPS
From: Jim Brown <[hidden email]>
To: [hidden email]
Sent: Saturday, May 9, 2015 1:48 PM
Subject: Re: [Elecraft] KAT500 Antenna Grounding

On Fri,5/8/2015 5:18 PM, David Ahrendts wrote:
> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active?

Several MAJOR points of confusion here. First, what do you mean by
"grounding?" Do you mean shorting the coax? Second, because any
transmission line transforms the impedance by an amount determined
entirely by its electrical length, shorting the coax in the shack will
only short the antenna if the line is some multiple of half-waves long
AT THE FREQUENCY WHERE INTERACTION IS THE CONCERN. Not only that, an
OPEN in the shack would be transformed to a short at the antenna if the
line were some odd number of quarter-wavelengths.

So -- if you're going to implement that switch in the shack, you need to
MEASURE the electrical length of the transmission line to that MA5B to
pretty good accuracy. If you don't own a good VIA or VNA, find someone
who has an AIM or VNWA and have them measure it for you. With that
information, use TLW (comes on the ARRL Antenna Book CD) or SimSmith
(free Smith Chart program, runs in Java) to figure out how much coax to
add or subtract to put the short or open.

73, Jim K9YC
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Jim Brown-10

Re: KAT500 Antenna Grounding

On Sun,5/10/2015 9:08 AM, WILLIS COOKE wrote:
> Jim, I am afraid that you are ignoring the fact that RF ground and DC
> ground are not the same thing.

I'm not ignoring that at all -- I'm attempting to help David with an
antenna interference issue, and understand how transmission lines work.
AND -- lightning is NOT a DC event, it is an RF event. The energy in
lightning is broadly centered around 1 MHz. Those feedlines should be
bonded to the tower at top and bottom, and the tower needs ground rods
around it.

> Any thing that refers to wavelength of coax is talking about RF
> grounding.

There is no such thing as RF ground.

> Anything that refers to lightning protection or personal protection
> refers to DC grounding. Anything that refers to antenna spacing
> refers primarily to interaction between the antennas. For interaction
> between the antennas a five foot mast is possibly enough. If you have
> an option for more, go ahead with more spacing. The widest spacing
> that I see is about 10 feet, but try what you think and see what you
> find.

The appropriate measure of spacing is wavelength, not feet or meters.

> You can always extend the mast if you have to because a six meter
> beam is small and the extension can hold a lot on a 1 inch mast that
> is 5 or 10 feet long. It is easy enough to add a coax switch such as
> an MFJ-1702 Which has an alternate selection for a dummy load or
> second transceiver which you can install on each of your antennas.

The wavelength in coax still applies.

> If the antenna is connected to your amplifier or transceiver there is
> surge protector which will protect your equipment to a certain extent
> if there is a strike when you are operating and a ground position when
> you are not operating or using a different antenna. You can also use
> the center position to ground your antenna to the station ground to
> check for interaction with the other antenna. If the SWR improves or
> your signal to the other station improves enough to consider, then you
> have a strong clue that you should ground that antenna when you are
> using the other antenna .

The antennas should ALWAYS be grounded. Again, there is this confusion
between multiple uses of the word "ground." The antenna is grounded
when we bond the coax to earth. That is the first element of protection.
The second element is bonding all grounds in a premises together (power,
CATV, telco, etc), bonding all station equipment and antennas together,
and bonding all of that to the collection of premises grounds . A
lightning arrestor is the third element -- if the coax is connected to a
rig, the arrestor shorts the center conductor to the shield in the event
of a strike, attempting to protect the rig. Depending on the nature of
the strike, that may be enough.

> Your path to the station ground must be low enough for the strike you
> are considering to bleed off without harming your equipment. The coax
> wave length property is a good one to use if you are having trouble
> withe SWR or Tuner settings.

This is only "good" if the SWR is fairly low. If it's high, the line can
get pretty lossy.

