Overview on Retevis' website:
Licensed by the Federal Communications Commission (FCC) and Industry Canada to operate in the license-free 900 MHz ISM (Industrial, Scientific and Medical) band.
Designed for business operations, the DTR Series radio will free your time from regulatory paperwork and licensing applications and saving radio licensing fees.
Are we talking about a Motorola DTR 900MHz FHSS digital radio or a Retevis 900MHz FHSS radio? The statement looks like a copy and paste from Motorola's documentation.
1. 900MHz FHSS license free radio
2. Digital and analog compatible
Support DMR digital and analog two communication modes to ensure that the original analog products smooth transition to digital products to meet different communication needs
FALSE. Can't be both of these at the same time. An FHSS radio is not compatible at all with a conventional analog or digital radio. An FHSS radio won't use DMR either.
3. Digital signaling function
Rich calling modes that support DMR protocol, including single call, group call and all call; supports remote inhibit function and other applications
FALSE. It won't be using DMR if it's an FHSS radio.
4. Interference free, private communications
Leverage Frequency Hopping Spread Spectrum (FHSS) technology for more reliable and private communication when compared to standard analog radios.
This is TRUE!
5. High sound quality
This digital two-way radio uses advanced AMBE +2TM voice processing technology to achieve higher quality
PARTIALLY TRUE. The digital audio from a Motorola DTR radio and other digital radios is high quality. The AMBE+2 vocoder is for a DMR conventional radio, not for an FHSS digital radio. The Motorola DTRs use Motorola's VSELP vocoder. VSELP was used in Motorola ASTRO digital radios before P25 Phase 1 which uses the IMBE vocoder. VSELP was also used by iDEN phones on NEXTEL and other iDEN networks.
6. Prominent functional keys
Programmable button can be used to quickly access call features like Call All/Page All, to talk to radios without searching through your channel list.[/quote]
The Call All/Page All refers to the Call All Available and Page All Available features in the Motorola DTR600/700 radios and Motorola DLR1020/1060 radios. The legacy DTR410/550/650 models (now discontinued) don't have the Call All/Page All features.
7. Supports the use of repeater
PARTIALLY true. FHSS radios such as the Motorola DTRs are simplex only and occupy the entire 902-928MHz band when they transmit. There is a repeater available for them ($1500) but it does not function like a conventional repeater. It consists of a pair of DTR radios running custom firmware and a controller to behave as a repeater. Each DTR radio uses a different frequency hopset. DTR radios talking on one hopset can talk to DTR radios on the other hopset using the repeater, and vice versa. It is one way operation at a time. The repeater has to be carefully placed to extend coverage areas. It is usually located where there is some overlap between an existing coverage area and the desired extended coverage area. The application for this is to extend coverage areas inside large buildings.
Some on-site business systems use the 900MHz band, including the Motorola DTR 900MHz FHSS frequency hopping spread spectrum handheld radios, which operate at 1watt ERP transmit power on the 902-928MHz ISM band using frequency hopping digital voice. Current examples include the Motorola DTR600 and DTR700 radios, These radios operate with 50kHz channel spacing and 8-level FSK digital FHSS. 902.525MHz to 927.475MHz coverage.
Mostly true. This statement reads like marketing literature. An FHSS device operating in the 902-928MHz band is required by FCC 15.247 to use a minimum hopset of 50 frequencies and with a maximum output power of 1 W (+30 dBm). The Motorola DTRs operate at 830mW (+29.2 dBm) to 890mW (+29.5 dBm). The measurement of transmitter output power is a conducted measurement made at the antenna connector. Output power is not specified in terms of ERP or EIRP.
The 50kHz channel spacing refers to individual frequencies in adjacent hopsets, NOT individual frequencies within a given hopset. The Motorola DTRs have 10 hopsets available, consisting of 50 individual frequencies, spaced 500 kHz apart. The 902-928MHz band has 26MHz of spectrum and gives 52 frequencies spaced 500kHz apart. The first and last frequency is not used due to being at the band edges so that leaves 50 frequencies available in a hopset. Frequencies in adjacent hopsets are offset by 50kHz. The spec'd 902.525MHz to 927.475MHz coverage is correct for the Motorola DTRs.
