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VERTICALS

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John Wiener

VERTICALS

Maybe I missed it, but I didn't see anyone mention SteppIR, though I
seem to remember a mention of it earlier.

I do not have one, but I've seen articles showing one masquerading as
a flag pole.

As many know, the SteppIR has a metal "tape" element that is metered
out from the base within a PVC (I think) tube. The antenna element
can be shortened/lengthened remotely to maximize performance on any
HF band. This design intrigued me. Seems many of us end up retiring
in CCR environments. Who can argue with a good ol' American flagpole?
http://www.steppir.com/

(I have no connection with the company.)

John
AB8WH
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Mark Perrin

Re: VERTICALS

I have a SteppIR Big Vert [10-40 meters] and it works great. Mine is
"hidden" in some shrubs and a small tree on back of my small city lot. I
use it on 40 and 30 and love it.

73, Mark N7MQ

>
> Maybe I missed it, but I didn't see anyone mention SteppIR, though I
> seem to remember a mention of it earlier.
>
> I do not have one, but I've seen articles showing one masquerading as
> a flag pole.
>
> As many know, the SteppIR has a metal "tape" element that is metered
> out from the base within a PVC (I think) tube. The antenna element
> can be shortened/lengthened remotely to maximize performance on any
> HF band. This design intrigued me. Seems many of us end up retiring
> in CCR environments. Who can argue with a good ol' American flagpole?
> http://www.steppir.com/
>
> (I have no connection with the company.)
>
> John
> AB8WH
> _______________________________________________
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>

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Ron D'Eau Claire-2

RE: VERTICALS

In reply to this post by John Wiener

John AB8WH wrote:
Maybe I missed it, but I didn't see anyone mention SteppIR, though I
seem to remember a mention of it earlier.

I do not have one, but I've seen articles showing one masquerading as
a flag pole....

Seems many of us end up retiring
in CCR environments. Who can argue with a good ol' American flagpole?
http://www.steppir.com/

-----------------------------------------

Yes, the SteppIR design is a really intriguing idea. The verticals are
apparently 1/4 wave verticals and a 1/4 wave antenna is highly-dependent on
a good ground, both close in and at a distance, for optimum performance.
Notice that their photos of verticals in action have them installed in
"vertical Heaven" - at the seashore!

Verticals do a very good job anywhere they are installed properly, but by or
on salt water is where they really stand out!

There are two issues with ground-mounted verticals - either one that is
actually 1/4 wave long or one that uses traps to 'disconnect' the unneeded
length on the higher bands.

1) On the higher bands, the active portion of the antenna is that part
closest to the ground. So, on the higher frequencies most vulnerable to
absorption by surrounding objects, the active part of the antenna is most
likely down among such objects.

2) They still need a ground, and the closer to the ground the antenna is
mounted, the more radials are required for equal performance. Tests have
shown that it takes nearly 100 radials on the ground to equal the
effectiveness of only four radials ten feet or so above the ground.

"Flag pole" antennas are a popular idea among those needing a stealth
antenna, but in some areas the developers have caught onto them. I
occasionally deal with real estate CC&R's (Covenants, Conditions &
Restrictions) and I've run across a number of places where they either deny
all permission to install a flag pole without seldom-given permission or
they specifically require that the flag pole be used *only* for the purposes
of flying the flag and that the pole serve no other purpose including
"...acting as an antenna for radio receiving or transmitting apparatus."

So if someone lives in a home with such CC&R's, read them carefully! Sure,
you can hire an attorney and challenge them, but I've got a hunch you'll
need very deep pockets and no guarantee of getting the results you want.

Ron AC7AC

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Geoffrey Mackenzie-Kennedy-2

Re: VERTICALS

In reply to this post by John Wiener

Ron AC7AC wrote:

There are two issues with ground-mounted verticals - either one that is
actually 1/4 wave long or one that uses traps to 'disconnect' the unneeded
length on the higher bands.

1) On the higher bands, the active portion of the antenna is that part
closest to the ground. So, on the higher frequencies most vulnerable to
absorption by surrounding objects, the active part of the antenna is most
likely down among such objects.

