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RF Amplifier Platform

RadioFlyerMan

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Inspired by @brett8883, I built a platform for 2.4 ghz RF amplifiers for my Mavic Pro Platinum controller. This thing is over the top, kinda unnecessary, and will probably scare small children. However, it is great for flying from your car in the winter. But most of all, I had fun building it. Gotta have something to do on those cold, windy days in the winter!

Then the grandkids started asking questions. So we talked about drone radio frequency, wave length, speed of light and the relevant math. Then down in the shop, we built some custom 2.4 ghz omnidirectional biquad antennas. It was fun working with them and a great learning experience.
 
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brett8883

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Inspired by @brett8883, I built a platform for 2.4 ghz RF amplifiers for my Mavic Pro Platinum controller. This thing is over the top, kinda unnecessary, and will probably scare small children. However, it is great for flying from your car in the winter. But most of all, I had fun building it. Gotta have something to do on those cold, windy days in the winter!

Then the grandkids started asking questions. So we talked about drone radio frequency, wave length, speed of light and the relevant math. Then down in the shop, we build some custom 2.4 ghz omnidirectional biquad antennas. It was fun working with them and a great learning experience.
Dude that’s wicked! I was gonna sl where you go those antennas so I could buy some too then I read that they were home made 🤣. I’d buy em if you were selling.

I like the frame you built for everything too. Seeing the amp status is key.

Much less scary than the wood block set up you Started out with.

Mod on my friend!
 
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RadioFlyerMan

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Dude that’s wicked! I was gonna sl where you go those antennas so I could buy some too then I read that they were home made 🤣. I’d buy em if you were selling.

I like the frame you built for everything too. Seeing the amp status is key.

Much less scary than the wood block set up you Started out with.

Mod on my friend!
You led the way for me. THANK YOU!
 

RadioFlyerMan

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Dude that’s wicked! I was gonna sl where you go those antennas so I could buy some too then I read that they were home made 🤣. I’d buy em if you were selling.

I like the frame you built for everything too. Seeing the amp status is key.

Much less scary than the wood block set up you Started out with.

Mod on my friend!
Here’s where I got the idea for the antenna
 

RadioFlyerMan

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Any idea how much more range comparative to a normal antenna + unamplified setup?
Yes, but it’s relative to my situation. I have a lot of 60 to 70 foot pine trees on my 15 acre home out in the boonies. The signal attenuation from trees is like a lead wall. And my amp is an attempt to overcome it. However, nothing will cure it altogether.

One of the flights I like to make is to fly a few feet off the ground and go out down various paths between the trees to a distant of 1000 ft or more. I have found that the amp adds 800 to 1000 feet to preserve a strong telemetry signal at 4 to 5 bars. I have not tested it in a direct signal line of site situation, although I’m sure it will add significantly more than a simple 7dbi dipole.

I have also done signal strength test when my pine trees are covered in snow, and under high humidity (fog). The attenuation basically doubles.

The bottom line is the amp helps and under certain situations I’ll continue to use it. However, when I’m traveling to various scenic sites around Michigan, I really don’t need it when in VLOS.

One of the questionable things I’ve done with this amp system is to amplify the diversity antenna. It may not be necessary. I chose to amplify both because it simply adds balance to the whole system, and allows maintaining the proximity of the diversity antenna to the main antenna. Of course the real reason it just looks cool!

I’m running three different antenna sets on this amp. An Alph directional antenna, a 7dbi dipole, and a homemade omnidirectional biquad as seen in the video. The biquad is slightly stronger than the dipole but less than the directional Alphas.

One more thing, the platform can accommodate other amps. There are other bidirectional amps that are stronger than the 3 watt ones I used.
 
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brett8883

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Yes, but it’s relative to my situation. I have a lot of 60 to 70 foot pine trees on my 15 acre home out in the boonies. The signal attenuation from trees is like a lead wall. And my amp is an attempt to overcome it. However, nothing will cure it altogether.

One of the flights I like to make is to fly a few feet off the ground and go out down various paths between the trees to a distant of 1000 ft or more. I have found that the amp adds 800 to 1000 feet to preserve a strong telemetry signal at 4 to 5 bars. I have not tested it in a direct signal line of site situation, although I’m sure it will add significantly more than a simple 7dbi dipole.

