FLDIGI and FLEX SDRs

Recently, I set up FLDIGI to work with the FLEX 5000A. I have made a few contacts including one with QRQcw member, Nathan KO6U. The reports have been good and I do like how it keys the Flex, however I have a "latency" problem which must be fixed before any full QSK QSOs can be made. If any one contacts some one using the FLEX 1k or 5k with FLDIGI, please pass along their call as I would like talk about their CW (A2) configuration. Currently, I am using UA9OV's "CWTYPE" and it exhibits very low latency with either Flex model. Flex has their own cw keyboard called CWX as part of their main software package but when the turn around response is reduced for QRQ, the element and space timing is no longer is acceptable (in my opinion). This will be fixed but in the meantime, CWTYPE is my choice for the now.

Here is the configuration I used with the FLEX:
Added another sound card (simple USB sound adapter - 8 bucks) and it's LINE OUT feeds LINE IN of the FLEX A to D. This avoids using virtual audio cables (VAC) and their inherent latency. The FLEX mode is set to SSB/USB and then the mixer for the USB adapter and FLEX are used to set drive levels (which works fine) for 100 w out. The latency appears to be caused by FLDIGI (using Windows version) rather than the FLEX because this same LINE IN has been used for other modes and I have not found it to cause delays of the magnitude I have now. I hope this is not true and FLDIGI is as responsive as CWTYPE.

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Permalink Reply by Mel Whitten on December 3, 2008 at 3:11pm

Here is an update on FLDIGI CW tx with the FLEX 5000.
First, the latency between keydown and audio out. Chuck, AA0HW came by the shack to pick up a 700 Hz filter from Midnight science so this gave me the opportunity to show him how FLDIGI works with the Flex. Chuck says the author of the progam "built in" this latency (abt a 100ms) that I thought was being caused by the latency of the configuration. I am still a bit "lost" why the program author did this, but those code, rule so I must change how I work QSK (?) or figure out some other way to make work/improve my cw. Without real concern for latency now, configuration became much simplier with no added sound cards. I just used the Virtual Audio Cables (VAC) in the "digital LSB" mode. I then set the tx offset (i.e. 700Hz) and the received sigs fell right into the RX bandpass for CW filters. The audio output level was set to "drive" the TX (just like mic audio) to 75 watts. This configuration was now ready for transmit with one exception! FLDIGI would not control the MOX (PTT) line with a key press! I found the mouse had to be used to click FLDIGI's "TX" button to control the MOX line and output audio. Not good. I did find that a macro from FLDIGI's "CQ" memory outputs a sequence to output audio and put the FLEX in tx. So, I am almost there. I have made a few contacts and had good reports on the cw keying/tone.

Still more work to do for keypress TX and understand why the author added the key press-to-audio out 100Ms delay. Until then, back to CW type. :-)

Mel, K0PFX