Sep 24, 2015, 06:49 AM
Registered User
Joined Mar 2006
248 Posts
Quote:
 Originally Posted by markus123456 I actually did watch the whole video. Opinions migth differ, and I'm surely not an advocate of those trying to ban FPV etc. Here is how we do it. We fly on a military airbase on weekends when they are closed. However, we are instructed to IMMEDIATELY land whenever a real aircraft aproaches us. Your attempt to follow one of those gliders was a risk. What if your RC control fails the moment you head towards them? Remember, we talk about real humans risking their ass in the air versus you standing on the ground. Look, I do not intend to start a war, so lets leave it at this, but following them was truly not the propper reaction wehter they entered "your" airspace or not. BR, Markus
Alright bro. Accept your advice and will not do that again.

Cheers
Oct 20, 2015, 01:21 AM
Registered User
Australia, VIC, Point Cook
Joined Sep 2013
32 Posts
Quote:
 Originally Posted by IBCrazy I found the stacked biQuad dimensions to be a little bit off. You also need to make the reflector plate much larger to accomodate the parasitic element. For the stacked BiQuad, the reflector should be 1.5 wavelengths instead of just 1 wavelength as in this tutorial. -Alex
Alex, I want to build a stacked biquad but would like to keep the reflector at 30cm (1.3 wavelengths) compared to 34.9cm as you suggested above. Standard biquad reflector size is 23.28cm for 1280mhz. Will this smaller reflector have a major impact on the total performance of the stacked biquad?
Oct 21, 2015, 01:14 PM
Registered User
Joined Jul 2013
210 Posts
Hello,

I'm having problems with my biquad antenna. It's giving about the same performance as my dipole antennas except on the 90 and 270 degree angle the signal is a bit better.

I build it for 1320mhz, so a 5,64cm length for a quarter wave. The element spacing ended up at 2,5cm instead of 2,8...would that cause the problem?
Or is the diameter of center tube too large?

What did I do wrong?

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Last edited by ShiftyPK; Oct 21, 2015 at 01:39 PM.
 Oct 25, 2015, 10:42 PM Engineer for Christ Amherst, VA Joined Jun 2006 11,224 Posts It doesn't look like anything is wrong... at least so long as the shield of the cable is bonded to the tube you are using. If so, you either have a damaged cable or a high noise floor. -Alex Latest blog entry: Project Covert Ops: Long range ground...
Oct 25, 2015, 10:44 PM
Engineer for Christ
Amherst, VA
Joined Jun 2006
11,224 Posts
Quote:
 Originally Posted by Johan9 Alex, I want to build a stacked biquad but would like to keep the reflector at 30cm (1.3 wavelengths) compared to 34.9cm as you suggested above. Standard biquad reflector size is 23.28cm for 1280mhz. Will this smaller reflector have a major impact on the total performance of the stacked biquad?
As stated in my response to your PM, this is not an issue. You might get a slightly larger rear lobe and thus lower your F/B ratio, but that's about it.

-Alex
Oct 25, 2015, 10:48 PM
Engineer for Christ
Amherst, VA
Joined Jun 2006
11,224 Posts
Quote:
 Originally Posted by mathieu974 Right ! 5dB at 90deg...not too bad this biquad will be my long range linear antenna, BTW i ve done a 4 lobes biquad omni for proximity flying (the 5 lobes seems to be good also) Thanks Alex!
First of all, nice work here. This antenna would be called a "pentaquad", not a BiQuad. Bi = 2. Quad = 4. This refers to the 2 X 4sided elements. Besides, pentaquad sounds awesome!

I believe it was you who had the Celtic knot antenna designed. If so, please PM or Email me for some improvements to it. There is great potential to that antenna that I'd rather not divulge publicly in case you decide to go commercial with it.

-Alex
Oct 25, 2015, 11:04 PM
400' ..... NOT
Joined Jan 2009
4,440 Posts
Quote:
 Originally Posted by ShiftyPK Hello, I'm having problems with my biquad antenna. It's giving about the same performance as my dipole antennas except on the 90 and 270 degree angle the signal is a bit better. I build it for 1320mhz, so a 5,64cm length for a quarter wave. The element spacing ended up at 2,5cm instead of 2,8...would that cause the problem? Or is the diameter of center tube too large? What did I do wrong?
Not sure from the pictures but stick a piece of foam to keep the center conductor away from the side of the tube so it doesnt short. No the diameter is not too large. My first couple of bi's I did used 1/2 " tubing.
Oct 26, 2015, 04:12 PM
Registered User
Joined Jul 2013
210 Posts
Quote:
 Originally Posted by Martin Y Not sure from the pictures but stick a piece of foam to keep the center conductor away from the side of the tube so it doesnt short. No the diameter is not too large. My first couple of bi's I did used 1/2 " tubing.
Thanks for the tips Martin en IBCrazy, and confirming nothing is wrong. I tried to make an as close as possible fit. In think there is about an 0,5mm gap in there, but its good, no contact.

I might have found the problem. Changing frequency from 1320 to 1200 solved allot of problems but I only managed to test this with my dipoles, need to test with my biquad once I receive my 100w solder iron to fix it again.
 Oct 26, 2015, 05:05 PM Registered User United States, CA, Eastvale Joined Sep 2007 677 Posts I've recently switched to using Biquad ground station from goggle cloverleaf; and what a difference! Yes, it's more clunky to carry the ground-station but the solid video from Biquad is amazing.
 Nov 24, 2015, 08:45 PM Registered User United States, NC Joined Dec 2013 165 Posts I am thinking of designing/3D printing an ABS "retainer" for the bow tie/resonator. Will plastic between the resonator and reflector cause issues? Last edited by astr0lite; Nov 24, 2015 at 09:25 PM. Reason: Clarity