On Mon, 25 Sep 2006 20:02:11 -0000, Dave Platt
wrote:
The elevation pattern of the antenna shows a hint of the high-angle
secondary lobes which characterize an EDZ.

This is definitely noticable on a log plot.

So, I'd conclude that you've developed a variant on the EDZ (or
something partway between an EDZ and a center-fed fullwave) which
yields slightly lower gain than an EDZ but has a simpler matching
section.

What sort of gain is expected from an EDZ? I tweaked the topology
of my design a bit in the hope of getting a broader bandwidth, but
instead got even more gain. For example, the version represented
below has a minimum gain of more than 4.7 dBi (at the side) and more
than 5.25 dBi in the forward direction. Previously I reported gain
values that ran from 4.2-4.7 dBi. So this one represents a bit of an
improvement. I may try building it this weekend. Thanks, --John

CM Model: expt5
CM parms = [4.68255, 3.41606, 36.4806, 7.22131, 11.9807, 3.02775, ];
CM
CM A1: 4-11/16 in.
CM A2: 3-7/16 in.
CM B1: 36-1/2 in.
CM B2: 7-1/4 in.
CM C: 12 in.
CM D: 3 in.
CM Wire diameter: 0.0640837
CM COM: (0 in., 9-1/16 in., 0 in.)
CM BBOX: dX=0, dY=11.9807, dZ=90.4316
CM COM Turning radius: 9.06615
CM Min Turning radius: 5.99035
CE
GW 1 3 0 0 9.10555 0 0 9.18245 0.000813863
GW 2 7 0 0 9.18245 0 0.30431 9.18245 0.000813863
GW 3 19 0 0.30431 9.18245 0 0.30431 10.1091 0.000813863
GW 4 5 0 0.30431 10.1091 0 0.30431 10.2925 0.000813863
GW 5 3 0 0.30431 10.2925 0 0.185373 10.2925 0.000813863
GW 6 3 0 0.30431 10.1091 0 0.217542 10.1091 0.000813863
GW 7 7 0 0 9.10555 0 0.30431 9.10555 0.000813863
GW 8 19 0 0.30431 9.10555 0 0.30431 8.17894 0.000813863
GW 9 5 0 0.30431 8.17894 0 0.30431 7.99552 0.000813863
GW 10 3 0 0.30431 7.99552 0 0.185373 7.99552 0.000813863
GW 11 3 0 0.30431 8.17894 0 0.217542 8.17894 0.000813863
GE 0
FR 0 201 0 0 144 0.02
EX 0 1 2 0 1
GN -1 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0
RP 0 1 73 1001 90, 0, 1, 5
EN

In article ,
John E. Davis wrote:

The elevation pattern of the antenna shows a hint of the high-angle
secondary lobes which characterize an EDZ.

This is definitely noticable on a log plot.

So, I'd conclude that you've developed a variant on the EDZ (or
something partway between an EDZ and a center-fed fullwave) which
yields slightly lower gain than an EDZ but has a simpler matching
section.

What sort of gain is expected from an EDZ? I tweaked the topology
of my design a bit in the hope of getting a broader bandwidth, but
instead got even more gain. For example, the version represented
below has a minimum gain of more than 4.7 dBi (at the side) and more
than 5.25 dBi in the forward direction. Previously I reported gain
values that ran from 4.2-4.7 dBi. So this one represents a bit of an
improvement.

For an EDZ in isolation (no mast) I believe it's around 3 dBd or 5
dBi, plus or minus a hair.

I modelled a copper-pipe EDZ, mounted at the top end of a conductive
mast. This one came out with 5.85 dBi in the favored direction, and a
2.5 dB front-to-back ratio.

CEDouble extended zepp for 2 meters
GW 1 7 0 0 2 0 0 6.5 1.25 # Upper segment of mast
GW 2 7 0 0 2 0 0 -2 1.25 # Middle segment of mast
GW 3 100 0 0 -2 0 0 -112.5 1.25 # Lower segment of mast
GW 4 15 0 0 2 13 0 2 0.5 # Upper support bar
GW 5 15 0 0 -2 13 0 -2 0.5 # Lower support bar
GW 6 7 13 0 2 13 0 -2 0.5 # Shorting bar
GW 7 7 13 0 2 17 0 2 0.5 # To top of balun
GW 8 7 13 0 -2 17 0 -2 0.5 # To bottom of balun
GW 9 15 17 0 2 28 0 2 0.5 # To top arm
GW 10 15 17 0 -2 28 0 -2 0.5 # To bottom arm
GW 11 40 28 0 2 28 0 46 0.5 # Upper arm
GW 12 40 28 0 -46 28 0 -2 0.5 # Lower arm
GW 13 5 17 0 2 17 0 -2 0.5 # Feedline attachment
GS 0 0 0.0254
GE 0
EX 0 13 3 0 1.0
FR 0 1 0 0 145.27 0.00E+00 0.00E+00 0.00E+00 0.00E+00
0.00E+00
RP 0 61 72 1101 0.0 0.0 3 5
XQ
EN

A stacked pair of them on a single mast yields 8.85 dBi in the favored
direction, with 2.38 dB front-to-back ratio.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Wed, 27 Sep 2006 04:40:51 -0000, (Dave Platt) wrote:

In article ,
John E. Davis wrote:

The elevation pattern of the antenna shows a hint of the high-angle
secondary lobes which characterize an EDZ.

