Elecraft › [K3]

Antenna Separation for Diversity

Classic

List

Threaded

9 messages Options

Brett Howard

Antenna Separation for Diversity

So I know I'm going to shoot for as wide as I can get things... But for
two main antennas on a k3 one being a Carolina Windom and the other
being a 43 foot vertical.

How much separation would one expect to be needed in order to prevent
the COR's from switching during TX @ 100Watts?

~Brett (N7MG)

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

W8JI

Re: Antenna Separation for Diversity

Brett,

No one can answer that question for you, because both antennas are
unpredictable in nearfield performance. Also the layout of the antenna and
what is around, under, and between the antennas is very important.

With such a large soup of unknowns, plus there might be other transmitters
on site (?), the only way to really know is to try it.

If you had a normal dipole and wanted interaction to a vertical of known
efficiency I have all that data. One thing I learned is minimum coupling
from a good dipole to a good vertical was with the dipole BROADSIDE to the
vertical, not at right angles as I assumed without thinking.

The problem is the Carolina Windom is nothing like a dipole and not nearly
as predictable as a dipole for nearfield or close farfield coupling, and
that goes on top of the other variables that are bad enough on their own.

Maybe you should go to an antenna forum, like on eHam or QRZ, armed with the
information of the safe signal level the K3 will tolerate. Other than the
safe signal level, this is really an antenna theory question and a good
answer would be too complex for a radio reflector.

73 Tom

- Original Message -----
From: "Brett Howard" <[hidden email]>
To: "elecraft" <[hidden email]>
Sent: Thursday, June 24, 2010 5:14 AM
Subject: [Elecraft] Antenna Separation for Diversity

> So I know I'm going to shoot for as wide as I can get things... But for
> two main antennas on a k3 one being a Carolina Windom and the other
> being a 43 foot vertical.
>
> How much separation would one expect to be needed in order to prevent
> the COR's from switching during TX @ 100Watts?
>
> ~Brett (N7MG)
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Brett Howard

Re: Antenna Separation for Diversity

Huh... Broadside to the vertical provided minimum coupling? Well I'm going
to be slapping things together tomorrow and trying them out and trying to
take a bunch of measurements and logging it all. Was just wondering if
anyone else here had a similar setup and might have an answer here. I'm
figuring I'll probably be able to pull off about 150 to 200 feet between
them... Lets hope its enough. If not I can always make one of them RX only
and put the ICE Receiver Limiter box on it.

~Brett (N7MG)

-----Original Message-----
From: Tom W8JI [mailto:[hidden email]]
Sent: Thursday, June 24, 2010 6:00 AM
To: Brett Howard; elecraft
Subject: Re: [Elecraft] Antenna Separation for Diversity

Brett,

No one can answer that question for you, because both antennas are
unpredictable in nearfield performance. Also the layout of the antenna and
what is around, under, and between the antennas is very important.

With such a large soup of unknowns, plus there might be other transmitters
on site (?), the only way to really know is to try it.

If you had a normal dipole and wanted interaction to a vertical of known
efficiency I have all that data. One thing I learned is minimum coupling
from a good dipole to a good vertical was with the dipole BROADSIDE to the
vertical, not at right angles as I assumed without thinking.

The problem is the Carolina Windom is nothing like a dipole and not nearly
as predictable as a dipole for nearfield or close farfield coupling, and
that goes on top of the other variables that are bad enough on their own.

Maybe you should go to an antenna forum, like on eHam or QRZ, armed with the

information of the safe signal level the K3 will tolerate. Other than the
safe signal level, this is really an antenna theory question and a good
answer would be too complex for a radio reflector.

73 Tom

- Original Message -----
From: "Brett Howard" <[hidden email]>
To: "elecraft" <[hidden email]>
Sent: Thursday, June 24, 2010 5:14 AM
Subject: [Elecraft] Antenna Separation for Diversity

dave-281

Re: Antenna Separation for Diversity

Let me add a bit, if I may. The vertical needs to be broadside and
centered on the dipole. Draw a line at 90 degrees from the center feed
point of the dipole and place the vertical on that line.

But if I understand what is meant by the term 'Carolina Windom' this is
an off-center-fed antenna and will consequently have unequal currents on
the feeder on some or all bands. This means the feeder will both radiate
and receive, and will be vertically polarized. Consequently there will
be coupling between the vert antenna and the feeder of the Windom.

