ICOM 735 and SDR Switch

Discussion in 'General Technical Questions and Answers' started by VA7SKW, Aug 15, 2021.

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  1. VA7SKW

    VA7SKW Ham Member QRZ Page


    I recently received an SDR switch from Banggood. I plan to use it with my ICOM 735 and SDRPlay RSP1A.
    I bought the switch based on favourable reviews online and on YouTube, where it performed well and looked to be well built.
    However, there are no instructions whatsoever. I understand that this is an RF sensing switch, but it also can be triggered by a PTT line out from the transceiver.
    Question: Where on the ICOM 735 should I connect the PTT line to? Some reading I've done suggests that I connect to the "send" jack on the rear panel.

    Thanks in advance.
    Best 73's and good DX
    Scott- VA7SKW
  2. AC7ZN

    AC7ZN Ham Member QRZ Page

    A copy of the IC-735 user manual can be found here:
    Refer to pages 12 and 13. The SEND jack (10) is what you want to connect to.

    The I'm not sure your unit is a copy of this but it might be similar:

    Glenn Ac7ZN

    VA7SKW likes this.
  3. VA7SKW

    VA7SKW Ham Member QRZ Page

  4. W4NNF

    W4NNF XML Subscriber QRZ Page

    I would strongly advise connecting the "Send" keying line, "PTT") to the switch and looking upon the RF switching as a failsafe. ;)
    VA7SKW likes this.
  5. KI5OMM

    KI5OMM Platinum Subscriber Platinum Subscriber QRZ Page

    I have that same switch. The PTT line will switch whenever the contacts are shorted. So if you have a jack on your transceiver that shorts to ground when you key the microphone, it will work.

    That being said, I was not all that impressed with my switch. You need to remove the jumper inside in order to enable the PTT if I remember correctly. Once that is done, then the super bright red LED xmit light stays on constantly with no way to turn it off which is annoying. Lastly, while it does kill the antenna connection, my RTL-SDR will still pick up my transmit RF anyway even without an antenna, enough to blow up the waterfall display every time I key up. Lastly the relay is pretty loud which is also annoying especially when using vox on a ragchew. I ended up taking my unit offline till I have more time to mess with it.
    VA7SKW likes this.
  6. KD9VV

    KD9VV Ham Member QRZ Page

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