RF systems

Excerpt: When it comes to RF systems, guess what? We don't have 'religion' regarding brands (and helis don't care) but we do have a few thoughts.

Ford vs Chevy mentality exists amongst remote control (RF) radio systems, also. Proof being cliques at flying fields where nearly all use Spektrum, or FrSky. What sucks is each brand's unique, so Spektrum transmitters don't speak to FrSky or Futaba receivers.

This article touches on receivers – but – it's really a warning about RF.

Introduction

We advise folks to use whatever RF-system's popular at your local field. It'll mean more programming help's available. Believe me, there's nothing like being odd-man-out where you have Jeti, and everybody else flies Radiomaster. Or vice versa.

Fundamentally, it's because there's no commonality in 'how' transmitters are programmed. But in truth, RF-brands don't actually matter because they all work.

Fortunately, your heli doesn't know (or care) about brands. And lacking a dog in the hunt (because we don't sell RF of any sort) means we can speak our mind!

Transmission bands

Back in the day transmission was one-way, from transmitter to receiver. This signal was Frequency Modulated (FM) and it was analog. Moreover, it was broadcast on 72MHz. Then one day Futaba introduced PCM (Pulse Code Modulation), and while still on FM, the signal was digital . . . ones, and zeros.

What's more, PCM instantly changed the modeling world. Suddenly JR (Japan Radio() introduced their own digital transmission system, and just like that, we were off the the races.

What was different? With analog RF-systems, as the model flew too far away, the signal rolled off. Losing the signal wasn’t instant. I recall once beginning to get too far with my model. Sensing my model wasn’t responding quite normally, I took off in high gear galloping toward the model transmitter held high overhead. I began to regain control and turned the aircraft back toward me. Heart still pounding, I landed the model and 'that' was a lesson about range I never forgot.

Thing is with digital, it's not quite the same. Like a digital television signal that first breaks up into garbage just before going black, and putting lost signal on the screen, what happened with PCM signals is similar. Perfectly solid, then instantly it falls off a cliff . . . zero!

A recent trend has formed. From straight 2.4GHz, to a combo 2.4GHz/900MHz setup. Originating in the drone world, the latter enables longer range control. Thing is, helis are flown close-in (else you can't see them well enough to maintain control). Plenty of folks are buying into the idea this is better. The usual justification is an issue with 2.4GHz at their field. One guy opts for dual band, then another, and suddenly, it's a land rush. Me? No issues so far. Meanwhile . . . I'm thinking;

• Watch out for lock-in!

Lock-in regards the business goal at Spektrum, FrSky, Jeti, Futaba, et al. of having you fly their product, exclusively. While they lost control of customers years ago (when they got stupid with servo prices), it doesn't stop them of dreaming of corralling you once again.

Their method is a mix of incompatible RF schemes (since receivers only work within the given brand), and to a lesser degree, incompatible programming schemes, and now, incompatible serial bus schemes. And no, in our opinion it's not by accident.

Interoperability

Servos interoperate . . . 3-wires, orange/brown/yellow, thus (+), (-), and PWM-signal.

Means Spektrum servos work with FrSky, or Futaba systems. But take heed, none of the serial bus architectures, interoperate. Could they be trying to box you in?

So as regards compatibility, servos yes (mostly), transmitter/receivers, nope.

Note; you commit for the long haul because switching obsoletes existing receivers.

Programming

RF-brands also seek to lock you in with different programming schemes.

Note; some claim Futaba are easier to program than Spektrum. Or that Jeti is harder to program than FrSky. We say bullshit! What it really boils down to is this; each brand does things their own way – differently – and for their own business reasons.

However, and regardless, before a model's flight ready (no matter the RF-brand) you have to accomplish these tasks, and in this approximate order;

1. Select model type (rotary-wing or fixed-wing)
2. If fixed wing, then surface-type (glider, v-tail, elevons, 4-servo wing . . . whatever)
3. If rotary wing (heli), then swashplate-type (CCPM, 4-servo . . . whatever)
4. Model name
5. Assign channels (which servo does what function, e.g. throttle)
6. Set direction of rotation (CW/CCW)
7. Center the servo (neutral position)
8. Establish throw (end points, travel adjust . . . whatever they name this)
9. Set up dual rates (if you use them)
10. Set up flight conditions (again if you use them)
11. Set up telemetry (if you use this)

And since every brand does functions differently, then there's a tendency to stick with the same brand next time you want an RF system. It's called soft-lock in, it's real, and guess what?

