Thread Tools
May 22, 2019, 05:39 AM
FJH
FJH
Registered User
Quote:
Originally Posted by Sockrat
I think would be great to develop a more powerful TX module - 300 or 500mW instead of 100 that will normally work in 100mW mode but in case of low RSSI automatically temporarily increase power.
Quote:
Originally Posted by montis
It is more important to improve the sensivity/link quality at the receiver side. Also at protocol level. Although the possibility to have higher output transmitter would be interesting. Just dont know how it would comply to CE requirements.
Max power level is limited to 100mW for 2.4GHz by EU regulation. Thus any increase will not get CE.
Sign up now
to remove ads between posts
May 22, 2019, 07:59 AM
Sagitta Fanboy
Quote:
Originally Posted by Sockrat
I think would be great to develop a more powerful TX module - 300 or 500mW instead of 100 that will normally work in 100mW mode but in case of low RSSI automatically temporarily increase power.
This will help with flyaway model or some rf noise spike at the field. With 5G networks which will cannibalize all available spectrum I think it will be more important.

As for me the most important in radio is connection reliability. I don't care about latency below 20ms and channels beyond 16.
But if I hear "telemetry lost" or see jittery behavior in the air - that's critical.

p.s. Also might be good to decrease it when RSSI>100 to get rid of annoying over saturation within 1m.
5G has no impact on us as all 5G bands are outside the ISM bands we use for both 2.4GHz and 900MHz.


The range performance of current 2.4GHz and 900MHz modules is more than good enough for any LOS operations and BVLOS is illegal most everywhere and increasingly on the radar for enforcement.
May 22, 2019, 05:30 PM
Registered User
I guess these frequencies will be determined at the auctions. But indeed, looks like here 2.4 is already sold out.
I lost plane once in 7 years with X8R due to connection and had many instances of temporarily telemetry/connection loss.
Our club is in a industrial area and there's a plant nearby with some sensors along the lake shore. They send signals like once an hour. If a sensor happen to be between you and the plane at that moment typically there's a loss of control. In addition now there are a few huge warehouses with incredibly strong wifi.

If you think 100mW is more than enough for anything - put a model on the ground and walk behind a metal mesh fence...
May 22, 2019, 07:14 PM
Sagitta Fanboy
Quote:
Originally Posted by Sockrat
I guess these frequencies will be determined at the auctions. But indeed, looks like here 2.4 is already sold out.
ISM bands like 2.4GHz and the 868MHz/900MHz band are not available for carriers. The bands up for auction are pre-allocated to cellular service and do not impact other bandwidth allocations including ours.

Quote:
I lost plane once in 7 years with X8R due to connection and had many instances of temporarily telemetry/connection loss.
Our club is in a industrial area and there's a plant nearby with some sensors along the lake shore. They send signals like once an hour. If a sensor happen to be between you and the plane at that moment typically there's a loss of control. In addition now there are a few huge warehouses with incredibly strong wifi.

If you think 100mW is more than enough for anything - put a model on the ground and walk behind a metal mesh fence...
Yes, ISM bands have other users. That's why they're called ISM bands (ISM stands for industrial, scientific and medical). That's also why there are specific requirements for ISM band use around ability to reject interference and power limits.

And I range out to the limits of LOS, as I fly competition gliders (>1.5Km ranges with 3m+ wingspans). 100mW is more than enough.

The issue with a metal mesh fence won't be overcome by power, but by not flying behind an RF blocker.
May 22, 2019, 08:52 PM
Registered User
RCAddiction's Avatar
Mawz, in theory you are absolutely correct. There should not be bleed-thru of 5G bands into the ISM bands like 900, 2.4, 5.8.

However, last year at an AT&T 5G test site adjacent to Baylor University, the 2.4 and 5.8 mesh network multicast radios used for the life safety notification system at Baylor went down, and stayed down until the 5G network tower was powered off. The best we could guess was that the noise floor was raised due to the enormous power output they were using. The radios were all FCC/CE approved and used commercially globally, including for high speed trains and for the military at forward operating bases in dangerous zones. The radios are pretty bulletproof (no pun intended) Or at least they were until 5G happened.

The failure at Baylor only affected the link between 2 of the radios most proximate to the 1 cell tower in question that was almost directly between them. Radios were replaced with new ones, channels changed, etc, etc to no avail.

