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Amp Modification decreased signal?

Daaaaman

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Hello,

I recently got a Mavic Pro and decided to boost it. I did the same thing for my Phantom 3 standard except the P3 also had a 5.8ghz amp. I had a P3 S that would fly farther than most P3 pros so I decided to do the same mod to my Mavic Pro 20180910_192649.jpg 20180910_192659.jpg 20180910_192649.jpg 20180910_192659.jpg


I was wondering if anyone has ever noticed a decrease in signal when boosted with Amps? I recently boosted both of my 2.4ghz antennas and the signal goes to 75% as soon as I hit the power switch for the Amps. Once I turn it off it goes back to 100%. This is from 5Ft away. Maybe it's too strong up close? I have 5V going to each signal. The antenna I have is a Nanosync, which does get a better signal than my factory antennas with parabolic reflectors. I'll post more info if needed but for now I'm just wondering if anyone else has experienced this when installing amps and if they solved the problem.
 
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Elton Hammonds

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I agree with the EMI possibility.

Additional possibilities that occurred to me are defective amps and/or a defective antenna.

Wait a second... Did I understand you're running two 2.4ghz amps on a Mavic Pro remote?

If so, you could try switching one for a 5.8ghz amp to see if there's any difference. (I think the Mavic 1 Pro relies on both, as the Mavic 2s do... )
 

Fron2233

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I agree with the EMI possibility.

Additional possibilities that occurred to me are defective amps and/or a defective antenna.

Wait a second... Did I understand you're running two 2.4ghz amps on a Mavic Pro remote?

If so, you could try switching one for a 5.8ghz amp to see if there's any difference. (I think the Mavic 1 Pro relies on both, as the Mavic 2s do... )
mavic 1 is 2.4 only!
 

The Bob

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Jeffm912

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You may also want to check what you are using to power the amps with. You need 8W and @ 5V you are needing 1.6A minimum but when you consider losses it will be over a 2A draw. If the battery cannot sustain that your amps are clipping the signal. Truely only 1 amp is needed on the left antenna to get the gains you are after. I have tested the right side and found no difference between using an amp or just connected to the controller.

No update in over 6 months. I think this is a lost cause by now.

Jeff
 
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The Bob

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You may also want to check what you are using to power the amps with. You need 8W and @ 5V you are needing 1.6A minimum but when you consider losses it will be over a 2A draw. If the battery cannot sustain that your amps are clipping the signal. Truely only 1 amp is needed on the left antenna to get the gains you are after. I have tested the right side and found no difference between using an amp or just connected to the controller.

No update in over 6 months. I think this is a lost cause by now.

Jeff
Thanks for the input!

The amp I am using is calling for: DC Supply Current : 435 [email protected] 28dBm 9V ~ Since it is a 4W Amp (way overkill for what I am doing) I will be running it about 7 volts.
Maybe my logic is wrong but I would rather have an over-sized amp and under power it to get the gain I am after... hoping the battery will last 60 minutes of flight. If not I will "adjust" my equipment / power input. Along with a 16db dipole I should be OK. (Just trying to overcome signal loss and interference in my area)

I got one of these batteries for now... hoping it is enough. Should get the power I am after. ;)
Amazon.com: FLOUREON 7.4V 1000mAh 20C 2S Lipo RC Battery with JST Plug for RC Car, Truck, Truggy, RC Racing Drone, Quadcopter, Helicopter, Airplane, DIY RC Hobby: Toys & Games

Now mounting this all to my controller is going to be the fun part... needs to be functional and not look like a science project. weeee
 
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Kilrah

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Reducing voltage won't reduce output power, but will increase current draw.

People never understand how RF amps work. A "4W amp" has an output stage that is capable of delivering UP TO 4W without burning itself out or introducing major distorsion. But the amp gain is usually fixed, so what you actually get out depends on what you put in. From the specs on this page it is not even possible to get 4W out, with everything just right you'd get 2.5.

A 16dB dipole is totally impractical for just about anything in our field.

It is my understanding that only the left antenna needs to be amplified... the right is almost useless.
One transmits, both receive. The amp also provides receive gain, so if things are well matched it should provide a benefit.
 
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The Bob

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Reducing voltage won't reduce output power, but will increase current draw.

People never understand how RF amps work. A "4W amp" has an output stage that is capable of delivering UP TO 4W without burning itself out or introducing major distorsion. But the amp gain is usually fixed, so what you actually get out depends on what you put in. From the specs on this page it is not even possible to get 4W out, with everything just right you'd get 2.5.

A 16dB dipole is totally impractical for just about anything in our field.


One transmits, both receive. The amp also provides receive gain, so if things are well matched it should provide a benefit.
Thanks for the info. I have a 5 and 9 dB dipole set as well. I am in trial and error stages so your help/info is appreciated.
To be clear.. are you saying the 4W amp I purchased will only do 2.5W with the voltage/battery I am using? Or is this best case with that amp?
I am OK with 2.5W because I think I really honestly only need 1W... I did not plan to "peak" the amp to burn out. 50% ideal ~ 80% max.
I am conflicted between running an amp on both sides or just the left side... I am hearing it both ways... "amp both sides"... "amp just left side".
Last thing I want to do is create interference issues with itself.
 
