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SDR: No longer just a budget option.

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  • #65213
    Profile photo of Joe (G.W.N.S.)Joe (G.W.N.S.)
    Moderator

    Software Defined Radios (SDR) have come a long way in a short time.

    I am not going to attempt to cover all there is about SDR, but will highlight some things I find interesting.

    I’ve recommended them as a budget alternative to various Radios to include Scanners and they can still fill this role.

    Software and hardware options continue get more diverse and they seem limited almost by the imagination of people.

    I’ve been following the various developments in SDR for a longtime and have dabbled in them, but much of the features available were not quite up to my needs beyond redundant backups. I’ve considered building what I wanted, but really didn’t have the time to dedicate to it, so have been waiting for others work proceed.

    Depicted below is one of my basic SDR setups.

    It’s a low cost tablet (Amazon Fire HD 8 $49.00), a RTL-SDR dongle/Antenna (RTL-SDR Blog R820T2 RTL2832U 1PPM TCXO SMA Software Defined Radio with Dipole Antenna Kit $29.95), and a OTG USB Cable.

    This one is running SDR Touch App for Android, but there are many options.

    More to follow.

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    #65218
    Profile photo of Joe (G.W.N.S.)Joe (G.W.N.S.)
    Moderator

    SDR Touch

    SDR Touch supports receiving FM radio, AM, SSB and CW broadcasts including HAM radio amateurs, police, air traffic, weather reports, fire department and emergency stations, taxi traffic, audio of analogue TV broadcasts, digital broadcasts and many more! Depending on the hardware used, its radio frequency coverage could span between 50 MHz and 2.2 GHz. Turn your mobile phone or tablet into an affordable and portable software defined radio scanner. SDR Touch currently demodulates WFM, AM, NFM, USB, LSB, DSB, CWU and CLW signals.

    RTLSDR RTL2832U DVB-T Tuner Dongles

    Briefly, our dongles come with the following improvements:

    <1 PPM temperature compensated oscillator (TCXO) – Accurate tuning and almost zero temperature drift (2 PPM max. initial offset, 0.5-1 PPM temperature drift)

    SMA female antenna port – Generic dongles use the less common MCX or PAL antenna ports. SMA is more common, so more adapters and antennas are available for it. It is also more durable and has lower RF insertion losses.

    4.5V USB powered bias tee – This allows the RTL-SDR to power low noise amplifiers (like the LNA4ALL, HABAMP, RTL-SDR Blog ADS-B LNA) and active antennas through the coax cable. Can be enabled in software (see V3 users guide).

    Experimental: HF Direct Sampling Mode – Listen to 500 kHz – 24 MHz with direct sampling. Simply connect an HF antenna to the SMA port, and choose the Q-branch mode. There is a built in 25 MHz low pass filter, but additional HF filters may be required for optimal performance (e.g. to attenuate strong MW AM).

    Aluminium case and passive cooling – These units come stock with an aluminium case and passive cooling via a silicon thermal pad. This stops reception failing due to heat above ~1.2 GHz.

    Improved Antennas – We provide an excellent dipole antenna starter kit for newbies. Use the included mounts and extension cable to mount the dipole in good position for optimal reception. Receives terrestrial and VHF satellite signals.

    Various additional improvements compared to other RTL-SDRs – R820T2 tuner, higher quality passive components, a choke on the USB line to reduce USB noise, a much improved PCB design for significantly less internal spurs and noise, various break-out pads, improved ESD protection, additional bypass capacitors and ferrite power line chokes, improved front end matching circuit and a better LDO.

    More to follow.

    #65219
    Profile photo of Tomxsquidgator
    Participant

    Have you listened to anything other than commercial FM radio with yours?
    I got one of the $20ish USB dongles and have used it as an FM radio on my PC. (running SDR#)
    I haven’t ever tried setting up my laptop out in the woods when I might be around people using handheld radios like MURS, FRS or the like, and I wonder how effective the little antenna that came with it would be for that application. Seems this thing would offer at least the potential of visually monitoring a range of frequencies.
    Thanks for sharing, until seeing this it hadn’t occurred to me to use a small tablet rather than a PC.

    CTT 10-2014, CTT 1504, RnG/CQB/FoF October 2016, 2017 Georgia CTT/DA, DCH 2018.

    #65224
    Profile photo of Joe (G.W.N.S.)Joe (G.W.N.S.)
    Moderator

    Have you listened to anything other than commercial FM radio with yours?

    NOAA WX, County Emergency Services, ADS-B, and I can certainly pull out commercial FM stations that can’t be received by regular radios.

    Using a tablet for mobile is the way to go, but less options in software. Note: You could even use a Phone vice tablet.

    #65248
    Profile photo of SeanTSeanT
    Moderator

    A couple years ago I did a radio talk up at MVT and had one of these. I was able to show on the screen down in the schoolhouse all the students cell phones as blips in the RF

    if you get 2
    You can use them to decode digital trunked radio systems as long as they are not also encrypted. One monitors the control channel and the softwate tunes the other to the comms freq

    #65249
    Profile photo of Joe (G.W.N.S.)Joe (G.W.N.S.)
    Moderator

    You can use them to decode digital trunked…

    :good:

    Hasn’t been a priority since my immediate area doesn’t use trunked at this time.

    #66107
    Profile photo of FransSaccoFransSacco
    Participant

    Hi..as per my knowledge it has more resolution. More resolution means more dynamic range, less signal imaging, a lower noise floor, more sensitivity when strong signals are present and better ability to discern weak signals. Some SDR’s give their resolution in ENOB which stands for effective number of bits.

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