This is definitely noticable on a log plot.

So, I'd conclude that you've developed a variant on the EDZ (or
something partway between an EDZ and a center-fed fullwave) which
yields slightly lower gain than an EDZ but has a simpler matching
section.

What sort of gain is expected from an EDZ? I tweaked the topology
of my design a bit in the hope of getting a broader bandwidth, but
instead got even more gain. For example, the version represented
below has a minimum gain of more than 4.7 dBi (at the side) and more
than 5.25 dBi in the forward direction. Previously I reported gain
values that ran from 4.2-4.7 dBi. So this one represents a bit of an
improvement.

For an EDZ in isolation (no mast) I believe it's around 3 dBd or 5
dBi, plus or minus a hair.

I modelled a copper-pipe EDZ, mounted at the top end of a conductive
mast. This one came out with 5.85 dBi in the favored direction, and a
2.5 dB front-to-back ratio.

Have I missed something here? As I understand the EDZ (is it not the Extended
Double Zepp?) it comprises a center-fed doublet with a 5/8 wl wire on each side
of the feed point. It's broadside gain is about 3.1 dBd, with a narrower lobe
than that of a dipole, from which the gain over a dipole is obtained. Am I
correct so far?

If so, then we have only a single radiator. How then can there be a
front-to-back ratio?

Walt,W2DU

On Wed, 27 Sep 2006 04:40:51 -0000, Dave Platt
wrote:
I modelled a copper-pipe EDZ, mounted at the top end of a conductive
mast. This one came out with 5.85 dBi in the favored direction, and a
2.5 dB front-to-back ratio.

Have you considered using the much simpler moxon? This one has a
forward gain of 5.6-6.4dBi (6.2@146MHz) and a front-to-back ratio of
18-31dBi (29@146MHz). It uses #12 AWG wire. Thanks, --John

CM Model: moxon for 2m
CM parms = [29.1337, 4.18345, 1.4995, 5.70003, ];
CM
CM A: 29-1/8 in.
CM B: 4-3/16 in.
CM C: 1-1/2 in.
CM D: 5-11/16 in.
CM Wire Diameter: 0.0808081
CE
GW 1 3 -0.10626 0 8.774 0 0 8.774 0.00102626
GW 2 15 0 0 8.774 0 0 9.514 0.00102626
GW 3 3 0 0 9.514 -0.10626 0 9.514 0.00102626
GW 4 3 -0.144347 0 9.514 -0.289128 0 9.514 0.00102626
GW 5 15 -0.289128 0 9.514 -0.289128 0 8.774 0.00102626
GW 6 3 -0.289128 0 8.774 -0.144347 0 8.774 0.00102626
GE 0
FR 0 401 0 0 144 0.01
EX 0 2 8 0 1
GN -1 0 0 0 0.0 0.0 0.0 0.0 0.0 0.0
RP 0 1 73 1001 90 0 1 5
EN

On 27 Sep 2006 02:49:55 GMT, I wrote wrote:
What sort of gain is expected from an EDZ? I tweaked the topology
of my design a bit in the hope of getting a broader bandwidth, but
instead got even more gain. For example, the version represented
below has a minimum gain of more than 4.7 dBi (at the side) and more
than 5.25 dBi in the forward direction. Previously I reported gain
values that ran from 4.2-4.7 dBi. So this one represents a bit of an
improvement. I may try building it this weekend. Thanks, --John

I found time this weekend to construct this antenna and it seems to
work quite well. See http://www.jedsoft.org/fun/antennas/omni.html
for the details including a picture of the antenna.

While testing it, I made a contact through a distant repeater (40
miles away) and was told that the signal was solid. This was with the
antenna in its test position with the center about 10 feet off the
ground and the transmitter power at 5 watts. Unfortunately I cannot
be more quantitation than that.

Unless I have overlooked some other design, this seems to be an
extremely simple and effective home-brew antenna.

Comments welcome.
Thanks,
--John

John E. Davis wrote:

Hi,

I created a "omni-directional" vertical antenna that NEC-2 reports to
have a free-space gain 4 dBi. The shape of the antenna looks like:


------+
A |
| B
|
+-----+
C * (* = feed point)
+-----+
|
|
|
------+

The lengths can be adjusted to give the antenna a 50 ohm feedpoint
impedence. The overall length of wire forming the antenna (4A+2B+C)
is on the order of 1.5\lambda and the height (2B) is something like
\lambda. I built this antenna for 2-meters and it seems to perform
quite well. The .nec files and parameters are available from my
antenna pages at http://www.jedsoft.org/fun/antennas/omni.html.

I am sure that I am not the first to create this simple antenna,
nevertheless a google search has turned up nothing similar. Have you
seen such an antenna before and if so, what is it called? I suspect
that it belongs to some class of antennas (antennae?). I would
like to give the proper credit and name for it on my web page.

Also, if you can find a flaw in my NEC modeling of the antenna, please
tell me. The prototype that I built does have an SWR of 1.05:1 as
given by my uncalibrated meter at the design frequency.

Thanks,
--John

Congratulations John, you appear to have re-invented a version of the
colinear vertical antenna on your own. I looked at your implimentation,
and it seems to be quite well done.

Keep it up, and have fun.

tom
K0TAR