SDR vs FT-991A

Discussion in 'Software Defined Radio (SDR)' started by KN4LXH, Jul 16, 2019.

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  1. KN4LXH

    KN4LXH XML Subscriber QRZ Page

    I have an SDRPlay rsp1a. When I connect it to my hex beam and then compare it to the receive on my FT-991A
    I find that the receive capability of the rsp1a is not nearly as good as the 991A. Is this normal? What is your experience?

    Jimmy
    KN4LXH
     
  2. PY2RAF

    PY2RAF XML Subscriber QRZ Page

    Hi there Jimmy,

    A FT-991A owner here.

    While I can not give you precise explanation, I can try to give a few guesses and opinions. So take my post with a grain of salt.

    While designing a panadapter board for my 991, I had the radio schematic all the time at my side - Since I don't hold a Electrical Engineering degree, lots of times I resorted to the radio schematic to find out "how someone that actually designs stuff for a living dealt with this problem". And I took a lot of ideas from my radio schematics. Yes, this is a well thought product, when you spend some good time at the schematics you start getting dazzled. I would highly recommend you. The Main Unit (pages 36-38) is amazing.

    In the end Jimmy, I found that the 991A transceiver is a equipment that is carefully crafted to perform a specific job. It works with a very narrow bandwidth (15 kHz tops), has a good lot of LPFs and BPFs (I have characterized a few of them in https://forums.qrz.com/index.php?threads/ft-991-a-preselector-rx-filter-characteristics.661132/ ; notice that there are *more* filters in the RX stage), selectable (and non-selectable) amplifiers, and it was built around picking up those narrow signals for analog (CW, SSB, AM, FM) or digital (C4FM) signal in this specific bandwidth, at specific band/frequencies. It is indeed a speciality hardware. And you pay... a grand for it.

    Now take the RSP1A. While some would surely buy it for a ham radio companion, it on the other hand it has big ears: It can receive up to a 10 MHz chunk of spectrum at time, while your radio works with... 15 kHz (or 3 kHz), tops. Not all RSP1A buyers has the same use case.

    So we have a speciality device versus something that is crafted to suit a lot of other potential use cases - There are compromises that the designer has to take into account.

    Taking this all into account, I built my overengineered panadapter and fed it to a RTL-SDR. I wanted to take advantage of the radio speciality signal conditioning and processing just before the roofing filter, without the need of antenna switchers, taps, relay boxes and for the current tuned radio band - then I'm limited just by the initial pre-selectors (input BPFs). And man, I'm enjoying it. Details in https://github.com/rfrht/FT991A-PAT/tree/NoUSB

    I am sorry for not being able to give you a precise answer, and as I told you - take this with a grain of salt :)

    My best regards, 73s de PY2RAF - Rodrigo.
     
    WD4IGX likes this.
  3. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    $109 dongle versus $1119 purpose built (per the above post) radio?

    Yeah, normal.
     
    KA0HCP likes this.
  4. N0YPD

    N0YPD Premium Subscriber QRZ Page

    My HF radio is a Yaesu 3000,and i also have an SDR Play and AIRSPY- HF ,and i gotta rate the airspy hf a little better,as far as filtering,and other audio settings. When i compare the airspy to my HF rig I really can't tell much difference. I do have the airspy in line with a t/r switch. So its easy to do an a/b comparison.
     
  5. VA3VF

    VA3VF Ham Member QRZ Page

    The RSP1A is one of the best values around, but that does not mean it's the best SDR out there. I had one, and replaced it with an AirSpy HF+. For my needs, and operating conditions, the HF+ is much better. Still, the HF+ may not be the best SDR out there. The upcoming HF+ Discovery 'promises' to be even better than the HF+, at a lower price.

    All that said, knowing how to 'drive' the SDR is critical. One can make a Perseus perform poorly, and an RTL-SDR to do a lot better, by not using the software properly with the former, and properly with the latter.
     
  6. KI5X

    KI5X Premium Subscriber QRZ Page

  7. K2XT

    K2XT Premium Subscriber QRZ Page

    What do you mean? That question could mean almost anything.
    Are you talking about overload capability, signal filtering, noise figure, audio quality, sensitivity, phase noise, spurious responses?
    The fact that software and the capabilities of the required computer are an integral part of the sdr system it makes it nearly impossible to agree with your observation or answer your question.
    If you could be a bit more specific........
     
  8. KU3X

    KU3X Ham Member QRZ Page


    I have both and you can not expect the same performance out of the SDRPlay as you can the FT 991A.
    Your results are as expected.
    Barry, KU3X
     

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