Again, in theory this should never happen. But it did.
May 22, 2019, 09:22 PM
Registered User
It is all explained by Quantum Field Theory... (lol)
May 23, 2019, 12:51 AM
Happy FPV flyer
Kilrah's Avatar
Quote:
Originally Posted by RCAddiction
the 2.4 and 5.8 mesh network multicast radios used for the life safety notification system
Huh??
By definition the ISM bands are "you can do anything in it but there's no guarantee anything will work", if someone used them for life safety systems they should be fired on the spot... There are dedicated and controlled bands for those uses. Yes that costs many times more, but...
May 23, 2019, 01:21 AM
Registered User
Quote:
Originally Posted by PeterVRC
It is all explained by Quantum Field Theory... (lol)
I think harmonics is enough. Especially if 1/2 or 1/4 wave antennas are used like on some Frsky rx.
Those sensors near our field have like 20cm antennas so must be several hundred MHz. However the power seems to be enough to saturate x8r amplifier.
May 23, 2019, 06:18 AM
Registered User
RCAddiction's Avatar
Quote:
Originally Posted by Kilrah
Huh??
By definition the ISM bands are "you can do anything in it but there's no guarantee anything will work", if someone used them for life safety systems they should be fired on the spot... There are dedicated and controlled bands for those uses. Yes that costs many times more, but...
You might be surprised to learn that most life safety systems (think Fire notification) that are implemented wirelessly, per UL and NFPA code, are being done on ISM bands. Mass Notification (think "Shooter on Campus" notifications), unless a university applies for and receives a license for another band, are also done on ISM bands specified by the university. Military applications for wireless mass notification (think "Take cover, incoming") are always on proprietary non-ISM bands, regardless of the location. The military radios are the physically the same as used in University Mass Notification, but they are set in firmware to a different band.

Some universities have shifted from 900 to 2.4 to 5.8 as each band had become crowded. This caused a time lag in response, which caused distant speakers to be out of phase and reduced the intelligibility of the voice announcement. But never an outright failure. The 5G network actually blocked several non-adjacent ISM bands from working altogether, which was prohibited. In this case, Life Safety won, AT&T lost. They were disrupting ISM bands and people get pissed when their WiFi doesn't work, either.
May 24, 2019, 02:02 PM
Registered User
Quote:
Originally Posted by mawz
And I range out to the limits of LOS, as I fly competition gliders (>1.5Km ranges with 3m+ wingspans). 100mW is more than enough.
These birds are slow and high. So if you get a jittery behavior or connection loss for a few seconds - nothing happens.
As for me I fly EDFs. When a $1000 plane is in a WOT dive at 250km/h 2 seconds of connection loss or servo jitter convert it into an impressive lawn dart.
I've experienced many times with Taranis and Horus planes "poorly listening" 300-500m away for a few seconds. Maybe it's just lipo shadowing antennas or rf spike. So, connection reliability for me is the top parameter.

Also since Kilrah is here - would be great to have log view in OpenTx. Jeti has one built-in. I've tried one from Tandago but it doesn't work with 2.2.3.

If bandwith allows - add channel info into telemetry from the rx. This would be very helpful to tune up SxR: often it's hard to understand why plane shakes in the air.
May 24, 2019, 03:36 PM
Registered User
landru's Avatar
As you said, there's not much time for error with the models you fly. Glider pilots often have the luxury of more time, but not always.

As a thermal glider guy myself, I'd say we tend to be pretty in tune with our models. Catching and staying in lift demands a very good appreciation of which small movements of the airplane are commanded and which are not. In the small handful of cases I experienced, the loss of control was instantly apparent even at long range.

Of course, you might say that there were other incidents that I missed. And I'd have no way to disprove it.

However, I'd be pretty darn nervous flying any model if I truly believed that loss of control was even remotely likely to occur. The incidents I experienced were a small handful of episodes in hundreds and hundreds of hours of flying. And they were all caused by only two issues: an intermittently failing servo and shaded receiver antennas.

Don't get me wrong. I have plenty of sympathy for your predicament. With the tools you have at hand, could you rule out the 'usual suspects' (e.g. antenna shading) before looking further afield?
May 24, 2019, 07:38 PM
Sagitta Fanboy
Quote:
Originally Posted by Sockrat
These birds are slow and high. So if you get a jittery behavior or connection loss for a few seconds - nothing happens.
As for me I fly EDFs. When a $1000 plane is in a WOT dive at 250km/h 2 seconds of connection loss or servo jitter convert it into an impressive lawn dart.
I've experienced many times with Taranis and Horus planes "poorly listening" 300-500m away for a few seconds. Maybe it's just lipo shadowing antennas or rf spike. So, connection reliability for me is the top parameter.

