Am i the only one curious about frsky L9R (3 times longer range) - RC Groups
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Apr 25, 2013, 12:56 PM
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jaas75's Avatar
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Am i the only one curious about frsky L9R (3 times longer range)


if regular range is around 1km that means 3+km with THIS setup (that would fit my needs for my low range FPV)

But how they got to do this:
-a more directional antenna??
-more output power??
-another frequency 1.2gHz, 900mHz, ...(any freq lower than 2.4gHz)??
A lot of people in the taranis thread have wondered why the antenna seems bigger than usual so i know its a long shot but possible


I cant believe is just a change in code/protocol cuz theres a limit a 50mW output and 2dbi antenna can do

Or is just hype

heres a link for the new line of transmitter and receivers
http://www.frsky-rc.com/NewProducts/
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Apr 25, 2013, 02:12 PM
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ttabbal's Avatar
The antennas on that page look the same on both new receivers. More power is probably on tap, which might cause issues in some countries. IIRC the DJT module does 60mW.

Part of it could be as simple as reducing the data rate (which could contribute to the channel limit being lower), lower data rates on some of these RF chips increase receiver sensitivity.

I don't think they would use another frequency, 2.4 is so common, and one of the only unregulated bands that is available in more than one country. The lower frequencies also have higher interference in many areas.

I doubt it's "just hype". They know that people here are going to be testing those claims. I haven't seen anything saying what's exactly going on though. It would be nice to know for would-be FPV users, which I assume would be the intended market. Perhaps some long range glider pilots, but I would think it would take a big glider for the range to be an issue with LOS flying.
Apr 25, 2013, 03:23 PM
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While I am not familiar with that particular receiver, it most likely is just a careful choice of receiver parts. By picking select components (those with minimum thermal noise), effictive coupling devices and careful shielding the receiver sensitivity can be greatly improved but at a higher component cost than is really necessary for most applicaions. Data rate (the slower the easier to decode or lift out of the noise floor) can be important.
Apr 25, 2013, 03:41 PM
Stuart
srnet's Avatar
Quote:
Originally Posted by jaas75
I cant believe is just a change in code/protocol theres a limit a 50mW output and 2dbi antenna can do
Is there, really ?

Does it not depend on how much money you want to spend ?

Three times range is only a 10dBm improvement, so modest increases in receive sensitivity and protocols or modulation methods could amount to this, why not ?

I have been playing with the RFM22B transceiver a fair bit recently (its used on some of the Open LRS stuff), I got a 12dBm improvement in signal reception just by putting a decent LNA in front of it ...........
Apr 25, 2013, 06:15 PM
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Data rate makes a big difference in range too.
Apr 25, 2013, 11:25 PM
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jaas75's Avatar
wow, i was not expecting so many responses. thxs for all the answers, it does make sense that a lower data rate and better components increase receiver sensitivity.
Apr 26, 2013, 07:38 AM
Smells like SCIENCE!!!
ibillwilson's Avatar
Quote:
Originally Posted by jaas75
wow, i was not expecting so many responses. thxs for all the answers, it does make sense that a lower data rate and better components increase receiver sensitivity.
I think the LR12 / L9R modes lack (most) telemetry. Also, with just 12 (or 9) channels compared to the radio's normal 16, LR12 probably does have a much lower data rate. Is that by itself sufficient to triple the range?

I guess the lack of telemetry will not be a big deal for FPV pilots doing extended range flying... Wouldn't you rely on an OSD in the video feed to get that data, anyway?

The only real question I have is whether you lose ALL telemetry, or retain at least RSSI? (Edit: answered my own question... Frsky page says you keep both RSSI and receiver voltage.)
Last edited by ibillwilson; Apr 26, 2013 at 07:44 AM.
Dec 21, 2013, 08:14 PM
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squishy654's Avatar
I am really curious about when it will be available for sale..
Dec 22, 2013, 07:24 AM
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jaas75's Avatar
Me too, I'm waiting for it anxiously
Dec 22, 2013, 02:46 PM
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richard hanson's Avatar
The 3 times longer range -is rather --interesting --
Reminds me of
"three times the gas milage"--
If they could do this with the same /similar info as others use - then -others would do it .
There -ain't- no free- lunch.
Dec 23, 2013, 11:48 AM
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squishy654's Avatar
It's a pretty good marketing campaign really. Tout great specs but then never release the product so the specs can never be verified or vilified..
Dec 23, 2013, 11:59 AM
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3x longer is not something to rave, depends what is the reference.
If the reference is the actual specs of their current receivers, i.e. 1.5km, then 4.5 km was been already done just by a bit of antennas tuning. I published one of the very early range tests using Frsky non-telemetry stuff, 5.3km, I am not the only with such figures. So, a bit of better QC and tuning, what is done today by skilled people, and you have the magic receiver that does this out of the box, for masses.

"The others" never claimed any figures, 1-2-3 or any number of km, simply because they are forbidden to do this, as well as offer to customers any feedback about real RSSI. Purpose: keep them close, uncertainty of real range is a good guard
Dec 25, 2013, 12:36 PM
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jaas75's Avatar
Quote:
Originally Posted by renatoa
as offer to customers any feedback about real RSSI. Purpose: keep them close, uncertainty of real range is a good guard
good one renatoa!! do you have any info of when is coming out?? Also shouldn't the tuning need to be done on the Tx side and the receiver.
All the records i have seen with stock Frsky have been with directional antennas on the Tx side and well tuned receiver antennas.
So i still believe theres something else like less data rate, more output power, better freq filters or more sensible receiver, even GOLD coated antennas for less ohms.
Dec 25, 2013, 01:38 PM
Registered User
The 5.3km I wrote above was with stock antennas on both Tx and Rx.
Not even tuned, just a small detail a different modulation scheme was an early one-way prototype, before the fall 2010 FCC certification of two-way system.
The tests during certification showed that this modulation can't be kept because works well on Tx only, not on Rx, showing some spurious radiation. To pass FCC things were changed that led to actual V2 modulation and power reduction to 60mW.
Yes, actual range is smaller than the first generation of Frsky stuff from summer 2010.
Given the fact L9R is one way only, not requiring any certification... hint, hint I don't see any reason why not revert to a modulation optimized for distance having same performance as a two-way system using directional antennas.
Jan 12, 2014, 06:42 PM
Registered User
I was able to attain 4.6 km with a stock Taranis and stock X8R PCB. Right when I crossed the line my signal dropped immediately. I will go back out and see if I can touch 5 km without any modifications.


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