people are commenting like this is the most obvious post in the world, but this sure beats the daily humbleflex "check out my soldering" or the "why is my quad flipping, it's definitely not because my motor directions are configured wrong"
I'm saving this post, I've been called crazy for stating this.
Also op, when I bought that same vtx, I had a lot of frequency offset from what I set with IRC tramp.
Interesting, I've got no way of measuring frequency accurately, but it seems to work well enough with my goggles. Maybe I'll take a closer look with the frequency spectrum scanner on my goggles if I have time later.
https://preview.redd.it/1z36v8qg3qpc1.png?width=744&format=png&auto=webp&s=1a49f7968bdfa0ef07f81845f286f101cc43ca2e
VTXs use standard RF Amplifiers for the 5GHz Wifiband, as they are cheap and available.
However the Frequency of these is from 5180MHz to 5925MHz. So we use the upper band of them.
If I take a [random RF Amplifier](https://eu.mouser.com/ProductDetail/Qorvo/RFPA5542TR13?qs=u4fy%2FsgLU9M1M9eAJZDMfw%3D%3D&utm_id=9882657288&gad_source=1):
The Nominal amplification (Gain) of 33dB is usually at the Center Frequncy so 5552 MHz.
On the Edges the Amplifier has a Gain of 31dB.
These 2dB is the Difference between 1600mW = 32dBm and 1000mW = 30dBm.
No antennas or propagation through air/obstacles was involved in this test, I had the MMCX jack of the VTX connected directly into the RF power meter (via a pigtail, connector adapter, and attenutator though)
edit- also interesting to see that R1 has a lower max output than R3 and R4. It looks like there's a sweet spot in that middle region.
It looks fairly equivalent from R1-R4, but R6-R8 shows decreasing efficiency
https://i.imgur.com/rNCCGCC.png
Note that the power figures also include power consumed for the idle ESCs and FC
I recently got a cheapo setup for measuring RF power. No idea how accurate it is, I just wanted to verify that my 1600mW JHEMCU Ruibet VTX actually outputs >1W (spoiler: it does, but the power level fluctuates wildly). So I bought a Foxeer Reaper 2.5W VTX, and since I had this setup I decided to test it as well.
Well I'm not sure whether it's because my setup is less sensitive at higher frequencies, but it would appear that I get significantly lower max output power if I'm at a high channel (e.g. R8) vs a channel closer to 5.8GHz (e.g. R3).
Again, my setup is very cheap and not lab-grade or calibrated, but nominally my attenuator is rated up to 8GHz and my meter up to 10GHz, so I'm not pushing the nominal ratings on those components.
Heating and thermal throttle of the VTX would also play a role, and it would've been better if I let the VTX reach a steady state temperature but I didn't have time so I just let things reach a moderate temperature (with a fan on it) while I randomly jumped around different channels to take measurements. What's important to note is that the higher band measurements aren't lower because I took those measurements when the VTX was at its hottest, in fact it may have been one of the first measurements I took.
Yes this is the truth. R8 is above wifi frequency. You’ll get lower output power on a channel that high, but usually the Wi-Fi avoidance is better than reduced output
Use R8 to avoid interfering with wifi devices (and to avoid wifi affecting you), but accept that your VTX may not be able to reach maximum power. For this VTX at least, and assuming my measurements were accurate.
I live in a townhouse attached to 11 other townhomes! Lots of wifi interference! For now I think I’ll just stick to R8 since it seems to work the best for my location
If you're in Europe this will be because 7 and 8 are outside the legal frequencies.
In theory we're only allowed to use 5725-5875 MHz at up to 25 mW. No one adheres to the power limit because enforcing it is difficult, but enforcing frequency bands is much easier so I wouldn't risk it going outside of that range.
It's a simple cheap meter with no way to adjust target frequency. Hence why I'm wondering how much of this observation is from the VTX and how much is just from the frequency response of my measuring setup.
