Modern Radios Supporting Wide SSB Reception?

Discussion in 'Ham Radio Discussions' started by KK5JY, Mar 31, 2019.

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  1. KK5JY

    KK5JY Ham Member QRZ Page

    There have been a small number of interesting threads over the past few days on the subject of digital modes that are typically operated without narrow filters. PSK31, JT65, and FT8 are examples of modes where people tend to congregate on a specific dial frequency, and then spread out their signals by placing them in different locations within a USB passband.

    Most of the (box with a knob) radios I have used limit the USB passband to 2800Hz or 3000Hz, but I have noticed that SDR dongles tend to have much more flexibility to select wider passbands without changing the mode. E.g, running GQRX with an RTL-SDR, I can easily select 7kHz or 15kHz, or anything in between. The (software) receiver doesn't care how wide the passband is, as long as the output audio device operates with high enough sample rate so as not to alias the data stream when demodulating.

    I have used that feature to copy several modes at once, e.g., FT8+JT9+JT65, all with a single receiver. Having such a wide bandwidth seems like a great feature for people who want to listen to lots of adjacent signals at once.

    So how many of you have transceivers that can operate USB with the receiver wider than 3kHz? Could you share the make & model with us? SDR, box-with-a-knob, or combinations -- I don't care, I'm just curious what's out there.
  2. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Every DSP transceiver I can think of can do this.

    Even my little Ten Tec Jupiter, which is now probably close to a 20 year-old design (although I bought mine new in 2004) allows you to select an RX passband from 150 Hz to 12 kHz or anywhere between at the turn of one knob. You can also select the TX passband (using a simple one-step MENU function) to anything you wish; depending on the mode. On SSB, I usually select a 3.0 kHz passband with a low-frequency rolloff at 300 Hz; and DSP is "brick wall" filtering, there's no "curve," so when you set 300 Hz as a rolloff, nothing below 300 Hz passes. If you select 3.0 kHz as the overall passband, nothing above or below that passes (although IMD products can cause greatly reduced products at multiples of the modulation frequency).

    Common to almost all IF-DSP transceivers AFAIK.
    KK5JY likes this.
  4. K3XR

    K3XR Ham Member QRZ Page

    KK5JY likes this.
  5. KK5JY

    KK5JY Ham Member QRZ Page

    Really? I have used quite a few DSP radios that don't, which is why I was curious.

    The TS-590, the IC-7100, IC-7200, the FT-450, etc., were all IF DSP radios, but all limited to basically 3kHz (or less) in USB mode.

    I can't remember what my K3 did... it was gone before I cared about this question. :)
  6. AG5CK

    AG5CK Ham Member QRZ Page

    My ftdx 1200 has a knob on the front panel to adjust from 1800 to 4000 hz. The Anan 100 SDR has a range of 0 to 9999 hz.
    KK5JY likes this.
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Compromise radios, not taking full advantage of what DSP can do.:)

    But also, if there's always a crystal filter engaged in addition to DSP, then it's not a "full DSP" rig, it's a combination of analog circuitry and DSP, and the crystal filter will certainly limit what it can do. "Full DSP" (which includes most SDRs) can do whatever the software tells it to do.

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