Audiomax/Kaimeda SRW-710S
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Very cheap (c $25) portable battery powered radio receiver, My interest was in utilizing this receiver in a rural type location, well away from all the man-made QRM & QRN, so that I could tune into |
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The times and frequencies and transmitter locations have all varied.
At the present time (2019) signal strengths from the
US transmitter sites can be very weak at my QTH in Perth Western Australia!
Text & images are decoded using the free (Text and ImagesVia Analog Radio)
Tivar App which is installed in my mobile phone.
Click to enlarge
However, quoting from : www.reddit.com shortwave: thoughts and experiences on the retekess v115
The SW sensitivity is poor. Really poor.
Even when it does pick up sw stations, the V-115 is really prone to imaging problems
(i.e strong FM signals plow through and over power the SW signals).
You will likely hear the SW signal and the FM signal at the same time,
which makes the SW signal unlistenable.
Just treat this machine as an FM/AM DSP radio and you will be happy.
Don't even think about attaching a wire antenna to boost SW sensitivity, it won't help.
The radio overloads easily with a wire antenna.
Because the SW band (HF) reception is so poor, I did some on-line research, and it seems that the
Shortwave (and FM) RF pre-amplifier transistor; Q3 an SMD J8 (decodes as BCX71JR PNP)
which when replaced with a BFR93A NPN 'should' restore the missing sensitivity!
The Russian radio-buffs seem to be a good source for information on the topic.
With SMD components much dexterity is needed removing and resoldering!
Even a retro-fit of BFR93A did little to improve performance on ShortWave bands!
After trying numerous other ideas, what I ended-up doing was;
remove C24 and "break-out" pin 20 (ShortWave in) of the AKC6955 digital signal processor
then connect it to the output of an outboard RF pre-amp
The V115 now picks up many stations across the HF spectrum!
It seems, that what was needed, is a tunable 'preselector' RF front end
to make the V115 perform as you might expect!
Click to enlarge
MANUFACTURER'S SPECIFICATION
Model Number: V-115
Frequency:
FM: 87-108MHz
AM: 522-1710KHz (9K), 520-1710KHz (10K)
SW: 4.75-21.85MHz
Memory: Support Micro SD/TF card, Max 32GB (not included)
Audio format: MP3, WMA
Output power: 2W
Power supply: 1000mAh BL-5C lithium battery (included)
Charging: DC 5V, Micro USB interface
Color: Black
Main Item Size: 12.0 x 8.0 x 2.2cm / 4.72 x 3.15 x 0.86in
Main Item Weight: 162g / 5.71oz
Package Size: 13.3 x 10.7 x 3.8cm / 5.23 x 4.21 x 1.49in
Package Weight: 211g / 7.42oz
Package List:
1 Retekess V-115 Radio
1 BL-5C Battery
1 USB Charging Cable
1 Hand Strip with Bracket
1 English User Manual
The outboard tuneable RF pre-amplifier covers 4-22MHz approx.
and is based on a design from Amateur Radio Mag' May 2004 by Drew Diamond VK3XU
A high-impedance input JFET amplifier followed by BJT emitter follower low-impedance output.
A small red LED gives a 1.6V source bias to the FET and also is a Pwr On indicator
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The receiving system in use, in local bushland July 2019.
References:
RetekessRadio V115 facebook page
Full Review of the Tivdio V115 AM FM Shortwave portable receiver
Tivdio V-115 AM/FM/shortwave MP3 recording radio review & test
TIVDIO V-115 Review Most Surprising Radio?
Do It All! Tivdio V-115 Clone AM FM Shortwave Portable Radio Review
Tivdio V-115 FM AM SW Portable Radio Receiver With Mp3 Player Recorder
Kaimeda SRW-710S on SW with BFR93A
To improve the reception you can simply replace J8 transistor with BFR93A.
С транзистором BFR93A на входе
Tivdio V-115 with input transistor BFR93A
Decoding the SW Radiogram Broadcasts with TIVAR (Mike Agner, KA1JJZ)
TIVAR Quick Start Guide (Mike Agner, KA1JJZ)
© 3Q 2019