Flex-1500 and WSJT-X with JT9
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Flex-1500 and WSJT-X with JT9 Expand / Collapse
Posted Tuesday, August 27, 2013 8:12 AM
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Any comments to this post are welcome, but this is mostly aimed at Dudley and the guys in tech support.

The new software from WSJT (WSJT-X ver 1.2 beta) allows you to view and decode both JT65 and JT9 signals at the same time. Typically, the JT9 frequencies are roughly 2khz above the normal JT65 operating frequencies, such as 7.076mhz for JT65 and 7.078mhz for JT9. PowerSDR-2.64 will allow me cover both sub-bands by extending the RX filter from 0hz to 4100hz. There is a setting in WSJT-X to decode JT65 signals from 0 to a certain offset (I set mine to 2600hz) and JT9 signals above that offset. Then I can see and decode both JT65 and JT6 signals at the same time. This is actually pretty cool and only SDR radios and some of the newer production radios have this capability to extend the receive bandwidth beyond the typical 2.7khz SSB bandwidth.

However, some JT9 signals are very close to or at 4000hz above the dial frequency. While these signals are correctly decoded, I cannot reply to signals in that upper range because the transmit filter (if that is the correct term to use) is not that wide. While the transmitter is correctly switched to transmit mode, the transmitted audio is outside the range of the transmit filter, so no signal is sent. It appears that the upper limit for transmitting is about 3625hz from the dial frequency. Anything above that transmits nothing.

I am wondering if this is a limitation of the PowerSDR software, or a limitation of the internal sound card in my laptop? While this is not a show stopper, it would certainly be nice to be able to cover the entire frequency range without resorting to using split transmit mode to cover the upper ranges. This works but is not as slick or cool. If the transmit filter range was able to be extended just a little bit, this would work perfectly.

Mark Griffith
Post #6815
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