Model Forum / Radio Controlled / Air Models / January 2009

essentially if you mean synthesized HF receivers, they simply tune into
the strongest signal when switched on. And stay there.

Apart from that they are just like a normal crystal receiver. Except the
oscillator may not be as 'pure' as a crystal, meaning they may be more
prone to interference.

Most (all?) the synthesized RXs have some kind of procedure to set the
frequency and lock it in.  Some have set switches, others have modules you
connect when changing the freq and then disconnect.  They stay "set" to the
chosen frequency until programmed differently.  They don't hunt for
frequencies the same way 2.4Ghz systems do.

I know Polk Seeker RXs will work with any 72Mhz TX.  Several third party RXs
will work with anything.  I don't know, but suspect JR synth RXs will still
only work with positive shift TXs and Futaba synth RXs will only work with
negative shift TXs....

PCPhill

Um... I can't say for all receivers, but what's for sure is that any
kind of "binding" is not in any way essential for the operation of
synthesized receivers.

Synthesized receiver is basically the same thing as an ordinary
receiver, except that in the ordinary receiver you have a crystal, which
assigns that receiver to a specific fixed channel. In a synthesized
receiver instead of a crystal, you have a bunch of dials that let you
set a specific fixed channel (or a bunch of buttons). In order to switch
the channel in the ordinary receiver, you need to replace the crystal.
In order to switch the channel in the synthesized receiver, you need to
turn a dial or two. That's it.

As for the "several transmitters" issue, these receivers are the same.
If another transmitter comes up on the same channel, the model gets shot
down, regardless of whether your receiver is synthesized or not.

There are synthesized receivers that can automatically adjust their
channel. Instead of turning dials, you have to bring your transmitter
close to the receiver, and the receiver will "learn and remember" its
channel. From the outside if might look like some kind of "binding" (and
it might be referred to as such), but in reality this is just another
way to set the channel in some synthesized receivers, instead of turning
dials. This is a mere convenience feature (you don't have to pull the
receiver out of the model to turn the dials), and once the channel is
set, the rest from that moment on works just like a good old receiver
with a crystal.

Finally, there are 72MHz FM receivers out there with "advanced features"
that involve the actual "binding" of the receiver to the transmitter of
some sort, i.e. the receiver somehow knows how the recognize its own
transmitter and ignore all others. However, firstly, this has nothing to
do with the receiver's being "synthesized" - the same thing can be
implemented in a receiver with a crystal. And secondly, once again, this
feature has rather limited effect in 72MHz systems, because once another
transmitter working on the same channel starts to overwhelm the proper
transmitter, there no way to ignore it anymore and the contact gets lost.

Of course, as long as they are compatible in all other regards.

Well, if Airtronics receivers in general are compatible with Futaba
transmitters (or if, say, the Futaba transmitter can be set up to send
the signal compatible with Airtronics receiver - like positive/negative
shift and stuff), then yes, you can use them. This is, again, an issue
of general compatibility between brands, completely unrelated to
transmitter's/receiver's being synthesized or not.

"spread spectrum" and "synthesized" are two different things. Lately binding
refers to Spread Spectrum 2.4 GHz radios.
mk