Connecting external antennas to the RC Plus?

[wrybread]

I'm trying to connect external antennas to my RC Plus controller. Does anyone know what the antenna jacks are?

Ultimately I need to connect antennas with RP-SMA male connectors, but I'm fine using adaptors.

 

[Starz]

Reading material?

Connectors, Adapters, & Cables

Explore SMA connectors, adapters, and cables offered by Amphenol RF and available at DigiKey.

www.digikey.com

 

[wrybread]

Solved! It's an MMX connector. Details and pics here:

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[rbad]

For around $80 bucks, Alientech (Alientech.cn) makes an “adapter bar” that has 2 male RF connectors on one side and 2 QMA connectors on the other side.

It’s made for use with their Duo-2 Duo-3 amplified antenna units and is outstanding for that use. It’s very well made and makes everything so much easier.

We have the Duo-3 and usually mount it right to the “adapter bar, but I also made up 2 pairs of cables for use in mounting the Duo-3 to a tripod. It gets the extra weight off of the controller and gets the Duo-3 up higher in the air. (the Duo-2 and Duo-3 both have standard tripod mounting threads on the bottom. 1/4x20). Do NOT use RG-58 or any poor quality coax cable or terminations. The signal loss/attenuation at the GHz freqs is high. I used RG-400 for 6’ cables and RG-223 for 15’ cables.


The RC-Plus is a phenomenal controller.
We purchased 2 of the “modified” controllers from an eBay seller in China. So so so much better than the RC, RCN1 with phone or RC-Pro. You just have to be careful not to update the controller firmware. I now know this from experience.

 

[High_Order1]

but I'm fine using adaptors.

At the frequencies and power these operate in, you want the absolute shortest runs of cables and no adapters.

You also want to use the highest quality cabling as well.

Several will be along to tell you their janky setups work 'great', I'm just suggesting that the higher risk your flight operations are, the fewer corners you may wish to not cut.

 

[rbad]

High_Order1 sounds like he’s exaggerating.

I’ve heard that can use up to 1500 feet of lamp cord and alligator clips instead of proper (and $ pricey) RF termination.
LOL

Actually,he is 100% correct! It’s great that the issue was brought up.

I’m a retired EE and mostly worked in the RF side of public safety communications system design. I’m shocked when I see the type of hardware and cabling being used in the RC world.

Especially the FPV folk. I’ve often wondered how transmitters continue to function after being run without termination / load / antenna for extended time. I’m guessing because they’re not pushing more than a few watts.

 

[rbad]

Forgot to mention = The “adapter” I recommended is from the manufacturer of the most popular directional antenna/bidirectional amp devices for drones.

Alientech states they custom fabricate these “adapter bars” using very good quality hardware and has excellent fit & finish. A bit pricey, especially with shipping from China (approx. $80 + $20 shipping), but absolutely worth it IMHO.

I will also admit that I’m super picky about the most minor details and would much rather pay once for good quality than deal with junk. I just wish DJI had thought enough about their customers and included STANDARDIZED external antenna connections to permit easy and less costly use of add-on devices and antenna repairs / replacements. (RC-Pro is a beast to disassemble and install external RF connectors and my arthritic hands and spine virtually ensure I will break something during the teardown and reassembly ).

 

[rbad]

Now the Alientech Duo-2 and Duo-3??
I’m beginning to believe they are a complete waste of money. Our testing (vol. fire dept) shows very little “real world” improvement in range/distance/penetration of the drone to controller comms.

We performed unscientific testing the other day.
Don’t hate.. our primary purpose for the distance is for BVLOS use of drones to do a quick wildfire sizeup. Operation only over heavily forested area with no people, vehicles, structures or….

The Air-3s with RC2 FAR outperformed the Mavic-3 (original model) with:
- RC-Pro
- RCN1
- RC-Plus (“modified” purchase from China based eBay seller)
- RC-Plus with Duo2
- RC-Plus with Duo3

By A LOT!

