When is 1W not necessarily 1W?! // DIGITAL VTX Output power testing 

Except me! In data we trust. 😁

Aha! 😅

Tldw gdit

Pretty sure the HDZero Freestyle VTX does hit 1W output power on R1...

@@Vousie Ok, but can how the stream quality compares?

@@sunnyfpv3694 HDZero has a great image. And remains at low latency. And doesn't just fully drop the link and remain gone when you go just barely out of range and come back. People who do mountain surfing have learned that the hard way...

Glad you enjoyed it! Unfortunately I can't afford a spectrum analyzer but these RMS power meters are really good for giving you a total mW output. Although I'm sure a $10K analyzer can integrate total power as well.

Isn't the resulting graph kind of one? XD

No it's not. A spectrum analyser shows the spectral components of an individual signal by converting it to the frequency domain (via FFT for example).

The work for just this video was around 60 hours.

But channel 7 is the most far away from wifi and other crap so people still get better range on some higher channels

To acknowledge packets, and to tell the VTX to resend ones that it has missed... Looks to me like the DJI system *has* to have a full picture - when it can't get a full one (even with low resolution tiles) it fully drops the link instead of being able to just show static in the spots it's missing. So a lower goggles transmit power would mean it would fully drop the link earlier.

I was thinking the same thing

Accoridng to chatgpt, a 250mw signal would be received at 3.5mw over 13km, assuming line of sight and normal atmospheric conditions of 25c at 50% humidity. 3.5mw is well above the operating range of wifi receivers so maybe it really is that weak of a signal operating at those distances. Hard to believe

@@devinfritchey7323oh my god. does anything you said make sense to you?

Well, many race organisers check the output power of each person with an RF power meter that they have with them (you can often see it on the screen in livestreams) and everyone's transmitting about the same amount (including analog pilots), so either these readings are not quite accurate or the pilots *are* using the 25mW adjust option to bring it down to the correct levels.

i bought three rush max solos to be able to fly next to dji pilots but i am still having bad signal to the level where i gave up flying with other people. when i am alone or with analog pilots, penetration and range are ridiculous compared to 69, unifys or trump nanos that i had so far

It seems to depend on the VTX. Some VTXs produce more power at higher frequency and some more at lower frequency. I'm not sure of the exact mechanism though.

O3 has higher latency than its predecessor, this would increase range and penetration for a given output power. The actual output power is about the same as the V2 system at 700mW, as Chris presented in his video.

@@disco.volante higher latency would not inherently increase range and penetration for a given output power... Latency is basically a measure of time delay... technically - "the delay before a transfer of data begins following an instruction for its transfer." Long story short, higher latency in any situation is Bad.

I am curious about this too. DJI claims 33dBm EIRP (2000mW) on the 5.8 frequency. If the O3 only outputs 200mw (23dBm) as shown in this test, even if they double it by adding both antennae, that's 400mw or 26dBm. That leaves 7dB to make up with with the omni antenna. I don't see that happening. I also don't them only using half of the front ends total power capacity, but then again, the O3 turns into an oven, so maybe it just thermally can't handle 400mw.

there is an "unlock" for the 03. The Ham file..

@@willpowerfpv3246 lmfao...

+1 !

Oh yeah, of course it's a two way link on the DJI fpv units... You can control your drone on the same link. Yeah I'd be they 100% use the same scheme as they do on the Mavic to keep the link stable. My point is that the link you are measuring may not be the same modulation or transmit power given the fact that the receiver/goggles isn't turned on etc. I'd bet that the actual conducted power changes in response to the goggles. Be real cool to set up a variable attenuator on the goggles and watch the power output of the tx side real time on a scope

That may well be the case. I wonder if O3 getting very hot might also limit how hard they can drive the amplifier.

@@ChrisRosser I agree with him as well. I think that's called slew-induced distortion? From your data, it looks like they are running these components to the edge. The output power is reflected in how far the amplifier can push before distortion(vs frequency/modulation characteristics). I'm sure heat is a factor, but the capability of the amplifier to resist distortion at higher frequencies is probably the bigger bottleneck. I will say though, RF is a bit of an artform... I could be completely wrong lol

if your not recording on the 03, there should be no problem running 1200mw

Yes that's how I got it in fcc mode.

Yeah it seems dji video signals really mess up analog if its anywhere near the same frequency. Do your dji pilot friends move to their higher frequency channels so you can use R1?

@@Voyajer. yeah i am always on R1, regardless, i have such crappy time that after a year of trying to solve that, i literally decided to give up flying with other people. i don't feel that it is ok that i am bullied into buying digital equipment but it seems to be a requirement if there is even one pilot with digital system...

The killer with DJI is the goggles transmit so you can't actually stand anywhere near dji pilots. If you're flying with DJI pilots you have to stand far away from them (which sucks). A more powerful VTX won't help that much if you're 1-2m away from the DJI goggles.

Maybe the power is increased automatically with distance

@@stormriderfpv I do have such thoughts, that because o3 is all dynamic in real world it would do that. But then again, I also remember that Chris unlikely would have missed this detail with how thoroughly he tests everything.

Yes that's true but don't the antennas have to be oriented in the same direction? DJI specifically recommend the antennas be oriented in different directions.

@@ChrisRosser now from point of maximum EIRP, statement is "true". To explain more if we have two ideal isotropic antennas then no mether of how they are oriented they have gain of 1 in all direction (EIRP is same as output power) so gain of 2 of them will have gain of 2. For practical case when there are (most commonly used) monopole or dipole and they are at angle of 90 degrees (worst case) then gain of two antenna would be same as single antenna, but they already have gain of 2 sp in both cases EIRP will be same and 2 times output power of transmitter. I am not too familiar how specific VTX use antennas (I usually do not fly FPV, I am old and I perfer flying turbine jet plains and helicopters), but there is option that they even produce with two linear polarized antennas at 90 degrees and proper pashe shif circular polarisation (i do not know why they would use that, but that is commonly used for satelite communications when you use two Yagi antennas at 90 degrees to get circular polarisation). If I remember correctly you are expert in matlab, and matlab have tools for simulation of antenna radiation pattern, so maybe you could do simulation what they do (I was only basic matlab user and thay was before I retired from work over 12 years ago).

I found on FCC site presentation how you calculate EIRP for muti antenna system (including cases with cross polarization) transition.fcc.gov/oet/ea/presentations/files/apr16/5.3-MIMO-Primer-RB.pdf

The slope of the ADL5902 (without voltage scaling) is 53 mV/dB. A 10 bit ADC with 5V vref has 4.88 mV/LSB so allows to measure ~ 0.1 dB/LSB. Do you really more precision than that?

I hope not. In general I've found that explaining how these systems perform makes people happier with the performance of their gear.

im stealing that for the next time I have to explain how antenna gain works

20:00

Hey doofus, give it time.. I'm sure he will.

This guy is the last guy I would be name calling on RU-vid. How you look rn 🤓

@@davidhoward2901 Ok, Doofus. haha

@@tektkite7255 doofus 🤓

Nobody cares about Canadian politics like you do buddy 🤓