On Wed, 16 Apr 2008 09:21:13 +0300, "JN" wrote:

.

----------------------------------------xxcenterxxx----
I_________

OR

----------------------------------------xxxxcenterxxx------
________I


73 Jouko OH5RM


Different text sizes seem to destroy the graphics, I used the medium size in
Outlook express.
Anyway the upper is OK , the lower should look like this

______________________________________/center/_____
___________I

OH5RM


from OP
My question:
Is there any difference if the shorted end is pointing to the center or to
the tip of dipole.
Only the stub portion has two wires in parallell, the rest is only one wire.

Jouko, I noticed this thread took a detour, but I never saw anyone
actually try to answer your question. I too, am looking to see the
answer on this.

It is amazing, all this talk about a Lattin antenna, that appears to
have lots of sites talking about how it works, but no one actually
having built one or used one, and a simple "yes" or "no" would answer
your question.

I don't have the answers or the means of testing one at this time. If
you get the answer direct, please post it here.

Thanks
Buck
N4PGW
--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

Jouko, I noticed this thread took a detour, but I never saw anyone
actually try to answer your question. I too, am looking to see the
answer on this.

73 for now
Buck, N4PGW

www.lumpuckeroo.com

Yes Buck it is often difficult to get an answer just to the question you are
asking.
Anyway very soon all snow has melted away here and then its possible to
testbuild it.

73 Jouko OH5RM

"JN" wrote in message
...
Jouko, I noticed this thread took a detour, but I never saw anyone
actually try to answer your question. I too, am looking to see the
answer on this.

73 for now
Buck, N4PGW

www.lumpuckeroo.com

Yes Buck it is often difficult to get an answer just to the question you
are asking.
Anyway very soon all snow has melted away here and then its possible to
testbuild it.

73 Jouko OH5RM

Hi Jouko

I thought Richard's statement that modeling would tell you about how the
design might perform, was good advice. If you use EZNEC, I'd be willing to
help you if you dont already know how to use it to model your antenna.

Jerry KD6JDJ

I thought Richard's statement that modeling would tell you about how the
design might perform, was good advice. If you use EZNEC, I'd be willing
to help you if you dont already know how to use it to model your antenna.

Jerry KD6JDJ


Jerry, thanks for the offert.
I dont know how good these modelling programs are in this situation.
But if it is easy, so could somebody do the following:

Take 20m of wire, that is half of a dipole.
Put a 1/4 electric wavelength shorted stub for 10,1MHz so that the open end
is 7,25m from center and the shorted end pointing to the tip of antenna. One
side of stub is the 20m wire itself, like in the upper picture. Ignore all
velocity factors to make it sinple.
Now tell me what are the resonance frequencies of that kind of element and
if possible feed point impedande (80m and 30m)

I know I could do it myself but as you know learning to use a new program
reliably takes lot of time.

73 Jouko OH5RM

"JN" wrote in message
...
I thought Richard's statement that modeling would tell you about how the
design might perform, was good advice. If you use EZNEC, I'd be willing
to help you if you dont already know how to use it to model your antenna.

Jerry KD6JDJ


Jerry, thanks for the offert.
I dont know how good these modelling programs are in this situation.
But if it is easy, so could somebody do the following:

Take 20m of wire, that is half of a dipole.
Put a 1/4 electric wavelength shorted stub for 10,1MHz so that the open
end is 7,25m from center and the shorted end pointing to the tip of
antenna. One side of stub is the 20m wire itself, like in the upper
picture. Ignore all velocity factors to make it sinple.
Now tell me what are the resonance frequencies of that kind of element and
if possible feed point impedande (80m and 30m)

I know I could do it myself but as you know learning to use a new program
reliably takes lot of time.

73 Jouko OH5RM

Hi Jouko

I am not sure I am reading your text properly. But, I did model a 40
meter wire with a trap on each side. You are welcome to E-mail me if you
want to see what EZNEC says about *my* model. Maybe you can help me model
your concept.
I have a friend in vasa Finland who can get you any information about
contacting me. Google Patrik Tast.

Jerry KD6JDJ

Jouko, OH5RM wrote:

Take 20m of wire, that is half of a dipole.
Put a 1/4 electric wavelength shorted stub for 10,1MHz so that the open end
is 7,25m from center and the shorted end pointing to the tip of antenna. One
side of stub is the 20m wire itself, like in the upper picture.