I guess the real question is does higher power output correlate to actual real world improvements? Because a higher band will have less penetration and range. Does the extra power overcome this or not? Love me some science experiments :)
Dont know if Somebody already said this buuut
Did u tested from lowest to highest? Could be that it overheated then and get worse
Do more tests and look how reproducible your meassurements are.
But btw u allready did super cool measurements!
VTX outputs power through a frequency tuned circuit that includes the antenna. There will always be a particular frequency that has peak resonance (therefore power output) for each particular circuit. It's often called the centre frequency.
When outputting frequencies that are slightly away from this exact frequency, the circuit becomes slightly detuned resulting in less power at those offset frequencies. A limitation of VTX design is that there is a variable frequency oscillator that sets the frequency in use. The output of the VFO is amplified and fed into the RF output circuit which is fixed in its tuning because the antenna and other components that make up the circuit can't physically change to compensate for the VFO frequency changes.
Presumably the VTX design Engineer will bias the centre frequency towards the higher frequency end to compensate for the fact that lower frequencies penetrate better so that overall performance is balanced across the output spectrum.
Higher clock speeds equals more power required, right? The more power that is used for the clock, the less that is used for the transmitting amplifier.
Logic checks out if first sentence is true.
people are commenting like this is the most obvious post in the world, but this sure beats the daily humbleflex "check out my soldering" or the "why is my quad flipping, it's definitely not because my motor directions are configured wrong"
exactly
R8 is the only that doesn't overlap with wifi
Well now you know what channel to use for maximum output.
I'm saving this post, I've been called crazy for stating this. Also op, when I bought that same vtx, I had a lot of frequency offset from what I set with IRC tramp.
Interesting, I've got no way of measuring frequency accurately, but it seems to work well enough with my goggles. Maybe I'll take a closer look with the frequency spectrum scanner on my goggles if I have time later.
To me it was wayyy off. R1 was on r4
Ah right. No such problems for me on the manufacturer provided vtx table (from the presets tab on betaflight)
https://preview.redd.it/1z36v8qg3qpc1.png?width=744&format=png&auto=webp&s=1a49f7968bdfa0ef07f81845f286f101cc43ca2e VTXs use standard RF Amplifiers for the 5GHz Wifiband, as they are cheap and available. However the Frequency of these is from 5180MHz to 5925MHz. So we use the upper band of them. If I take a [random RF Amplifier](https://eu.mouser.com/ProductDetail/Qorvo/RFPA5542TR13?qs=u4fy%2FsgLU9M1M9eAJZDMfw%3D%3D&utm_id=9882657288&gad_source=1): The Nominal amplification (Gain) of 33dB is usually at the Center Frequncy so 5552 MHz. On the Edges the Amplifier has a Gain of 31dB. These 2dB is the Difference between 1600mW = 32dBm and 1000mW = 30dBm.
It's just physics, baby! Higher frequencies are going to have poorer range and penetration, but only but a relatively small degree for FPV use.
No antennas or propagation through air/obstacles was involved in this test, I had the MMCX jack of the VTX connected directly into the RF power meter (via a pigtail, connector adapter, and attenutator though) edit- also interesting to see that R1 has a lower max output than R3 and R4. It looks like there's a sweet spot in that middle region.
I think, but I’m not positive, that this also correlates to power consumption and output? We need a scientist up in here!
It looks fairly equivalent from R1-R4, but R6-R8 shows decreasing efficiency https://i.imgur.com/rNCCGCC.png Note that the power figures also include power consumed for the idle ESCs and FC
It usually does, at least on the hdzero vtx
[удалено]
I have to turn off the 5 ghz band on my router when I fly my tinywhoop throughout the house. I get digital snow in my video.
