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Home New Retevis MB2 CB Review

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,213
1,717
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Retevis recently contacted me to see if I would evaluate their new MB2 CB mobile radio. Of course, I can't resist an offer like that. This is a new AM/FM, small form-factor mobile CB which Retevis is positioning to comply with regional CB regulations (FCC, EU, etc.). I've spent the last month working with this radio and am ready to share my thoughts.

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As you can see, this radio is very small, much like a Uniden Pro 520XL. It easily fits on just about any dash or overhead mount with the included mounting bracket. I tested this in my wife's car sitting on her dash with the optional, included mag mount antenna, which is rated at 200 watts:

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Antenna

The optional mag mount is well designed with a standard SO-239 connector for the antenna and no-brand RG-58/U coax. The antenna is a center loaded, 45 inch antenna that reminds me a lot of the old Radio Shack CB antennas.

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I used my Rigexpert AA-600 to sweep the antenna SWR bandwidth; it easily covers the entire CB band and then some with no adjustments. I just attached the whip, tightened the set screw and measured it.

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Power hook-up

The MB2 CB comes wired with a cigarette / 12v accessory plug as standard. My vehicles still have this plug, but some users with newer vehicles without this plug may want to cut off the plug for other connections. If you're going to move this radio between vehicles or use on the base with a power supply, I suggest inserting a set of Anderson Power Poles to give you ultimate flexibility when hooking up for power. (Hint, if you're going to use Anderson Powerpole connectors, use authentic ones such as these sold on Amazon. The copy cat ones will cause nothing but grief.)

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For a basic radio, it has a fairly full feature set: AM and FM, VOX, 6 different digital roger beeps, a Lock to prevent accidental changes, and even an automatic squelch (ASQ button) that works really well.

Audio Tests and Mic

For initial audio tests, I had my wife drive the car away from the house and key up on both AM and FM so I could hear how the radio sounds (video of this audio demonstration coming soon). Retevis told me that the supplied mic is an electret condenser type. The resulting audio on both AM And FM is clear, but underwhelming as it doesn't have nearly enough gain. You have to put your mouth right up on the mic so you lips are touching to get enough audio out of the radio. I've provided feedback to Retevis that the mic and mic gain is something that needs to be improved, but consider that this is an entry-level radio at an entry-level price point. The mic is a 5 pin DIN connector, which is a bit unusual in the CB world, but it's fine. Retevis supplied me a pinout of the mic; I verified that it is indeed an electret condenser as I measured 5v present on pin 1, which is not currently documented in the manual.

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Power Output and Mods
As I said earlier, Retevis has produced a radio that complies with FCC regulations, from a power-output perspective. Hooked up to a power meter, I see that on AM it keys at about 3.5 watts average carrier and never exceeds 4 watts average under modulation. When measuring PEP using a Bird 43P and 50 watts slug, I get mixed results, and I'm not sure why...I suspect it has something to do with ambient or transistor temperature. One day, I measured 4 watts carrier, and16 watts PEP (into a dummy load, of course). and another day it only measures about 12 watts PEP. Either of these measurements are considered acceptable, for a stock, FCC compliant radio. On FM, you strictly get 4 watts of output.

But it getts better. Retevis has supplied a power modification inside the radio from the factory. There is a white wire jumper on the main board toward the front of the radio, next to a 3 pin jumper block. If you clip this wire, new functionality and power output capabilities are unlocked. In this image, you can see that the "L" LED Is lit up., which means "Low". Under un-modified circumstances, neither the "Low" or "High" LEDs function. After modification, you can change power output by long-pressing on the AM/FM button.

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On Low power setting, the radio power output is the same as out-of-the-box. But when the radio is in High power mode, I measured as much as 18 watts FM! The AM carrier on High is 8 watts, but it still only peaks somewhere between 12 and 16 watts. The high power output for FM is significant and will really help extend the range over the stock 4 watts. But on AM, the carrier to peak ratio isn't right and on-air reports described the audio as "muffled", as you would expect with a situation like this. For use on AM, I recommend leaving the radio on low power, but on FM, high power is your friend.

Frequency Modifications
The MB2 CB is also intended for use in other regions, such as the EU. To change regions, you simply move the jumper on the 3 pin jumper block to suit your needs. The explanation, as well as a footnote about the power mod follows:

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Other Considerations
I inquired about other useful design features designed into some CBs such as high SWR protection and RX overload protection. As expected, these design choices were not built into a radio at this price point. However, I have intentionally keyed up the radio at both high and lower power settings into a high-SWR load and the radio seems to function fine...YMMV.


Final Thoughts
The Retevis MB2 CB is an affordable yet feature-rich radio at its price point that features both AM and the newer authorized FM mode. It is available in two versions on Amazon: Radio only, or Radio with 45 inch Mag-mount antenna. The mic and mic gain could be a bit better, while the high power mod is very useful for FM operations. Overall, the radio and supplied antenna are plug and play with no adjustments needed. The Auto Squelch (ASQ) works surprisingly well. Overall, this is a good, entry-level radio for the individual, intended for the operator just wants a basic radio for communication on a road trip, while 4x4'ing, or even around the ranch/farm. I hope Retevis is committed to this market, and it will be interesting to see what they come out next based on the feedback I've provided.
 

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