Peter Christy

In the module section of the transmitter setup, one of the variables is the receiver number. This is a number that you set for each receiver so that the transmitter can warn you if you have the wrong model selected. This also clearly means that you cannot use the same number for different receivers - or different Tx modules using the same receiver. That is what the message is trying to tell you. Simply choose another number that is not already in use, and you should be good to go. If you set the number to zero, then this safety feature is turned off. You could try that for experimental purposes, but don't make a habit of using it!

I think T9 get their receivers "bare", ie with no firmware installed, and then flash them with whatever the customer orders. It could be that yours have slipped through the net and haven't had any firmware installed at all. Happened to me a while ago. A quick phone call to T9 should confirm this. I already had the firmware, so I just flashed it and all was well. -- Pete

Yes, I'm talking about relatively small packs. I've only got one model I would call "big", and it isn't that big in the greater scheme of things! 😁 However, I'm still very wary of LiPos and LiIons. Its not that long ago that laptops and cell-phones were catching fire in airliners and on trains! The technology hasn't changed, though the quality control has, hopefully! I do use both LiPos and LiIons. The LiPos because for traction motors there is no real substitute, and the LiIons because I've got two transmitters that came with them. My preferred technology for both transmitters and receivers is either NiMh or (if the system can take the higher voltage) LiFe - purely on the grounds of safety! Remember that even Boeing were having trouble stopping LiIons catching fire in their Dreamliners! Mind you, given their recent history, that's probably not a good example....! 🤣 If you are comfortable charging them in situ, then that's your call. Personally, I'm not. But that's just me being very cautious. I have seen a couple of horrible accidents caused by momentary short circuits when the chap connecting things got distracted for a moment. There's an awful lot of energy stored in those cells, and you don't want it being released all at once! <Gets off soapbox!> 😁 -- Pete

They are fine for Tx use. Many modern Txs use them (FrSky, Radiomaster, etc). For Rx use, they are heavier than LiPos for the same capacity and the voltage is slightly different. These observations assume that the voltage is correct for the application. Most modern transmitters (2.4 GHz) are quite happy operating in the 6-8volt range. Older transmitters (27/35MHz) require either 10 or 12 volt, depending on their age. Similarly, for LiPo/LiIon use in receivers, you need to be sure that both the servos and receiver can accommodate the higher voltage. My own preference is either Eneloop NiMhs or LiFe cells for airborne use. Both can be charged safely in situ. LiIon and LiPo both have a chequered history in that respect.....! I wouldn't want to charge them in a model.

X6R receivers readily available: https://www.t9hobbysport.com/frsky-rx6r-receiver

E.D.: Genuine Eneloops still available from Overlander (AAA-800mAH, AA-2000mAH).

It is in a Hirobo Bell 47 helicopter (an early Mk 1). On the AA cells it couldn't get off the ground! The engine sounded fine, no misfires or anything, just a severe lack of power. It would get light on the skids, and you might see daylight under them momentarily, but it certainly wouldn't "fly". Switching to sub-C cells restored normal power. It would lift off, hover and fly round with no problems. To be fair, it is NOT over-powered! But neither is the full-size one! It does force me to fly it in a realistic manner! 🤣 -- Pete

Quite correct! In AA sizes, anything over 2000mAH is pushing your luck! You will be much better off sticking with 2000mAH rather than going for the higher capacity. 2000mAH is quite adequate for most of our applications. Don't get fooled by "the bigger the number, the better" syndrome. It ain't necessarily so! I've never had an issue with genuine 2000mAH Eneloops. My personal experience with Vapex has been mixed... -- Pete

Well, the genuine FrSky X4R receiver is only £26 and is tiny. These are full range receivers. I've used one in a smallish helicopter (Micro-Mold Lark) without any issues. Why mess with a clone, when the genuine article is so cheap? https://www.t9hobbysport.com/frsky-x4r-receiver (No connection to T9, other than as a happy customer!) -- Pete

My Rxcel is an early version, and the instructions contained dire warnings against using more than 4-cell NiMhs. I believe the later ones are more tolerant, but I can't speak from experience with those. AA-cells are NOT sufficient. Although the average current draw is only a few hundred mA, the PEAK draw (when charging the capacitor) is a lot higher, and AAs cannot meet that peak quickly enough. I switched to 4x sub-C cells (nominally 4.8V), which instantly solved all my power loss issues. -- Pete

