MFJ 1708 SDR

Discussion in 'Software Defined Radio (SDR)' started by KF5NAJ, Dec 14, 2018.

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  1. KF5NAJ

    KF5NAJ Ham Member QRZ Page

    When using a MFJ 1708 SDR it appears to be making the switch from Trans to Rec, problem is that I can hear myself thru the speaker the whole time while I'm transmitting not just a little spike at the end

    Thank you
     
  2. WB2CAU

    WB2CAU Ham Member QRZ Page

    The MFJ-1708SDR is intended to switch the antenna off the SDR (or any receiver) when you transmit and ground the antenna input to the external receiver (SDR). It does not provide a means to mute the audio on the receiver. According to the manual I downloaded for the MFJ-1708SDR there is no provision to use a contact on the relay to mute the audio. However, the MFJ-1708 (non-SDR) does have an auxiliary contact to use for such a purpose. I don't know why MFJ didn't provide that on the SDR version.

    Maybe MFJ had a reason for the exclusion, or maybe it was an oversight. I was about to order one myself earlier this year until I noticed the provision lacking. I figured sooner or later enough users would complain and they would come out with a new version with the provision. Then I will order mine.

     
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    There is a unused contact on the relay that switches to ground that could be used for mute.

    upload_2018-12-16_7-14-49.png
     
  4. KF5NAJ

    KF5NAJ Ham Member QRZ Page

    Thank you
     
  5. KB4MB

    KB4MB Ham Member QRZ Page

    I use my rig to receive audio, and just use the sdr as a panadapter (no audio)... this will also solve it. The reason is even though it is disconnected on transmit, there is enough bleed through to be picked up just fine with the antenna disconnected (when transmitting).
     
  6. WB2CAU

    WB2CAU Ham Member QRZ Page

  7. N2DQG

    N2DQG Ham Member QRZ Page

    I got the original 1708 and not too happy with the results. The swr on 2 meters increased from 1:2 to a crazy 3:2 contacted MFJ still waiting for a callback. checked so239 connections internally all have continuity tried playing with delay etc. still no good.
     

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