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Why is the RF gain control not continuous?

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WK2Y
WK2Y Member ✭✭
in SmartSDR for Windows

Just out of curiosity, why is the RF gain control limited to only a few fixed levels, e.g., +10db +20db etc. When I think back to my old HQ-110A. if I remember correctly, it was continuous control. Was the sensitivity control something different than the current RF gain control?


Thanks and 73,

Bob, WK2Y

Best Answers

  • Martin AA6E
    Martin AA6E Member ✭✭✭
    edited March 2021 Answer ✓
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    oops

  • Mike VA3MD
    Mike VA3MD Member ✭✭
    Answer ✓
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    I have a high noise level on 80\40 meter band, I find that the fixed Preamp gain works the best. It is a constant value that make it easier to use. Most modern radios of the last 25 year have a fixed gain preamp with only one selection on or off. With flex 6xxx the use of the preamp and the AGC T makes 80 meters usage for me, there is some great video's that Mike VA3MW has made to take a look.

    https://www.youtube.com/watch?v=OJ36HMBQS7U

    Mike, VA3MD

Answers

  • Martin AA6E
    Martin AA6E Member ✭✭✭
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    In a word, yes. The Flex 6xxx just appears to switch in 1 or 2 fixed gain preamp stages (or attenuators). Old tube radios would have a potentiometer that continuously varied the gain of a single RF stage. The modern radios are much better. You don't need to adjust RF gain very often.

    I yearn for the days when we got real schematics (even block diagrams) for our radios, so we could understand how they work a little better.

    73 Martin AA6E

  • K0FLY
    K0FLY Member ✭✭✭
    Options

    Martin is correct. The Flex RF gain control selects an attenuator or fixed gain RF preamps. Other manufacturers call this function RF preamp on/off and Attenuator on/off. If you are look for a function similar to the RF gain on analog radios use the Flex AGC Threshold slider. I lik e the AGCT function better.

    Gayle K0FLY

  • Mike VA3MD
    Mike VA3MD Member ✭✭
    Options

    I have a high noise level on 80\40 meter band, I find that the fixed Preamp gain works the best. It is a constant value that make it easier to use. Most modern radios of the last 25 year have a fixed gain preamp with only one selection on or off. With flex 6xxx the use of the preamp and the AGC T makes 80 meters usage for me, there is some great video's that Mike VA3MW has made to take a look.

    https://www.youtube.com/watch?v=OJ36HMBQS7U

    Mike, VA3MD

  • WK2Y
    WK2Y Member ✭✭
    Options

    Yes, the whole thing that got me thinking about this was Tim's presentation at QSO Today. Great stuff.

    Thanks.

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