I did just that with EZNEC, but with a free-space dipole. Without the
stubs, the antenna resonated at 3.6 MHz. With the stubs, that dropped
to 2.75 MHz and additional low-impedance points were noted at 6.5 and
11 MHz. The patterns at 2.75 and 6.5 had the desired dipole shape,
but the 11 MHz pattern had multiple lobes.

Jim Bromley, K7JEB
Glendale, AZ, USA

Jim, K7JEB wrote:
Jouko, OH5RM wrote:

Take 20m of wire, that is half of a dipole.
Put a 1/4 electric wavelength shorted stub for 10,1MHz so that the open end
is 7,25m from center and the shorted end pointing to the tip of antenna. One
side of stub is the 20m wire itself, like in the upper picture.

I did just that with EZNEC, but with a free-space dipole. Without the
stubs, the antenna resonated at 3.6 MHz. With the stubs, that dropped
to 2.75 MHz and additional low-impedance points were noted at 6.5 and
11 MHz. The patterns at 2.75 and 6.5 had the desired dipole shape,
but the 11 MHz pattern had multiple lobes.

Great minds think alike. :-) I was doing the same thing
at different frequencies. I noticed that a 1/2WL dipole
with 1/4WL stubs on each end tends to resonate on frequencies
in a ratio of about 2.57:1. 18.14/2.57=7.06 so such an
antenna should be resonant on both 17m and 40m. EZNEC
agrees. Here are the approximate dimensions for the dualband
40m/17m antenna. Cutting and trying will be necessary for
fine tuning to resonance. Note that the antenna is about 13
feet shorter than a 1/2WL dipole on 40m. It has a dipole
pattern on both 40m and 17m and a 50 ohm SWR less than 2:1
on both bands. It appears to be linear-loaded on 40m and
stub-matched on 17m.

26.8' 26.8'
+-------------------------FP-------------------------+
| |
+------------ ------------+
13.3' 13.3'

Since 10.125/2.57=3.9 MHz, this antenna should be scalable
to become a dualbander on 75m and 30m.
--
73, Cecil http://www.w5dxp.com

After a bit of e-mail correspondence and the
exchange of a single, crucial, 1000-word, picture,
I think we've bottomed-out on this. I'm seeing two,
distinct, dipole-like responses, one at 3.6 MHz
and one at 10.2 MHz. The EZNEC outputs and
source file are at:

http://www.arizona-am.net/test/Antenna_Stubs_SWR.pdf

http://www.arizona-am.net/test/Anten...bs_picture.pdf

http://www.arizona-am.net/test/Anten..._10MHz_SWR.pdf

http://www.arizona-am.net/test/Anten...s_3MHz_SWR.pdf

http://www.arizona-am.net/test/Antenna_Stubs_wires.pdf

http://www.arizona-am.net/test/Antenna_Stubs_Patt.pdf

http://www.arizona-am.net/test/Ant_End_Stubs.EZ

Jim, K7JEB

Jim, K7JEB wrote:
After a bit of e-mail correspondence and the
exchange of a single, crucial, 1000-word, picture,
I think we've bottomed-out on this. I'm seeing two,
distinct, dipole-like responses, one at 3.6 MHz
and one at 10.2 MHz.

10.2/3.6=2.8 It appears that frequency ratios
between about 2.4 and 2.8 can be easily achieved.
That's 75m+30m, 40m+17m, 30m+12m.

Unfortunately, a 2:1 ratio seems difficult to
achieve.
--
73, Cecil http://www.w5dxp.com

On 16-Apr-2008, "Jim, K7JEB" wrote:

After a bit of e-mail correspondence and the
exchange of a single, crucial, 1000-word, picture,
I think we've bottomed-out on this. I'm seeing two,
distinct, dipole-like responses, one at 3.6 MHz
and one at 10.2 MHz.

I also played around with this yesterday on EZNEC. Started with a 75 M
center fed half wave at 30 feet high, added 20 M quarter wave stubs one
quarter wave (20 M) oout from the center. Got two low SWR points at ~3.5
MHz and ~14 MHz. By changing the distances to the stubs, the length of the
stubs, and the length beyond the stubs, I got the low SWR points to 3.9MHz
(2.8:1) and 14.2 MHz (1.2:1). Azimuth pattern on 14.2 MHz was sort of
omni-directional with major lobes at 45, 135, 225, and 315 degrees.
Pattern on 75 M was omnidirectional at high angles and max gain straight
up.

Conclusions: Might be useful as a way to add 20 Meters to a shortened 75 M
dipole. High SWR on 75 would still require a tuner. Losses were not
determined. More height might help.

Ken Fowler, KO6NO