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Jan 05, 2021, 04:15 PM
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Question

Which FlySky Receiver(s) should I buy (and more)?


I'm a newbie for the 1st time buying receivers for my FS-i6X (AFHDS 2A) radio. Some receiver descriptions don't say they're suitable for planes (but mention drones, boats, cars, ...). Need I heed this?

I'm presently needing a lightweight and compact receiver to put into a small glider (890mm wingspan) with an internal fuselage width of 13mm (not a typo). I'm intending to convert it to RC. My choices are (1) FS-RX2A (1g), (2) FS-X6B (4.5g), or (3) FS-X8B (3.7g) - see links below. Although for this plane I only need 2 channels it won't hurt to later reuse the receivers. If I can't fit the receiver, battery and micro/mini-servos inside the fuselage then I intend to imbed them in the side.

I intend using a 1S lipo (4.2V) to save weight ... but would it be OK for me to power receiver (1) and servos with a 2S lipo (8.4V) when it only wants 5V max (Receivers (2) and (3) are both happy with 8.4V)?

Links to each receiver are:
1. https://www.phaserfpv.com.au/product...s2atransmitter
2. https://www.phaserfpv.com.au/product...i4xtransmitter
3. https://www.phaserfpv.com.au/product...usminireceiver

Do you recommend any particular brand of micro/mini-servo (I think I'm going to set them up with springs in each of the rudder and elevator)?
Last edited by Neil_from_Sydney; Jan 05, 2021 at 05:45 PM.
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Jan 05, 2021, 10:48 PM
treefinder
springer's Avatar
Are you gonna fly it like a glider, thermal soaring, at high altitudes, or just fly it around, parkflyer style? If the former, you want full range RX. If the latter, then a ground rated RX should be ok. Generally they have shorter range. I use 3 rx in my FlySky radios. R6B, the 6 ch AFHDS2 full range one (probably have 40 of them, they used to go on sale for $7usd), the 3ch gp3 which is ground rated and also AFHDS2 protocol. Finally, fsia6b the AFHDS2a 6ch full range with twin antennas. I fly the r6b and fsia6b in gliders to 1400ft agl and out as far as I can see (easily a quarter mile). The gp3 is only good for park flyers, I have had glitches at 4-500 feet out. So far they are momentary and I regain control before crashing . This RX is more sensitive to TX and RX orientation, which I believe is a big factor in the signal loss. I haven't tried any of the micro RX, but I recall one generally gets good reviews for good range and the other seems more park type range. Would have to re browse the reviews for them on banggood.
Jan 05, 2021, 11:51 PM
Registered User
Hi,
I don't think any of those listed options are ideal for you.
Firstly the FS-RX2A is serial outputs only - no PWM so it's basically looking for a flight controller serial input such as on a quad.
The FS-X6B has got PWM outputs but is only showing as -95dBm sensitivity - park flyer or ground vehicle only. It will work but you really want -105dBm.
The FS-X8B is also only serial outputs so not suited for a simple set up and requires a flight controller.
Curiously the FS-iA6 receiver is labeled "Park Fly" yet has a sensitivity of -105dBm. It has 2x whisker monopole antennas whereas the FS-iA6B has the same sensitivity but uses sleeved dipole antennas and is too big for you anyway. The FS-iA6 would be good but if 13mm is your limit you would need to unsolder the output connectors and replace the vertical headers with horizontal ones to give a low profile with connectors fitted. Not for the faint hearted but I have done it myself.
I certainly wouldn't power a receiver with more than the specified maximum voltage. You may get away with it but basically the manufacturer is saying all bets are off if you exceed that figure. You can buy some small linear regulators or better still a switching regulator (more efficient and less heat) . The switching types come in the simple buck type (step down) or boost/buck which can step up or down say if your supply started at 6V and dropped to 4V it still provides 5V output.
Good luck and don't forget to get back if we can confuse you further.

Cheers,
David
Jan 06, 2021, 12:50 AM
Registered User
Hi Springer,
The FS-GP3 and the FS-R6B are only AFHDS I believe, not the AFHDS2 protocol.
I always have to stop and think about them and I had used several of them in model boats before getting the FS-i6 tx. Another forum member kindly explained that I didn't need to obsolete them because the tx had selectable protocols and could talk to all my old receivers and the newer AFHDS2 types, something I've been most grateful for.

Cheers,
David
Jan 06, 2021, 09:34 AM
treefinder
springer's Avatar
David (and Neil) yes, but. . . One of the few confusing things about FlySky is the naming of their protocol levels. As far as I know they have had 4 levels: AFHDS (v1) sometimes just called AFHDS sometimes AFHDS V1 - a 2.4ghz single channel non hopping protocol, AFHDS2 ( now sometimes just called AFHDS but previously called AFHDS2 or V2) - a full spectrum channel hopping protocol, AFHDS2a (so far always called AFHDS2a) - essentially the same as AFHDS2 except added bi-directional communication allowing telemetry, and finally AFHDS3, about which I know nothing, except it is only available on their priciest radios. To me, a major fail is to not be clear on the protocols of RX and TX. One reason I liked FlySky was none of the confusing plethora of varieties of Spektrum and Futaba protocols. But now they are getting nearly as confusing. At least we dont have frame rate to worry about!

