Glenn: Without knowing or seeing the exact components or circuitry involved, here’s my speculation regarding these transmitter glitches. I’ll try to minimize the technical jargon.

First, all of the switches, control sticks, buttons, or knobs on the external of the transmitter are “analog” devices – meaning that they send all or some portion of a voltage through the device based on actuation of the switch, stick, button, or knob. For example, a voltage is present at a potentiometer i.e. a trim control, and any adjustment of that control sends a bit more or less of that voltage into an analog to digital conversion circuit. Even a so-called “digital” trim performs this function; though what happens in that case is a bump on the trim switch digitally increments an IC chip/amplifier to output a digital set of pulses representing the desired directional adjustment. This principle remains the same for all of the external switches, knobs, or buttons.

How the internal amplifiers respond to movements of major control inputs (i.e. rudder, elevator, and aileron) is determined by special circuits (exponential, proportional, or logarithmic) that calibrate the signal from the control sticks by some algorithm. When I first got into the hobby everything was “proportional” but now we have options for how the amplifier circuits respond.

Second, all of those various inputs from the external switches, etc. are used to create “modulating” pulses for the transmitted signal. Basically, in any transmitter/receiver system (AM, FM, PCM, QPCM, etc.) the “information” that is needed at the receiver to provide control signals to the servo motors onboard the aircraft is impressed onto the radio frequency carrier for the “channel” on which the transmitter is operating. Without going further into that concept, the transmitted output on each “channel” is a basic radio frequency (RF) carrier signal that has been modified with discrete “information bits” that the onboard receiver must decode and properly distribute to the servos or other devices in the aircraft. This is the basic RF modulation/demodulation theory, whether we’re discussing digital or analog transmitter/receiver links.

With the Eclipse and Optic systems (we’re talking about Hitec transmitters, but the same principle applies for Futaba or JR products with the synthesizer capability) we have the capability of dialing up a “channel” on the Spectra module. When we’re selecting a channel, all we’re doing is tuning a frequency network inside the RF module to use a particular output frequency as its base carrier signal to be modulated with the “information” we intend to transmit.

When we experience what we laypeople call a “glitch” we can narrow the possible root causes of the problem to the transmitter if the onboard receiver or servos are isolated/eliminated by obvious things like changing receivers, eliminating crossover caused by wiring, problems with the onboard battery, solder joints, breaks in wiring, or onboard servo-amplifier problems. We also can narrow the possible root cause to the transmitter by ensuring there are no environmental problems of other transmitters creating interference by direct transmissions on our selected channels or what is called “Third Order Inter-modulation.” Third order inter-modulation (also known as harmonic distortion) has not been a problem for us since the introduction of the so-called “narrow band” transmitter/receiver systems.

If the onboard equipment (including the receiver) and the environment are eliminated as root causes of the “glitch” then this leaves us a very narrow community of possibilities for the sporadic servo transitions, inconsistent output signal, and apparent “deadness” of the channel that some of us are experiencing.

Let’s take them in order: sporadic transitions on one and only one function e.g. ailerons is a different creature from wild and crazy transitions of ALL functions. I’m experiencing sporadic transitions on ALL functions. In my mind’s eye, this represents an “encoding” problem – something inside the transmitter is causing the RF signal to be “modulated” sporadically, erratically, and absolutely independent of the switches, knobs, or buttons on the external case of the transmitter.

Unless ALL of the analog to digital and amplifier circuits are populated inside the Spectra module, this points to a board inside the transmitter rather than the frequency module.

Inconsistent output signal can be caused by an inconsistency in the physical signal path to the antenna – maybe a loose wire or a crack in a track on a circuit card. It could be caused by the RF cavity/oscillator/crystal being unstable. It could be caused by antenna problems at the transmitter or onboard the aircraft.

“Deadness” of the output is the tricky part of this discussion because what may appear as deadness, or absence, of the modulated output signal could really mean the base carrier frequency is NOT being modulated by any “information” inside the transmitter. The net result is the symptom witnessed would be that the aircraft does not respond to any stick, button or knob adjustments on the transmitter. The only way to know if there is absolutely NO output radiated from the antenna is to use a field strength meter to sample the environment; or a person could use an RF spectrometer to visually graph transmissions in the selected portion of the RF spectrum. One real benefit of a spectrometer is that you’d also have a visual on the purity/quality of the radiated signal.

Okay, now why did I object to the “electrical tape” solution? I objected because there is nothing in that solution that makes sense from a technician’s perspective. The module is secured by lock tabs so that physical movements are virtually nil. Second, the pins on the connector block inside the Spectra cavity penetrate nearly .5” into the module; there’s no problem of physical connections there. If the issue is a crack in a track on a circuit card, stabilizing the module is NOT a solution because it does not correct the real problem. Taping the module will not fix an overheating problem or an issue with a component that has unstable operation. If there are conditions inside the transmitter creating spurious signals that are modulating the RF signal erratically/sporadically, tape on the module is not a solution.

Now that I’ve written this book, I rest my case. As indicated, I have already dispatched my transmitter to Hitec Customer Service, and (on your suggestion) I’ve prayed for the technicians. I promise not to beat this horse anymore.

PS: I don’t personally beat horses, I don’t know anybody who has or does beat horses, and I neither condone nor endorse the beating thereof.

Pastor Mike