Fractal TV Antenna Research & Development - Page 5 - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #61 of 341 (permalink) Old 2008-12-12, 10:16 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
It's not that bad for the size about 24" by 22".
Yeah, for the middle channels its gain is better than almost all indoor antennas sold. Since its a fractal gen2 and I modeled the 4 leg gen1, the high end channels should drop off even quicker probably before channel 40. The lower channels should pick up gain quicker though.

My builds/plans (not the latest models) are located here.
300ohm is offline  
Sponsored Links
Advertisement
 
post #62 of 341 (permalink) Old 2008-12-13, 07:05 AM
 
Join Date: Sep 2008
Posts: 551
Here are the numbers for 2/3rd's and full GH gen2 fractal in %.

Ch14 60 90
Ch21 100 100
Ch39 100 100
Ch41 90 90
Ch43 80 90
Ch44 80 90
Ch45 100 100
Ch58 90 100
Xauto is offline  
post #63 of 341 (permalink) Old 2008-12-13, 01:38 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Is 60% enough to lock the station on ? Channel 45 must be very strong.

My builds/plans (not the latest models) are located here.
300ohm is offline  
 
post #64 of 341 (permalink) Old 2008-12-13, 04:48 PM
 
Join Date: Sep 2008
Posts: 551
It work fine at 60% strenght, because the quality is at 100%. I find that any thing over 50 in strenght and quality in the 80's is ok. If the quality gos to below 25% the pic. drops out. So this little guy is good until Feb.2009 (or if I fine a longer piese of wire) when Ch58 gos to Ch7. Then I may need to go to 4 bay bow-tie 9.5X9 with 36X40 screen @15". I have a 8.5X8 do you think that would work?
Xauto is offline  
post #65 of 341 (permalink) Old 2008-12-13, 05:47 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
I have a 8.5X8 do you think that would work?
Yes, but the 9.% X 9 would have more gain on the lower channels. But if you dont need the extra gain, 8.5 X 8 is fine. The large reflector on the bowties is what gives it the VHF-Hi gain. It doesnt work that way with a GH. (maybe on a quad bay GH ?? But then its an insanely large monster)

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #66 of 341 (permalink) Old 2008-12-20, 10:18 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Just a technical quibble with the thread title. Its not really a 2/3 scale GH, but rather a full scale fractalized GH with only one diamond section.

2/3 scale would imply re-scaling all dimensions, which would put the antenna well out of UHF TV range, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #67 of 341 (permalink) Old 2008-12-20, 11:05 PM
OTA Forum Moderator
 
Join Date: Jan 2005
Posts: 24,878
Changed it - is this more accurate?
stampeder is offline  
post #68 of 341 (permalink) Old 2008-12-21, 12:24 AM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Yeah, thanks. I just had a PM about the 2/3 rds GH, and realized it was misleading.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #69 of 341 (permalink) Old 2008-12-28, 05:03 PM
Rookie
 
Join Date: Sep 2008
Location: Pittsburgh, PA
Posts: 1
notes and suggestions

Hay, all! I've just read this thread, and figured I would post a message with some notes. I've been interested in fractal antennas for wifi purposes (of course), and have also built myself a SBGH out of waste materials. I'm looking to build a system for fractal antenna design - just to see how to do it.

Fabrication - I figured that since the fractals are self-similar, you should be able to print out a design of a smaller subset of the whole piece, and make a bunch of smaller pieces. You should be able to screw them all together onto a substrate to make the whole pattern. This would allow for more uniform pieces.

Having access to a waterjet/laser cutter would probably be the best way to fabricate some of these shapes, such that they are as exact as possible. The more complex shapes would eat a lot of material unless they were broken down into smaller pieces as mentioned above.

(I assume that having an element that is exact in size and position will have more ideal electrical features. I can't help wondering if my homebuilt SBGH is 'lumpy' in some way, and not working as well as it could. Wouldn't this be exacerbated when using fractal antennas?)


Modeling and Mining - I'm also sure there are variations in the shape that may improve with minor adjustments. I was wondering if L-systems may be used to 'grow' a better antenna (http://en.wikipedia.org/wiki/L-systems). Think the Folding@Home for antennas.

My plan was to write some terrible shell scripts to couple the output of the L-systems generator to whatever 4NEC variant I could get working with a qualifier at the end.

I'll go read the modeling software thread.
drewzhrodague is offline  
post #70 of 341 (permalink) Old 2008-12-31, 01:39 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Keep in mind, with fractalization you lose some gain in trade for smaller size. Cell phones use fractal antennas because the full size would be tough to fit into your pocket, heh. If you dont need the compact size (at those frequencies they are small already), I wouldnt fractalize the wifi antenna. The biggest benefit of fractalizing the GH antennas is with the VHF-Hi GH version.

Quote:
Fabrication - I figured that since the fractals are self-similar, you should be able to print out a design of a smaller subset of the whole piece, and make a bunch of smaller pieces. You should be able to screw them all together onto a substrate to make the whole pattern. This would allow for more uniform pieces.
At wifi size, printing on a copper printed circuit board would be the way to go. There are some techniques posted on the web for using laser printout (not inkjet AFAIK, unless using some of that iron on T-shirt paper) to serve as the resist for etching the copper.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #71 of 341 (permalink) Old 2009-02-13, 02:48 PM
 
Join Date: Sep 2008
Posts: 551
GH gen2 fractal with C2 underlay

Just for the fun of it. At the very top you can see the venetian blind slat(NOROD)
Xauto is offline  
post #72 of 341 (permalink) Old 2009-02-13, 05:47 PM Thread Starter
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
And...............................your results are ?

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #73 of 341 (permalink) Old 2009-02-13, 08:23 PM
 
Join Date: Sep 2008
Posts: 551
Well that used up the day with not a thing to show for it. It added very little to the low Ch.s like 14 and about the same at 50.
Xauto is offline  
post #74 of 341 (permalink) Old 2009-02-13, 10:21 PM
 
Join Date: Jan 2009
Posts: 452
Xauto did you test her with reflector on her ?
wildwillie is offline  
post #75 of 341 (permalink) Old 2009-02-14, 07:56 AM
 
Join Date: Sep 2008
Posts: 551
Yes, but it was at 15". I need to try the reflector at about 4". Ok 3hr.s of testing ( I'm not the fastest) shows that the C2 underlay has not value add, and that about 3.8" is just a little better than 15" for reflector spacing. After June I will see if 15" is good for Ch.7 or 3.8"(NOROD are a value add).
Xauto 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










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