Loading ...
Sorry, an error occurred while loading the content.

drive levels, isolation and clicks

Expand Messages
  • Hamish Moffatt
    I just bought a new rig (FT-847) and connected it (from the HF DATA in/out socket) to the sound card. I find that receive audio levels are fine and I can
    Message 1 of 1 , Apr 1, 2000
    • 0 Attachment
      I just bought a new rig (FT-847) and connected it (from the HF DATA in/out
      socket) to the sound card. I find that receive audio levels are fine
      and I can afford to use quite a bit of input gain. Transmit audio
      levels are a bit low though; maximum power out through this interface
      is about 50W, although I can do 100W on CW key down.

      I put 1:1 isolation transformers in the transmit and receive audio
      paths. Audio out of the sound card on the MT63 terminal's tune 1 signal,
      or the Feld Hell tuning signal, is about 200mVp-p, which should be
      plenty. On the other side of the transmit transformer, I only get
      40mVp-p (which looks very noisy on the scope, too).

      The unofficial FT-847 FAQ has an interface circuit which suggests
      a 1k:8 ohm audio transformer in the transmit line and no transformer
      in the receive audio. Is that a better choice of transformer?
      I thought 1:1 would have been ideal. (Of course, with the quality
      control at the electronics store, they could be some other ratio
      too for all I know).

      Another problem -- I seem to get clicks in the transmited audio,
      even just listening on the PC speakers. Presumably they've always
      been there. Anyone know why that might be and how I can fix it?
      They seem to occur at all sorts of volume levels. I also changed
      the PC type settings (486/P100/P200+) in the Hell terminal to see
      if that changed the sampling rate and fixed the problem, but there
      was no difference.


      thanks

      Hamish
      --
      Hamish Moffatt VK3SB <hamish@...> <hamish@...>
    Your message has been successfully submitted and would be delivered to recipients shortly.