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Old Oct 17, 2011, 03:12 AM
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Quote:
Originally Posted by Shikra View Post
The BiQuad here is for linear antennas - not the best match for your cloverleaf which is CP.


The BiQuad you want is here....
http://fpvlab.com/forums/showthread....e-Quad-antenna

It is directional though unlike the skew plana you have, so you will have to fly in the beam, manually aim or use a tracker

What is best depends upon what you want to do and style of flying !!
Hi

Thanks for your reply.

I have not state my intent clear.

My current plan is to use Cloverleaf and Skew Plana Wheel for all round flying in near field and switch to longer range (at specific direction) using the Biquad, possibly hock them up using video diversity.

That is why I ask whether the CP and Biquad are compatible or not.

So are you saying I need to use inverted V and Biquad combo?


Thanks for your help.

Regards

Formosa
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Old Oct 17, 2011, 04:33 AM
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They will work, but you will get better results by either using using linear or CP antenna throughout.
This biquad is linear, but there is a CP version at the link above

As you already have the other CP antennas I would choose a CP one

CP patch - easiest to make. I would try first. It should give very good results. Less range than the others, but a wide beam

or for maore range, but less flyable beam...
CP biquad -
CP helical -
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Old Oct 17, 2011, 07:39 AM
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Unless you are planning on flying reflections, you want CP on both ends or linear on both ends. A Vee/Biquad is a long range system. Vees are so simple to make it's ridiculous. On the CP side should you choose to stay CP, CP patches are ok, but the helical is where the performance is.

On the other hand, a BiQuad will do fine with the Cloverleaf. The beam is pretty narrow, so multipathing is minimal. It's just not optimal.

-Alex
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Old Oct 17, 2011, 07:41 AM
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Quote:
Originally Posted by Shikra View Post
I made up a biquad and it gives same, maybe even better performance than my 14db Lcom patch. Very pleased.

As it is so easy to make I am making a double biquad.

But I have a question.

Is a stacked double biquad viable?
Would both use the same dimensions, with 1/4 wave separation?

As I use a tracker, happy to have a narrow beam width..


http://postimage.org/image/170yz8qdg/
Yes a stacked double BiQuad is viable. It would be a bit of a monster, but it would work. You will need to build a double BiQuad and then stack it like catamar's.

-Alex
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Old Oct 17, 2011, 08:08 AM
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The nice thing those is it is so quick and easy to make up the element. I found much easier than the CP designs. Especially hugo's 8 lobe turbine.

I was also thinking about separately stacking 2 double biquads with Y/T coax impedance match. I haven't seen that anywhere and my limited knowledge tells me that its realistic and that would achieve better gain over parasitic type stacking.

mmm maybe quad separate stacked with H impedance match.... small footprint high gain. Time to google !!


Just looked at Catamars picture - that is spot on. Thanks for the tip. All the info I need. Thank you !!

Thanks,
G
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Old Oct 17, 2011, 08:10 AM
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Quote:
Originally Posted by IBCrazy View Post
Unless you are planning on flying reflections, you want CP on both ends or linear on both ends. A Vee/Biquad is a long range system. Vees are so simple to make it's ridiculous. On the CP side should you choose to stay CP, CP patches are ok, but the helical is where the performance is.

On the other hand, a BiQuad will do fine with the Cloverleaf. The beam is pretty narrow, so multipathing is minimal. It's just not optimal.

-Alex
Dear Alex & Shirka

Thanks for your advice.

So I will leave my 5.8GHz thing to close range and use 1.2GHz for long range using inverted V and Biquad. I have the gear anyway.

Thank for your advice, it is clear now.

One more question, for 1.2GHz 800mW VTx, what kind of range I can expected when using inverted V and Biquad combo?

Regards

Formosa.
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Old Oct 23, 2011, 01:15 AM
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Oklahoma, USA
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I built the biquad and it works better than my patch. I really like being able to have it higher than the patch needs to be. I was hoping it would get rid of some interference I get after I get out about 2000 feet. Here's a snippet of the interference. I get it on both the patch and the biquad. Can anyone identify the source? My video signal is good and so far I've gone out more then 8000' with my Spektrum and the interference stays about the same. I can still fly but it's distracting and the video quality is affected.

Here's the video:
20111020 Radian FPV Flight-1-Raw Snipet.avi (0 min 14 sec)


Her are pics of the biquad:

Thanks.
Steve

P.S. I'll post this is some other threads too.
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Old Oct 23, 2011, 07:57 AM
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Looks to me like external interference. I could be multipathing, but the video doesn't show a shift, just a disturbance. I suspect there is a transmission tower nearby. Just a guess. Your BiQuad looks very good!

