It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?

I know more separation is better and I doubt I can predict the future
well enough to model expected configurations.

The first in place is the existing crank up mast with power winches
that allow me to lay the whole works down for maintenance. HF tri band
in place at about 55 feet.

About 50 feet north of that tower is my field of 36 radials where I
currently have a 40 meter self supporting vertical. I would really
like to not compromise the radials or the operation of whatever
vertical I choose.

I am thinking of putting the "new" tower about 20 feet West of the
vertical & radial field. The plan calls for 4 sticks of Rohn 25 on a
tilt plate with a utility pole doing the stabilizing. Winches as
required.

That is a little more co ax than I would like, but my real concern is
whether this will be a major hit for the vertical and other antennas.

I would appreciate any thoughts and especially experience.


John Ferrell W8CCW

On Mon, 25 Oct 2010 18:31:16 -0400, John Ferrell
wrote:

About 50 feet north of that tower is my field of 36 radials where I
currently have a 40 meter self supporting vertical. I would really
like to not compromise the radials or the operation of whatever
vertical I choose.

I am thinking of putting the "new" tower about 20 feet West of the
vertical & radial field. The plan calls for 4 sticks of Rohn 25 on a
tilt plate with a utility pole doing the stabilizing. Winches as
required.

Hi John,

Consider the spacing of elements in an array (any, even vertical
arrays that are installed for directional AM stations). The
dimensions there are in the tenths (or less) of wavelengths and
couplings are very strong. You propose a second structure that is
still quite near (about .15 wave) on the basis of this simple metric
alone.

What it does is another matter. It will certainly disturb the
radiator's loading. It will certainly absorb signal. It will
certainly re-radiate that same signal. It will certainly introduce a
phase shift that combines with the original signal. The combination
can either produce a lobe or a null OR it may be unproductive in the
practical sense (all certainties go by the wayside).

One might pause and reflect that the new tower could easily (this is a
hail mary pass) serve as your 40M radiator. Why have two vertical
structures (ignoring that we will actually be talking about the
installation of a THIRD vertical structure if we include the south
tower)?

73's
Richard Clark, KB7QHC

On Oct 25, 8:31*pm, John Ferrell wrote:
It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?



I would appreciate any thoughts and especially experience.

John Ferrell W8CCW

I have used for the past three years a 40M vertical and and 80M loop.
I use the 40M vertical for 40 and 15M and the loop as a multiband
80-10M. The pair worked great for me at my location. The loop WAS
supported by four 25-32ft trees. When I tried to improve the system
by raising all the corners of the loop to 32 ft, by using some 32 ft
lengths of metal tubing I pieced together, my 40M vertical did not
seem to work as well. There was not a big difference in the 80-10M
loop it worked fine both setups from what I could tell. Note that I
never used the loop for transmit on 40M as the vertical worked great
and my reason to increase height was not to improve performance of the
loop but for the wire to clear the tops of the trees and not get
tangled as often.
With the metal tubing supporting the corners of the loop it seemed
like the 40Mvertical was a totally different antenna(not as good of
one). As well, resonance the 40M vertical shifted slightly. As my
antenna is in a fairly dense wooded area when it rain heavily or we
have freezing precipitation I also see a similar effect.
The metal vertical support for the corner of the loop was about 37ft
from the base of the 40M vertical. I used this setup over a period of
time and when I removed the metal support tubing , resonance shifted
back on the 40M vertical and it seem to play as it did before , like
the on I home brewed originally.
I'm sure I could have used decoupling techniques so the 40M radiator
did not "see" the vertical elements in close proximity but never did
put the tubing back up when it came down, used much better wire that
didn't tangle.
So how close is to close? I think 37ft was too close for a 40M
vertical in proximity to a 32ft support mast for optimum performance
for the vertical, but if its a second tower I'm sure the gain will be
much better than losses of coupling especially if it means a new 3
element 40Meter monobander as the antenna on the "new tower". I have
ON4UN's Low Band DXing, which is awesome and a must have for all
Ham's, John I believe uses or has used a 160M vertical in the center
of a four square, and uses decoupling techniques between the two. If
there is an issue with the closeness of the two, decouple at that
point. Hope this helps.

On Oct 26, 1:53*am, brett wrote:
On Oct 25, 8:31*pm, John Ferrell wrote:

It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?

I would appreciate any thoughts and especially experience.

John Ferrell W8CCW


So how close is to close? I think 37ft was too close for a 40M
vertical in proximity to a 32ft support mast for optimum performance
for the vertical, but if its a second tower I'm sure the gain will be
much better than losses of coupling especially if it means a new 3
element 40Meter monobander as the antenna on the "new tower". I have
ON4UN's Low Band DXing, which is awesome and a must have for all
Ham's, John I believe uses or has used a 160M vertical in the center
of a four square, and uses decoupling techniques between the two. If
there is an issue with the closeness of the two, decouple at that
point. Hope this helps.

MY mistake you would not put a 3element 40m monobander on a 40ft
tower, bad example. Hope the rest helps you,, good DXing.

On Mon, 25 Oct 2010 21:07:26 -0700 (PDT), brett
wrote:

On Oct 26, 1:53*am, brett wrote:
On Oct 25, 8:31*pm, John Ferrell wrote:

It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?

I would appreciate any thoughts and especially experience.

John Ferrell W8CCW

I am going to listen and think on the subject for a while. I need to
acquire another stick of Rohn 25 anyway.

There is no urgency, I would just like to get back to some VHF work
other than repeaters.