-----------------------------------------------------------------

Good point Ron, and a fact of life that is very seldom mentioned in the text
books as far as HF antennas are concerned.

If it is not possible to put up a vertical taller than a 1/4 wave in among
small trees and shrubs, in my experience better results can be obtained if
the antenna is turned upside down so that the high current portion is at the
top, and the bottom end a few feet above ground. This way the antenna has a
better chance of looking over the vegetation. The T antenna is an example of
this scheme, and can be voltage fed at the bottom with a parallel LC 'tank'
with link or tap for the coax feed. Personally I prefer to feed this type of
antenna, or vertical 1/2 wave dipoles, at the high current point which is
1/4 wave plus a few feet above ground using coax. The centre of the coax
connects to the top of the vertical, the braid to the horizontal 'radials'.
If the coax is run alongside the vertical, the antenna's radiation pattern
can be and usually is affected, with the main lobe being moved to a higher
take-off angle. To avoid this problem the coax can be run inside or tied to
the vertical element, and where the coax feeder leaves the bottom of the
vertical it is coiled so that the braid of this coil forms the L of a high
impedance LC trap tuned to the operating band. A simple choke coil could be
used, but is not so effective since it has to present a very high impedance.

A neater method can be used with vertical centre fed 1/2 wave dipoles. The
top 1/4 wave section is made from wire (Flexweave is good) with its 'bottom'
end connected to the centre conductor of the coax feeder, the braid is not
connected to anything. The bottom 1/4 wave part of the dipole uses the
outside of the coax feeder's braid. The RF current flowing on the inside of
the feeder loops over to the outside of the braid at the open end of the
coax, and continues to flow down the outside of the feeder untill told to
stop.This is done by introducing a high impedance trap, again using a coiled
length of the feeder as part of a trap, approximately 1/4 wave down from the
feeder's open end. The velocity factor of the coax is not involved in
working out the length of this 1/4 wave section because only the electrical
length of the outside of the coax braid is of importance, but the jacket and
diameter of the coax do have some effect on electrical length although they
tend to cancel in practice. At the feedpoint the coax must be well supported
by the top 1/4 wave wire so that the coax's centre conductor is not under
stress.

Anything to get rid of flapping feeders!

73,
Geoff
GM4ESD

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Don Wilhelm-3

RE: VERTICALS

Geoff,

A half square antenna is also a phased pair of 'upside-down' verticals -
easy to get up if you have 2 supports just a bit more than 1/4 wave high and
a bit more than a half wavlength apart. Feed at the upper corner directly
with coax or with a parallel resonant tank at the lower end of the vertical
section.

I have one observation about the 'coax dipole' that you described - the
choking impedance must be very high for it to work properly - consider that
the impedance at the end of a halfwave dipole is quite high (4000 ohms or
so), to effectively de-couple the remaining coax shield at the 1/4 wave
point, you would need a choking impedance at least 5 times the impedance at
that point - more like 20,000 ohms. The impedance of a few turns of coax is
not going to make an effective choke at this high impedance point. I might
consider it to be a 3/4 wave dipole fed at the 1/4 wave point with the choke
placed at a point 1/2 wavelength down the coax. I guess I have to try one
just to see how the feed impedance works out, several folks report success
with these coax antennas, but I do not understand how the choke could work
at 1/4 wavelength down the coax.

73,
Don W3FPR

> -----Original Message-----
>
> If it is not possible to put up a vertical taller than a 1/4 wave in among
> small trees and shrubs, in my experience better results can be obtained if
> the antenna is turned upside down so that the high current
> portion is at the
> top, and the bottom end a few feet above ground. This way the
> antenna has a
> better chance of looking over the vegetation. The T antenna is an
> example of
> this scheme, and can be voltage fed at the bottom with a parallel
> LC 'tank'
> with link or tap for the coax feed.

