scanSydney

So I notice my trusty DTS96 is trunking to the new 420MHz VFs on Chullora using the existing band plan

Lo Ch Hi Ch Offset Base Step
16384 20479 16384 412.4750 06.25

But when I enter the new Nattai GRN site's Control Channel 422.3375MHz, the scanner does nothing.

Looking at the band plan decoded by a 996

0. 851.00625 mhz Input base/ Input spacing 6.25 khz
1. 762.00625 mhz /6.25 khz
2. 851.0125 mhz/ 12.5 khz
3. 762.00625 mhz / 12.5 khz spacing
4. 412.475 mhz / 6.25 khz spacing
5. 420.0125 mhz / 6.25 khz spacing

I'm assuming the 420.0125 MHz / 6.25KHz base and step need to be added to the DT96's multitable to trunk with the new control channel.

How does one work out the lo channel and hi channel to add to the table?

Mike

G'day Mike,

Only bandplans 04 & 05 are in use at the moment. I would expect that one of the other bandplans will become the UHF-H freqs when (or should that be *IF*) the PF migrate to the GRN proper, similar to how the VICMMR handles police channels?

The readout above seems correct for bandplan 04 but not for 05? I have the base frequencies as:

LCN 04-0000 is 412.4750
LCN 05-0000 is 420.0000

From my list, the frequency 420.01250 would be LCN 05-0002, I hope my list isn't wrong otherwise the sites list here has a lot of mistakes in it!

Andrew

EDIT: I forgot... Each bandplan has 4,095 LCNs (which is 0xFFF in hexadecimal).

If you want to work out the highest frequency for each bandplan, multiply the LCN by the Spacing and add the base frequency.

So LCN 04-4095 would be (4095 * 0.00625) + 412.47500 = a high LCN 04-4095 with a freq of 438.06875 MHz
Or LCN 05-4095 would be (4095 * 0.00625) + 420.00000 = a high LCN 05-4095 with a freq of 445.59375 MHz

But you will likely never see any of those higher LCNs used because our offset is so small that the Base TX freqs start to overlap the Base RX freqs at the beginning of each bandplan, and the Base RX freqs overlap the Base TX freqs at the end of each bandplan (or the other way around as the case may be), and to add to that, the two bandplans actually even overlap each other.

Not impossible to manage of course but it means you have to be careful to isolate overlapping LCNs geographically and by NAC.

Bigfella237 wrote:
From my list, the frequency 420.01250 would be LCN 05-0002, I hope my list isn't wrong otherwise the sites list here has a lot of mistakes in it!

You are correct Andrew. It is 420.000MHz. The list I posted above was cut and pasted from another forum - either it's old info or a typo.

I'm still having trouble working out how the DTS96 table equates 412.475 as a lo Chan of 16384 and a high chan of 20479. There is a difference of 4095 between them. That would mean the 420.000MHz lo chan would be 17588 and high of 21683. But the scanner doesn't track correctly with those figures added to the table. It trunks to a VF 18.075MHz too high.

Mike

Hopefully someone who knows these scanners will chime in but, from a quick search of the internet, that 16384 number is apparently the offset not the channel number? I assume there is a table somewhere as I can't equate that number to the actual values at all?

The actual offset of bandplan 04 is +9.45MHz while bandplan 05 is -5.2 MHz (or maybe that should be -9.45 and +5.2 I can never remember which way around it's supposed to be).

Andrew

Hi all,

The offset is 20480



That should make it work

Cheers

That did the trick Longreach. Thanks

And you only have to enter the last two bandplans - at this stage.

*Note. In the last bandplan above, base 420.0125 is incorrect. Should be 420.000MHz.



Cheers
Mike