Narrow Band emission designators

[arlojanis]

What is the difference between 11K0F3E and 11K2F3E? Is the 0 a letter or a number? Which one is correct for narrow band FM voice communications?

[MassFD]

I looked all over and the only thing I can find is this doc from Vermont that on page 3 says 0,2 or 3 is acceptable for a narrowband license.

http://vcomm.vermont.gov/sites/vcomm/fi ... 07_10_.pdf

Every place else I found states that the first 4 positions are the bandwidth and give info on the first 3 but omit the info about the fourth.

We modifyed our licenses about 5 years ago and used 11k0f3e on the advise of Motorola but I have seen a few in our area recently use 11k3f3e

[WB6DGN]

The clearest explanation I've found is here: http://www.comsearch.com/articles/emission.pdf
As I read it, in your example (11K2) the "K" serves as both a decimal point and the "unit of bandwidth". So, 11.2kHz is the necessary bandwidth in this example. The digits denote the quantity and the "K" places the decimal point and gives the unit of measure, ie. K = kHz. So 11K0 would be 11.0kHz necessary bandwidth, 11K3 would be 11.3kHz necessary bandwidth, etc. The fact that there are three different designators for, essentially the same emission tells me that there was some disagreement about the actual maximum necessary bandwidth required. Therefore, 11K3 would probably be the safest entry. Seems unnecessarily complex to me but it was derived at ITU so what do you expect.
Tom

Now that I think about this a little, this is nothing more than an adaptation of the same system that has been used to specify component values for years now. For example, a 25000 ohm resistor is specified in ITU units as 25K0 ohms. A 25300 ohm resistor is written as 25K3 ohms, and a 47,700,000 ohm resistor would be written as 47M7 ohms, etc. Nothing new after all, but when you don't use ITU units every day, it gets confusing.
Tom

[MassFD]

Yours is the best explaination I have seen so far, from the link you provided if you look at the 12.5 entry the 12K5 then makes sense. I still do not understand why if we are spliting channels and the old was 20k0, why is the new not 10k0. I do not think it matters what you use 11k0, 11k2 or 11k3, your transmitter is still limited to a maximum of 2.5, leaves plenty of guard band either way.

[WB6DGN]

if we are spliting channels and the old was 20k0, why is the new not 10k0

While it is true that you are "splitting" channels by reducing modulation (deviation) and somewhat cleaning up the modulation sidebands, it is another issue to reduce transmitter noise and distortion, and increase frequency stability to actually be able to split those channels exactly in half. Furthermore, I don't remember for sure, but I don't believe that the old "wideband" occupied bandwidth was as low as 20kHz. It seems to me that it was more on the order of 25 to as much as 30 kHz. In any case, while you are reducing occupied bandwidth by reducing modulation, you are still much more limited as to what you can do to reduce other noise products. The narrower the modulation goes, the greater the part played by transmitter noise.
Tom