DLR Series.... Channel Pool?

[CopperWhopper67]

I have been trying to find the list of frequencies that Motorola DLR radios use in the 900 MHz ISM band. The user manual does not list the freqs unlike the manuals of other radios. Does anybody have a list or know where I can find one? Thanks

 

[Will001]

I have been trying to find the list of frequencies that Motorola DLR radios use in the 900 MHz ISM band. The user manual does not list the freqs unlike the manuals of other radios. Does anybody have a list or know where I can find one? Thanks

They are frequency-hopping from what I’ve heard.


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[n1das]

I have been trying to find the list of frequencies that Motorola DLR radios use in the 900 MHz ISM band. The user manual does not list the freqs unlike the manuals of other radios. Does anybody have a list or know where I can find one? Thanks

The DLRs have 18 hop sets of 50 frequencies each. This is up from the DTRs having only 10 hop sets to work with. The first 10 hop sets in the DLRs match the 10 hop sets in the DTRs. Hop set #1 is the default frequency hop set in the DTRs and DLRs.

Digital modulation on a given hopping frequency is according to an 8-level FSK scheme. The vocoder used is VSELP.

I looked up the FCC test reports in the FCC's Equipment Authorization database for one of the DTR models a while back and happened to find the info you are looking for. It should be in the reports for the DLRs. For each hop set, the information is listed as a base frequency in the 902MHz range and follows a formula with a step size to calculate the 50 frequencies in the hop set. A frequency hopping spread spectrum (FHSS) device operating in the 902-928MHz band is required by FCC15.247 to use a minimum hop set of 50 frequencies. The DTRs and the DLRs spend no more than 90ms within a 400ms period on any given frequency in the hop set. The entire 902-928MHz band is used when these radios transmit.

DTR410 FCC ID = AZ489FT5842
DTR550/650 FCC ID = AZ489FT5852

DLR1020/1060 FCC ID = AZ489FT5870, AZ489FT5871

In case anyone is wondering, forget about trying to monitor these on any consumer grade receiver (scanner) because you can't.



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[CopperWhopper67]

The DLRs have 18 hop sets of 50 frequencies each. This is up from the DTRs having only 10 hop sets to work with. The first 10 hop sets in the DLRs match the 10 hop sets in the DTRs. Hop set #1 is the default frequency hop set in the DTRs and DLRs.

Digital modulation on a given hopping frequency is according to an 8-level FSK scheme. The vocoder used is

Can you explain in more detail what a hop set does and why hopping needed for this band?

Thanks

 

[n1das]

Can you explain in more detail what a hop set does and why hopping needed for this band?

Thanks

From the FHSS article on Wikipedia........
https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum

A spread-spectrum transmission offers three main advantages over a fixed-frequency transmission:

1. Spread-spectrum signals are highly resistant to narrowband interference. The process of re-collecting a spread signal spreads out the interfering signal, causing it to recede into the background.
2. Spread-spectrum signals are difficult to intercept. A spread-spectrum signal may simply appear as an increase in the background noise to a narrowband receiver. An eavesdropper may have difficulty intercepting a transmission in real time if the pseudorandom sequence is not known.
3. Spread-spectrum transmissions can share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be used more efficiently.

In the US, FCC part 15 on unlicensed spread spectrum systems in the 902–928 MHz and 2.4 GHz bands permits more power than is allowed for non-spread-spectrum systems. Both frequency hopping and direct sequence systems can transmit at 1 Watt, a thousand-fold increase from the 1 milliwatt limit on non-spread-spectrum systems. The Federal Communications Commission (FCC) also prescribes a minimum number of channels and a maximum dwell time for each channel.

The DLRs and DTRs spend no more than 90 ms on any given hopping frequency in a 400 ms period. The hopset of 50 frequencies spreads the transmitted signal out over the entire 902-928 MHz band.

 

[n1das]

DLR information

Chickenhawk's DLR review:
https://www.twowayradioforum.com/forum/showthread.php?t=5991

Motorola DTR audio:
https://www.youtube.com/watch?v=aaNdMWPmVZI

 

[n1das]

The DLRs and DTRs spend no more than 90 ms on any given hopping frequency in a 400 ms period. The hopset of 50 frequencies spreads the transmitted signal out over the entire 902-928 MHz band.

As a minor clarification, the DLRs and DTRs spend no more than 90 ms on any given hopping frequency before changing to the next frequency in the hopset of 50 frequencies. The radio may revisit a recently used hopping frequency one or more times during a 400 ms period. The accumulated dwell time on any given frequency in the hopset cannot exceed 400 ms per FCC 15.247.

I assume the OP wants to listen to DLR and DTR radios. I do too! The DLRs and DTRs are not monitorable on any consumer grade receiver (i.e., scanner) so don't even bother trying with these. The only inexpensive and practical way to monitor these is with another DLR or DTR radio, AND it has to programmed to the same frequency hopset and talkgroup ID. The DLRs also have a 4-digit Profile ID to enable another level of privacy. If using a DLR, the Profile ID also has to match in order to hear anything. DTR radios don't have the Profile ID feature. The Profile ID in a DLR has to be set to 0000 (Off) for a DLR to work with a DTR. All settings have to match in order to hear other traffic on a given hopset, group ID, and profile ID (DLR only).

DLR and DTR radios will talk to each other right out of the box at their factory default programming. They are usable without needing to program anything at all. Customization of settings and features and setting up private groups requires the CPS. I have monitored some DLR and DTR traffic when traveling through major urban areas. I am finding that most users simply use these radios as they come out of the box at their factory default programming, just like GMRS/FRS bubble packs. Users who have set up Private Groups won't be monitorable at all by a DTR or DLR that's not member of the Private Group. While technically not encrypted, these radios can be made very secure. It's essentially security through obscurity.

I have set up a Private Group in my own fleet of DTRs and DLRs and purposely kept the rest of the programming at the factory defaults so I can listen for activity on the default public groups. I do catch occasional local chatter on them from time to time.

 

[n1das]

The DLRs have 18 hop sets of 50 frequencies each. This is up from the DTRs having only 10 hop sets to work with. The first 10 hop sets in the DLRs match the 10 hop sets in the DTRs. Hop set #1 is the default frequency hop set in the DTRs and DLRs.

Digital modulation on a given hopping frequency is according to an 8-level FSK scheme. The vocoder used is VSELP.

I looked up the FCC test reports in the FCC's Equipment Authorization database for one of the DTR models a while back and happened to find the info you are looking for. It should be in the reports for the DLRs. For each hop set, the information is listed as a base frequency in the 902MHz range and follows a formula with a step size to calculate the 50 frequencies in the hop set. A frequency hopping spread spectrum (FHSS) device operating in the 902-928MHz band is required by FCC15.247 to use a minimum hop set of 50 frequencies. The DTRs and the DLRs spend no more than 90ms within a 400ms period on any given frequency in the hop set. The entire 902-928MHz band is used when these radios transmit.

DTR410 FCC ID = AZ489FT5842
DTR550/650 FCC ID = AZ489FT5852

DLR1020/1060 FCC ID = AZ489FT5870, AZ489FT5871

In case anyone is wondering, forget about trying to monitor these on any consumer grade receiver (scanner) because you can't.



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EDIT: The DLRs and the new DTR700 and DTR600 models have only 10 frequency hopsets available to work with, not 18 hopsets as previously mentioned. The 10 hopsets of 50 frequencies across the 902-928MHz band are the same hopsets used in the older DTR models. I was confusing the 18 Profile IDs for a channel in the DLRs with frequency hopsets. My bad.