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Old 05-16-2018, 3:53 PM
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Default Convert scanner bandplan to Relm KNG Channel IDs (implicit system)

I have a Relm KNG-P400, and I am trying to receive (Rx only) a " implicit " Phase I trunked system.

I have successfully monitored other non-implicit trunked systems with this radio, with no problems. However, the system I am trying to monitor now is a EF Johnson system, and told its implicit.

The 1st photo below is the bandplan in the scanner. The 2nd photo is the "Channel IDs" in the relm.

The bandplan (shown in the 1st photo) is what is in the scanner now, and it works fine. In other words, I can monitor this system fine using my PRO-197, with the bandplan shown in the 1st photo.

However, when I use the following bandplan in the Relm, it is not tracking the system.

Bandwidth= 6.25
Tx Offset= +
Tx Offset= 5.0000
spacing= 2.5
Base= 451.000
Type= FDMA

How would I take the bandplan in the 1st photo, and convert it into the 2nd photo?

I guess what is throwing me off is the Lo Chan and Hi Chan. Also, the scanner has 16 rows.

Thanks for any help I can get.
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Last edited by MegaHertz315; 05-16-2018 at 4:03 PM..
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Old 05-16-2018, 4:07 PM
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Im guessing the system is not broadcasting the band plan..
Not related but on my KNG2-P800 every system i have monitored filled in the fields for me.
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Old 05-16-2018, 4:11 PM
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Correct. When I use unitrunker, it is not showing me the bandplan. Also, Pro96Com won't display the system properly.

I normally do not need to know the bandplan/channel IDs either, as all the other UHF systems I have monitored automatically fill in, in the P400 for me as well.

However, this type of system will not automatically fill them in for me.

The scanner is the same way. It will not monitor the system in "P25 Auto." Won't track. I have to custom the bandplan (photo 1) in order for it to track.
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Old 05-16-2018, 4:37 PM
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Honestly, watch the control channel on Pro96Com or Unitrunker as it won't tell you the frequency, it will tell you the channel number it is assigning to calls. Once you get that, pull the license up and work backwards (the system may even give you the callsign).

The formula for calculating a frequency is as follows... F = Base+(Chan*Spacing).

Say it shows one Chan is 1094 and another is 1158. Now take the difference between the two (64 channels) and compare it to the license. At 2.5 kHz spacing, you should see two frequencies 160 kHz apart on the license while at 6.25 kHz you should see two frequencies 400 kHz apart in spacing. Then from there, you can take a corresponding frequency and channel number and calculate the base frequency (as it may not actually be 451.000 MHz).
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Old 05-16-2018, 4:52 PM
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I believe that formula is missing offset. Should be:

f = BASE MHz + spacing MHz * (CHAN +/- OFFSET)

Where BASE is the base frequency for the calculation, CHAN is the received channel number, and OFFSET is a value that will make the formula give the correct frequency. In addition to the channel number reported by unitrunker or Pro96Com, it would also help to know the system frequencies (or a link to the system in RRDB).

The table for the scanner is saying:

For any received channel grant on channels 0-4095, calculate the frequency as:
451.000 + .00625 * CHAN

For any received channel grant on channels 4096-8191, calculate the frequency as:
451.000 + .00625 * (CHAN + 4096)

For any received channel grant on channels 8192 and 1287, calculate the frequency as:
451.000 + .00625 * (CHAN + 8192)

and so on.
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Old 05-16-2018, 5:52 PM
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Quote:
Originally Posted by UPMan View Post
I believe that formula is missing offset. Should be:

f = BASE MHz + spacing MHz * (CHAN +/- OFFSET)

Where BASE is the base frequency for the calculation, CHAN is the received channel number, and OFFSET is a value that will make the formula give the correct frequency. In addition to the channel number reported by unitrunker or Pro96Com, it would also help to know the system frequencies (or a link to the system in RRDB).

The table for the scanner is saying:

For any received channel grant on channels 0-4095, calculate the frequency as:
451.000 + .00625 * CHAN

For any received channel grant on channels 4096-8191, calculate the frequency as:
451.000 + .00625 * (CHAN + 4096)

For any received channel grant on channels 8192 and 1287, calculate the frequency as:
451.000 + .00625 * (CHAN + 8192)

and so on.
For the intents and purposes of working backwards from the control channel data, we really don't need the offset (though it's assumed to be +5 MHz but that's work we can let the SU do after the bandplan is built). Now, VHF systems are a whole different ball game as the offset is information typically given with the channel grant by the controller but UHF and above has standard offsets which are defined by the band plan.

I find it weird that channel numbers are setup to go above 4096. As far as I know, 4096 is the high channel number officially defined by the P25 spec and other systems would simply add an additional channel ID into the system (ex. ChanID 1, Channel 1095 and ChanID 2, Channel 3891). See this more when using VHF, 700 and TDMA though.
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Old 05-16-2018, 8:17 PM
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Quote:
Originally Posted by UPMan View Post
In addition to the channel number reported by unitrunker or Pro96Com, it would also help to know the system frequencies (or a link to the system in RRDB).
https://www.radioreference.com/apps/db/?sid=8440

453.1500 a
453.3125 a
453.3625 primary
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Last edited by MegaHertz315; 05-16-2018 at 8:26 PM..
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Old 05-16-2018, 9:33 PM
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Quote:
Originally Posted by MCore25 View Post
I find it weird that channel numbers are setup to go above 4096. As far as I know, 4096 is the high channel number officially defined by the P25 spec and other systems would simply add an additional channel ID into the system (ex. ChanID 1, Channel 1095 and ChanID 2, Channel 3891). See this more when using VHF, 700 and TDMA though.
P25 systems have 65536 channel IDs (16 ranges times 4096 channels per range), so it's perfectly normal.

Channel 0: Range 0, channel 0.

Channel 65535: Range F, channel FFF.
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Old 05-17-2018, 7:11 AM
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Not sure why the PRO scanner is requiring such an extensive band plan. I come up with:

Base: 451 MHz
Step 6.25 kHz
Offset: 0

That math works for every LCN in the log:

Code:
Base	   Step	   Offset	CHAN HEX	CHAN DEC	FREQUENCY
451	   0.00625	0	158		344		453.15
451	   0.00625	0	16A		362		453.2625
451	   0.00625	0	172		370		453.3125
451	   0.00625	0	17A		378		453.3625
451	   0.00625	0	198		408		453.55
Since Offset is 0, frequency can be calculated ignoring the offset as:

451 + .00625 * (CHAN DEC)
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