> Personal protection is usually good enough from the power source if
> you have a DC bond to ground

I certainly don't want the Green wire to be the path to ground for a
lightning strike. Rather, I want ground rods at the base of the tower
and where coax enters the shack.

> and watch what you touch because a direct strike will cause many amps
> of current in the ground path and only a few milliamps are needed to
> harm you or your equipment.

Right.

73, Jim K9YC

> Willis 'Cookie' Cooke,
> TDXS Contest Chairman
> K5EWJ & Trustee N5BPS
>
> ------------------------------------------------------------------------
> *From:* Jim Brown <[hidden email]>
> *To:* [hidden email]
> *Sent:* Saturday, May 9, 2015 1:48 PM
> *Subject:* Re: [Elecraft] KAT500 Antenna Grounding
>
> On Fri,5/8/2015 5:18 PM, David Ahrendts wrote:
> > I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B
> mini-beam rather closely — like five-feet vertical separation (Rohn
> five-foot tripod on the roof in a tight lot). Cushcraft recommends
> using an antenna switch to ground the unused antenna since the two
> would react with each other at 17M. Both would be connected to the
> KAT500. So here’s the question: are the un-selected antennas out of
> the three on the KAT500 grounded through the KAT500 or do they remain
> just unattached but active?
>
> Several MAJOR points of confusion here. First, what do you mean by
> "grounding?" Do you mean shorting the coax? Second, because any
> transmission line transforms the impedance by an amount determined
> entirely by its electrical length, shorting the coax in the shack will
> only short the antenna if the line is some multiple of half-waves long
> AT THE FREQUENCY WHERE INTERACTION IS THE CONCERN. Not only that, an
> OPEN in the shack would be transformed to a short at the antenna if the
> line were some odd number of quarter-wavelengths.
>
> So -- if you're going to implement that switch in the shack, you need to
> MEASURE the electrical length of the transmission line to that MA5B to
> pretty good accuracy. If you don't own a good VIA or VNA, find someone
> who has an AIM or VNWA and have them measure it for you. With that
> information, use TLW (comes on the ARRL Antenna Book CD) or SimSmith
> (free Smith Chart program, runs in Java) to figure out how much coax to
> add or subtract to put the short or open.
>
> 73, Jim K9YC
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email] <mailto:[hidden email]>
>

daleputnam

Re: KAT500 Antenna Grounding

the commercial installation grounding practices covered by the
R56 grounding Standards are a wonderful tool to learn, and adhere to,
without deviation.
that will allow a 200 ft tower to sustain multiple strikes during a single T-storm,
while radios are in operation, with their antennas active on that tower, without
damage to either the radios or the antennas. Obviously, YMMV... but after
spending many hours repairing damage to radios installed on the same tower,
prior to the R56 standard... and none after... it bears reading... three or four times.

Have a great day,

--... ...--
Dale - WC7S in Wy

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David Woolley (E.L)

Re: KAT500 Antenna Grounding

In reply to this post by Elecraft mailing list

Lightning rise times correspond more to low HF than to DC, e.g.
<http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6344272&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6344272>

You can't, in general, treat lightning as DC.

--
David Woolley
Owner K2 06123

On 10/05/15 17:08, WILLIS COOKE via Elecraft wrote:
> Jim, I am afraid that you are ignoring the fact that RF ground and DC ground are not the same thing. Any thing that refers to wavelength of coax is talking about RF grounding. Anything that refers to lightning protection or personal protection refers to DC grounding. Anything that refers to antenna spacing refers primarily to interaction between the antennas. For interaction between

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Wes (N7WS)

Re: KAT500 Antenna Grounding

In reply to this post by Elecraft mailing list

You've received some other advice/opinions about whether or not "ground" is
"ground."

I won't expand on that but will address the real problem that you pose. IMHO,
whether or not you "ground", "short" or otherwise screw up the impedance of the
driven element of the inactive antenna, there will be interaction between the
two antennas. Regardless of what you do to the inactive antenna's DE, all of
the elements on both antennas are coupled. To what extent, who knows?

