Bk DPH Emissions Bandwidth & Channel Spacing

[jbaker6953]

I have a BK DPH radio that lists the following emissions:

16K0F3E
11K0F3E
8K10F1E
8K10F1D

Since the F1 designates digital transmissions, I'm assuming that it means the following:

1. In analog wide band mode, the bandwidth is 16 kHz
2. In analog narrow band mode, the bandwidth is 11 kHz
3. In digital mode, the bandwidth is 8.1 kHz
4. The F1D covers OTAR.

Does that sound about right?

If so, would it also be true that I could realistically space channels 7.5 kHz apart using the 11 kHz bandwidth (which is 5.5 kHz on either side of center), and 5 kHz using the 8.1 kHz bandwidth?

Thanks.

 

[jbaker6953]

I sort of answered my own question. The BK radio I have is ±2.5 ppm, but most amateur gear is ±5 ppm. That means in the 2M band we're talking about ±730 Hz. An 11 kHz signal would be ±5.5 kHz from center, and adding the 730 Hz gives about ±6.25 kHz needed on each side of center. That means, naturally, that channels should be spaced at 12.5 kHz when using 11 kHz modulation in the 2M band, and that's packing it in tight. For an 8 kHz modulation (as in DSTAR or P25), the channel spacing should be at least 10 kHz. It could be argued that a lot of amateur gear, or broken gear, could fall outside of the ±5 ppm specification and cause interference with adjacent channels in such a tightly-packed scheme. While true, I think the gain in capacity by packing channels closer together more than offsets the limited number of cases where malfunctioning equipment will cause interference.

Someday we might be able to free up some space on crowded amateur bands by narrow banding all or a portion of certain bands and packing the channels in closer together. In Southern California the 2M band is already mostly at 15 kHz spacing. 12.5 kHz spacing would add 20% additional capacity.

Now this is probably the wrong forum

 

[rescuecomm]

When you say ppm, you are talking about the frequency stability of the radio. However, most amatuer radios opererating above 50 mhz using wideband FM have frequency steps of 5 khz which allows band plans of 15 khz or 20 khz repeater spacing. The capture effect of FM receivers does not require PLL references to be 2.5 ppm. The FCC does require higher frequency stability on public safety radio gear. Of course an amatuer station is responsible for remaining inside the limits of whatever band he/she is using. Thus a station using 15K0F3E would be out of band if transmitting on 147.995 mhz but not at 147.990 mhz. My take on the 11K0F3E is that amatuer radio will probably transition directly to digital modes in the future rather than waste money and effort on the FM narrowband. As far as repeaters go, there is a shortage of frequencies around the country, but most repeaters around here sit idle through the day so the usage is really not there except at rush hour or net time.

Bob