Area 51 for Antenna Modelers & Builders (See Post #1) - Page 4 - Canadian TV, Computing and Home Theatre Forums

 1Likes
Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #46 of 1311 (permalink) Old 2009-04-29, 11:52 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
I don't know what's up with the dip at channel 48.
Nothing really. Thats typical of what occurs on the GH at the breakup at the high end frequencies of its bandwidth. Also since the SWR dips at the same time, the net gain curve is smoother.

A prerequisite to building a 2nd or more iteration fractal antenna should be to have training in the Japanese fine art of origami, heh.

For some odd reason, I seem have a copy of "Fractal Programming in C" by Roger T. Stevens 1989, in front of me. The example programs are on 5 1/4 inch floppy, MS/PCDos format (unopened). If you think some may be useful, Ill see if the disk still reads once I dig thru my collection of old hardware crap, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
Sponsored Links
Advertisement
 
post #47 of 1311 (permalink) Old 2009-04-29, 02:14 PM
 
Join Date: Feb 2009
Location: Upstate NY
Posts: 180
Thanks, but I think I'll pass on the ancient code offer. I seem to have Koch Curves figured out, and I don't think I'm going to go any further with them. If I get bored, I may do a more in-depth analysis of a full size GH fractal.
firimari is offline  
post #48 of 1311 (permalink) Old 2009-04-29, 02:46 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
What ? No Peano, Hilbert, Sierpinski, Dragon, Phoenix curves, not to mention the Mandelbrot set ? Heh, heh.

Yeah, theyre basically only practical for cell phone/PDA type antennas printed on some kind of pcb.

That Italian Job antenna, with its nice wide front pattern, may make a nice wifi antenna for my use once I scale it for 2.4 GHz. Of course, I got to find a cheap source for the cable/connectors. They seem to want a fortune for a measly 25 foot piece, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #49 of 1311 (permalink) Old 2009-04-29, 04:55 PM
 
Join Date: Sep 2008
Posts: 527
300ohm: If you make it for 2.4 Ghz., you may need 1/4 wave lenght separators between the diamonds. Google Quados.
Xauto is offline  
post #50 of 1311 (permalink) Old 2009-04-30, 09:53 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
That doesnt look bad either. Im wondering if I use the same technique on the Italian Job, that it will be even better still, ie wide beam, high gain.

My biggest problem is finding cheap coax and connectors for it. It goes totally against my grain and principles to spend $50 to $100 for a measley 25 ft piece, or $10+ for a connector : http://www.newegg.com/Product/Produc...82E16833998039
If I did that, I would be kicking myself in the butt for a long time, heh.

Its pretty obvious that a lot of those Youtube wifi antennas havent been modeled.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #51 of 1311 (permalink) Old 2009-04-30, 11:05 PM
 
Join Date: Apr 2009
Location: Ottawa
Posts: 502
X51 Modeled from photo

Here is the NEC file for the dual half folded dipole seen from BT

I discussed the modeling results here

4nec2 & Other Antenna Design Modeling Software (Post #265)

CM Omnidirectional FM Antenna
CM Based on a photo in the Blonde Tongue catalogue
CM Optimized for 98 MHz
CE
SY h=3.009341
SY f=25.3431 'Inches
SY g=33.5266 'Inches
SY v=2.452685 'Inches
SY Wire=0.0404 'Inches
SY Tilt_angle=3.997235 'Tilt angle of the dipole
SY i=h*0.41421 'Circle approximated with an octagon
SY h1=0.70711*i
SY h2=h1+i
SY tilt1 = h1*tan(Tilt_angle)
SY tilt2 = h2*tan(Tilt_angle)
SY tilt = h*tan(Tilt_angle)
SY s0_z4=-v*0.5
SY s0_z3=-v*0.5-h1
SY s0_z2=-v*0.5-h2
SY s0_z1=-v*0.5-h
SY s0_z5=v*0.5-h
SY s0_z6=v*0.5+h1-h
SY s0_z7=v*0.5+h2-h
SY s0_z8=v*0.5
SY s0_y1=-f
SY s0_y2=-f+h1
SY s0_y3=0
SY s0_y4=0.75
SY s0_y5=g
SY s0_x1=-f
SY s0_x2=-f+h1
SY s0_x3=0
SY s0_x4=0.75
SY s0_x5=g
GW 1 23 Tilt s0_y3 s0_z1 Tilt s0_y2 s0_z1 wire
GW 2 3 Tilt s0_y2 s0_z1 Tilt2 s0_y1 s0_z2 wire
GW 3 3 Tilt2 s0_y1 s0_z2 Tilt1 s0_y1 s0_z3 wire
GW 4 3 Tilt1 s0_y1 s0_z3 0 s0_y2 s0_z4 wire
GW 5 55 0 s0_y2 s0_z4 0 s0_y5 s0_z4 wire
GW 6 1 Tilt s0_y3 s0_z1 s0_x4 s0_y4 s0_z1 wire
GW 7 23 s0_x3 Tilt s0_z5 s0_x2 Tilt s0_z5 wire
GW 8 3 s0_x2 Tilt s0_z5 s0_x1 Tilt2 s0_z6 wire
GW 9 3 s0_x1 Tilt2 s0_z6 s0_x1 Tilt1 s0_z7 wire
GW 10 3 s0_x1 Tilt1 s0_z7 s0_x2 0 s0_z8 wire
GW 11 55 s0_x2 0 s0_z8 s0_x5 0 s0_z8 wire
GW 12 1 s0_x3 Tilt s0_z5 s0_x4 s0_y4 s0_z5 wire
GW 13 5 s0_x4 s0_y4 s0_z1 s0_x4 s0_y4 s0_z5 wire
GS 0 0 0.0254
GE 0
GN -1
EK
EX 0 13 2 0 1 0
FR 0 21 0 0 88 1
EN

