Alfred Electronics Attenuatiator Help

Discussion in 'General Technical Questions and Answers' started by KI5DJ, Feb 22, 2021 at 9:48 PM.

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  1. KI5DJ

    KI5DJ Ham Member QRZ Page

    Need help with how to wire this up for use and specifically wiring unit for use. Do I feed it DC or AC and how. Any help would be appreciated. It came from an old HP Spectrum Analyzer.
     

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  2. W1NB

    W1NB XML Subscriber QRZ Page

    Wiring it for what? What are you trying to do with it? Have you looked for the service manual on line for the spectrum analyzer from which it was removed? That should give you an idea of how to control it.
     
  3. W6MK

    W6MK Ham Member QRZ Page

    There are lots of pin diode attenuator schematics to be found simply by googling "pin diode attenuator."

    That should get you started.
     
  4. KI5DJ

    KI5DJ Ham Member QRZ Page

    Just want the ability to use it for say a receive antenna for a SDR yet mute the input when using a station transmitter.
     
  5. W5RKL

    W5RKL Ham Member QRZ Page

  6. W1VT

    W1VT Ham Member QRZ Page

    PIN diodes work better at VHF--it is hard to find diodes with enough carrier lifetime to be low distortion on 160M.
    If you find the low band distortion excessive this is likely to be the reason.

    Zak W1VT
     
  7. W1NB

    W1NB XML Subscriber QRZ Page

    Don, if you can tell us what model spectrum analyzer it came out of its possible we can find information on the correct wiring.

    As far as the SDR is concerned, you may be better off with just a make/break relay setup on your antenna controlled by the PTT line on your transmitter. I am assuming your transmit antenna is separate from your SDR antenna.

    Feed the relay common to the receiver. Terminate the break (normally closed or NC) side of the relay with a 50 ohm resistor to ground. Feed the make (normally open, or NO) side through to the antenna. When your transmitter is in standby, the antenna will be passed through to the SDR. When you key the transmitter, the relay will close and the antenna feed to the SDR will be terminated.

    If the transmit antenna and the SDR antenna are the same, then you will want a slightly more complex relay configuration and, preferably, a relay sequencer. Also, if you are receiving into the VHF and UHF bands or higher, you will want to use coaxial relays rated for your transmit power and highest operating frequency.
     

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