...(snip)

>
> A neater method can be used with vertical centre fed 1/2 wave dipoles. The
> top 1/4 wave section is made from wire (Flexweave is good) with
> its 'bottom'
> end connected to the centre conductor of the coax feeder, the braid is not
> connected to anything. The bottom 1/4 wave part of the dipole uses the
> outside of the coax feeder's braid. The RF current flowing on the
> inside of
> the feeder loops over to the outside of the braid at the open end of the
> coax, and continues to flow down the outside of the feeder untill told to
> stop.This is done by introducing a high impedance trap, again
> using a coiled
> length of the feeder as part of a trap, approximately 1/4 wave
> down from the
> feeder's open end. ...(snip)
> 73,
> Geoff
> GM4ESD
>
>

Bruce Bowman

Re: VERTICALS

In reply to this post by John Wiener

I have a SteppIR vertical, the one they call the BiggIR which tunes 40m
thru 6m. They work great in that they are always the correct length and
with options can track the radio dial, automatically adjusting the
physical length in small increments every 50 KHz. Unless you do
something really dumb, the design is very durable with copper-berylium
tape for the radiating element housed inside nested fiberglass tubes.
The antenna requires guys at 8' above the base and you must use radials.

If you really would use it as a flag pole, I have my doubts. It's pretty
'whippy' in a breeze with nothing attached. I suspect a flag could cause
too much bending and snap an upper section in a stiff breeze. A Force 12
would be a better choice for that sort of thing.

This antenna, and I'm confident any 1/4 wave vertical, is very sensitive
to grounding. I've had to mount mine on the roof, and the vertical
doesn't like being mounted up there (13' up in our case with the radials
are layed out on our flat roof). I was warned by Fluid Motion (the mfr)
this elevation would be an issue unless I could get it > 0.2 wave
lengths off ground; that means more than 8m up to use the 40m band. At
anything over 8m elevation, sloping the radials will improve the
performance. It'a all in the report available on their site.

In my own case the real component of impedance dropped to very small
values- I've seen < 2 ohms depending on the band. At 2 ohms, that means
most of the power is being dissipated back in the 50 ohm finals of the
K2 and not out at the antenna. Yes, the KAT2 matches the complex
component of impedance, but it doesn't do anything about matching the
real component of impedance... that takes a matching transformer. Simply
getting a low SWR doesn't necessarily mean you're getting power out to
the antenna.

If you can mount the antenna at ground level, then the real component of
impedance should move up to 35-40 ohms and you should be a happy camper.
Btw, the SteppIR will tune 40m - 6m as a vertical, and in a pinch will
even tune 2m. For beams and the dipole from Fluid Motion, I believe you
have to buy an accessory to tune 6m.

Also, there's a photo on their site of a pretty stealthy installation
using their 20m-10m dipole (I don't know if it will tune 6m) mounted
flat on a roof right at the ridge. You would have to know what you were
looking for to spot it since it's only an inch or 2 off the surface.
Check their site if that's of interest.

If you want to request info about any of the SteppIRs, don't bother with
their e-Mail. They've given up because of spam and only respond to phone
calls.

Bruce NM5B
Santa Fe, NM

----- Original Message -----
From: "John Wiener" <[hidden email]>
To: "Elecraft email" <[hidden email]>
Sent: Wednesday, June 14, 2006 6:02 PM
Subject: [Elecraft] VERTICALS

>
> Maybe I missed it, but I didn't see anyone mention SteppIR, though I
> seem to remember a mention of it earlier.
>
> I do not have one, but I've seen articles showing one masquerading as
> a flag pole.
>
> As many know, the SteppIR has a metal "tape" element that is metered
> out from the base within a PVC (I think) tube. The antenna element
> can be shortened/lengthened remotely to maximize performance on any
> HF band. This design intrigued me. Seems many of us end up retiring
> in CCR environments. Who can argue with a good ol' American flagpole?
> http://www.steppir.com/
>
> (I have no connection with the company.)
>
> John
> AB8WH
> _______________________________________________
> 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
>

Geoffrey Mackenzie-Kennedy-2

Re: VERTICALS

In reply to this post by Don Wilhelm-3

Don,

You are quite right about how easy it is to put up a Half Square, and it is
quite a forgiving antenna as far as dimensions are concerned, although
symmetry seems to be important. When they were up I fed each of my 40m Half
Squares at its corner using the outside braid of the feeder as one leg of
each antenna, along with a high impedance L - C tuned trap a 1/4 wave down
from the feedpoint using the braid of coiled feeder as the L - solenoid
wound not scrambled. I used two Half Squares at right angles because the
nulls off the ends of a Half Square are quite deep at low angles.