This is true whenever there are two or more antennas in proximity Sometimes the
effect is useful (stacked antennas); sometimes not. The only real way to know is
to do some modeling. You might see some effect upon the driven impedance of the
active antenna, but this doesn't predict directivity effects. One option might
be to rotate one boom 90 degrees to the other. Of course, now the boom of one
antenna might upset the elements of the other. Absent a science project, I
suggest that you don't worry about it.

If you want to have some fun, however, you could ask Cushcraft to explain
themselves.

Wes N7WS

On Fri,5/8/2015 5:18 PM, David Ahrendts wrote:
>> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active?

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David Ahrendts

Re: KAT500 Antenna Grounding

Thanks everyone for all of the advice. Declaring this thread concluded.

> On May 11, 2015, at 9:55 AM, Wes (N7WS) <[hidden email]> wrote:
>
> You've received some other advice/opinions about whether or not "ground" is "ground."
>
> I won't expand on that but will address the real problem that you pose. IMHO, whether or not you "ground", "short" or otherwise screw up the impedance of the driven element of the inactive antenna, there will be interaction between the two antennas. Regardless of what you do to the inactive antenna's DE, all of the elements on both antennas are coupled. To what extent, who knows?
>
> This is true whenever there are two or more antennas in proximity Sometimes the effect is useful (stacked antennas); sometimes not. The only real way to know is to do some modeling. You might see some effect upon the driven impedance of the active antenna, but this doesn't predict directivity effects. One option might be to rotate one boom 90 degrees to the other. Of course, now the boom of one antenna might upset the elements of the other. Absent a science project, I suggest that you don't worry about it.
>
> If you want to have some fun, however, you could ask Cushcraft to explain themselves.
>
> Wes N7WS
>
> On Fri,5/8/2015 5:18 PM, David Ahrendts wrote:
>>> I’m considering stacking the Cushcraft A503S 6M yagi with my MA5B mini-beam rather closely — like five-feet vertical separation (Rohn five-foot tripod on the roof in a tight lot). Cushcraft recommends using an antenna switch to ground the unused antenna since the two would react with each other at 17M. Both would be connected to the KAT500. So here’s the question: are the un-selected antennas out of the three on the KAT500 grounded through the KAT500 or do they remain just unattached but active?
>
> ______________________________________________________________
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David Ahrendts [hidden email]

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k6dgw

Re: KAT500 Antenna Grounding

In reply to this post by Wes (N7WS)

Indeed. We live on a more or less rectangular 5 acres. A 69 KV tie
line connecting two hydroelectric power plants N and S of us transits
the SE corner of the property. Under it are primary 12 KV distribution
lines.

When preparing my comments to the FCC during the BPL bruhaha some years
ago, I noted most of the comments focused on BPL interference *to* ham
operations. The other side of that equation is equally troublesome if
my operations destroys my neighbor's Internet access.

So, I modeled the 12 KV distribution lines and my closest antenna in
EZNEC-4. I found that on 80 - 10, the coupling between my antenna and
the power lines was a fairly constant -28 dB. On 160, it was -17 dB, I
think because the lines and antenna are in each other's near field at
that low frequency. A -30 dB coupling coefficient means that 1 KW puts
1 W into the into the power lines, which no doubt would have saturated
my neighbors BPL modem had BPL actually been deployed around here.

If the "antennas" are in the near fields, the coupling would have put
around 50 watts into the power lines. The power lines are essentially
non-resonant, so yes, a nearby unused antenna can produce significant
amounts of power just from proximity to a working antenna.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org

On 5/11/2015 9:55 AM, Wes (N7WS) wrote:

> I won't expand on that but will address the real problem that you pose.
> IMHO, whether or not you "ground", "short" or otherwise screw up the
> impedance of the driven element of the inactive antenna, there will be
> interaction between the two antennas. Regardless of what you do to the
> inactive antenna's DE, all of the elements on both antennas are
> coupled. To what extent, who knows?

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