RC-Concepts

Nice, it has a wide beam (Phi). Do you have the dimensions of it?

I tried your 45degrees, but I changed back to horizontal bow-tie. The reason for not using 45degrees is I got a wider horizontal beam with the horizontal bow-ties. For FPV, I need the horizontal beam to be as wide as possible.

Thanks for the tip. 45degrees will cover both vertical polarization and horizontal polarization too. I have changed the transmitting antennas to vertical polarization so I have all 4 Biquads positioned in vertical polarization (horizontal bow-tie) now. I did more range test in different urban evironments and here are the results:

I might buy it

Thank you for posting it for price comparison, I think it is a nice spectrum analyzer for hobbyist, and it has a good price too. It is a great tool for measuring S11 and S21 since it has dual ports. Although the spectrum analyzer sweep is terrible (non granular span steps and super slow), it is useful for tuning antennas for HDTV (UHF band), 2.4ghz(WiFi/BT/RC), 433mhz, 868mhz, 915mhz (telemetry/LRRC), 1.2ghz (FPV) and 1575mhz (GPS) because the inbuilt 3ghz Signal Generator and Signal Detector could measure the reflected co-efficient (plot SWR/ return loss curve) with adding the optional 9usd directional coupler.

You need to buy the 9usd SWR bridge ( directional coupler), to measure SWR on this device. Also, this device can only measure antennas for frequency less than 3ghz because it has a signal generator/tracker which is only up to 3000mhz. The 9usd SWR bridge also supports up to 3ghz only. The biquad we want to measure is 5.8ghz. Therefore, it cannot be compared to the Owl RC which has a 5.8ghz signal generator and a directional coupler that is designed for 5.8ghz.

105usd from Aliexpress

Yes the SWR meter can be DIY, if you see my video below, we can have RF switches controlled by Arduino to switch the video transmitter’s connection and the antenna’s connection to the directional coupler (without removing them physically), to measure FWD and REV voltages (output from the RF power detector) using the same Arduino and plot the SWR curve to a screen. As this is a lot of work, buying the SWR meter from Owl-RC is a better option.

Thanks, I haven’t tried maximum distance yet. In my video above, the drone was able to fly 300m away in the direction of my 9 o’clock when 2 biquads are pointing at my 11 o’clock and the other 2 are pointing at my 1 o’clock. This performance was pretty amazing. The SWR is built by Owl-RC and it is available here: http://www.owl-rc.com/product/SWRMETER.html

It is year 2020 now. And today we have digital HD FPV. Here I have built the same PCB 5.8g biquad and used it for the DJI digital FPV system. My feed points are slightly different and my center frequency is lower as a result. Test result appears promising in the video below:

Thanks for sharing this!

Alternatively, if the simulation software allows you to specify properties of the coaxial cable directly, the RG402 coaxial should have capacitance of 98.1 PF/m . Since our coaxial is 71mm long, the capacitance is 7PF. The capacitance (around 0.34PF) between signal (PCB A) and ground (PCB B) is necessary for the Pagoda.

I think you need to add PTFE tube of outer diameter 3mm and inner diameter of 0.9mm between PCB A and PCB C. This PTFE tube has a dielectric constant of 2.02 and a loss tangent of 0.00022

RG402 coaxial used for each antenna is 71mm. After PCB A and B are aligned, you mean VSWR is still 6.74 in your simulation? This is strange.

Great work! How about the radiation pattern and SWR curve after u solved it?

Thanks for the simulation. There appears to be a problem with PCB A and PCB B. You need to rotate one of them until the 3 markers are perfectly aligned for the 2 discs. Refer to red arrows in below pictures.

Thanks for adding the measurements, it is useful for anyone who wants to build it.

Your numbers are all ok except one is wrong. Please change 9.4 to 7.29. Quarterwave is 7.29mm according to relative permitivity of 1.22 for FR4.

3.04mm wide for the 50ohm trace. 0.68mm wide for 100ohm trace. Transformer for converting 100ohm to 50ohm is the quarter-wave micro strip which measures 7.29mm long and 1.59mm wide. The length of the 50ohm traces(3.04mm wide) and the length of the 100ohm traces(0.68mm) do not matter. They can be made longer or shorter to allow the desired separation distance between the 2 pagoda antennas. However, the two traces after the T-joint must be equal lengths. I used a separation distance of 43mm between the 2 pagoda antennas. Hope this helps.

Nice collection of drones antenna on this thread. Here is a pair of twin pagoda antennas with corporate network match, for 5.8g FPV drones. Dimensions in mm for the microstrip to be fabricated on 1.6mm FR4 (copper-cladded on both sides, bottom side not etched). Here is the video showing its gain and performance

After my parents complained that my previous DIY antenna (the common design of a pair of double fractal-elements matched to 75ohms from 300ohms via a TV balun) could not pick up any overseas channels at their house, I made the Biquad antenna based on the first Biquad (581.68mhz in simulation) that was provided in this thread. I resized all the original dimensions (x 0.83) for my intended frequency of 682mhz so that it could receive overseas HDTV channels at my parents house. A check with my VNA revealed that my resized antenna was tuned to the center frequency of 572mhz. It is usable for a range from 400mhz (1.5 SWR) to 750mhz (1.5 SWR). At my desired 682mhz, SWR is close to 1.3. Thank you admin, the design is great. Now, my parents are able to watch foreign channels. Here is my build and test video: www.youtube.com/watch?v=-2KVS-wrvQM

Thank you sir! I will try to make your 5.8g version next.

Thanks Admin, I made one for RC toy bird and it doubles the RC range!