Just to add, usually the single-conversion receiver crystals are all the same: 3rd overtone, 455KHz below the transmitter frequency. I think at one point one of the early Japanese sets may have used 455 KHz above the Tx frequency, but I'm not sure. This would have the effect of inverting the pulses at the receiver output on an FM system, and stop the decoder working, if used in the wrong receiver. FM transmitter crystals are generally half the required output frequency, BUT may be designed to work with a different capacitive load. It is varying the capacitive load that generates the frequency swing, so using (say) Brand X crystals in a Brand Y transmitter may end up with the Tx being slightly off frequency. It is important to use the specified crystals in an FM transmitter. -- Pete

I've have actually used LiFe cells to power the motor on an electric glider I've got. Its a 3-cell 2200MAh pack. The power plant in the glider is a geared Graupner Speed something or other (bigger than a 600). It was designed to run on 8-cell nicads, but the 3-cell LiFe is the right voltage, but lighter and smaller! Performance is - er - leisurely! 🤣 But its great on calm summer evenings - if we ever get any again....! -- Pete

Its not a question of LiPo being better/worse than LiIon. Its horses for courses, and each has its merits and disadvantages. Its true that LiFe cells are also Lithium based, but the internal chemistry is quite different. LiFe cells are much less prone to combusting when abused, making them more suitable for installation in hard-to-get-at places. However, they have slightly less capacity for a given size. They also can't deliver quite the same peak current as LiPo/LiIon cells, which is why they are rarely used for traction motors. -- Pete

Channel 73 is 35.130 MHz. 34.675+0.455 (single conversion IF) = 35.130. Therefore the receiver crystal is for channel 73. I don't know where you got 35.193 from! The nearest "standard" frequency to that would be 35.190 (Ch 79). FM transmitter crystals typically work at either half or one third of the intended output frequency, so 17.565 or (less likely) 11.71 MHz. They are, however usually marked up for their intended output frequency, not their actual frequency. In short, you have the right receiver crystal, and ignoring the frequency tables, you should have the right transmitter crystal. If its not working, then more testing / info needed! -- Pete

That could well explain why they don't play nicely with Nick's Overlander charger! -- Pete

Nick: I've never had an issue with LiFe cells and Overlander chargers. All mine came from Hobbyking (yeah, I know!) mainly because, at the time, nobody else seemed to stock them. Even now, they are the only source of 3-cell LiFe packs, which make very good substitutes for "Old School" transmitters that run on 8-cell NiMhs, as the voltages are almost identical. I would suggest you get someone to try and charge your packs on their charger, to see if the issue is the cells or the charger. It sounds like one or the other is faulty to me. I've never come across Spektrum LiFe packs, but I would assume they buy them in from a supplier, and put their own stickers on them - just like everyone else! 😉 LiIon is the same chemistry as LiPo, the primary difference being the packaging. They are somewhat less prone to physical damage, but can be more sensitive to abuse. The metal case can't "puff up" to help relieve the pressure if they are abused! I believe they do have vents for such situations, but in a severe situation, these could become clogged. Basically LiIon has no significant advantages over LiPo, and will probably be heavier for the same capacity. They are quite often found in modern transmitters, where they are well protected both physically and electrically. In a model they may be more exposed to both!

I had issues using eneloops on ignition systems. It was in a large scale Bell 47 helicopter and could barely get daylight under the skids! Switching to sub-C cells brought it back to life, and it flies fine on those, with no other changes. The AA cells have a higher internal resistance, which is fine for receiver use - even with power hungry servos (though not if you have more than four, I would suggest!) - but the ignition system I was using was a capacitor discharge type. The higher internal resistance meant the capacitor couldn't fully charge between strokes, resulting in a loss of power. I couldn't use LiFe's on it, as it was restricted to 5V, with dire warnings for the consequences of exceeding that! I believe the later versions are more tolerant! Similarly, the servos in the heli were JR, which don't like more than 5V. I ended up using 4-cell sub-C packs for both, which proved more than adequate and reliable. If your servos and ignition system will tolerate higher voltages, then LiFe cells are good. Just remember that although the nominal voltage is 6.6 volts for a 2-cell LiFe, fresh off charge, they can exceed 7V! Make sure your servos/ignition will tolerate this - however brief it may be!