Build IBCrazy's 10dbic CP Double Quad antenna

[Pen]

Picture please!

[Coyote]

I did indeed, up to 3km its frekin awesome

Pictures as requested :


Heres the antenna :



I got a vacumm formed cover made for it ( pre trimmed ) :



And here it is on my GS :



It performs better behind it than the £120 shop bought CP Patch and only falls 1km short but cost £115 less

Stay tuned for my Cp Patch ( around 12 dbi ) homemade coming soon

For reference for others :

1.5 wavelength = 7450 x 6 = 44700

Wire length in cm = 29800/f in MHz = 5.14

¼ wavelength in cm = 7450/f in MHz = 1.28

1.5 reflector size = 44700 / 5800 = 7.70cm

Middle of reflector 3.85cm

Phase shifting impedance transformer (covered part) where Vf is the cable velocity factor:
Cable in cm = 21336 * .84/ 5800 = 3.09cm

Primary element height:
Height in cm = 3724/f in MHz = 6.4mm

Cross fed element height:
Height in cm = 2286/f in MHz = 3.9mm

[IBCrazy]

12dbi CP patch? Are you dual feeding or going for a geometry type?

-Alex

[Coyote]

Geometry type, single feed point, but work in progress

[IBCrazy]

So a 1.5 lamba panel with a center slot to drive the circularity? Trimmed corners doesn't seem to react well for higher gains.

-Alex

[Coyote]

Lol nope, all wrong

On another note, the 3km distance that i got was on a good day, but the 4.2km point with picture degragation was on a day with the skies full of thick rain clouds.

I think could have seriously impaired its performance, so i might repeat on a clear skies no clouds day to see if i can get further out.

Both tests were using a cloverleaf on the planbe btw

[GregSilver]

Alex, can you explain the short range loss for this antenna, in human talk?

My cp biquad tested pretty good.

However, close range it has really bad drop outs.

[IBCrazy]

First of all it looks like both of your elements are a bit too long. I can also tell that they are slightly different sizes by your plot (I am assuming you are flying on 1280MHZ).

Short range dropouts have to to with the low axial ratio of the antenna. It was never meant for short range. The beam is very narrow at short range so venturing out to the edges of it is easy. Due to the high singal strength and low axial ratio at the peripherals, the reflected signal is attenuated less than it would be at long distance thus making the multipathed signal appear stronger than normal.

That's about the best I can explain it.

-Alex

[Mykro]

Could someone explain to me what is the "Cable Velocity Factor" (VF) ?.. This is needed for the calculation for the" phase shifting transformer"... I assume this number is on the cable?

[IBCrazy]

When a standing wave is contained within a coaxial cable the speed that the wave travels is reduced by a velocity factor determined by the dielectric within the cable.

The velocity factor can be found on the cable spec sheet.

-Alex