The Air-3s outperformed everything by thousands of feet and has the tiniest little antennas on the RC2 vs a directional bidirectionally amplified antenna system.!
I just wish we had waited on our recent Mavic-3 Pro purchase.
The Mavic-4 with 04 and a more robust controller should be a huge improvement.

Also, our battery inventory and accessories are all “Mavic-3”.
Even our Tundra lights are physically specific to the M3.

Note: We use the Duo2 & Duo3 mounted directly to the RC-Plus via the “Adapter Bar” AND, using cabling, we sometimes use them mounted to tripods or on the rooftop of rescue apparatus which we use for communications and IC use. Short length and high quality mil-spec Belden RG400 and RG223 (double shielded / silver plated conductors / kinda $$) is used.

Some REAL testing needs to be done on Alientech products.
Even without a teardown, testing can still be done using test gear. (advice = do NOT get into THAT hobby. If you think drones are costly, wait until you price out RF test gear like spectrum analyzers, VNAs, etc..)
When you’re spending $1k for an Alientech unit and even more for the RC-Pro or RCxxxxx controller connector installation, you expect to see phenomenal performance increases. Something DJI achieved in 04 without the bulky and expensive hardware.

(Not disparaging Alientech. Just looking for concrete performance that is predictable..

 

[GadgetGuy]

Now the Alientech Duo-2 and Duo-3??
I’m beginning to believe they are a complete waste of money. Our testing (vol. fire dept) shows very little “real world” improvement in range/distance/penetration of the drone to controller comms.

We performed unscientific testing the other day.
Don’t hate.. our primary purpose for the distance is for BVLOS use of drones to do a quick wildfire sizeup. Operation only over heavily forested area with no people, vehicles, structures or….

The Air-3s with RC2 FAR outperformed the Mavic-3 (original model) with:
- RC-Pro
- RCN1
- RC-Plus (“modified” purchase from China based eBay seller)
- RC-Plus with Duo2
- RC-Plus with Duo3

By A LOT!

The Air-3s outperformed everything by thousands of feet and has the tiniest little antennas on the RC2 vs a directional bidirectionally amplified antenna system.!
I just wish we had waited on our recent Mavic-3 Pro purchase.
The Mavic-4 with 04 and a more robust controller should be a huge improvement.

Also, our battery inventory and accessories are all “Mavic-3”.
Even our Tundra lights are physically specific to the M3.

Note: We use the Duo2 & Duo3 mounted directly to the RC-Plus via the “Adapter Bar” AND, using cabling, we sometimes use them mounted to tripods or on the rooftop of rescue apparatus which we use for communications and IC use. Short length and high quality mil-spec Belden RG400 and RG223 (double shielded / silver plated conductors / kinda $$) is used.

Some REAL testing needs to be done on Alientech products.
Even without a teardown, testing can still be done using test gear. (advice = do NOT get into THAT hobby. If you think drones are costly, wait until you price out RF test gear like spectrum analyzers, VNAs, etc..)
When you’re spending $1k for an Alientech unit and even more for the RC-Pro or RCxxxxx controller connector installation, you expect to see phenomenal performance increases. Something DJI achieved in 04 without the bulky and expensive hardware.

(Not disparaging Alientech. Just looking for concrete performance that is predictable..

Basically, OS4 already optimizes range. Not much more Alientech can do to it. The Alientech setups were designed for improving OS2 and OS3 range, not OS4 range, so you reach a point of diminishing returns on an already natively optimized system with OS4.

 

[High_Order1]

I just wish DJI had thought enough about their customers and included STANDARDIZED external antenna connections to permit easy and less costly use of add-on devices and antenna repairs / replacements.

...
There is a reason they do not. It is the same reason you should not be able to unscrew the antenna on a FRS radio.

 

[High_Order1]

Now the Alientech Duo-2 and Duo-3??
I’m beginning to believe they are a complete waste of money. Our testing (vol. fire dept) shows very little “real world” improvement in range/distance/penetration of the drone to controller comms.

The issue as I see it is this:

These systems don't use the legacy way to communicate. It's not even a diversity setup. It's called MIMO, and part of that has to do with antenna spacing.

