Originally Posted by Aeronut41

AC, Yes the WT would interfere with your setup! I'm using Frsky 2.4 with L9R rx so no interference there. I was getting a buzz in the WT RX which I traced to it being too close to the DJI goggles. Moving it to my shirt pocket cured that. Sure wish DJI would come out with a firmware update that gave us live audio!

Yes, it would be so simple with a minor hardware upgrade. Maybe they're keeping it in their back pocket as a model upgrade ingredient..
I would guess 1080p with stereo audio will happen one day, the stereo option would be the holy grail being able to determine sound direction as well as having FHD.. it would require more directional microphones, but it's not hard.
I am still waiting for a standalone HDMI receiver for their system before I buy, yet again it's just wait and hope...

AC, That would be the ultimate To add to the immersion factor I have found using earbuds on my WT's really helps to put you in the aircraft! Come-on DJI!

Yeah, surely the read these forums for inspiration (pun intended)
They're missing out if they don't... we literally hand them the best ideas for free..

Originally Posted by alicecooper

Yes, it would be so simple with a minor hardware upgrade. Maybe they're keeping it in their back pocket as a model upgrade ingredient..
I would guess 1080p with stereo audio will happen one day, the stereo option would be the holy grail being able to determine sound direction as well as having FHD.. it would require more directional microphones, but it's not hard.
I am still waiting for a standalone HDMI receiver for their system before I buy, yet again it's just wait and hope...

I don't think they even need a hardware upgrade. The following quote from the main DJI thread is the only concrete thing I've seen about it, but if the info is accurate then they might be able to work it out in software...

Originally Posted by pkvillager

A dude named Arthur commented on one of my videos recently saying he works for DJI in China and does FW. I asked if we would ever be able to get audio to stream from the AU to the goggles. He said they are testing it but having latency issues. If true I'm am excited about that, I really like to be able to hear my motors and even more so when flying from inside my house in bad weather.

Depending on what latency issues they were having, it might be possible still, and I'd be willing to deal with some added latency (though not a whole lot) if required. Now that they have 50Mbps mode, maybe they could use that extra bandwidth for audio such that you could have menu options: 'Audio Off' and everything stays the same as it is now, and 'Audio On' with the same video quality as 25Mbps mode, but operating in 50Mbps mode. I don't really know if it could work that way, but I would be happy with that if it could.
I'm doubting at this point that they will ever implement it simply because there aren't enough of us who want audio, so it's probably pretty low on their priority list. I could be wrong though (and hope I am).

In the meantime... baby monitors it is, heh.

Originally Posted by Aeronut41

AC, That would be the ultimate To add to the immersion factor I have found using earbuds on my WT's really helps to put you in the aircraft! Come-on DJI!

In full agreement... the immersion factor is off the charts when the audio is directly in your ear vs coming from an external speaker. For me it's in the "driver's seat" rather than the cockpit, though (because flying anything anywhere close to me is 100% illegal... well except for my cheap tiny whoop that I *attempt* to fly indoors, heh).
I've also input transmitted audio (from analog setups) into my vehicle's speakers via a 3.5mm jack and driven FPV sitting in a real driver's seat... That's pretty darn immersive as well. I really want these options with the baby monitors but don't know if that's feasible. However, just having the audio alone, even poor quality through an external speaker, is 85% of the way there for me, and I can live with that. The other 15% would be high quality stereo audio directly into my ears... that would be FPV audio perfection.

Originally Posted by Aeronut41

Great to see options for DJI's omission of live audio! They really dropped the ball on this! Your baby monitor conversion looks like a good solution for ground based vehicles! I have been using the Walmart walkie talkie board on my FPV aircraft with good success. Have only tested it out to around 1000 feet but good clear signal! I use an old ebay Motorola WT as my receiver and clip it on a shirt pocket. Makes a lot of immersion difference to be able to hear the motor while flying! The small setup works great on my Aeroscout fpv test plane! Keep up the good work, Aero

That's nice and compact, that size would be ideal for my buggy. What frequency does it run on and what power output?

Hi Rev, The frequency is 462.5625mhz which is channel 1 on the little Motorola WT. Don't know the output. I got the WT set at Walmart last year for like $15 on sale.. If you want to try it out the set was the Paw Patrol. They had a bunch of different ones. Cheap way to experiment Good luck to all of us working on this stuff!

Okay, thanks for the info. That's the FRS/GMRS band. I have Cobra two-way radios on that band that I tried first (both 462 and 467, every channel) and they stomped on the control Rx so bad that I couldn't drive more than 15 feet away in clear LOS, even with the bottom null of the Tx handheld pointed toward the control Rx and as far away as it could get on the rig. It might have everything to do with their multi-watt power output (I forget exactly how much), but it was so bad that I'm afraid to waste more time and money trying that band again (maybe that's unreasonable).

The 900MHz that I've been toying with, at least at these low power levels, seems to be completely invisible to the control and video both and that gives me warm fuzzies.
I could be biased for no good reason though. Maybe a <25mW FRS/GMRS Tx would work as well or better?