Last edited by stampeder; 2009-04-30 at 11:33 PM. Reason: Fixed URL - please use Post numbers instead of page numbers
RamKat is offline  
post #52 of 1311 (permalink) Old 2009-05-01, 07:14 AM
 
Join Date: Sep 2008
Posts: 527
RamKat: Is the feed to 75 ohms, and is it only off the 1/2 folded leg of each. I have a yagi that use's 1/2 folded. The feed is from the center of the dipole to the 1/2 folded leg. Have you tried flipping the bottom element to change the feed point space?
Xauto is offline  
post #53 of 1311 (permalink) Old 2009-05-01, 07:52 AM
 
Join Date: Apr 2009
Location: Ottawa
Posts: 502
XAuto, it feeds to 300 Ohms with a SWR of very close to 1.0. I set it up to feed between the short legs of the two elements (was not clear from the picture if this was where it should have been) Do you mean treating the two half folds as seperate antennas and then combining the feed?

Here is the layout

http://img17.imageshack.us/img17/9839/framee.th.jpg

Here is the donut

http://img14.imageshack.us/img14/7918/dhdp3d.th.jpg

Yes I tried the flip but was having some other finger trouble so maybe I should try it again.
RamKat is offline  
post #54 of 1311 (permalink) Old 2009-05-01, 08:30 AM
 
Join Date: Feb 2009
Location: Upstate NY
Posts: 180
My current optimization project: Take all of j3d's GH{4,6,8,10} and re-optimize them for my build style (6 gauge copper / quarter inch aluminium), and my channel range (17-47)

If only I had four cores instead of two on my windows box.
firimari is offline  
post #55 of 1311 (permalink) Old 2009-05-01, 09:42 AM
 
Join Date: Sep 2008
Posts: 527
RamKat: Thank you for the info. If you do treat the two half folds as seperate antennas and then combine them, it will just make the phase lines move complex.
Xauto is offline  
post #56 of 1311 (permalink) Old 2009-05-01, 09:48 AM Thread Starter
OTA Forum Moderator
 
Join Date: Jan 2005
Location: North Delta, BC (96Av x 116St)
Posts: 24,427
Cool How to upload your pics/images to this site

RamKat, can you try posting your images this way:

How to create a photo album for use on the Digital Forum
stampeder is offline  
post #57 of 1311 (permalink) Old 2009-05-01, 03:19 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
If only I had four cores instead of two on my windows box.
There is a benchmark thread on this site for that. It seems 4nec2 only will use 3 of the 4 cores. My gut feeling is, more mhz on a dual core is better overall.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #58 of 1311 (permalink) Old 2009-05-02, 12:46 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
Yes I tried the flip but was having some other finger trouble so maybe I should try it again.
Yeah, that is somewhat weird. I was also expecting the gain to be a bit better on that design. Oh well.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #59 of 1311 (permalink) Old 2009-05-03, 01:08 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
A kick butt antenna design modeled in 4nec2

I found Ross Andersons, W1HBQ, site while perusing the web. He has posted the NEC files for his models. The Curtain Quad is the one with the most interest. 221 element, 26.55 dbi raw gain, and about a 1 degree beamwidth, BI-DIRECTIONAL, heh. Stick a reflector on that baby, and youll get over 30dbi !
http://home.comcast.net/~ross_anderson/

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #60 of 1311 (permalink) Old 2009-05-03, 02:04 AM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
The Sasquatch Killer - Rescaled Quad Curtain for 635mhz

Dont let this small picture fool you, this is one large antenna ! 241 inches wide by 307.20 inches high, heh. (20 by 26 feet !) (but still probably easier to build and get right than a 14 - 20 ft parabola)

At 635mhz:


Rescaled, I got 26.25 dbi Raw Gain bidirectional, with an SWR of 3.29 at 300 ohms at 635mhz. Net Gain is about 24.85 dbi. Not too shabby, heh. Will run frequency sweep later.

The NEC file : http://www.wuala.com/300ohm/Document...urtainQuad.nec

My builds/plans (not the latest models) are located here.
300ohm is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome