Originally Posted by mark hitchman

I was wondering what happens if you use a reflector which is way too big?
I am using a 6 turn 1010mhz helical with my computer case door as the reflector. It has worked really well and I was about to get a piece of galv sheet cut the correct size but did not want to lose any performance. Would the correct size work better for long distance or the oversize one?




Mark

In general that will only increase the size of the sidelobes slightly. It will reduce gain very little as the signal is pushed to the sides just a bit.

-Alex

Originally Posted by IBCrazy

In general that will only increase the size of the sidelobes slightly. It will reduce gain very little as the signal is pushed to the sides just a bit.

-Alex

Thanks Alex, I will cut out a circular one the right size then and test it out. My official test is at what altitude I lose video at 10km, a touch and go would be nice

Mark

Hello,
can I use a pcb as a reflector? How would it influence the performance?
Thanks

I've finally did some test.

I'm running on a 1200Mhz using the Fox700 tx

My previous setup was a stock rubber antenna for my Rx and a V-antenna for my Tx. The video got blurred during sharp banks and turned into black and white sometimes fading with flashes in an random pattern when i exceed flying beyond 1200ft LOS.

Now with the new helical antenna + Clover combo, i got clear images all the way, even beyond 1200ft. There are still flashes but it happens in one short burst (100ms) for every min which is many more times better than my previous combo.

Thanks IBCrazy for your wonderful tutorials and guides to making superb antennas.

Originally Posted by aSa2

Hello,
can I use a pcb as a reflector? How would it influence the performance?
Thanks

IBCrazy, could you please give me the answer

It will work fine. No problems.

IBcrazy, Would 17 gauge copper wire work? If not, I will just make a SPW and make the helical later.

Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375”
1280x2.1875= 2800 !!!

Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...

Originally Posted by -katana-

Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375”
1280x2.1875= 2800 !!!

Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...

I based mine off the mid ground frequency. So 5705mhz therefore my measurements came out pretty easy

I brought a 16 mm wooden dowel
13mm spacing
and my reflector was something like 5.something square.

It is not hard to make at all. The hardest part is making the hecker transformer. I believe mine is off somehow but I have nothing to test it on.

Originally Posted by -katana-

Thanks for these tutorials, I built two antennas SPW and CL, with surprising results!
Now I like to build the helical for my 5.8 ghz kit
I read the tutorial but I found a discrepancy in the coil spacing measure

in detail:

Cross insulated Helix for 5800Mhz:
Cross width in inches: 3600/f in MHz (+/- 10% tolerance) 15.7mm
Coil spacing in inches = 2900/f in MHz 12.7mm
Cross length = number of turns * coils spacing 3x1.27=38.1mm
Reflector plate size = 11732/f in MHz 51.4mm

later in the tutorial I read this:

For my wooden former, I marked the following on one side:
0, 2.1875, 4.375, 6.5625, 8.75, 10.9375”
1280x2.1875= 2800 !!!

Coil spacing in inches = 2900/f in MHz or 2800/f in MHz ?

maybe I'm doing something wrong...

Actually, either works fine. This antenna is VERY wideband (as in +/- 80MHz). The precise measurement is 2850. So either 2800 or 2900 works.

-Alex

My first atempt at making a 2.4G Helical.

Freq = 2510Mhz
Number of turns = 6 (10.5 dbi)
PVC pipe former outer diameter = 42mm
Coil spacing = 28mm
Reflector plate size =118mm
The IBCrazy microstrip Width = 5.7
The IBCrazy microstrip height = 4.6

Wire, 1.25mm enameled copper.
Reflector, Blank Printed circuit board.

Wasn't too hard to make and hopefully I haven't messed up any of the calculations. It's quite light so won't be a problem for the tracker. I'll be testing it on Sunday.

Hey I was going to put mine on a tracker, too, but was worried about the weight (of course, I'm using a 900 mhz version). Let me know if you've bench tested or actually flown with the helical/tracker and how it works. Thanks.

Originally Posted by Infernal Bill

Hey I was going to put mine on a tracker, too, but was worried about the weight (of course, I'm using a 900 mhz version). Let me know if you've bench tested or actually flown with the helical/tracker and how it works. Thanks.

The 2.4G version will be alot smaller than the 900M. I also use blank PCB for the reflector which is a bit lighter than sheet metal. So not probs using a tracker. Haven't tested it's RF performance yet though.

Yup, but it looks like you've got more turns than me. Mine is shorter and fatter. We're still talking about antennas, though, right?

Thanks for the heads up.

Bill, ReadymadeRC has CP patches that will fit an antenna tracker: http://www.readymaderc.com/store/ind...roducts_id=489

Axial ratio isn't nearly as good as your helical (.75 vs.95), but it does just fine for me.

And before anyone asks, no it is not the same as the goof-proof patch.

-Alex