Rev, Yeah, I had the same experience with the powerful Motorola WTs. They completely wiped out my 2.4 control! That's when I tried the low power Walmart kids WTs and they don't bother the 2.4 control or DJI signal at all. The multi mile WTs are like a blowtorch and even wiped out my TV signal! Anyway, will watch with interest your antenna work with the baby monitors and hope they work ok! Might be good for ultra long range!

Hmm, that's tempting to try because of the small size, though I don't imagine that it's filtered as well as the baby monitor based on what alicecooper said. There's obviously way less going on with the toy WT's. Though you bring up an EXCELLENT point... you can get handhelds that will work with them with audio-out jacks for the aforementioned immersion. Equivalent 462 MHz antennas need to be about twice as big as 900 MHz antennas though, and that's a problem for the buggy, so maybe it's out.

I remembered that I have an RTL-SDR unit and an app for my phone called RF Analyzer which I haven't used in a couple years. I fired it up and looked at the frequencies of the two baby monitor Tx's.

The first one I bought which is newer (we'll call this the blue set since the Tx has a blue PCB) has 10 channels that are dead-on from 905.0 to 907.25 MHz in perfect .25 MHz increments.
The second one which is older (we'll call the green set since the Tx has a green PCB) has 2 channels that are a hair above 906.0 MHz and about 906.67 MHz for some reason (hard to tell with its wide bandwidth and this analyzer setup).

Channel 5 on blue and channel 1 on green are very close, but the bandwidth on green is much wider for some reason. The blue set Rx won't pick up any audio from the green Tx, but the greet set Rx WILL pick up the audio from the blue Tx.

The point in all this is because I want to see if I can find any other audio receiver that can pick up these frequencies AND has an audio-out jack. Bonus if it already has a good antenna. I'll have to start searching again. *sigh*

If youre experimenting with WT transmission, heres a couple of things to try that might make them play. Most of the tiny radios output 500mW into a monopole antenna which is counterpoised to the radio pcb, battery and sometimes case lining. In that situation there is loads of interference potential as everything connected effectively becomes part of the radiator. The best solution is to use a centre fed dipole antenna (with coax) that effectively isolates the radio itself from the rf output. Doing that also allows you to use an attenuator to limit the huge output power and even 6dB would have little impact on range, but cut near field radiation massively.
The next trick is to ground the radio's earth circuit to the other car ground (RC circuits) which stops the other parts from behaving as a sympathetic resonator. Just keep the ground connection short and straight if possible (no loops).
One last technique is to shield the radio pcb and ensure the shield is grounded. A good system is to use large heatshrink covered with adhesive copper tape, and cover the ends, any holes can make the whole thing useless.
Just do a few tests first to check the output device doesn't run too hot, if it does add a small heatsink radiator with epoxy.
Hope that may help.

Experimenting I will be. I'd really like external audio out from the Rx if possible which the baby monitors don't have. I can't find nearly anything that will receive those frequencies period, much less with an audio output.

I ordered a set of those Paw Patrol WT's new for $8 shipped (hard to go wrong there). I would think they put out less than 500mW but I don't know. If I can get the 462/467 band to play with everything else then there is a plethora of both Tx and Rx (with audio out) options to choose from because they're everywhere and nearly all compatible with each other. IOW, I wouldn't have to use matching units so I can tailor the setup of the Tx end to the car and the Rx end to me.
I don't think I'll be able to use a straight half wave dipole at that frequency on the buggy though... too long. However, no problem with that on the receiving end.

Actually I just thought about it then researched a bit... Adding an external audio output to anything with an internal speaker is stupid easy by making a voltage divider using a pot or a couple resistors and wiring it all to a 3.5mm jack, so that's not too much of a consideration.

There are pros and cons of all of these options. I should make a list.

Originally Posted by Reversion

Actually I just thought about it then researched a bit... Adding an external audio output to anything with an internal speaker is stupid easy by making a voltage divider using a couple resistors and wiring it all to a 3.5mm jack, so that's not too much of a consideration.

There are pros and cons of all of these options. I should make a list.

Yeah, I got my son a set of those uber cheap WT's for about the same money, but they sound amazingly bad.. although his are labelled Bell South, I suspect the tiny mylar speaker is the main cause, they sound about the same as a greeting card.. if you're ripping into them the earphone option can only make it better. Also, the microphone module could easily be upgraded for about 20 cents too, or get something good.
Re the dipole, just a 1/4 wave would do fine, you can get end fed ones as a whip cheap as on ebay (if they can be trusted..) with SMA attachment, and use a flange mount connector to panel fit it.
like these https://www.ebay.com/itm/SMA-female-...4AAOSwcOFWbm6B

All good to know, thanks. That whip would work as long as I can remove the plastic tube without damaging the antenna. I require flexible antennas (at least above the roll cage) so that tumbles (and overhead hazards) don't destroy things.
I would only be using the cheap toy WT's for the Tx side because of the PCB size so the speaker doesn't matter, but the mic does.

For the Rx side I would be using something a bit better. In fact, I've been wanting to buy a Baofeng UV-5R for a while now for offroading (1:1 scale) use anyway, so I just ordered a UV-82 (newer model) and a recommended 450-470 MHz antenna for it. It also comes with earbuds. So if that band works out for this use (because it won't do 900 MHz) then I should be all set on the Rx side.