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Retevis Retevis 900MHz license-free radio

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alcahuete

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I found this interesting radio while surfing Retevis' site. Not sure what to make of it yet.


It's a great price! Still Chinese crap, but great price. :) :)


Unrelated, but this, too:

Didn't know anyone was making 49MHz radios anymore. Kind of interesting. Wish they had some more info on it.

Wow!!! I haven't seen 49 MHz in probably 20 years or more.
 

RichardKramer

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Their 49MHz radios are old stock. They use the same 5 freqs the old RS 49MHz radios used. I have several RS single and 5ch units; use to use them to call my daughter for dinner back in the 80's. They all use 100mw output. When we lived in the apt complex, we heard a lot of cordless phones coming thru on some of the freqs.

Rich - N3VMY - KAG0096
 

hill

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Both the 49 MHz and the 900 MHz radios show a 45 business day delivery timeframe. Guess they aren't finished production or are being shipped from China.
 

NC1

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Only one watt on 900 MHz, that's not going to get you very far.
I'm guessing about possibly a mile and be somewhat reliable? Maybe 1.5 under really good conditions.
 

n1das

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Only one watt on 900 MHz, that's not going to get you very far.
I'm guessing about possibly a mile and be somewhat reliable? Maybe 1.5 under really good conditions.

It's funny how people are always obsessed with getting "X" miles of range out of a pair of radios while range as you know depends on multiple factors. 1W (+30dBm) is the FCC Part 15 legal limit for a frequency hopping spread spectrum (FHSS) device operating under FCC 15.247 in the 902-928MHz band. The Part 15 legal limit for a non-frequency hopping device in the 900MHz band is 1 mW (0 dBm), IIRC.

Don't underestimate a FHSS digital radio on 900MHz just because of the 1W transmitter power. My range record with a pair of 900MHz Motorola DTR650 FHSS digital portables transmitting at 890mW (+29.5dBm) stands at 12 miles from the Cocoa Beach Pier in Cocoa Beach FL to the top of the steps from the parking lot leading down to Hightower Beach in Satellite Beach FL. The top of the steps are about 30 ft or so above sea level. There is a bit of coastline in the way so it's not entirely line of site. Myself and a friend of mine who helped me test the DTRs also had 4W UHF Part 90 portables with us which we had on GMRS to compare to. (We are both GMRS licensed.) We were able to communicate on GMRS simplex but the received signal strength was noisy and scratchy and we each had to find a hot spot and stay there in order to communicate. The DTRs were crystal clear because of the digital modulation and overall was more reliable and finding a hot spot for them was less critical.

Motorola DTRs on 900MHz are capable of outperforming VHF and UHF conventional portables on simplex. Where the DTRs beat VHF and UHF conventional portables is when operating inside buildings due to buildings being much more open at 900MHz compared to 150MHz and 450MHz. Where the 900MHz DTRs blow all others away on simplex is when operating aboard cruise ships. People who have used DTRs aboard cruise ships report having full ship coverage on all decks compared to a pair of 4W UHF portables on GMRS simplex which had trouble penetrating more than about 2 decks. When operating aboard a cruise ship, you are essentially operating inside a compartmentalized metal box. The shorter wavelength signals at 900MHz reflect in an out of the many nooks and crannies of the ship where longer wavelength signals at VHF and UHF won't. The many reflections actually help with the FHSS operation because individual hot spots and dead spots also hop around as the frequency hops. The FHSS operation effectively stirs the modes so to speak.

I own a small fleet of Motorola DTR650s and a small fleet of DTR700s. I never got them to set any range records. I got them for reliable local on-site simplex type use with family and friends. They are my professional quality digital replacement for GMRS/FRS for local simplex type use and they totally blow FRS away. A coworker once asked me why not just use FRS? My answer was that I have already been doing that since FRS was created in 1996 and longer than that as a GMRS licensee since 1992 with Part 90/95 commercial gear. I want a secure, high quality digital solution that is higher quality and more professional than FRS. The fact that they are totally scanner proof comes as a bonus. They are not monitorable on any consumer grade receiver (scanner) so don't even bother trying.

I was curious about the Retevis 900MHz radio because I own fleets of Motorola DTR radios.
 
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RaleighGuy

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Both the 49 MHz and the 900 MHz radios show a 45 business day delivery timeframe. Guess they aren't finished production or are being shipped from China.

