The receiver Retekess V115 (also known as Tivdio V115 and Kaimeda SRW-710S Mini and Audiomax SRW-710S and VR robot WC-710S and HanRongDa K-603) version F9205A came into my hands when I ordered it on AliExpress to replace the lost Tecsun PL-310ET. We needed a compact and inexpensive all-wave CB-HF-VHF-FM receiver with direct frequency input and good sound.

Purchase

I ordered the V115 receiver from the official Retekess store for 1220 rubles. The hyperlink was removed on 08/31/2023 in order to avoid violation of Federal Law No. 274 of 06/24/2023 “On Amendments to the Code of the Russian Federation on Administrative Offences”, paragraph 16 of the Law (administrative liability: for failure to provide information about online advertising to Roskomnadzor). The law comes into force on September 1, 2023
Delivery is free. The order was made on May 6, the receiver was delivered by courier to the house on May 11. The total delivery time was 11-7=4 days.

Packaging and accessories

The Retekess V-115 receiver came in a white cardboard box.

Inside the package are instructions in English, a BL-5C battery, a miniUSB cable for charging from a 5V adapter, and the receiver itself.

The receiver is small, fits in the palm of your hand and fits into any pocket. Dimensions - about the size of a pocket dictionary.

Battery - BL-5C with a capacity of 1000 mAh.

It lasts for 10 hours of listening at medium volume. Charging is slow, from the adapter 0.5-1A, takes about 2.5 hours. (The manufacturer prohibits the use of 2A fast charges).

When you turn it on for the first time, a welcome message appears, then the receiving frequency of 4.750 MHz is turned on.

Looking ahead, the receiver has a continuous tuning range from 4.750 to 21.8 MHz, without gaps. AM modulation, 5 kHz step.
There is also an FM band 87.5-108, which can be switched through the menu to 64-108 MHz. Step 0.1 MHz.
In the medium wave range, the step is 9 kHz (for the eastern hemisphere - ITU region 1).

First of all, the sound is surprising for such a small receiver - clear and with a confident baritone. Noticeable on percussion instruments and double bass. Songs and pop music also sound more spacious on the V115 compared to the “flat” sound of the Tecsun. This uses a small bass reflex port on the rear panel of the case. But there is no “muttering” or body resonances; I don’t notice them. The maximum volume is high, there is no distortion.

Field trip May 14, 2022

I took my relatives to the garden - May is the time to plant potatoes. At the same time, I checked the receiver when working with the built-in telescopic antenna. Also, I had to learn how to operate the receiver.

The case on the right side has no buttons, but it has rich connection options:

• 3.5 mm headphone jack
• linear input "Line In" (the receiver can work as an external speaker)
• memory card slot
• connector for charging from a microUSB cellular adapter
  

On the rear panel there is a battery compartment, the ability to install a listening stand on a table, and a subwoofer output.

The Retekess V-115 receiver has three tuning modes:

• automatic search for stations across the entire range: activated by long-holding the central "Play / Pause" button with storing the frequencies of radio stations in memory (in this case, old assignments are overwritten - this function is not a duplicate of ETM, since the receiver is inexpensive, the search is somewhat simplified).
• shift HF range button S.W., then scanning up or down within a range, the stop occurs at the next radio station.
• manual frequency input numeric keypad 1,2,3,4,5,6,7,8,9,0 and confirmation with button "input" play/pause.

Volume adjustment - with a key in the form of a swing: "-" down and "+" up.

There are no control knobs, nor are there any +5 kHz buttons. Therefore, at first the control is confusing, but then you get used to setting the frequency using the buttons and begin to control the receiver quickly. (Enter the frequency using the numeric frequency buttons and confirm with the "play/pause" key). From my point of view, buttons are more durable than variable resistors or a rotary encoder.

There is a "Menu" button - when you hold it for a long time, you get to the receiver settings. You can change the step in the medium wave range of 10 or 9 kHz, select the language - there is Russian. Also, I recently discovered the possibility of switching on “Soviet VHF” from 64 to 74 MHz.

On VHF radio stations are entered into the memory bank during scanning. Each scan that the user initiates by long-holding the play/pause button overwrites the bank cells. There's no temporary ETM memory here, but that's not a deal-breaker considering the price. There is a function for deleting the contents of memory cells (if the receiver has clogged the cells with weak stations or interference, these cells can be cleared). After removing a frequency from memory, the remaining cells retain their numbers.

Radio stations can be called up like channels in a regular radio using buttons such as 23 and "enter" (play/pause). Or enter two numbers and wait 6 seconds.

When receiving short waves on the built-in whip antenna, in the absence of transmission, internal noise of the receiver is heard - rattling with a frequency of 25 Hz. (I was even upset about this at first).

The recording was made at 09:33 UTC, frequency 17650 kHz - radio of China to Europe. A crackling sound is heard - internal noise from the processor and digital lines.

Later, as it turned out, reception was excellent in the evening bands SW4-SW5 when the strength of the signal from the antenna suppresses internal interference. This will be discussed in the next article about using an external antenna.

Reception of local FM VHF stations is excellent. Recording from the Retekess V-115 speaker to a mobile phone voice recorder without processing.

Addition dated May 17 about reception of weak VHF transmitters

Sensitivity in the FM range is sufficient for 100% reception of all radio stations within the city. From a room located in deep “shade” the reception is subjectively better than that of Tecsun. In the “Soviet” VHF range, reception is also subjectively 2-3 times better than that of the Tecsun PL-310ET.

However, in an open area 10 km from the city, the reception of distant, weak radio stations in the FM range is interfered with by powerful local transmitters, from which numerous weak “phantoms” are heard at free frequencies - duplicates, with a hearing level of . Obviously, for DX reception on VHF you need to travel 50-60 kilometers outside the city, where the influence of transmitters from the metropolis is reduced. A higher-class receiver (for example, in a car radio) copes with reception in the city and is not overloaded.

According to N9EWO, the article on QSL.net uses the AKC 6951 / 6955 chip from the Japanese company ETC, instead of the American Silicon Laboratories Si 473x.

Sensitivity according to datasheet:
*AKC 6951 - 7 dbuV = 2.2 uV*(at Mod=22.5k Ref. out, SINAD=30 db)
Si 4730 - 1.1 uV**(at (S+N)/N=26 db).

Record radio to MP3

Charging the battery

It is better to charge using a micro USB adapter with a small charging current - 0.5...1 Ampere.

Links:
*Retekess V115 manual translated into Russian on the official website
V115-Russian.pdf.

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