Alientech appears to have created a passive coupler as a no-cut solution. The problem then becomes sidelobes at the connection point, and other issues with simply setting one antenna next to another antenna.

Because it is MIMO, the system is VERY smart about adjusting and self-healing, and the end user doesn't notice a lot of the dropouts that may occur. At microwave frequencies, passive coupling is super wasteful of RF, I suppose the transmitter makes up for it by ramping up to max constantly. (Does the fan seem to kick on more than usual in the cooler months? It would be an interesting experiment.)

MIMO is spooky stuff. Spend years reducing or eliminating multipath, and now this system THRIVES in the environment.

 

[High_Order1]

Basically, OS4 already optimizes range. Not much more Alientech can do to it. The Alientech setups were designed for improving OS2 and OS3 range, not OS4 range, so you reach a point of diminishing returns on an already natively optimized system with OS4.

From my perspective;

the MIMO implementation scheme (1T 2TR to 2TR if I understand correctly) should help. But, in RF Land.... antennas uber alles.

First, all handheld transceivers (which is what the controller partly is) suffer from a lack of ground to earth, no ground plane concepts be damned.
Second, even though those patch antennas are amazing (there are some good pics and VNA readings out there) a tiny antenna at ground level will never be as good as a larger antenna, properly spaced, with even a little height.

Also, even those goofy clipons really do help a little by helping to reduce the noise floor and redirect the rear lobe away from the equipment and towards the sky where the airframe (hopefully) is.

DJI has to be super careful about antenna selection and access. It can potentially invalidate the license the FCC (In the US, there are other rules in other countries obviously) grants to the unit. Putting any antenna that fits can increase customer dissatisfaction through degrading the wireless link, and potentially, as he says above, burning up the transmit finals, or worse, like in a lot of modern radios, turning the power down (or off).
Putting larger, higher antennas also increases the risk of hearing (and causing co-located interference to) other things in the bands these are on. These things may be considered airplanes to the FAA, but they do not hold a priority ability to use ISM and other bands by the FCC.

... rereading the last couple of posts, because I am new here: please do not think I fancy myself the 'radio police'. When I got started in... uh, dronery, I was really jazzed to play with the antennas in the system. (Putting better antennas on the drone would absolutely increase surety in the link).

I'm not super interested in being able to go far. I live in the hills, and have no desire to dig through bear poop with a stick looking for my investment when it decides to immediate forced land 2 miles out of my visual capability to observe.

But, for this current drone (my T&E testbed), I would like to illegally be able to fly at low level completely around my house to provide close air support to the wife's cats. (Anyone know how to fill out that form? Anyone? LOLOL)

From the radio perspective, it goes, improve the antennas>improve the physical links>then add power on one end. Most people just throw an amplifier into the mix and call it a day. At microwave frequencies, you have to be very picky about the components you choose - they can cause more issues than they solve.

Unless the booster is smart enough to ramp down, I am honestly surprised that more drones don't have problems on short final. You can 'swamp' the front end of the drone side of the link blasting a lot of power at something designed to be super sensitive.

... I am sorry op for thread sliding you. Just excited to be somewhere I can discuss this kind of stuff.

 

[High_Order1]

Solved! It's an MMX connector. Details and pics here:

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One minor note. I didn't realize that was what they were using for those ports.

Those connectors were not designed to be mate/demate cycled a bunch, and with the collar I see, DJI engineering was trying to transfer some of the axial stress off of the connector into that collar.

If you are interested, go read in the smartphone repair forums about how easy it is to jack one of those up, and how little stress they can accept before the inner pin wallows the female side out and issues start.

I personally would use some method to semi-permanently attach those adapters to the collar area, and not have it go port>adapter>freestanding antenna.

There was no benefit for DJI to intentionally choose that connector over something more robust like SMA (side tangent, RP-SMA was created as a way to get around FCC regulations pertaining to non-removable antennas)

This strongly suggests to me they did NOT want the antennas removed after installation. (shrugs)

Anyways, rambling again. Let us know how they fare against salt air and actual use!!