I have also done signal strength test when my pine trees are covered in snow, and under high humidity (fog). The attenuation basically doubles.

The bottom line is the amp helps and under certain situations I’ll continue to use it. However, when I’m traveling to various scenic sites around Michigan, I really don’t need it when in VLOS.

One of the questionable things I’ve done with this amp system is to amplify the diversity antenna. It may not be necessary. I chose to amplify both because it simply adds balance to the whole system, and allows maintaining the proximity of the diversity antenna to the main antenna. Of course the real reason it just looks cool!

I’m running three different antenna sets on this amp. An Alph directional antenna, a 7dbi dipole, and a homemade omnidirectional biquad as seen in the video. The biquad is slightly stronger than the dipole but less than the directional Alphas.

One more thing, the platform can accommodate other amps. There are other bidirectional amps that are stronger than the 3 watt ones I used.
It’s certainly not questionable to amp both sides. I think you said it best that amping the right side doesn’t increase range necessarily but it improves the reception within the range limit of the set up. This makes sense too. Having two of the same amps and antennas of the same power doesn’t add power to the equation but the job of the diversity antenna is to increase the number of paths the RF radiation can take.

You’ve convinced me to add another amp too. But just looking at it from a cost stand point the improvement from one amp over no amps is much much greater than two amps over one amp. This is really only relevant on the Mavic Pro as all the newer drones Needs amps on both sides anyway.
 

brett8883

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One interesting tid bit is that I just bought the DJI goggles and the amps on the remote increase the range of the goggles to be the same as the remote and live view on the normal app. Therefore DJI must not be telling the whole truth when they say the goggles get the live view directly from the drone. It must be in relay with the remote. Which is good cause now I don’t have to open the goggles to figure out how to amp them like I thought I would have to.
 

lee82gx

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Yes, but it’s relative to my situation. I have a lot of 60 to 70 foot pine trees on my 15 acre home out in the boonies. The signal attenuation from trees is like a lead wall. And my amp is an attempt to overcome it. However, nothing will cure it altogether.

One of the flights I like to make is to fly a few feet off the ground and go out down various paths between the trees to a distant of 1000 ft or more. I have found that the amp adds 800 to 1000 feet to preserve a strong telemetry signal at 4 to 5 bars. I have not tested it in a direct signal line of site situation, although I’m sure it will add significantly more than a simple 7dbi dipole.

I have also done signal strength test when my pine trees are covered in snow, and under high humidity (fog). The attenuation basically doubles.

The bottom line is the amp helps and under certain situations I’ll continue to use it. However, when I’m traveling to various scenic sites around Michigan, I really don’t need it when in VLOS.

One of the questionable things I’ve done with this amp system is to amplify the diversity antenna. It may not be necessary. I chose to amplify both because it simply adds balance to the whole system, and allows maintaining the proximity of the diversity antenna to the main antenna. Of course the real reason it just looks cool!

I’m running three different antenna sets on this amp. An Alph directional antenna, a 7dbi dipole, and a homemade omnidirectional biquad as seen in the video. The biquad is slightly stronger than the dipole but less than the directional Alphas.

One more thing, the platform can accommodate other amps. There are other bidirectional amps that are stronger than the 3 watt ones I used.
Hi RadioFlyerMan,

I'm very interested to hear more about your experience with the various antennas too...

Now this paper states the gain of the biquad antenna is around 5-6dBi:

I wonder what is the actual improvement or experience compared to a 7dBi dipole...which must be quite narrow in the vertical plan also.

Which Alfa antenna do you also use? Is it the Alfa APA-M04 (7dBi, 2.4G only) or M25 (10dBi, dual band)
 

RadioFlyerMan

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One interesting tid bit is that I just bought the DJI goggles and the amps on the remote increase the range of the goggles to be the same as the remote and live view on the normal app. Therefore DJI must not be telling the whole truth when they say the goggles get the live view directly from the drone. It must be in relay with the remote. Which is good cause now I don’t have to open the goggles to figure out how to amp them like I thought I would have to.
Now that is interesting!!!
 

