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Author Topic: What's considered a good Rssi value?  (Read 309 times)

Offline tipsy trucker

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What's considered a good Rssi value?
« on: October 09, 2018, 10:41:42 »
I'm not entirely sure how I did it but I've now got Rssi showing on my tx - trouble is, the figure doesn't mean a lot to me. Indoors and a couple of brick walls between  tx & rx, iirc the reading was -60db

From the little I know, a positive number would be better but that's as much as I know really. Can anyone explain it in layman's terms for me please?

Offline ched999uk

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Re: What's considered a good Rssi value?
« Reply #1 on: October 09, 2018, 17:58:17 »
That's a good question. If I remember correctly on my i6 it starts off at 90 or 99db that might be minus can't remember.
I think I have mine set to alarm at -40db. I have only had 1 alarm but that was after a crash that took one of the rx antennas out and the other was hidden by frame and battery. So it was expected. That said I only really fly round a football field so no real range. I think FrSky tx/rx can be set to range test by lowering the tx signal somehow but FlySky doesn't have this feature.

What you can do it do a manual range test. i.e. have the quad powered so it gives a RSSi figure when you are next to it, then walk away as far as you can and watch the RSSi.

The RSSi (Received Signal Strength Indicator) is sort a bit weird as it's the tx signal that is received at the rx on the quad and then the value is transmitted back to the tx.
On acro or racing quads running BetaFlight etc sometimes the RSSI figure is then transmitted back to the quad as a control signal so it can be displayed on an OSD in goggles!!!

That's the best I can do mate  ::)

Offline tipsy trucker

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Re: What's considered a good Rssi value?
« Reply #2 on: October 09, 2018, 20:47:05 »
Thanks for that ched, once it's back together I'll see how it looks outside. I'm still short of a motor, but already toying with the idea of bigger motors, props and long arms - maybe if I order them now, I'll have them by the time I've got the hang of flying the thing 🤔

Offline Elmattbo

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Re: What's considered a good Rssi value?
« Reply #3 on: October 10, 2018, 04:16:37 »
Rssi is logarithmic, so you’ll find that almost anything will make it drop from 95 to 85 dbi, but then 85dbi to 75dbi is a much longer distance and 75 to 65 even further still. Most default alarms are around 40 but signal quality will soon degrade after that with the inherent risk of a failsafe.

I find I glance at it occasionally if I know I may be pushing the range on my radio but I’ve never failsafed due to range on frsky.


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Offline Bad Raven

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Re: What's considered a good Rssi value?
« Reply #4 on: October 10, 2018, 06:48:12 »
You have to be careful here! RSSI is a WiFi industry standard term, BUT there is no standard scale to use to display it,  FrSky uses 0-100 and the default setting for alarms starts at 45 or lower though that setting is user alterable.

Example text from WiFi systems website :- "RSSI is a term used to measure the relative quality of a received signal to a client device, but has no absolute value. The IEEE 802.11 standard (a big book of documentation for manufacturing WiFi equipment) specifies that RSSI can be on a scale of 0 to up to 255 and that each chipset manufacturer can define their own “RSSI_Max” value. Cisco, for example, uses a 0-100 scale, while Atheros uses 0-60. It’s all up to the manufacturer (which is why RSSI is a relative index), but you can infer that the higher the RSSI value is, the better the signal is."

As an example, I was a Beta tester for FrSky on Horus. Initially there was much variation and it didn't take much to produce on the face of it rather low numbers. By the end of Beta that area (along with many others) had been well trodden with all sorts of models, circuit alterations made, and the default alarm setting was now a sensible and reliable level. It does depend though on the volume and quality of other 2.4GHz traffic close by. It is quite easy to produce good results, it is not so easy to produce good results that do not splatter FR everywhere and affect others. Some makers are not so willing to "play ball"!!

Since its a relative term, the "My Spoktaba gives better RSSI than your FrySki" (or the reverse) is a nonsensical argument, but one I have heard spouted out on flying fields more than I care to!!

Here's one for you to play with, put your model on the ground (bad signal location), stand by it and measure RSSI. Then walk 20 metres away and repeat. Then turn round so the Tx is blocked line of sight by your body and repeat. You can regale other members for WEEKS on the result!!!   :wack0 :laugh:

Now a question for YOU....what is SWR and why was it displayed like RSSI initially, only to largely be forgotten and buried away from view by the masses?

Answers on a postcard......................................   :rofl:

Offline tipsy trucker

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Re: What's considered a good Rssi value?
« Reply #5 on: October 10, 2018, 07:59:55 »
Standing wave ratio, the signal coming back to the tx when transmitting (having been "reflected" back 0by nearby objects or the antenna itself. (I've had cb radio in the past), I'm not too sure where it fits in here however? Having only ever used it for tuning the antenna and groundplane

Offline shawdreamer

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Re: What's considered a good Rssi value?
« Reply #6 on: October 10, 2018, 09:44:48 »
go field.... take off.... fly about.... have fun.... land....go home to recharge

= good Rssi

go field.... take of.... watch frame fly away in a unwavering un-commanded straight line while you desperately chase after the rapidly disappearing spec in the sky

= bad Rssi

...think that pretty much covers the basics ~~
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Offline trebor

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Re: What's considered a good Rssi value?
« Reply #7 on: October 10, 2018, 11:33:01 »
Strange thing with my Taranis the Rssi value always improves with the Tx antenna laid horizontal not vertical, does not make any difference on the Rx antenna positions. Could never understand it myself, still I just take it out of the case and use it.

Offline Elmattbo

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Re: What's considered a good Rssi value?
« Reply #8 on: October 10, 2018, 13:09:08 »
That’s good info BR, thanks!


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Offline Bad Raven

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Re: What's considered a good Rssi value?
« Reply #9 on: October 11, 2018, 18:50:46 »
Strange thing with my Taranis the Rssi value always improves with the Tx antenna laid horizontal not vertical, does not make any difference on the Rx antenna positions. Could never understand it myself, still I just take it out of the case and use it.

The signal strength "map" from a std Tx 2.4GHz aerial looks like a ring doughnut, so the max strength/furthest reach (but narrowest width) is at 90 degrees to the aerial axis. Since many people move to look at a model (ignoring FPV), pointing the aerial at the model sends the weakest signal.