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Old Jan 31, 2011, 06:20 AM
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The thicker the wire the better. 3/16" tubing would be better if you can make it work. Wider tubing helps with manufacturing tolerances and increases the bandwidth slightly.

-Alex
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Old Jan 31, 2011, 06:21 AM
Engineer for Christ
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@DerekS - That looks much better! I think all of your video problems just got solved.

-Alex
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Old Jan 31, 2011, 12:50 PM
The one and only
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Awesome!
Thanks Alex
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Old Feb 07, 2011, 08:20 PM
Fidler & twidler
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Cranfield U.K.
Joined Mar 2004
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Quote:
Originally Posted by IBCrazy View Post
Efficiency drops considerably after 12 turns. You can go as many as you want, but the efficiency drops greatly and the gain increases slowly.

-Alex
Memory from the late 60's
4 (probably) 8 turn's mounted 1 wavelength apart mounted on a trailer for the command destruct transmitters on the Canaveral test range.
?? = 6db extra gain ?? (correction welcome)
Mike
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Old Feb 09, 2011, 02:41 PM
Videopilot
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United States, NC, Charlotte
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Originally Posted by IBCrazy View Post
Method 5 - IBCrazy's tapered match
Advantage - Provides the best match and maintains the antenna integrity. Also tolerant of manufacturing errors.
Disadvantage: Hardest to make.

I came up with this one experimenting with my directional Wattmeter. It has been the best method for me. You simply make a metal strip that is tapered so that the width is equal to the height over the reflector and follow the normal helix winding.

Width at wide point in inches = 700/f in MHz
Width at starting point - Sharp pointed.

Use this as the first 1/4 turn of your helix making it follow the natural helix winding spacing. The shape keeps the signal from being attenuated and also allows for some manufacturing error. This match is not supported by any reference I know of. It is something I made up by a tapered transmission line calculation and empirical measurement.
Is this the new one that I should try? I dont remember seeing it before. Also, does it run parallel to the existing copper helix, or do you trim the copper away so it begins where the tapered match ends?
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Old Feb 09, 2011, 09:45 PM
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I just added the new match, details and pictures. All of your questions should be answered.

-Alex
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Old Feb 09, 2011, 10:21 PM
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Excellent, very clear. I will do that before the weekend Just got TLRS wired up so I can hopefully play without my darn 72mhz ppm glitching all over the place.
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Old Mar 01, 2011, 08:20 PM
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For the conductor match, when you say it replace the 1st 1/4 turn, you mean that where the helix at the very top (or end) ends exactly there on teh bottom near the reflector, is where the match begins, right?
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Old Mar 01, 2011, 09:17 PM
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United States, NC, Charlotte
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While I wait for Alex's reply before I trim, I will introduce my new helical. it is just per Alex's build tutorial, just with some aesthetic liberties taken on the former.

-The frame was designed in sketchup and laser cut out of 3/16" luan plywood.
-The coil is just romex wire, 12ga I think
-The impedance matcher is 1/4" copper tube for icemakers.
-The pigtail is from ebay, RG58 I think
-It has a 1/4-20 blind nut epoxied in the center for tripod mounting.
-The reflector is the real wonder. It was drawn on a piece of steel, then trimmed with a metal shear to get it close to round. Then it was mounted to a jig where I could rotate it against a grinder, and get it near perfectly round.

On this one since it was laser cut the dimensions are perfect on the former, and it has relief notches so the coil was guided perfectly. It has 4 notches per turn. I think the build craft was as meticulous on this one as I am capable of with my tools. Hope it works, wish me luck.
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Old Mar 02, 2011, 04:05 AM
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Danmark, Hovedstaden, Hellerup
Joined Dec 2006
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Hi Guys. This is truly amazing work and I hope I can copy your findings to my ability's of soldering/tinkering. As I have not yet started to fly FPV yet you're all far ahead of me, however I am a little slow in building and only wants the best solutions, while being on a moderate economical leach/wife - you can understand it sometimes takes longer time than first anticipated.
I truly enjoy reading and studying all your findings tho and seldom stop reading before 1.30 am. Maybe this is why my builds take so long.
  • Futaba FF9 CAP - Thomas Scherrer LRS 433mHz
  • Two LRS receivers
  • Two NR receivers
  • Spectrum DX8 with a lot of diff. receivers (small and large)
  • Easy Glider from Multiplex ready for FPV.
  • Tiger Trainer ready for FPV
  • Large 4m Glider from Graupner non FPV
  • Currently building on a URSUS from Poland, however it's beeing cladden with 0,6mm balsa and Lighttex. Will be ready for FPV in springtime.
  • one 1.2-1.3 GHz 8 channel 0,8W TX from ElectronicaRC Spain
  • Two 1.2-1.3 GHz 8channel receivers also from Spain and one Eagle Eyes FPV Station
  • one 1,2 GHz 8 dBi Patch antenna
  • Two cameras small and one GoProHD
  • one EzOSD from Globe flight, I need to change the power managing system to a 100Amp
  • one flat screen TV 7" and FPV Goggles from Headplay
  • one Autopilot II
Thank you all again.
Poul.
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Old Mar 02, 2011, 06:30 AM
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Amherst, VA
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Quote:
Originally Posted by Derek_S View Post
For the conductor match, when you say it replace the 1st 1/4 turn, you mean that where the helix at the very top (or end) ends exactly there on teh bottom near the reflector, is where the match begins, right?
Yes, it replaces the first 1/4 turn all together. Attach your coil to the insdie of that tube instead of the top. Also, the end of your first turn should end at 2-1/8" above the ground plane. Thus the first turn spacing will be a little off due to the conductor being parallel rather than tapered. Just be certain that it ends at the right place.

I will do some experimenting with a more easily repaetable match that maintains the coil integrity through the first turn. The tapered match works, but is hard to get perfect.

-Alex
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Old Mar 02, 2011, 07:39 AM
Oopss. Oh well.
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In the tropics
Joined Jan 2006
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Derek,
Your laser cut antenna components looks so very promising as a 'kit-able' product - it can be dismantled and ship it in a small box.
Customers need only CA and hot glue to put it together. I'd buy one if the price was right.



Due respect and thanks to Alex of course.




BB
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Old Mar 02, 2011, 08:02 AM
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Canada,Quebec
Joined Jan 2005
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Quote:
Derek,
Your laser cut antenna components looks so very promising as a 'kit-able' product - it can be dismantled and ship it in a small box.
Customers need only CA and hot glue to put it together. I'd buy one if the price was right.
It also look like some kind of futuristic rail gun
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Old Mar 02, 2011, 09:03 AM
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United States, NC, Charlotte
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Quote:
Originally Posted by borneobear View Post
Derek,
Your laser cut antenna components looks so very promising as a 'kit-able' product - it can be dismantled and ship it in a small box.
Customers need only CA and hot glue to put it together. I'd buy one if the price was right.

Due respect and thanks to Alex of course.

BB
Edit : Maybe in the near future. We shall see.
Quote:
Originally Posted by Hugeone View Post
It also look like some kind of futuristic rail gun
You caught me it is. It is not an antenna, but a rail gun for shooting down other FPV planes in my way
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Old Mar 02, 2011, 09:13 AM
Engineer for Christ
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Amherst, VA
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Quote:
Originally Posted by Derek_S View Post
I thought about offering a few. The laser is used on borrowed time so it might not be possibly to really sell them full scale, but a few here and there are possible. I would be glad to cut a couple extras for my cost plus shipping. Probably less than $10 depending on how many turns you want it to be... luan is cheap.

However I only have the 1280mhz one designed for now, and cannot really garuntee it in any way! It dimensionally is correct, but performance wise who knows...

If you want one PM me, I would love to send a few out just to see what others think. I can also somewhat easily make minor mods to the design, such as filleted corners for a softer look, or a more bluntly cut nose. I kinda liked the futuristic look, so I left it 'industrial' style.
Send a sample to me for verification. I will test it, tune it, and send it back to you. Then you'll know where you stand

-Alex
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