All that said, (and done ranting) the r6b and gp3 are AFHDS2, and as you noted both FS-i6 and fs-i6x will run that protocol selectable in RX setup on TX. As long as one isn't using telemetry they've fine. My experience is that notwithstanding what some ads say, the r6b is full range, which agrees with your signal dB rating. The gp3 has the single whisker antenna and will lose signal lock at around 500ft (in my experience) particularly if the antenna gets pointing at the TX . Again, my experience; I tend to just lay the antenna in the fuse pointing toward the tail. This works fine for most park flying or indoor venues, as the plane flys back and forth in front of me presenting the side of antenna 90% of the time. However when I fly out back behind my house over 100 acres, I get adventuresome and let planes fly directly away then directly back. You know what happens when the antenna laying in the fuse is pointing directly away from the tx!

Neil, if you are just flying around your "yard" or a local park, etc. I would choose the gp3 and remove the plastic case. All the micro RX are caseless too. Wrap it in tape if you are concerned about the exposed electronics. If you are really interested in soaring, I would do the same with an r6b and accommodate it in the fuse somehow. The dual antennas on the fsia6b and larger case will make packaging even more difficult, and if you aren't using telemetry is work for no value.

While the micro versions are indeed small, you will need to read specs and many reviews to understand what you might be getting. You don't want sbus or ibus only output, but actual ppm to servos. You will want to read reviews of range experienced. I recall that there was one micro RX on banggood that users claimed had good/full range, but can't remember which. You can read through the listings and perhaps find it.

Also as David noted, BECs are generally tiny and will solve your battery concerns. I just bought a few switching BECs to use on an EDF plane that was sagging the lipo and hitting LVC usually at worst times. I'd read that the internal BEC circuit in ESC was linear and sucked lots of amps. Haven't wired one in yet, but when I got it was impressed at it's small size. The wires are more bulky than the BEC!
Last edited by springer; Jan 06, 2021 at 09:47 AM.
Jan 06, 2021, 05:51 PM
Registered User
Thread OP

Grateful thanks


David and springer, thank you both so much. I expect to do mostly slope-soaring but perhaps hunt for thermals. At a wingspan of 980mm (39") I'll need to keep the plane quite close to stay in sight.

It looks like I still have some homework to do before choosing my Rx. Yes I certainly don't want to include a flight controller. I'm a soldering newbie (with good motor skills) so maybe I can overcome this seeming issue. As the i6X Tx is AFHDS 2A then I assume it can 'talk' to any AFHDS Rx version. I guess an Rx with 2 aerials placed at right angles will give me the most flying distance.

My limit isn't 13g I just thought the lighter the better and minimal size. David it seems you've proven the usefulness of the R6B and I suppose that 25g is actually no problem for this plane. Or, better, the iA6B which has twin aerials, can 'do' i-BUS, weighs 14.5g and seems to cost less than the R6B at the moment.

I'll report back. Here's the plane: https://i.pinimg.com/originals/9f/03...713ed0cd4c.jpg http://www.model-plans.co.uk/west%20wings.htm.
Last edited by Neil_from_Sydney; Jan 06, 2021 at 06:05 PM.
Jan 06, 2021, 06:06 PM
treefinder
springer's Avatar
Nice looking build. So are you launching it by hand, bungie, ? Looks tall enough to fit an rx.
Jan 06, 2021, 06:11 PM
treefinder
springer's Avatar
The i6 and i6x use only AFHDS2 and AFHDS2a . But 9 don't think you can get any V1 rx anymore, and only a few AFHDS3 are available so far. I still don't know how you intend to fly her, small area park flyer or large area, long range. That intended usage is important to how you set her up.
Jan 06, 2021, 09:04 PM
Registered User
Now I'm confused.
I thought that both AFHDS andAFHDS2 were both frequency hopping (aFHds) but AFHDS2 had the one way telemetry data (plane to tx). AFHDS3 has two way data transmission (plane to tx, tx to plane plus control data.

https://www.rcgroups.com/forums/show...08&postcount=6

Cheers,
David
Jan 06, 2021, 10:53 PM
treefinder
springer's Avatar
Don't be, hifin was wrong , both in his characterization of naming and telemetry. What he called AFHDS and fairly described it is afhds V1. It didn't channel hop. I know this because I have one. Got it from hobbyking it is branded hobbyking even. It came with a 6 ch rx and remote aux RX. One good way to tell a V1 is the port for the aux. Otherwise it looks like a r6b V2 RX. I got the radio as my first venture into 2.4 ghz specifically for indoor, afraid to put too much money in it, was $25. It worked fine, had far less problems than others flying Spektrum. I would get little dips while they would crash, uncontrolled. It was never clear to me if their problems were brown outs or just slow relink which both dsm and dsm2 exhibited.