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Jeffm912

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Thanks for the info. I have a 5 and 9 dB dipole set as well. I am in trial and error stages so your help/info is appreciated.
To be clear.. are you saying the 4W amp I purchased will only do 2.5W with the voltage/battery I am using? Or is this best case with that amp?
I am OK with 2.5W because I think I really honestly only need 1W... I did not plan to "peak" the amp to burn out. 50% ideal ~ 80% max.
I am conflicted between running an amp on both sides or just the left side... I am hearing it both ways... "amp both sides"... "amp just left side".
Last thing I want to do is create interference issues with itself.
Bob,
That amp has a fixed output @ 4W. With a 2S lipo you are pulling over 1.5A constant current. The dragon amp uses NAND gates in its circuit. Only the right side does anything. I have tested both on my setup and running a second amp does nothing but cost you extra money for no practical gain.

Jeff
 
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Kilrah

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Or is this best case with that amp?
This.
As per the spec this amp has a gain of 13 +/-1dB. Its input is max 20dBm. So Max output will be at best, with max input and supposing you get a "good" amp 20+14 = 34 dBm, which is 2.5W. That's regardless of the input power supply as long as it's within the operational voltage range and can deliver enough current.

The "fixed output @ 4W" mentioned in the previous post is completely wrong. Given the fixed gain 4W would be achieved with 36-14 = 22dBm in, but that's above the max rating.

So something is wrong i that amp's specs, like often.

Note that the 20dBm max input means you should have your controller in CE mode, in FCC you'd overdrive it.
 

Jeffm912

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This.
As per the spec this amp has a gain of 13 +/-1dB. Its input is max 20dBm. So Max output will be at best, with max input and supposing you get a "good" amp 20+14 = 34 dBm, which is 2.5W. That's regardless of the input power supply as long as it's within the operational voltage range and can deliver enough current.

The "fixed output @ 4W" mentioned in the previous post is completely wrong. Given the fixed gain 4W would be achieved with 36-14 = 22dBm in, but that's above the max rating.

So something is wrong i that amp's specs, like often.

Note that the 20dBm max input means you should have your controller in CE mode, in FCC you'd overdrive it.
It is good to know the remote puts out up to 26dbm. Feel free to enlighten me. I will not argue but the degree in my drawer does say BS Engineering with a sub classification of electrical. You are correct in your opinion but the tested facts of this amp are beyond the specifications. Buy a 50c lipo from a cheap source and see if it delivers, you can argue what it is rated at all day but the fact of the matter Is that specs mean nothing on chinese electronics.

I meant your left side tx/rx. I changed my controller with the modification so I do not have 2 sub-par insulated cables one overtop of the other creating noise.

Jeff
 
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The Bob

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.... "Only the right side does anything." .....

Jeff
Sorry did you mean the left side does anything?
I had learned that the left is the main and the right is mainly for diversity; at least on a Mavic Pro that is.

Thanks!
 

Jeffm912

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Bob,
Sorry about that, I changed that in my last post. I changed mine so the cables do not run on top of one another. My right your left antenna.

Jeff
 
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The Bob

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I am just trying to grasp what you 2 are talking about. lol I get some of it.. but what I am hearing is the amp I purchased is a pile and has over-exaggerated specs. (as with most)
What then (if any) would be the ideal RF amp / battery combo for boosting the left antenna of a Mavic pro? Is there any hope for what I purchased or should I just cancel and send it back?
 

Jeffm912

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The amp you bought is under rated. They are very good amps for the price. I use one myself. They do run at optimal temp though when powered correctly. Mine stay at a nice toasty 120* F. Electronics all have an optimum temp before you reach diminished returns.
I also use a 3S lipo for mine because small gauge wire losses are larger when it is using more current. It is more efficient to volt up and amp down.
Jeff
 

The Bob

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The amp you bought is under rated. They are very good amps for the price. I use one myself. They do run at optimal temp though when powered correctly. Mine stay at a nice toasty 120* F. Electronics all have an optimum temp before you reach diminished returns.
I also use a 3S lipo for mine because small gauge wire losses are larger when it is using more current. It is more efficient to volt up and amp down.
Jeff
Thanks! I just got the cheaper 2S - $10 battery to test with; I am also concerned with mounting size / weight etc and trying to keep it as compact as possible.
Thanks again for the great info. Hopefully I can get a bit more range in my WiFi congested area. I try to get to the open field to fly but sometimes I only have time for the back yard.
 
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Texas Mavic

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Folks, I missed this post. I experienced the SAME PROBLEM. Jeffm912 has nailed down this issue. He helped me fix my issue. Underpowered amps or mismatched powered amps/antennas are the problem. Delivery of adequate power to the amp is essential. Short cable runs, well grounded cabling, and you are good to go. Jeffm912 is the man to listen to on this one. By experience.
 

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