I agree with your comment about the choking impedance offered by a simple
coil of coax, which is why I use high impedance tuned L-C traps in these
applications with the braid of the coiled feeder coax acting as the L. A
simple coil of coax could be used if its interwinding capacitance resonated
with the inductance of the coil at or very close to the operating frequency
thus increasing the impedance, but not a good idea. One penalty gained when
using the braid of the feed coax wound as a coil for a tuned L - C trap is
that the jacket of the coax has to be opened at the start and end of the
coax coil to gain access to the braid for connecting the capacitor, so
weatherproofing is very important at those points. The function of the trap
is simply to establish the length of the outside of the feeder's braid that
acts as the bottom 1/4 wave of the dipole, or leg in the case of a Half
Square, and prevents the real antenna current going any further. The trap
has no effect on the feeder itself, other than to increase its length, since
the feed currents are flowing inside the coax.

Hope that this clarifies some.

73,

Geoff
GM4ESD

Don W3FPR wrote:

> A half square antenna is also a phased pair of 'upside-down' verticals -
> easy to get up if you have 2 supports just a bit more than 1/4 wave high
> and
> a bit more than a half wavlength apart. Feed at the upper corner directly
> with coax or with a parallel resonant tank at the lower end of the
> vertical
> section.

> I have one observation about the 'coax dipole' that you described - the
> choking impedance must be very high for it to work properly - consider
> that
> the impedance at the end of a halfwave dipole is quite high (4000 ohms or
> so), to effectively de-couple the remaining coax shield at the 1/4 wave
> point, you would need a choking impedance at least 5 times the impedance
> at
> that point - more like 20,000 ohms. The impedance of a few turns of coax
> is
> not going to make an effective choke at this high impedance point. I
> might
> consider it to be a 3/4 wave dipole fed at the 1/4 wave point with the
> choke
> placed at a point 1/2 wavelength down the coax. I guess I have to try one
> just to see how the feed impedance works out, several folks report success
> with these coax antennas, but I do not understand how the choke could work
> at 1/4 wavelength down the coax.

Vic K2VCO

Re: VERTICALS

In reply to this post by Bruce Bowman

Bruce Bowman wrote:

> This antenna, and I'm confident any 1/4 wave vertical, is very
> sensitive to grounding. I've had to mount mine on the roof, and the
> vertical doesn't like being mounted up there (13' up in our case with
> the radials are layed out on our flat roof). I was warned by Fluid
> Motion (the mfr) this elevation would be an issue unless I could get
> it > 0.2 wave lengths off ground; that means more than 8m up to use
> the 40m band. At anything over 8m elevation, sloping the radials will
> improve the performance. It'a all in the report available on their
> site.

As you get closer to the ground, the system behaves more like a
ground-mounted vertical, and so you need to treat the radial system as a
capacity-coupled counterpoise, as opposed to the resonant radials of a
ground plane antenna. This means that you need more radials.
Otherwise, much of the ground return current will flow in the lossy real
ground. If I were putting a BigIR or similar on a low roof, I would
start with about 16 radials.

> Yes, the KAT2 matches the complex
> component of impedance, but it doesn't do anything about matching the
> real component of impedance... that takes a matching transformer. Simply
> getting a low SWR doesn't necessarily mean you're getting power out to
> the antenna.

I would put it differently. The matching is fine -- the problem is that
the RF current to the antenna divides between the radiation resistance
of the antenna and the effective ground resistance. If the radiation
resistance of the antenna is very low, then most of the power ends up
heating the ground.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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