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Where is the HF digital modes activity?

Discussion in 'Working Different Modes' started by W0BTU, May 9, 2011.

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  1. K0RGR

    K0RGR Ham Member QRZ Page

    I have built a number of the KH6TY interfaces that were in QST a short while back.

    This interface provides audio isolation transformers in both transmit and receive lines. It uses the center tap on the primary of the transmit side transformer to double the voltage from the PC audio, then runs it through a rectifier/voltage doubler circuit again, to provide high enough voltage to fire a transistor that serves as a PTT switch.
    It will work with about any radio, in place of a VOX circuit.
  2. W0BTU

    W0BTU Ham Member QRZ Page

    The one I just built is very similar, but without any PTT circuit. I'm using VOX in lieu of PTT. Rig is an IC-765.

    (When I was using a laptop for PSK31 ten years ago, I didn't have the ground loop problem I now do, and so I didn't even need the transformers. Just a resistive voltage divider to cut the signal level from the sound card to the IC-751A's mic input.)

    All the PSK31 interface schematics that I've ever seen key the transceiver's PTT line. Why? Why is there a need for any type of PTT circuit in a PSK31 interface? We have to run audio to the transceiver's mic input, so why not just use VOX? What am I missing here?
    Last edited: Jun 1, 2011
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Already doing that. :) I just need more than 1GB, so HRD is faster. I just downloaded DXLab under Virtualbox/XP last night, but haven't had time to do anything more than install it.

    Thanks! I was looking around 7.070 and 7.080, per Wikipedia.

    I like the sound of that.
  4. W0BTU

    W0BTU Ham Member QRZ Page

    I've done some reading about this mode, and am somewhat confused.

    There are at least three groups about JT65 on HF. Their very group names imply that there are different implementations of JT65 on HF:

    The spots on all say "JT65A". I see no "JT65HF" spots.

    And I've found different software for JT65 on HF. Which software do you recommend?
  5. G0GQK

    G0GQK Ham Member QRZ Page

    Oh there's plenty of activity, you just have to get yourself a good antenna and point it towards Europe. Radio conditions have been poor lately, things will improve towards September, try 14.070 and 21.070.
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