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Jun 06, 2019, 09:28 PM
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Question

Is transmitter or receiver more crucial for good signal?


I’m desperate to improve signal on my setup. I have had entirely too many failsafes and now own 2 busted quads as a result.

I fly a Mobula7 (Flysky), and a Tyro79 (FS-A8S rx). My tx is a Flysky FS-i6. My signal is so terrible if I fly around my house or even behind a tree I will failsafe. The mobula has a built in SPI rx with a tiny antenna on the bottom so I’m sure it’s not the greatest.

Part of me wants to take everyone’s advice and make the switch to Frsky. I really can’t afford to dish out for a QX7 and swap my quads for Frsky RX. Is the transmitter more responsibile for good signal? Or is it the rx on the quad?

I’ve seen some people mod their FS-i6 with new 2.4ghz u.fl antenna. Would this be a better option? Thanks in advance for all advice!
Last edited by GordonBombay; Jun 06, 2019 at 09:29 PM. Reason: A word
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Jun 07, 2019, 12:13 PM
Registered User
Both transmitter and receiver are critical for a good signal and control link. That transmitter should be fine for normal range flying if it's working correctly. I would suspect your receiver / antenna. Many of these small quads do have a limited range but not as limited as you are seeing. I would try some antenna position mods and do a range test to try to get better range. But eventually, you will want to upgrade to a better Transmitter / receiver. (QX7 is a good choice if you are on a budget) R-XSR is a good FrSky receiver.
Jun 08, 2019, 06:20 AM
FA3PR9WM79
Oldgazer's Avatar
+1 on doing a range check.

Early FlySky radios are notorious for having poor range and flying behind solid objects will only make matters worse.

Antenna positioning is also critical for good signal reception.
Jun 09, 2019, 07:12 PM
We are not men, we are DEVO 7e
xanuser's Avatar
Quote:
Originally Posted by Oldgazer
+1 on doing a range check.
a bike is a great tool in a range test.
Latest blog entry: MY notes/ Ascent 2"build notes
Jun 09, 2019, 08:04 PM
Registered User
Most good transmitters have a reduced power mode for range test so you only have to go out 30-50 yards max. If you have RSSI telemetry it's a piece of cake to see when you are getting marginal signal.
Jun 09, 2019, 08:51 PM
We are not men, we are DEVO 7e
xanuser's Avatar
well sure, that will give you comparisons from one model to the next at that reduced transmitter power. but for a real test to see how far you can actually go with fullpower, like through some trees ect, a bike is perfect.
Latest blog entry: MY notes/ Ascent 2"build notes
Jun 12, 2019, 08:44 AM
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Ace12GA's Avatar
The FS-A8S should be good for about 400m direct line of sight. Obstructions are hard for any radio system, and putting a house between yourself and your craft is going to create radio link issues. It will cut your range massively. Trees will also cause issues, but less so.

The FS-A8S is a single antenna unit, no diversity. The placement of the antenna is going to make a difference. This type of whip antenna is a linear omnidirectional antenna. That means the radio signal is best received from the sides of the active element of the antenna, with dead zones at the top and bottom of the axis of the antenna. It will be important to have the active element of the antenna outside of the frame of the quad, and oriented in a way that will keep the sensitive active element in contact with the transmitter signal.

I use FrSky diversity Rx's, with two antennas, and mount them perpendicular to the arms of the quad on zip ties. It means that at pretty much any orientation, I have some of the active element of the antenna oriented correctly for the Tx signal. That looks like this one one of my birds.
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You have a single antenna, keeping in mind your quad is tilted forward in flight, you want that antenna outside of the frame, and mounted in an orientation that will maximise it's ability to receive a signal.

Lots of Spektrum guys have problems with this, using those little satellite Rx's with stubby antennas that don't get outside the frame. Those guys fail safe in under 200m direct line of sight, simple because the signal can't get through.

FlySky has better signal characteristics than DSM2 and even DSMX, though newer DSMX stuff is pretty good. None of them touch FrSky though. FrSky stuff is just better. Way better channel hopping. At the track I mainly fly at, FrSky guys don't fail safe. If it does happen, it's because the antenna was cut during a mid air. Spektrum guys reliably fail safe in a couple of corners with elevation changes dipping into near line of sight, and FlySky guys fair better, but get the odd fail safe. It's not hype, FrSky is better. The XM and XM+ Rx's are cheap too. Nothing is going to allow you to fly behind large structures 400m away. One of the places I fly is a school out in the country. On the weekend the place is deserted. If I put the school between myself, and my quad, I fail safe. End of story. I can manage to fly around trees just fine, and my backyard puts a small outbuilding and lots of trees between me and my quad 200m away when I'm flying around the trees behind my home, with no major signal loss. It's pretty solid.

So take some time to orient and mount your antenna's well. Have realistic expectations about where that signal will reach. Understand that FrSky is a good next step all around, and worth investing in if you're sticking in the hobby. The antenna mod you're talking about may help, by increasing the output from your radio, but it's not a fix all magic solution.
Jun 14, 2019, 08:05 PM
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Thread OP
Wow, thank you for such a detailed response! You guys are a lot of help. Spent the last week or two waiting on parts/rebuilding my busted fleet. Swapped out the garbage A8S for the iA6b that came with my radio. I never considered using it with my Tyro79 because it’s about the size of my entire canopy frame but it has diversity antenna and although my quad looks crazy with this huge receiver mounted on top I am willing to sacrifice looks for peace of mind. Haven’t tested it out yet but will let you know the results!
Jun 15, 2019, 07:19 PM
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Thread OP
Regarding the 2.4ghz antenna mod, what strength dBi would work best? The two I am seeing are 6 dBi and 10 dBi. Thanks
Jun 17, 2019, 07:40 AM
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Ace12GA's Avatar
Quote:
Originally Posted by GordonBombay
Regarding the 2.4ghz antenna mod, what strength dBi would work best? The two I am seeing are 6 dBi and 10 dBi. Thanks
10dBi is the stronger gain, but may put too much strain on the Tx. I wouldn't go further than the 6 dBi antenna.


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