Questions on Narda rf transfer switch

Discussion in 'General Technical Questions and Answers' started by N0CTL, Apr 15, 2019.

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  1. N0CTL

    N0CTL Ham Member QRZ Page

    I picked up a few of these at the TRW swap and just recently got a chance to look at them in more detail. The are Narda model 130-B0-A1c-4B1, which breaks down to a DC-18GHZ latching transfer switch (SMA connectors). Its got pin 1, pin 2 and ground. Applying 24v to pin 1 or pin 2 switches the latch in the relay and reroutes the signal. Simple enough. But how are these transfer switches used? I've been trying to come up with a way to use something like this and I come up empty. Here's how the connections work when pin 1 is active and then when pin 2 is active:

    Narda Transfer switch.jpg
  2. N0CTL

    N0CTL Ham Member QRZ Page

  3. AA7QQ

    AA7QQ Ham Member QRZ Page

    RF in J1, RF out J2.
    Amplifier between J3 & J4.
    This way, the amplifier is only inline when needed.

  4. WB5WPA

    WB5WPA Ham Member QRZ Page

    It also "wires" the amplifier's output to its input in one position ...
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    I've used them in professional applications such as switching a 50 ohm filter or amplifier in line and bypassing it otherwise using the same basic connections Ed suggested above. I've also used them in lab test fixtures to switch between a bypass condition and the device under test.
  6. WB5WPA

    WB5WPA Ham Member QRZ Page

    re: "I've been trying to come up with a way to use something like this and I come up empty."

    Radios on J1 and J3 will swap antennas back and forth ... (antennas on J2 and J4)
    N0CTL and K7TRF like this.
  7. AI3V

    AI3V Ham Member QRZ Page

    You have a "baseball" switch.

    Look here at page 88: - Satellite Earth Station Handbook ok.pdf

    Up at the top, see the two "baseball" looking circles?

    Those are your switches.

    You could "turn around" one of the lna's (low noise amplifiers) and instead use a power amplifier.

    That what I do with my 5760mhz gear.

    Note that the unused ports of the amplifiers are terminated with a resistor, usually 50 ohms (read dummy load)

    N0CTL likes this.
  8. AI3V

    AI3V Ham Member QRZ Page

    Amp (radio)#1 output J2
    Amp(radio)#2 output J4
    Antenna J1

    You will automatically terminate the unused amp(radio).

    W2VW and N0CTL like this.
  9. N0CTL

    N0CTL Ham Member QRZ Page

    Ohh, ok that's a good use case.. Nice way to switch antennas between an SDR and a transceiver. I do build some QRP rigs (ubitx and others) and this might also work to switch the amp in/out as well. Thanks for the feedback guys!
  10. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Yes, as discussed these are for switching something like a preamp or amplifier in and out of line; normally bypassed, but when energized, then the device is switched in.

    I didn't research that model number, but anything with SMA connectors is not suitable for a high-powered amp, like a typical kW HF amp or anything like that. That the coil is 24V implies the original application was likely airborne.

    I have a lot of Transco coaxial switches like that, but they're bigger and have N connectors and can handle a kilowatt.
    N0CTL likes this.

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