| Frank (or anyone else for that matter):
| I bought some equipment form a person and part of the deal included a
| receiver on channel 28 (I thought) which included a crystal. The crystal,
| however, is printed with "61.650 MHz SS-9406". I'm wondering what this is.
| In doing a little surfing last night, I came across the chart at the below
| link. I guess I don't understand what it means, and I'm asking for someone
| to help me interpret what I'm reading. From what I can see, single and dual
| conversion frequencies are different from each other (but complementary?).
| also the terms "actual" and "mirrored" are new to me as are the terms "Image
| Fr+/-". What does all this mean, and is the 61.650 MHz crystal really a
| channel 28 crystal in disguise?
You've actually already figured out the hard part -- finding this
chart. Such a chart is useful in figuring out interference, trying to
figure out why your plane is having problems even though there's no
actual interference on the frequency that your plane is supposed to be
Basically, what you have is a crystal that resonates at 61.650 MHz --
which is used to pick up a signal at 72.350 MHz. Since this tends to
confuse people, R/C crystals are generally stamped with the frequency
that they're meant to receive rather than the actual frequency they
resonate at, but this isn't always the case.
More on exactly how these receivers work can be found here --
and note that a dual conversion receiver (which you probably have) is
called a `Double Conversion Super Heterodyne' by this article, and the
two IF frequencies are 10.7 MHz and 455 KHz.