Also since Kilrah is here - would be great to have log view in OpenTx. Jeti has one built-in. I've tried one from Tandago but it doesn't work with 2.2.3.

If bandwith allows - add channel info into telemetry from the rx. This would be very helpful to tune up SxR: often it's hard to understand why plane shakes in the air.
If you think EDF's are faster than competition gliders, think again, the opposite is in fact true.

Sure often I'm often ranging out and loafing at best L/D or min sink, but 200+km/h dives are very much not out of the question when I'm late in a window with an F3J or F5J ship and need to shed 1000+ feet, or I'm flying an F3B glider doing a speed or distance run or an F3F glider in a race. DS ships can exceed 500mph and are the fastest RC aircraft by a noticeable margin. And all of these are $2k plus airframes.

Sailplane pilots have pretty much no tolerance for control link issues when flying competition full house ships. It's a major safety concern when you are ranging out near the limits of sight and you have a signal interruption, and even more so when you are in a high speed dive with a $2k+ spear with wings.
Last edited by mawz; May 24, 2019 at 07:43 PM.
May 25, 2019, 12:00 AM
Registered User
Quote:
Originally Posted by landru
With the tools you have at hand, could you rule out the 'usual suspects' (e.g. antenna shading) before looking further afield?
I always place antenna tips perpendicular to each other and as far as possible. But in EDFs you don't have a full fuse for that so typically they are close to the lipo. Lipo is typically 5Ah 6s and is comparable to 2.4GHz wavelength of 12.5cm . So, compared to smaller batteries it can actually shadow the signal nearby. Plus typically there's a metal shroud, esc and lots of wires. So, usually for any antenna placement you can find an angle at which one antenna is pointing away and the other one is shadowed.
In this case signal reflected from the ground is the only source. When grass is tall and wet it absorbs 2.4GHz very well so the reflected signal is weak.
I don't want to switch to 900MHz due to antenna size and significant investment (change RX on 30+ models). Plus I seldom go beyond 500m. Just need the link to be reliable 100% of the time in that range. The same applies to quad racers where failsafe (if setup to the rules) bricks the drone immediately.
Last edited by Sockrat; May 25, 2019 at 12:08 AM.
May 25, 2019, 12:25 AM
Registered User
landru's Avatar
My case of antenna shading occurred only in an very specific orientation of model to receiver: model at about 15m altitude, traveling away from transmitter in about 10 degree horizontal vector. The third time it happened, I realized it was more than coincidence. Geometry made identification of the culprit straightforward. One antenna was fully end-on to tx, the other was completely obscured by the battery.

I moved the antennas outside the fuse to a new location away from the battery. The problem hasn't happened again in over 100 hours of flying time. I was lucky the model survived my learning experience.

Antennas outside the fuselage aren't aesthetically pleasing. And, as you noted, steps are required to ensure ninety degree separation. But what can you do?** As my wife says of many things, the alternative is worse.

** Adding a redundant receiver is one thing you can do.
May 25, 2019, 12:40 AM
Registered User
Quote:
Originally Posted by Sockrat
I always place antenna tips perpendicular to each other and as far as possible. But in EDFs you don't have a full fuse for that so typically they are close to the lipo. Lipo is typically 5Ah 6s and is comparable to 2.4GHz wavelength of 12.5cm . So, compared to smaller batteries it can actually shadow the signal nearby. Plus typically there's a metal shroud, esc and lots of wires. So, usually for any antenna placement you can find an angle at which one antenna is pointing away and the other one is shadowed.
In this case signal reflected from the ground is the only source. When grass is tall and wet it absorbs 2.4GHz very well so the reflected signal is weak.
I don't want to switch to 900MHz due to antenna size and significant investment (change RX on 30+ models). Plus I seldom go beyond 500m. Just need the link to be reliable 100% of the time in that range. The same applies to quad racers where failsafe (if setup to the rules) bricks the drone immediately.
I get a fair bit antenna shadowing on my 70mm edf's and "rssi critical" is heard more than I would like, not lost control yet thankfully.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Frsky Horus X12S Enable Gyro Function futaba1024 Radios 5 Jan 05, 2018 09:55 PM
Discussion Wristwatch GPS based Transmitter (full function) vtolharrierbnice Multirotor Drone Talk 2 Dec 29, 2017 12:26 PM
Discussion New ESC with reverse function for seaplane Tim Wan Foamies (Kits) 13 May 11, 2017 03:40 PM
Help! Remap Switches's Function? FrSky Taranis Plus klepper Radios 3 Aug 19, 2015 07:52 AM