That's with a MOQ: 200 Sets (minimum order quantity) for the $60 price
 

DanRollman

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Motorola DTRs on 900MHz are capable of outperforming VHF and UHF conventional portables on simplex. Where the DTRs beat VHF and UHF conventional portables is when operating inside buildings due to buildings being much more open at 900MHz compared to 150MHz and 450MHz. Where the 900MHz DTRs blow all others away on simplex is when operating aboard cruise ships. People who have used DTRs aboard cruise ships report having full ship coverage on all decks compared to a pair of 4W UHF portables on GMRS simplex which had trouble penetrating more than about 2 decks. When operating aboard a cruise ship, you are essentially operating inside a compartmentalized metal box. The shorter wavelength signals at 900MHz reflect in an out of the many nooks and crannies of the ship where longer wavelength signals at VHF and UHF won't. The many reflections actually help with the FHSS operation because individual hot spots and dead spots also hop around as the frequency hops. The FHSS operation effectively stirs the modes so to speak.

I can echo this. I bought a set of DLR1020's specifically for use on a cruise, and it was one of the best radio investments I've made and they have become our primary radios around the neighborhood too. If you're measuring range as true line of sight, perhaps 1 watt FHSS at 900 MHz isn't your best solution. But if by "range" you mean how many building floors it can penetrate, or whether it can get out of the third sub basement, then two buildings over, then back into a sub basement in the neighboring building, 1 watt of FHSS at 900 MHz will blow any 150 MHz/450 MHz analog or DMR radio out of the water.

So put another way, on the cruise ship the "range" of my DLR1020 1 watt FHSS 900 MHz radio was "16 decks" while the "range" of my 4 watt and 5 watt VHF and UHF analog and DMR radios was just a few decks. So "range" totally depends on your application, and is not always best measured in miles anyway.

I have no idea whether this Retevis radio is legit. But given how well Motorola DLR and DTR radios work - how much better they work than conventional analog and digital radios for many applications - it would be great to see more manufacturers make use of unlicensed 900 MHz FHSS technology.
 

DanRollman

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Another application - Disney World and similar theme parks. From the line deep inside the "Thunder Mountain Railroad" structure, my son and I had no trouble communicating with my wife and daughter deep in Space Mountain on the other end of the park on our DLR1020 radios. Couldn't reach them at all on our CS750 radios on either DMR or analog mode given the metal obstructions (and cell phones become useless once you get into the core of several thick attractions).
 

n1das

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I have no idea whether this Retevis radio is legit. But given how well Motorola DLR and DTR radios work - how much better they work than conventional analog and digital radios for many applications - it would be great to see more manufacturers make use of unlicensed 900 MHz FHSS technology.

This is exactly why the Retevis radio caught my attention. If it is legit and is compatible with the DTRs and DLRs, that would be cool too. Motorola has been keeping the DTR/DLR protocol close to the vest for a long time but if they work with the DTRs/DLRs, it could be a sign that Motorola has finally opened the protocol up to the world to help grow the market.

I've been to WDW in FL only once in my life back in the 1970s. I was about 15 at the time and rode Space Mountain a month after it first opened. Epcott Center hadn't been built yet.
 
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DanRollman

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This is exactly why the Retevis radio caught my attention. If it is legit and is compatible with the DTRs and DLRs, that would be cool too. Motorola has been keeping the DTR/DLR protocol close to the vest for a long time but if they work with the DTRs/DLRs, it could be a sign that Motorola has finally opened the protocol up to the world to help grow the market.

I would be beyond shocked (and that's putting it mildly) if Motorola is or does anything to aid competition and compatibility with the DTR/DLR series. My best hope has been that another manufacturer will see the benefits of 900 MHz FHSS technology and develop a product line that operates in that way, but I would never dream that they would be compatible with DTR/DLRs.

Unlike P25 or DMR, there is nothing about Motorola's implementation of 900 MHz FHSS that is intending to create and promulgate a "standard," so I can't imagine FRAND licensing rules would apply the way they do for P25, DMR and similar "standards based" technology. I'm sure Motorola is quite content to sell the DTR and DLR lines as forever proprietary.
 

n1das

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I found this interesting radio while surfing Retevis' site. Not sure what to make of it yet.

This radio is not real. It is VAPORWARE. Retevis put some specs on their website but they are not for this radio at all. There are a number of red flags all over the place. It resembles a hilarious copy and paste job from multiple sources. Can you spot them all? (LOL) I copied and pasted the specs below.

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.

Features:

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

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

4. Interference free, private communications

Leverage Frequency Hopping Spread Spectrum (FHSS) technology for more reliable and private communication when compared to standard analog radios.

5. High sound quality

This digital two-way radio uses advanced AMBE +2TM voice processing technology to achieve higher quality

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.

7. Supports the use of repeater


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.


