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Yet Another Use for Full Duplex

KD0RC Member, Super Elmer Moderator

I recently added CW keying to my TeensyMaestro using the Flex TCP/IP API for remote operation. I assume that I am doing it the same or a similar way as the Maestro does (that is just a guess...) so this might be applicable to Maestro owners who operate remotely and wonder about their keying quality over a poor link.

I discovered when keying over the LAN, I had to add 30 ms of delay to prevent choppy CW. This week when I was operating remotely from one of my mountain fishing spots, I had to set it up to 100 ms to get clean keying. My cell hotspot barely works at this location, so I thought I should check to see if the 30 ms would be adequate (it wasn't).

To check on my keying, I went to a quiet band, opened a second panadapter and put slices A and B on the same freq ( CW, of course...). I set my RF power to 1 on ANT 1 of Slice A (TX) and RX A on Slice B. I then turned on FDX and keyed the rig over the WAN (not with CWX). I kept increasing the Delay until I got clean CW, then added a bit more for safety.

Full Duplex is a really useful tool for setting transmit parameters (like CW Delay) because it lets you hear your signals directly over the air. In my case, since I was away from my shack and spare receivers, I could do everything remotely and get a definitive answer on my keying quality.

I am guessing that setting the Delay to a higher value, gives more time for my 6400 to buffer up key on and key off API commands. Since a time stamp is part of the "key" command, the radio can reconstruct the CW accurately using the timing sent by the TeensyMaestro. Maybe Tim or Mike can confirm (or deny) that this is how it works.

This little exercise makes me keenly aware of just how difficult it is to make a real-time, timing-critical mode like CW work over non-real-time media like the Internet. It is counter intuitive that our simplest mode (CW) is so difficult to get right remotely.

Note that using CWX to transmit over the Internet is a different animal. It sends ASCII characters which are then translated to CW by the radio. Dots and dashes are essentially perfectly timed, and the only delays that may occur are between letters.


  • Ken Wells
    Ken Wells Community Manager admin

    Which Delay are you adjusting?

    The CW Delay? (which adds delay after you stop sending before returning to Receive)

    or the TX Delay? (that adds a delay BEFORE sending any RF out after the PTT or CW Key has been pressed)

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Hi Ken,

    CW Delay.

    I use the key 1 API command to key the rig and key 0 to unkey (with the time stamp and other parameters, of course...).

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