SDR vs FT-991A

Discussion in 'Software Defined Radio (SDR)' started by W4MUF, Jul 16, 2019.

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  1. W4MUF

    W4MUF 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.
     
    NY4Q and KA0HCP like 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
     
  9. KF5PAL

    KF5PAL Ham Member QRZ Page

    I have both the 991A and a RSP1A as well. Each has its own strong points. For the under $125 price tag, the RSP1A is amazing. I do find the 991A Rx to be a tad better in most circumstances but, the SDR with well tweaked sw is not far behind. Where these 2 devices really shine is when they are used in a combo and you take advantage of each of their strong points. Use the RSP1A as a panadapter displaying a big chunk of spectrum sync'd to the FT991A for point and click tuning. Use the 2 to work the satellites full duplex.
     
    N3AWS and PY2RAF like this.
  10. KC8QVO

    KC8QVO Ham Member QRZ Page

    I read through this thread again and noticed the post dates. The one prior to yours was dated July 19 of 2019, 4 months ago. That's not a bad thing, but reading your statement of the comparison between the RSP1a and 991A and how you tie the two together as a panadapter makes me curious what you were searching for (as if you had a question about the two to work together) to find this older thread? If the information about how you tie the RSP1a to the 991A as a panadapter was the point - why hide it in this thread and not separate it as its own thread on that subject? It just seems odd to me to add the panadapter information to an old thread on a different subject, that's all.

    On a side note, I have a 991A also and never thought about the panadapter idea you mention. I have thought about that on other rigs (I tried it with an FT-857D years ago with an actual spectrum analyzer in a service monitor years ago, not much luck) but since the 991A has a panadapter in it I never gave it much thought.

    However, the above having been said - one limitation of the panadapter (built-in screen) in the 991A is it is a feed off the sole VFO/IF in the radio. That means the VFO can not tune the rig up and down the visible band live on the screen - the visible band on the screen is centered on the VFO (receive, if you have split enabled the receive is what it will track) frequency. This makes it impossible to scroll to signals on the waterfall and spectrum without the waterfall and spectrum bringing those signals to the center (disrupting the flow of them).

    You reference the panadapter use of the RSP1a allowing "point and click tuning" of the 991A. Do you have a pre-VFO level tap of the IF so what feeds the RSP1a is not affected by the VFO of the radio to allow the waterfall and spectrum to remain stationary while the radio VFO tracks up and down it?

    For what it is worth, I did find you can pause the spectrum and waterfall displays on the 991A and then scroll to signals. However, pausing it means they aren't drawing live so no new signals come in during the time of the pause. You have to unpause, redraw, and pause again to maintain a more up-to-date screen to view as you tune.

    If am thinking about this correctly, also, the A upgrade to the original 991 was the split live tap of the IF to feed both the receiver (conversion to AF) AND the spectrum/waterfall screen live. Whereas the original 991 worked somewhat like the FT-1200 screen where it would take "snapshots" to display. During each "snapshot" sweep of the spectrum the audio is muted as the feed to the receiver is transferred to the display for the "sweep" time. I got to sit with a 1200 once and that drove me up a wall. Though, I am assuming the draw/sweep rate of the screen on the 991 has always been fast (both the 991 and 991A) its just the A model added the simultaneous operation of the feeding of both the receiver and screen from the same source. For a radio in it's class (covering 160-6m, 2m, 70cm) being able to do that is still pretty slick. It looks like the IC-705 (although a portable/low power radio) is the only competition in display ability in an HF radio that covers 2m and 70cm also (though not out yet).
     
    Last edited: Nov 19, 2019

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