Q: "Malachit" SDR receiver"??

Discussion in 'Software Defined Radio (SDR)' started by WB2GCR, Mar 13, 2021.

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  1. EI4HWB

    EI4HWB XML Subscriber QRZ Page

    Did you bother checking if it's the same version?
    I'm not affiliated with the designer, I just share what I could find about this receiver with this forum.
     
  2. N2DTS

    N2DTS Ham Member QRZ Page

    The Hermes lite 2 has a much more limited dynamic range. 12 bit A/D converter at 80 Mhz I think.
    The guys on 3885 could overload it.
    The airspy seems to be overload proof, even when I TX 300 watts carrier it does not overload.
    I have NEVER seen it overload.
    It also covers vhf, plus its much smaller, you could put about 15 Airspy's in a Hermes, plus its powered by the USB port,
    the Hermes needs 12 volts.

    It would be very interesting to have the airspy or something like it hooked up to a nice big tablet, maybe velcro it on and
    use the tablet touch screen to power and control the airspy.
    A large well working Malachit...


     
  3. N6YWU

    N6YWU Ham Member QRZ Page

    The HF+ has an internal AGC controlled attenuator, so it makes one think its not being overloaded by turning down its RF gain before one notices. You can get the same input signal reduction with an HL2 by manually turning down its RF gain, or using SDR software AGC, which can engage its internal attenuator.

    The HL2's 76.8 MHz sample rate plus filtered sample rate reduction inside the FPGA provides a lot more than 12 bits of usable dynamic range in practice (not on the lab bench), due to RF noise dithering plus DSP processing gain . The Airspy HF+ also uses a high sample rate sigma-delta ADC plus sample rate reduction for processing gain. So the 2 implementations are actually somewhat similar. I think the difference in actual usable dynamic range might be "only" 3 to 6 dB. But some good comparison lab tests, using realistic RF inputs, is needed to confirm this.

    The HL2 is usually assembled into a metal case to provide heat sinking for the 5W of Tx. But if you only want to receive, the bare HL2 circuit board works outside the case, and fits in an square greeting card envelope. The HL2 uses a networked connection, so has a bit lower in latency for QSK use, and etc. Because of the network connection, the HL2 also works with just an iPhone Mini, even smaller than an Android tablet with an HF+.

    I have both an HL2 and an HF+, and use both. I also have an RSP2 (which uses a Mirics tuner chip like the Malachit), but don't use it for HF, mainly due to its IMHO strange installer and undocumented software driver.
     
    Last edited: Apr 3, 2021
  4. N2DTS

    N2DTS Ham Member QRZ Page

    Yes, however it does it, the Airspy hf+ discovery works very well.
    Any agc action is transparent.

    Transmitting 300 watts (1200 watts pep) locally did not overload the airspy, while strong ham signals on 80 meters did overload the HL2
    in default settings.

    I did turn of the RF preamp on the airspy on 40 meters and down as it added slightly to the noise level, but still did not overload.

    Most tablets have a USB connector, but most do not have an ethernet connection, so how would you set the HL2 up
    to talk to the tablet?
    Some sort of wifi out of the HL2?
     
  5. WB2GCR

    WB2GCR Ham Member QRZ Page

    to be fair, I just now went and looked.
    Yes, that looks to be an even earlier version of the "manual".
    Unfortunately, the criticisms remain.

    IF I knew enough about some of the settings, I would go ahead and write one myself.
    Should I do that, it would remain incomplete.

    People seems to be mostly poking at it, and seeing what stuff does - then you post on one
    site or another, and someone comes along and the routine goes something like this:
    - did you read the (useless) manual?
    - your version of the software is NG, go buy the "official" software
    - oh, just poke it here and set it like this...

    Now, that doesn't happen here very much, but it has gotten frustrating and annoying to
    try to get good information...

    Anyhow, I have it running, and I like it well enough, sitting as a standalone off the back of the R-390A.
    (given what I paid for it... at the full boat price? No way) It's NOT going to be competitive with a
    real receiver, imho. I would not use it as my main receiver in the shack. No way.

    _-_-
     
  6. EI4HWB

    EI4HWB XML Subscriber QRZ Page

    I guess it was never meant to be the main receiver in anyone's shack. In my case it's going to be my travel companion.
     
  7. WB2GCR

    WB2GCR Ham Member QRZ Page

  8. N6YWU

    N6YWU Ham Member QRZ Page

    Even fast WiFi connections very often have latency timing issues with the HL2. For just SWL/receive only, a fast WiFi connection though an access point over a fairly clear WiFi channel will sometimes work. But for a reliable connection and for portable ops Tx, I use a Lightning-to-ethernet dongle so I can run an ethernet cable directly from my HL2 to my iPhone or iPad. Or a USB-C-to-ethernet dongle between my M1 MacBook Pro and my HL2. The dongles seem to add less latency that network routers. The HL2 self-assigns itself an IP address (usually 169.254.19.221) if there's no router or DHCP server in between.
     
  9. N6YWU

    N6YWU Ham Member QRZ Page

    Are there any small portable multi-band RF preselectors or preselector kits?
     
  10. N2DTS

    N2DTS Ham Member QRZ Page

    I thought it might be useful for finding noise sources.
    Bear has a good idea in using it on a fixed frequency and mode.
    The problem is, you may turn it off and it may never work again...
    Two of mine had the screen go away, the radio worked but no display no matter what I did.
     

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