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


Frequency range​
902.525 - 927.475 MHz​
Channel Capacity​
30/50CH (up to 200)​
Channel Spacing​
25KHz/12.5KHz​
Operating Temperature​
-25℃~+60℃​
Operating Voltage​
DC 3.7V​
Antenna Impedance​
50Ω​
Microphone Impedance​
2.2KΩ​
Battery​
1800mAh​
Dimension​
128×54×32mm
(No including antenna)​
Weight​
223g​


Transmission

Output power​
1W​
FM modulation​
25/16K¢F3E 12.5K/8K¢F3E​
4FSK digital modulation​
12.5KHz for data:7K60FXD 12.5KHz for data and voice :7K60FXE​
Vocoder type​
AMBE++or SELP​
Digital Protocol​
ETSI-TS102 361-1,-2,​
Harmonic​
≥70dB​
Signal-to-noise Radio(wide/narrow)​
25K≤-45 dB
12.5≤-40 dB​
Rated audio Distortion​
≥5%​
Frequency Stability​
±2.5ppm​
Max Frequency Stability​
12.5K≤-40dB​


Reception

Sensitivity (12dB SINAD)​
Analog 25K≤-121dB 12.5K≤-119dB​
Digital 0.3μV/BER5%​
Signal-to-noise Radio​
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​
≥65 dB​
Audio power​
1W​
Audio distortion​
<5%​
Frequency Stability​
±2.5ppm​
Battery life under 5-5-90duty​
14.8 hours(with 1600mAh Li-ion battery)​
20.9 hours(with 1600mAh Li-ion battery)​


Epic FAIL.
 
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gman1971

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Indeed.

I guess someone either thought they could cut'n'paste and it would be 'close enough', or they really thought people would buy it and not know the difference.

Yet another reason I do not waste my money on these low tier radios.

+1.

I wouldn't even call those "low tier radios", those are garbage radios, period. If you want a low tier radio find a used commercial grade Moto, Vertex, Kenwood, Icom, etc... on places like eBay, etc... models like the XPR6350, EVX-531, for example... those are low tier radios that outperform anything CCR and can be had for real cheap. Heck, I've even seen DTR radios go for bargain prices on eBay... just takes a bit of time and patience to find the right deal... and in doubt, ask... there are plenty of forums nowadays where people will help you find a good radio.

G.
 
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N4KVE

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One could pick up a pair of Nextel phones that could do “Direct Talk” between each other. It’s a similar 900 frequency hopping” mode, & they work real well.
 

SuperG900

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There's no mystery to 900Mhz FHSS, and you don't need an expensive sophisticated superhet design - direct sampling is most often employed. I used to write firmware for 900Mhz RFID interrogators - the high speed tollway type. If I can pickup backscatter at 100mph, you can bet that it's gonna be a lot easier job for something purpose designed for communications. This was 25 years ago.

Although some Chinese radios are indeed cheaply (or rather, poorly) built, not all and not even most. The fact is, technology, especially *digital* technology amortizes itself *way* faster than way you'd think - and *that's* why we have so many inexpensive radios. Of course, all the big LMR players have their radios built where labor is cheap - and there's not all that much new under the analog sun, and there's little incentive for Chinese companies to *not* copy designs. Who can blame them? You exploit their cheap labor to sell at usurious prices in the west, they copy your designs... There's no such thing as a free lunch.
 

n1das

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The Retevis 900MHz radio is Vaporware as far as I can tell. I can't find an FCC ID for it and the tech specs are conflicting and incompatible with FHSS. The published specs are for DMR and analog conventional radios. The specs resemble a copy and paste from multiple sources. I can't find any evidence that this radio is real. EPIC FAIL.

One could pick up a pair of Nextel phones that could do “Direct Talk” between each other. It’s a similar 900 frequency hopping” mode, & they work real well.

Replacement batteries are still readily available if you have a bunch of these phones and want to keep them going. I recently re-batteried my DTR650 fleet with factory fresh new batteries and they use the same battery.

The one gotcha with these phones is they require a SIM card that has previously activated on an iDEN network such as NEXTEL in order for the off-network DirectTalk feature to work. This is required because the 11-digit private ID used by the feature is formed from 1 plus the area code and phone number in the SIM card. The DT feature will not work at all without the 11-digit private ID.

My wife (g/f at the time) and I have owned a pair of i355 iDEN phones on the NEXTEL network back in the day and we used the off-network DirectTalk feature. It worked great. I also learned of the legacy DTR410/550/650 models back then and figured out that the DTRs are similar to the DirectTalk feature and share a common design.

The DTRs were actually a spinoff from the DirectTalk feature. The DTRs use the exact same FHSS system but the DTRs were coded differently and are incompatible with the DT feature in the phones. The differences are software only and supposedly was done on purpose. I suspect the DTRs became incompatible with the phone's DT feature when DTR-specific features were added to the DTRs. The DT feature in the phones got left behind because of the need to keep it simple for phone users.

The off-network DT feature in iDEN phones is based on the old Motorola MOTO Talk platform. The Motorola DTR series and DLR series 900MHz FHSS digital radios represent the latest implementation of MOTO Talk.
 
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