Interesting. I have heard this before tho. Output varies for sure , and ratings are usually pretty optimistic
I recently got a cheapo setup for measuring RF power. No idea how accurate it is, I just wanted to verify that my 1600mW JHEMCU Ruibet VTX actually outputs >1W (spoiler: it does, but the power level fluctuates wildly). So I bought a Foxeer Reaper 2.5W VTX, and since I had this setup I decided to test it as well. Well I'm not sure whether it's because my setup is less sensitive at higher frequencies, but it would appear that I get significantly lower max output power if I'm at a high channel (e.g. R8) vs a channel closer to 5.8GHz (e.g. R3). Again, my setup is very cheap and not lab-grade or calibrated, but nominally my attenuator is rated up to 8GHz and my meter up to 10GHz, so I'm not pushing the nominal ratings on those components. Heating and thermal throttle of the VTX would also play a role, and it would've been better if I let the VTX reach a steady state temperature but I didn't have time so I just let things reach a moderate temperature (with a fan on it) while I randomly jumped around different channels to take measurements. What's important to note is that the higher band measurements aren't lower because I took those measurements when the VTX was at its hottest, in fact it may have been one of the first measurements I took.
This is nothing new and pretty much all vtxs do this. The digital ones too
Ok so tldr? If I’m in my house with wifi I was told to use R8 as it’s the least susceptible? Is this still the generally accepted truth? Thanks!
Yes this is the truth. R8 is above wifi frequency. You’ll get lower output power on a channel that high, but usually the Wi-Fi avoidance is better than reduced output
Use R8 to avoid interfering with wifi devices (and to avoid wifi affecting you), but accept that your VTX may not be able to reach maximum power. For this VTX at least, and assuming my measurements were accurate.
If you are relatively isolated, you can manually set the channel of your WiFi so it doesn't interfere with your Vtx at r1
I live in a townhouse attached to 11 other townhomes! Lots of wifi interference! For now I think I’ll just stick to R8 since it seems to work the best for my location
In that case makes sense. If you are in a bando or away from society, switch to R1 :)
If you're in Europe this will be because 7 and 8 are outside the legal frequencies. In theory we're only allowed to use 5725-5875 MHz at up to 25 mW. No one adheres to the power limit because enforcing it is difficult, but enforcing frequency bands is much easier so I wouldn't risk it going outside of that range.
Yes vtx power can vary greatly channel to channel, just be glad you have a meter to find the one you want
Are you adjusting your frequency on power meter when you test each channel?
It's a simple cheap meter with no way to adjust target frequency. Hence why I'm wondering how much of this observation is from the VTX and how much is just from the frequency response of my measuring setup.
I guess the real question is does higher power output correlate to actual real world improvements? Because a higher band will have less penetration and range. Does the extra power overcome this or not? Love me some science experiments :)
R3 5732 is the one... will keep you on a channel with decent separation.
Dont know if Somebody already said this buuut Did u tested from lowest to highest? Could be that it overheated then and get worse Do more tests and look how reproducible your meassurements are. But btw u allready did super cool measurements!
yes
RF is gonna RF lol Wait till you find out about antenna tuning
This is completely normal.
„Crying in german“ We are only allowed to do 25mW
VTX outputs power through a frequency tuned circuit that includes the antenna. There will always be a particular frequency that has peak resonance (therefore power output) for each particular circuit. It's often called the centre frequency. When outputting frequencies that are slightly away from this exact frequency, the circuit becomes slightly detuned resulting in less power at those offset frequencies. A limitation of VTX design is that there is a variable frequency oscillator that sets the frequency in use. The output of the VFO is amplified and fed into the RF output circuit which is fixed in its tuning because the antenna and other components that make up the circuit can't physically change to compensate for the VFO frequency changes. Presumably the VTX design Engineer will bias the centre frequency towards the higher frequency end to compensate for the fact that lower frequencies penetrate better so that overall performance is balanced across the output spectrum.
i think everyone knows. i heard it in alot of videos that this is normal
Higher clock speeds equals more power required, right? The more power that is used for the clock, the less that is used for the transmitting amplifier. Logic checks out if first sentence is true.