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SDR vs Analog; what is your preference?

Discussion in 'Ham Radio Discussions' started by N3AWS, Oct 10, 2018.

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  1. KV6O

    KV6O Ham Member QRZ Page

    How do you know if a bad is open, unless you listen? With an SDR, you might be monitoring 15 thru 6M in the background. Or gathering propagation data using WSPR or FT8 decodes. It's not like you're listening to 8 nets on 8 bands simultaneously. Working 6M an up contest this becomes useful, especially if your in an area where there isn't lots of activity!

    Lots of folks have a radio sitting on a "dead" band, like 6M. This is no different, but instead of having multiple radios, I can use one and can monitor 10M & 6M, my local VHF repeater, while working on 20M, just as an example.

    There are other possibility as well - diversity receive with multiple antennas, for one. If you're using a beam on a band, having another receiver on the same band on a vertical might be useful, or vertical and horizontal antennas. For some stations with real antenna farms, why switch between antennas pointed in different directions to a single receiver, when you can switch between real-time receivers receiving ALL of them simultaneously?

    It can be a game changer... but nobody is forcing you to use 8 receivers either. :p
    Last edited: Oct 12, 2018
    KA2RRK likes this.
  2. KD8TUT

    KD8TUT Platinum Subscriber Platinum Subscriber QRZ Page

    I'm a huge SDR fan and love the system I've put together. Though you make a good point.

    Being able to receive many band slices is cool. But with my 2 ADCs most of the time I use the second for noise cancellation and beam-forming. I can't listen to more than 2 conversations at once. The closest I've gotten is running a digital QSO while listening to two different SSB QSOs (and that was kind of taxing).

    At the same time having that massive FPGA means I can at a glance see all the activity from 160 meters to 6 meters. Stitched receivers lets me see a whole band at once.

    The upshot is that it's more about processing power than listening to 8 QSOs. Though the radio companies do sell a lot of radios based on all those slices. I dislike that they do not make the pitch based more on people end up actually using the technology.

    Though, in a practical sense, those abilities end up being used to accomplish other goals. But it's not listening to 8 band slices. That's ridiculous marketing-speak.

    Yes my shack is like "NASA": But I'm not about to tell you that your love of superhet radios is bad. All I care about is if you are on the air... I just want to talk to you.
  3. WN1MB

    WN1MB Ham Member QRZ Page

    Please! You can barely begin to imagine what I can imagine.
    W4ZD likes this.
  4. W6UV

    W6UV Premium Subscriber QRZ Page

    I'm not sure I'd want to. ;)
  5. KV6O

    KV6O Ham Member QRZ Page

    Beam-forming is another area I'd like to experiment in. A traditional 4 square uses phasing delays to accomplish directivity, 4 receivers implemented in a FPGA could do this too, but not be limited by a specific band, or one of 4 directions...

    Multiple receivers opens up all sorts of possibilities...
  6. KK5JY

    KK5JY Premium Subscriber QRZ Page

    The four-square also requires physical separation between the antennas. You could do the delay part in software, if you had four antennas with equal-length feedlines, but not the physical separation between multiple antennas.

    Maybe you were already assuming that? :)
  7. AF7TS

    AF7TS Ham Member QRZ Page

    Someone else mentioned software bloat as a downside of SDR, and I want to agree that this is a _potential_ downside.

    One way that SDR is implemented is to have an ADC system feeding a stream of data into a general purpose computer running some standard OS. People do this with Linux, Windows, Android, etc.

    In this case you have _all_ of the issues of bloatware found in these operating systems.

    On the other hand, SDR can be implemented in a tightly coded microcontroller, with minimal bloat. There is still _some_ bloat associated with compilers and the like, and unless you actually do careful machine code review, there is always the chance of code that you don't know about.

    In the extreme case, you have implementations that are hard coded in special purpose chips; at which point it really can't be called _software defined_ radio, but rather something else (firmware defined? mathematically implemented? ) People have called the Cheap Chinese Radios 'SDR', but while the mo/demodulation is done numerically using I and Q techniques, the modulation cannot be changed in software at all.

  8. KV6O

    KV6O Ham Member QRZ Page

    Yes, however the traditional rigid "square" separation wouldn't be so rigid. An in-plane array can do forming. Or some lopsided array. A number of active, broadband antennas at a site, or even multiple sites, can be manipulated mathematically in a digital domain to create synthetic "antennas". You could simultaneously steer a "beam" to capture a desired signal, while rejecting noise in another direction. All done by math - must likely FPGA's with today's technology. A cheap WiFi router does stuff like this today!

  9. KK5JY

    KK5JY Premium Subscriber QRZ Page

    Yes, okay, I thought you were saying something else. My bad. :) I thought you were saying that the software techniques could make a single antenna look like several in a phased array.

    As long as you have multiple, physical, separated antennas, the games you can play in software are indeed virtually limitless.

    Cool stuff.
    N3AWS likes this.
  10. KI3U

    KI3U Ham Member QRZ Page

    Well it sounds like you believe that digital systems cannot tell a lie.

    Berj / KI3U

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