AFHDS2, while a full spectrum channel hopping protocol is only one way. Try binding an r6b using the AFHDS2a process and see if it works. Pulling the bind plug before shutting off power sets up the 2 way communication for AFHDS2a rx. It kills the bind for AFHDS2.

AFHDS2a is FlySky 's first two way and telemetry RX and first to use ibus.
Jan 06, 2021, 11:13 PM
Registered User
Hi Springer,
I can't actually find out much about the various types but did see this from Oscar Liang-

"Flysky TX Protocols
There are 2 different Flysky TX protocols:

AFHDS
AFHDS 2A
AFHDS stands for Automatic Frequency Hopping Digital System, and is a digital protocol that ensures 2 or more radios can operate at the same time without interfering each otherís respective aircraft (or receiver).

AFHDS 2A is the 2nd generation of the system that added 2-way communication capability and allows for telemetry."

So I'm guilty of using the term AFHDS2 when I really should have used AFHDS2A.
I have a few Hobby King receivers which are obviously AFHDS as they bind fine with the FS-i6 tx when it's set for AFHDS transmission. I think I can live without AFHDS3.

Cheers,
David
Jan 07, 2021, 08:47 PM
treefinder
springer's Avatar
David and Neil, after rummaging through a bunch of my receivers, I have found the solution although I'm not sure it helps a lot. The original FlySky protocol was used in my hobbyking radio HKT4A . This was the single channel, no hopping 2.4g radio. Since it didn't hop, it couldn't technically be called AFHDS (Automatic Frequency Hopping Digital System). But they (hobby king) brought out a version that used the FlySky hopping protocol, that was called HK4TA V2, which made the original radio and RX V1 in their ads. The HK version of the r6b, was called TR6A V2 and the protocol picked up the moniker V2 as well. I note that a newer FlySky R6B I have just says AFHDS on it with no mention of V2. So I guess the guys you quoted are mostly right Flysky has 3 AFHDS protocols. AFHDS (sometimes called AFHDS2), AFHDS2a and AFHDS3.

I noted in browsing HK that they mentioned the original protocol HK4TA in a comparability paragraph, but they no longer list any of the RX. So it is completely obsoleted.

So, if you buy a FS r6b RX it will be shown as AFHDS, but if you get the equivalent HobbyKing rx it will be a TR6A V2.

For Neil, the pics may be of interest, especially the three gt2 (3ch), r6b/tr6a v2 and fs-ia6b.
Jan 08, 2021, 01:04 AM
Registered User
Great work Springer.
That all fits together nicely. I have two of the HK txs but both are V2 versions so are frequency hopping. It seems the HK HK-T4 V2 was really a Flysky AFHDS (1) standard and certainly quite different to the earlier HK-T4A.
Something that once had me fooled for a bit was the binding differences between AFHDS and AFHDS2A. The AFHDS sends a unique tx ID to the rx but if you have several receivers all powered on at the same time they will all respond. With AFHDS2A the tx sends its unique ID to the rx and the rx sends one back to the tx so even with other receivers powered only the linked pair will respond. At least that's my take on it.

Still don't understand why the FS-iA6 is called "Park Fly" when it's receiver sensitivity is -105dBm - as good as their best receivers.

Cheers,
David
Jan 08, 2021, 07:33 AM
Registered User
I'm worry FlySky don't supply a range of sensors and Rx as comprehensive as FrSky one;it would be great with a 10ch Rx -FrSky don't have- and prices very competitives...
Jan 08, 2021, 11:08 AM
treefinder
springer's Avatar
Yup, David you described in your post 13 what is essentially FlySky version of Spektrum model match. The key for telemetry, model match, etc is that return signal. 2a RXs are receivers and transmitters, whereas all previous FlySky versions were receivers only.

I've not heard any good reason either on the fsia6. Perhaps it is simply because it doesn't have telemetry enabled, which doesn't relate to range per se, but overall capability. Park flyers don't need telemetry??? Who knows?

Neil, I wouldn't worry about lack of sensors in FlySky vs FrSky . Unless you are a real technogeek you will never find use for most of the sensors from either supplier. I got all excited about all the possibilities of telemetry/sensors, but when I really sat down and decided what I wanted to monitor, I came up with altitude for my gliders. I found the FlySky/Turnigy CAT01 sensor (just saw it is available both at HK and BG) for $10usd. When I set it up with my flyplus v1.75 firmware i6, I found I got altitude and variometer. A pleasant surprise! The only other things of some utility or interest are 1. actual flight pack voltage (instead of the included RX voltage), but I haven't bothered to do the simple mod to enable it - not that important, I guess. 2. Airspeed or ground speed. I get that from my diy gps data logger that displays info onscreen on the i6. I built the data logger as a fun project, not as something I really needed but it is fun to use anyway. What other sensor info would you want?


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