72 Mhz Channel Nummbers

Hi Glynn: I was on the AMAFrequency Committe with Fred Marks, who was chairman of it back then. I do not remember why they started at Channel

11...however. I think the JR thing is because all JR receivers (with a couple of exceptions) are single conversion and there was some problem with 3rd order intermodulation at the low end of the 72 mhz band for them which brought the exclusion of certain channels in their offerings. Frank Schwartz

---------------

I remember reading about you, Fred and the other folks on the frequency committee many years ago. Thanks to you, Fred and the others for the hard work, Frank.

I'm sure that many younger folks do not realize the contribution to the hobby that you and many others have made. We are fortunate to have you and the remaining members amongst us.

Ed Cregger

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?

In short ................. HELP! Again, just as I thought I was beginning to understand the technical aspects of the hobby, I get new information which baffles me.

Speaking about mirrors, Frank, I'll mirror Ed's comments. Thanks for taking the time to make things better for all of us who came along later in the hobby/obsession.

Harlan

| Does anyone know the quick answer as to why the 72Mhz band starts at Ch 11. | I have several guesses but would like to know the true skinny. Maybe a | pointer to a web site/article would help.

Well, the frequencies in the 50 MHz band are numbered from channel 00 to 10, so maybe that's why the 72 MHz band starts at 11 -- to leave room for the 50 MHz ham band which starts at 00.

or maybe that was added later ... I don't know.

| Also, a little off topic, but why didn't JR make equipment for Channels | 11-14?

JR equipment is almost all single conversion. Channels 11-14 are vulnerable to some other sort of interference in single conversion receivers or something like that. I forget the specifics, but I'm pretty sure it's about interference, either caused by the use of those channels or affecting those channels.

From what I see in that chart frequency 61.650 is channel 28 dual conversion negative shift.

| 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 using.

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.

Gentlemen: Thanks for the kind words. This 81 year old builder and flyer appreciates what you have said. And, 72.350 MHZ is channel

1. Regards to all, Frank Schwartz AMA123 81 years young and still building and flying....life is sweet!!!

Ham goes from 00 to 09, so I don't know where the elusive channel 10 went. Maybe the same hole as channel 1 on TV sets...

I did have the history of the channel numbers at one time, but CRS has caused me to misplace it. IIRC, the 50 MHz Ham channels were to be 1 through 10 but at the last minute they were designated 00 through 09.

It would be easy to add number 10 as 51.00 MHz which is the next in the sequence.

BTW, TV channel one is the 50 to 54 MHz 6 meter Ham band. That was another anomally of numbering systems much like the one we are discussing.