-Alex
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Old Oct 23, 2011, 03:12 PM
But often down to earth
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Oklahoma, USA
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Quote:
Originally Posted by IBCrazy View Post
Looks to me like external interference. I could be multipathing, but the video doesn't show a shift, just a disturbance. I suspect there is a transmission tower nearby. Just a guess. Your BiQuad looks very good!

-Alex
Thanks. That's what I think too. Probably something near the ground station since I get the same interference in all directions. Some days I don't get it at all. I use two receivers with the EagleEyes and even switched the antennas during the last flight and both receivers get the same signal. The new guardian from Eagletree is so good I switched the antennas while just letting the plane fly on heading hold. It still made me nervous while the video was off.

Steve
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Old Oct 25, 2011, 08:22 AM
^Its what I do^ - FPVholic
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Quote:
Originally Posted by IBCrazy View Post
Since this is a closed loop resonator and I'm going to assume that the pilot is not flying in the rain, there will be no degradation factor. I use a direct speed of light calculation. There are 3 calculations you need:

Full wave length:

Full wavelength in inches = 11732/f in MHz
Full wavelength in cm = 29800/f in MHz
For the following frequencies you have:
910 MHz = 12.89/32.75cm
1280MHz = 9.17/23.28cm
2450MHz (2.4GHz) = 4.79/12.16cm

Section length (this is simply your full wave length divided by 4):



Section length in inches = 2933/f in MHz
Section length in cm = 7450/f in MHz
For the following frequencies, the section lengths are as follows:
910 MHz = 3.22/8.18cm
1280 MHz = 2.29/5.82cm
2.4GHz = 1.197/3.041cm

Element spacing
(this is your full wavelength/8):

Element spacing in inches = 1467/f in MHz
Element spacing in cm = 3725/f in MHz
For the following frequencies, your element spacing is as follows:
910 MHz = 1.61/4.09cm
1280 MHz = 1.15/2.91cm
2.4GHz = .6/1.52cm

That wasn't so hard was it? Now write down those numbers and on to the next step.
Hey iBcrazy,
You recommended a biquad for my 1900Mhz cellular broadband connection. In this post you said your calculations are assuming there is no rain. Will that mean if it rains I will suffer a performance loss?
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Old Oct 25, 2011, 10:59 AM
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Moisture degrades any antenna. Yagis degrade quickly. BiQuads still degrade, but not nearly as fast. I'd expect the SWR to shift from 1:1 to 1.8:1 or so in rain.

-Alex
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Old Oct 25, 2011, 11:34 AM
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Joined Jul 2010
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Quote:
Originally Posted by Floater73 View Post
I built the biquad and it works better than my patch. I really like being able to have it higher than the patch needs to be. I was hoping it would get rid of some interference I get after I get out about 2000 feet. Here's a snippet of the interference. I get it on both the patch and the biquad. Can anyone identify the source? My video signal is good and so far I've gone out more then 8000' with my Spektrum and the interference stays about the same. I can still fly but it's distracting and the video quality is affected.
As said by IBCrazy, it looks like some external interference. I've experienced this problem too, and i found out that it was caused by airport radars/transmission towers... changed frequency and everything is OK now. Here's a video (advance to 3:37):

http://www.youtube.com/watch?v=xgOIvlJ-P3A
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Old Oct 25, 2011, 03:33 PM
^Its what I do^ - FPVholic
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Thanks guys
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Old Oct 27, 2011, 12:30 PM
^Its what I do^ - FPVholic
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USA, MO, Slater Flying Club
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Alright, Verizon ponied up a magnetic car antenna. I dont need that but it comes with an adapter from my tiny device connector to a FME Male connecter.

Or does anyone know what connector this is, the tiny one


If not, could I buy this cable with a FME female connector and use it to make my antenna? I didnt see if it was 50ohm or not.
http://usacoax.com/20ft-cell-antenna...cable-lmr-240/
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Old Oct 27, 2011, 04:44 PM
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Canada, QC, Blainville
Joined Aug 2009
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Alex, is this the right RG58U wire
http://www.ebay.ca/itm/STEREN-50ft-R...item3a6b859789
i will cut off the connector.

Thanks.

and is this the correct sma connector ?
http://www.ebay.com/itm/10X-RP-SMA-C...item4cf28cd6ff

Any good suggestion for a crimper ?

thanks
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Last edited by bakchos; Oct 27, 2011 at 04:54 PM.
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