• They are all hard to learn.
• None are intuitive.
• No exceptions.

Interestingly, once throttle/collective are moving in the proper direction, and right cyclic tilts the swashplate to the right, and left/right is established with the tail rotor (and initial gyro gains are set for hover at ~60-70% and forward flight is 30-35%), and you've set up the collective pitch range (-5°/+11° or -11°/+11°, whatever), and cyclic pitch is set (maybe 6-8°), then and only then, are you actually ready to test fly the model. It's whilst flying that you'll refine these initial settings. So the initial setup only gets you in the ball park.

True for all brands of RF.

Intuitive programming

Moreover, despite claims – nobody's system is intuitive – e.g. easier, to program. We've got them all, and we consult the manual for each (until learning the intricacies for a given brand). This is true whether it's Spektrum, Futaba, Core, Jeti, FrSky, JR . . . whatever!

Note; neither does it matter if you have a preference for OpenTX, ExpressLRS, or if you dream of using ArduPilot flight controllers to achieve autonomous operations. Nothing is so obvious you don't need the manual, aka intuitive.

Programming steps must be followed in order when setting up regardless of brand.

Signal loss

Let me share an important detail. Signal loss can be a real problem for carbon side frame models. It's because the carbon weave is opaque to RF. This becomes a big deal in certain orientations, maybe turning in level flight, or whatever.

Some RF systems are better/worse than others. Explains why some RF-systems use satellite receivers to help get around the issue.

Anyway, with polymer side frames – signal loss and drop outs – are of zero concern.

Drop outs

Circling back to lost signal. In practice this means what are called drop outs. Remeber, back in the day (when radio system were analog), the signal was continuous. These days, RF systems are digital. So signal control is actually established through a stream of discrete packets of data. Not continuous.

Drop outs are lost packets. Experience enough lost packets and you don't have control (model crashes). Believe me, this is bad juju.

Big enough deal some RF systems have built-in drop-out counters. Others sell a dedicated dropout counter (a gizmo you plug into the receiver similar to connecting a satellite receiver). Idea is you monitor lost packets and relocate the receiver within the model (or add satellites) to improve.

• Goal is reducing lost packets.

If this weren't real, there wouldn't be a menu item, nor would they sell an accessory drop-out counter. Since 'no dog' also means we don't hesitate to put the hay down where the goats can get it, consider yourself warned.

Next up are brownouts.

Brownouts

Brownouts happen when the current demand is so high the voltage at the receiver drops below the set-point level. Varies by brand. Some are more sensitive than other.

What's happening is voltage drops enough (due to loads), the receiver thinks it's been turned off. Happens in an instant – but – it takes time for the receiver to reboot. Enough time to crash. Sucks!

Real issue . . . so just Google brand plus the compound word brownout, e.g. Spektrum brownout or Futaba brownout to get a sense of which brands to stay away from.

Don't say nobody told you.

Surveillance

Last thing. Surveillance has become a thing in the digital world. Since we market our heli for defense, and because we supply avionics packages, they can't be packaged with servos, possessed of external vulnerability. Just means a reduced attack vector so servos can't be programmable, or require updates.

Why is this important? Recently, the US government blocked certain products from certain countries (think DJI drones). Why? Due to concerns regarding spying. Point being, reflect carefully (regarding country of origin) before placing your RF-bet. Why?

Well, the exact same concern (regarding bi-directional data transfer during updates), also extends to our hobby-grade RF systems. Saying our mutual Uncle is getting serious about other countries obtaining intelligence via unknowing actors (via users, e.g. unconventional means).

Sure suck if whichever bandwagon you jump on were to get banned, right? Food for thought.

Wrapping up

Ultimately, as with engines, servos, and gyros, our advice regarding RF is . . . do what's best for you because your helicopter doesn't care! We believe it's wise to watch out regarding what the lack of interoperability (serial bus servos, included) may mean in terms of locking you in. Especially if a system gets banned (maybe lean toward systems by friendly allies).

Bottom line regarding RF? These days, there are more factors than what someone at the field recommends, or some 3D-god is paid to promote than in the past. Saying political considerations have entered the market. Or put another way . . . choose wisely.

Heads up!