The current tower has a Cushcraft A3S and a 3 element fan dipole that
I find works so good on all bands that I stopped at three. The dipoles
are cut for 17M, 30M, and 80M. I have no idea what is really
radiating when I manually tune up. I always start with minimum
inductance in hopes of fewer tuner losses. I have not tried 160M
though. 40M works well on both antennas so it would not be a big
issue to loose the vertical. It has served more as an all band antenna
than strictly a 40m antenna anyway. The EZNEC patterns for a 30 foot
vertical are not impressive with it, but it does work with an SGC 237
tuner.

I can get the second tower in place with very little cash outlay at
this time. I am leaning towards the project...

And I am expecting a few "issues" along the way.

John Ferrell W8CCW

On 10/25/2010 06:31 PM, John Ferrell wrote:
It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?

I know more separation is better and I doubt I can predict the future
well enough to model expected configurations.

The first in place is the existing crank up mast with power winches
that allow me to lay the whole works down for maintenance. HF tri band
in place at about 55 feet.

About 50 feet north of that tower is my field of 36 radials where I
currently have a 40 meter self supporting vertical. I would really
like to not compromise the radials or the operation of whatever
vertical I choose.

I am thinking of putting the "new" tower about 20 feet West of the
vertical& radial field. The plan calls for 4 sticks of Rohn 25 on a
tilt plate with a utility pole doing the stabilizing. Winches as
required.

That is a little more co ax than I would like, but my real concern is
whether this will be a major hit for the vertical and other antennas.

I would appreciate any thoughts and especially experience.


John Ferrell W8CCW

Hello, and just to tack on to the other comments: If the second
antenna's presence changes the feedpoint impedance of the first antenna,
you can be sure the second antenna is in the induction (close coupling
(non-radiating)) field of the first antenna. If the second antenna
could be located about 2-3 wavelenghts from the first it would be in the
far-field and its contribution to the radiation pattern of the first, if
any, would be minimal. Alas, since this might not be practical, perhaps
some modeling using NEC/EZNEC prior to antenna installation would allow
for some optimum trade-offs regarding parasitic effects introduced by
the second antenna with the goal of saving time (and money). Sincerely,
and 73s from N4GGO,

--
John Wood (Code 5520) e-mail:

Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337

Dear John: As others have said - expect a lot of coupling. However, even a
second read did not disclose what you wish to place on a 40 foot tower - or
if you expect to use the new tower as the end for one or more wires.

Clearly the example of a 3 element 40 meter beam at 40 feet makes no sense.
73, Mac N8TT
--
J. McLaughlin; Michigan, USA
Home:
"John Ferrell" wrote in message
...
On Mon, 25 Oct 2010 21:07:26 -0700 (PDT), brett
wrote:

On Oct 26, 1:53 am, brett wrote:
On Oct 25, 8:31 pm, John Ferrell wrote:

It looks like I am going to have the resources to install a second
antenna tower. I never thought it would work out this way so I have
not planned it as I put other things in place.

The question is: How close is too close?

I would appreciate any thoughts and especially experience.

John Ferrell W8CCW

I am going to listen and think on the subject for a while. I need to
acquire another stick of Rohn 25 anyway.

There is no urgency, I would just like to get back to some VHF work
other than repeaters.

The current tower has a Cushcraft A3S and a 3 element fan dipole that
I find works so good on all bands that I stopped at three. The dipoles
are cut for 17M, 30M, and 80M. I have no idea what is really
radiating when I manually tune up. I always start with minimum
inductance in hopes of fewer tuner losses. I have not tried 160M
though. 40M works well on both antennas so it would not be a big
issue to loose the vertical. It has served more as an all band antenna
than strictly a 40m antenna anyway. The EZNEC patterns for a 30 foot
vertical are not impressive with it, but it does work with an SGC 237
tuner.

I can get the second tower in place with very little cash outlay at
this time. I am leaning towards the project...

And I am expecting a few "issues" along the way.

John Ferrell W8CCW

On Fri, 29 Oct 2010 22:15:08 -0400, "J. Mc Laughlin"
wrote:

Dear John: As others have said - expect a lot of coupling. However, even a
second read did not disclose what you wish to place on a 40 foot tower - or
if you expect to use the new tower as the end for one or more wires.

Clearly the example of a 3 element 40 meter beam at 40 feet makes no sense.
73, Mac N8TT

Thanks for your advice! The more views I get, the less likely it is
for me to make bad decisions.

Here is where my thinking is now:

I need to put the second tower wherever it will be most useful to my
purposes. The existing vertical array and its radials are expendable.
It can be reconstructed if desired at another time. I believe it has
served my purpose and it is time to move on. Installing a tower is not
a trivial matter and the decisions should be made to take advantage of
the opportunities it provides.

My interests are a little different than most Hams. I enjoy studying
more than operating. Building and using antennas is an important part
of the hobby (addiction?) to me. When I made the retirement move to
this location I made certain that I would be able to pursue that path.
I have enough real estate, wife does not care what I choose to do with
the hobby, and the neighbors are indifferent as well! I consider all
the antennas to be temporary and everything must be accessible. Twice
this past week I have lowered the existing Tribander to 25 feet
because of weather forecasts. Change is the rule rather than the
exception!

If I encounter excessive interaction I will just consider it another
condition to explore. I started out with the idea that this would be a
30 foot VHF-UHF structure but it appears that I can reach a little
higher and stronger than that.

I will keep the options open as best I can to provide a second
structure that lends itself to further experiments.

At least that is what I am thinking today...

John Ferrell W8CCW