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JT65-HF Transmit Waveform

PostPosted: Mon Feb 16, 2015 2:09 am
by enghamradio
I am trying to get JT65-HF software working. Receive is OK. When I transmit I am getting an unexpected waveform. It is amplitude modulated. What should the JT65 waveform look like? What can I do to get the correct waveform?

Below are two scope captures of the TX waveform with different timebase setting:

Dennis
KE2GT

DS1Z_QucikPrint1.png
DS1Z_QucikPrint1.png (62.77 KiB) Viewed 5450 times


DS1Z_QucikPrint2.png
DS1Z_QucikPrint2.png (61.32 KiB) Viewed 5450 times

Re: JT65-HF Transmit Waveform

PostPosted: Mon Feb 16, 2015 3:31 am
by W4MMP
Hi Dennis,
I'm a bit of a loss. A bit like jumping into the middle of something. Do other modes work (CW, SSB, PSK)?? Did you get WSPR working?

Re: JT65-HF Transmit Waveform

PostPosted: Mon Feb 16, 2015 5:03 am
by enghamradio
Hi Ron,

I got WSPR working. FM and SSB work fine. I have two Peabody transceivers that were built for different bands. They both work on 40M. They both produce the same TX waveform. I am able to transmit JT65 on one radio and decode the signal correctly on the other radio. Maybe the audio is being overdriven in HDSDR? I tried lower the MIC gain in HDSDR a little. The TX waveform still has the same shape.

Dennis
KE2GT

Re: JT65-HF Transmit Waveform

PostPosted: Mon Feb 16, 2015 5:12 am
by W4MMP
Hi,
Hum, I will need to install JT65-HF and give it a go. The only JT application I run is WSJT-X.
Will let you know what I find.

Re: JT65-HF Transmit Waveform

PostPosted: Wed Feb 18, 2015 2:27 am
by enghamradio
Hi Ron,

I found the problem was the "Input mode for channel TX" setting in HDSDR. I was set to "I/Q". I changed it to "Left channel only" and the TX waveform stopped being amplitude modulated. I was able to make several contacts after the change.

Thanks,

Dennis
KE2GT

Re: JT65-HF Transmit Waveform

PostPosted: Wed Feb 18, 2015 3:32 am
by W4MMP
HI Dennis,
Glad you found that one. I would never have thought of that. I'm a firm believer in KISS and keep things as plain vanilla as possible in my SDR journeys. I don't even use virtual audio devices. I have two USB audio adapters wired back to back to provide audio back and forth between HDSDR and the digital applications :roll:

Good catch. Have fun !

Re: JT65-HF Transmit Waveform

PostPosted: Wed Feb 18, 2015 3:52 am
by AE9RB
W4MMP wrote:I have two USB audio adapters wired back to back to provide audio back and forth between HDSDR and the digital applications


Put your PSoC skills to work and make a dongle. This will give you a perfect VAC with only one USB port.

Re: JT65-HF Transmit Waveform

PostPosted: Thu Feb 19, 2015 3:17 am
by W4MMP
AE9RB wrote:
W4MMP wrote:I have two USB audio adapters wired back to back to provide audio back and forth between HDSDR and the digital applications


Put your PSoC skills to work and make a dongle. This will give you a perfect VAC with only one USB port.


I just may give that a go. I'm looking at the USBFS data sheet as I type. But first I am focused on a new ExtIO_xxx.dll to transparently handle multiple Peaberrys (at least from a frequency control stand point of view). The real tricky part will be making multiple Peaberrys look like one audio device.

Re: JT65-HF Transmit Waveform

PostPosted: Thu Feb 19, 2015 5:28 am
by TerryFrench
Assuming the whole graph stuff (for video) on windows applies there to audio path too, you'd might want to create a mixer. if you set the frequency on the extio dll in the (configurable in a file or registry) range, switch the mixer to 100 audio for one peaberry for that range, 0% for the other. Possibly always multiplex the output to all peaberries.
I'm much less clear on what triggers transmit, as you only want the right peaberry to transmit.