Re: RF Frequency Range

"John D. Hays" <john@...>

The specification is for the entire 70cm Amateur radio band,  420-450 mHz.  (75% of our team lives north of Line-A, so 420-430 on air tests require getting south of the line!)

The bandwidth is dependent on a number of factors, but for 56K GMSK the modulation mask is in the 73-80 KHz range.  FCC rules dictate a bandwidth of less than 100 KHz.  We will be providing spectrum analysis charts for the production units.

The radio is capable of additional modulation methods, e.g. 4FSK, which also fit the D-STAR specification, that may give us more bits per KHz., but at least for the domestic market we need to stay in the 100 Khz. bandwidth for data and the modulation methods that are being used.  There is a 100 KBPS hard limit on the RF-IC (which contains the modem).

There are some things that could be done with respect to error correction to improve reliability while preserving the D-STAR data format.

John D. Hays
PO Box 1223, Edmonds, WA 98020-1223 

On Wed, Jul 11, 2012 at 8:13 AM, George Jones <hamfiles@...> wrote:

What frequency range will the RF cover?
What is the transmitted bandwidth at 56K?

For some time now we have wanted to leverage the use of the 430 - 440 MHz
portion of the US band for D-STAR data.
There is a lot of wide open frequencies in many parts of the country that go
unused in this section. With some careful planning we should be able to
coordinate frequencies in this part of the band taking into consideration
protection for the satellite sub-band and weak signal work. Our friends in
Europe seem to be doing a better job at band planning for spectrum
efficiency than our coordinators in the states. With every new mode comes
the thought of what frequency should I use. By thinking of these things
now, maybe we can avoid some of the issues we have seen in the 440 - 450 MHz

The 420 - 430 MHz part of the band is also available in many parts of the
US. My hopes would be that the designers could build the RF such that it
could cover the entire 420 - 450 MHz range. This would give the end user
more flexibility in building a network with these new radios. I know this is
a tall order with government approvals required for intentional radiators.

George W4AQR

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