So long as the vert and the Windom are used on different bands it will
likely work OK, but there will probably be too much coupling to use them
both on the same band. If a center fed dipole is used with a vertical as
described above (or another dipole at 90 degrees and centered) they can
both be on the same band with a few kHz separation. We do that every FD.

73 de dave
ab9ca/4

Brett Howard wrote:

> Huh... Broadside to the vertical provided minimum coupling? Well I'm going
> to be slapping things together tomorrow and trying them out and trying to
> take a bunch of measurements and logging it all. Was just wondering if
> anyone else here had a similar setup and might have an answer here. I'm
> figuring I'll probably be able to pull off about 150 to 200 feet between
> them... Lets hope its enough. If not I can always make one of them RX only
> and put the ICE Receiver Limiter box on it.
>
> ~Brett (N7MG)
>
> -----Original Message-----
> From: Tom W8JI [mailto:[hidden email]]
> Sent: Thursday, June 24, 2010 6:00 AM
> To: Brett Howard; elecraft
> Subject: Re: [Elecraft] Antenna Separation for Diversity
>
> Brett,
>
> No one can answer that question for you, because both antennas are
> unpredictable in nearfield performance. Also the layout of the antenna and
> what is around, under, and between the antennas is very important.
>
> With such a large soup of unknowns, plus there might be other transmitters
> on site (?), the only way to really know is to try it.
>
> If you had a normal dipole and wanted interaction to a vertical of known
> efficiency I have all that data. One thing I learned is minimum coupling
> from a good dipole to a good vertical was with the dipole BROADSIDE to the
> vertical, not at right angles as I assumed without thinking.
>
> The problem is the Carolina Windom is nothing like a dipole and not nearly
> as predictable as a dipole for nearfield or close farfield coupling, and
> that goes on top of the other variables that are bad enough on their own.
>
> Maybe you should go to an antenna forum, like on eHam or QRZ, armed with the
>
> information of the safe signal level the K3 will tolerate. Other than the
> safe signal level, this is really an antenna theory question and a good
> answer would be too complex for a radio reflector.
>
> 73 Tom
>
> - Original Message -----
> From: "Brett Howard" <[hidden email]>
> To: "elecraft" <[hidden email]>
> Sent: Thursday, June 24, 2010 5:14 AM
> Subject: [Elecraft] Antenna Separation for Diversity
>
>
>
>> So I know I'm going to shoot for as wide as I can get things... But for
>> two main antennas on a k3 one being a Carolina Windom and the other
>> being a 43 foot vertical.
>>
>> How much separation would one expect to be needed in order to prevent
>> the COR's from switching during TX @ 100Watts?
>>
>> ~Brett (N7MG)
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>

Bob Cunnings NW8L

Re: Antenna Separation for Diversity

In reply to this post by Brett Howard

> Huh... Broadside to the vertical provided minimum coupling?

Apparently so. See the article by K6STI in the Sept. 1995 QST "A
Receiving Antenna that Rejects Local Noise" for an explanation.

Bob NW8L
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Brett Howard

Re: Antenna Separation for Diversity

I'm totally going to print this and bring it with me as I'm certain no one
will believe this unless I let them sit down and read through it themselves.
Quite interesting though!

~Brett (N7MG)

-----Original Message-----
From: Bob Cunnings [mailto:[hidden email]]
Sent: Thursday, June 24, 2010 7:30 AM
To: Brett Howard
Cc: Tom W8JI; elecraft
Subject: Re: [Elecraft] Antenna Separation for Diversity

> Huh... Broadside to the vertical provided minimum coupling?

Apparently so. See the article by K6STI in the Sept. 1995 QST "A
Receiving Antenna that Rejects Local Noise" for an explanation.

Bob NW8L

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Guy, K2AV

Re: Antenna Separation for Diversity

Given that the vertical has low or ground radials, and the dipole is
up a quarter wave or more, the vertical antenna off the end of a
dipole on the same band will have a lot of energy coupled from the
dipole. It is not intuitive until one has gotten used to it. This
is easy to model to see the kind of coupling that takes place.

73, Guy.

On Thu, Jun 24, 2010 at 10:41 AM, Brett Howard <[hidden email]> wrote:

> I'm totally going to print this and bring it with me as I'm certain no one
> will believe this unless I let them sit down and read through it themselves.
> Quite interesting though!
>
> ~Brett (N7MG)
>
> -----Original Message-----
> From: Bob Cunnings [mailto:[hidden email]]
> Sent: Thursday, June 24, 2010 7:30 AM
> To: Brett Howard
> Cc: Tom W8JI; elecraft
> Subject: Re: [Elecraft] Antenna Separation for Diversity
>
>> Huh... Broadside to the vertical provided minimum coupling?
>
> Apparently so. See the article by K6STI in the Sept. 1995 QST "A
> Receiving Antenna that Rejects Local Noise" for an explanation.
>
> Bob NW8L
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

W8JI

Re: Antenna Separation for Diversity

In reply to this post by Brett Howard

I really don't think this is the best place for antenna topics, but I want
to be clear about my comments.