RadioFlyerMan

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Hi RadioFlyerMan,

I'm very interested to hear more about your experience with the various antennas too...

Now this paper states the gain of the biquad antenna is around 5-6dBi:

I wonder what is the actual improvement or experience compared to a 7dBi dipole...which must be quite narrow in the vertical plan also.

Which Alfa antenna do you also use? Is it the Alfa APA-M04 (7dBi, 2.4G only) or M25 (10dBi, dual band)
Regarding the biquad, I agree, although the whole thing is untested in the technical sense. I was worried that the impedance (unknown) was going to be way off, causing a reflected wave. But it must be close to 50 ohms by luck.

Here’s the Alpha I got via Amazon. They provide the horizontal and vertical signal profiles. So I did some experimentation when the AC was about 2000 ft away. When I turned away 180 deg, the signal stayed basically the same. Weird! Maybe it was because of the amps? Dunno

Alfa 2.4HGz WiFi Antenna - 7dBi... Amazon.com: Alfa 2.4HGz WiFi Antenna - 7dBi RP-SMA Panel Screw-On Swivel for Netwrok Adaptors - Also Works for 3DR Solo Drone, DJI Phantom 3 Drone, Yuneec Typhoon H ST16 Controller, adds Range: Computers & Accessories
 
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RadioFlyerMan

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One interesting tid bit is that I just bought the DJI goggles and the amps on the remote increase the range of the goggles to be the same as the remote and live view on the normal app. Therefore DJI must not be telling the whole truth when they say the goggles get the live view directly from the drone. It must be in relay with the remote. Which is good cause now I don’t have to open the goggles to figure out how to amp them like I thought I would have to.
Regarding the goggles, please confirm something for me. When I had my goggles, I did not use them enough to know what they can or cannot do. I thought/misinterpreted the googles response when I wanted to shoot video in 4k 3480x2160. It would not allow it, or that’s what I thought. Can you shoot in video in 4k???
(It’s really a moot issue because they made me dizzy 🤪)
 

brett8883

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Regarding the goggles, please confirm something for me. When I had my goggles, I did not use them enough to know what they can or cannot do. I thought/misinterpreted the googles response when I wanted to shoot video in 4k 3480x2160. It would not allow it, or that’s what I thought. Can you shoot in video in 4k???
(It’s really a moot issue because they made me dizzy 🤪)
Yea you can record in 4K. It reduces the live view to 720p but the same can be said for the live view in the regular app
 
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lee82gx

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Hi RadioFlyerMan,

I'm very interested to hear more about your experience with the various antennas too...

Now this paper states the gain of the biquad antenna is around 5-6dBi:

I wonder what is the actual improvement or experience compared to a 7dBi dipole...which must be quite narrow in the vertical plan also.

Which Alfa antenna do you also use? Is it the Alfa APA-M04 (7dBi, 2.4G only) or M25 (10dBi, dual band)
It looks like you are having the APA-M04 which are wider in the beam width ie more easy to point almost 120degrees according to manufacturer.

the specs also say that at 180degs the signal strength is perhaps only 5db less so if your amps are working it translates so still having sufficient signal strength in total. The true null is at 120 degrees. But it’s a very acute angle at which it will be 20 to 30db less.
I have to ask for best effect for flying around at say 2000ft which is your preferred setup?
 

RadioFlyerMan

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It looks like you are having the APA-M04 which are wider in the beam width ie more easy to point almost 120degrees according to manufacturer.

the specs also say that at 180degs the signal strength is perhaps only 5db less so if your amps are working it translates so still having sufficient signal strength in total. The true null is at 120 degrees. But it’s a very acute angle at which it will be 20 to 30db less.
I have to ask for best effect for flying around at say 2000ft which is your preferred setup?
That depends on where I'm at and the degree of attenuation. If I'm in a public space maintaining VLOS, my simple 7dbi dipoles with no amp will do, although I think on most days I'd have to have my wife assist in the VLOS @2000 ft. She's pretty good at it! However, at my home, it depends on which way I go, East or West. I can only go 500 ft East with the amp and Alphas'. It's awful. To the West, not so bad and so I can use the dipole with or without the amp. I can't fly North or South at such distances out of respect for neighboring property.