The mention of the 8-level FSK digital modulation for the FHSS operation is correct for the Motorola DTRs and refers to the modulation used on each hopping frequency. The occupied bandwidth of the 8-level FSK modulation on a given hopping frequency is wider than what a narrowband receiver will accept, even if you were to stop the FHSS and have the transmitter sit on a single frequency.
Technical specs on Retevis' website: A mixture of DTR, DMR, and analog specs (LOL). At least they got the DTR freq range right!
Main technological specification
902.525 - 927.475 MHz
30/50CH (up to 200)
(No including antenna)
Freq range: Correct for the Motorola DTRs.
Channel capacity: Channels in the Motorola DTRs refer the number of public talkgroups or Profile ID talkgroups that can be programmed. The "up to 200" refers to the maximum number of private contacts that can be programmed for setting up private talkgroups and for private 1 to 1 calling. This is NOT the RF channel capacity like in a conventional radio.
Channel spacing: Incorrect. This is the channel spacing for conventional analog and digital radios in wide and narrow bandwidths and is N/A for an FHSS radio.
4FSK digital modulation
12.5KHz for data:7K60FXD 12.5KHz for data and voice :7K60FXE
Rated audio Distortion
Max Frequency Stability
Output power: Correct.
FM modulation: Incorrect and refers to conventional and analog radios. N/A for FHSS digital radios.
4FSK digital modulation: Incorrect. Refers to DMR digital modulation for conventional radios. N/A for FHSS and the Motorola DTRs which use an 8-level FSK modulation scheme on each frequency in a hopset.
Vocoder type: Incorrect. AMBE++ is used by DMR. SELP = ? The Motorola DTRs use Motorola's VSELP vocoder.
Digital Protocol: Incorrect. The ETSI standard listed is for DMR. N/A for FHSS analog or digital.
SNR (wide/narrow): Incorrect and N/A for FHSS. The spec is for conventional radios.
Sensitivity (12dB SINAD)
Analog 25K≤-121dB 12.5K≤-119dB
25K≥45 dB 12.5K≥40dB
Adjacent channel selectivity
25K≥65 dB 12.5K≥60dB
Intermediation (Wide/ narrow)
25K≥60 dB 12.5K≥55dB
Spurious Response Rejection
Battery life under 5-5-90duty
14.8 hours(with 1600mAh Li-ion battery)
20.9 hours(with 1600mAh Li-ion battery)
Sensitivity: Incorrect. The spec listed is for conventional wide/narrow operation. N/A for FHSS.
SNR: Incorrect. The spec listed is for conventional wide/narrow operation. N/A for FHSS.
Adjacent channel selectivity: Incorrect. The spec listed is for conventional wide/narrow operation. N/A for FHSS.
Intermodulation (intermediation LOL): Incorrect. The spec listed is for conventional wide/narrow operation. N/A for FHSS.
Spurious Response rejection: N/A for FHSS.
The Bottom line: EPIC FAIL. Too many glaring mistakes with specs which are N/A and incompatible with FHSS operation. I have to call BS here and say this radio is Vaporware.
There were some analog 900MHz FHSS radios made by TriSquare a number of years ago. These were the eXRS radios and were marketed as an alternative to FRS. They operated on 900MHz and used FHSS. The similarities with the Motorola DTR radios ended there. The eXRS radios were analog and used a hopset of 50 frequencies per FCC 15.247. They spent 400ms on each frequency in the hopset, the maximum accumulated dwell time allowed per FCC 15.247. This meant they hopped very slowly and you could sort of monitor them with a scanner if it was fast enough and only scanning the specific freqs in the hopset. Using a divide and conquer approach by employing multiple scanners with each scanner covering a portion of the hopset worked better. You would hear the audio ping pong between multiple scanners but at least you could sort of monitor the eXRS radios. The eXRS radios were notorious for synchronization problems and took a long time to re-sync if synchronization was lost. The bottom line is these radios were total JUNK and the company is out of business. OTOH, the Motorola DTRs are professional quality and 100% digital and packed with features and work amazingly well. The DTRs spend no more than 90ms on any given hopping frequency, which works out to around 11 hops/second. The fact that the DTRs are completely scanner proof comes as a bonus.