In my case I measured a well-constructed dipole without significant feedline
radiation. The vertical was a good clean vertical with a good ground. The
spacing was 3000-feet.

The strongest coupling by far was with the dipole almost, but not quite, off
the ends of the dipole. The deepest null was with the dipole directly
broadside to the direction of the vertical.

This makes total sense when we look at the real polarization and pattern of
a dipole. A dipole is only perfectly horizontal polarized directly
broadside, and has increasing vertical tilt to polarization as we move off
towards the ends.

The Carolina Windom, however, has an unpredictable polarization tilt to the
pattern. It is NOT dual polarization or diversity, it is simply a dipole of
sorts with significant feedline radiation, and as such will be unpredictable
in polarization tilt with direction and elevation.

This all would be better on an antenna forum, so this is my last comment.
:-)

73 Tom

--- Original Message -----
From: "Brett Howard" <[hidden email]>
To: "'Tom W8JI'" <[hidden email]>; "'elecraft'" <[hidden email]>
Sent: Thursday, June 24, 2010 9:20 AM
Subject: RE: [Elecraft] Antenna Separation for Diversity

> Huh... Broadside to the vertical provided minimum coupling? Well I'm
> going
> to be slapping things together tomorrow and trying them out and trying to
> take a bunch of measurements and logging it all. Was just wondering if
> anyone else here had a similar setup and might have an answer here. I'm
> figuring I'll probably be able to pull off about 150 to 200 feet between
> them... Lets hope its enough. If not I can always make one of them RX
> only
> and put the ICE Receiver Limiter box on it.
>
> ~Brett (N7MG)
>
> -----Original Message-----
> From: Tom W8JI [mailto:[hidden email]]
> Sent: Thursday, June 24, 2010 6:00 AM
> To: Brett Howard; elecraft
> Subject: Re: [Elecraft] Antenna Separation for Diversity
>
> Brett,
>
> No one can answer that question for you, because both antennas are
> unpredictable in nearfield performance. Also the layout of the antenna and
> what is around, under, and between the antennas is very important.
>
> With such a large soup of unknowns, plus there might be other transmitters
> on site (?), the only way to really know is to try it.
>
> If you had a normal dipole and wanted interaction to a vertical of known
> efficiency I have all that data. One thing I learned is minimum coupling
> from a good dipole to a good vertical was with the dipole BROADSIDE to the
> vertical, not at right angles as I assumed without thinking.
>
> The problem is the Carolina Windom is nothing like a dipole and not nearly
> as predictable as a dipole for nearfield or close farfield coupling, and
> that goes on top of the other variables that are bad enough on their own.
>
> Maybe you should go to an antenna forum, like on eHam or QRZ, armed with
> the
>
> information of the safe signal level the K3 will tolerate. Other than the
> safe signal level, this is really an antenna theory question and a good
> answer would be too complex for a radio reflector.
>
> 73 Tom
>
> - Original Message -----
> From: "Brett Howard" <[hidden email]>
> To: "elecraft" <[hidden email]>
> Sent: Thursday, June 24, 2010 5:14 AM
> Subject: [Elecraft] Antenna Separation for Diversity
>
>
>> So I know I'm going to shoot for as wide as I can get things... But for
>> two main antennas on a k3 one being a Carolina Windom and the other
>> being a 43 foot vertical.
>>
>> How much separation would one expect to be needed in order to prevent
>> the COR's from switching during TX @ 100Watts?
>>
>> ~Brett (N7MG)
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>
>

Craig Smith

Re: Antenna Separation for Diversity

In reply to this post by dave-281

As several have pointed out, this will be quite dependent on the specific
antennas and orientation. But don't give up hope. I have one data point
for you. Due to severe space limitations here, my K9AY RX antenna is 50 ft
from both a 43 ft vertical and a 102 ft horizontal doublet during my
contesting operations. I run 100W CW on 80, 40, 20 and 15. I've never
tripped the COR on the K3 RX antenna input. The worst case power I've
measured at the input to my Clifton Labs RX distribution amp is about +15
dbm.

73 Craig AC0DS

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html