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I recently completed assembling my QDX and and updated the firmware. I have been testing it before stuffing it into its case. WSJT has no reported problem controlling the QDX. It receives on all four bands as expected. I wound T1 3:2, get 4.4 watts out with 12 volts power on 40 meters and have made several contacts. On the other three bands I can receive, and on selecting tune or transmission the led indicates transmission, but there is zero.zero watts power out. The current draw also does not increase from that of receive mode.
From the 40 meter Xmit I know the PA transistors are good. Since I don't see a higher current draw on Xmit on the other bands I assume it's not that the other LPFs are hosed. The led indicates transmission so the controller got the message and from 40 meters I know it can activate transmission. Any ideas what to test next?
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? 73
??? KD8CGH

Hello Bob,

Congratulations on your 40 meters success.? This does indicate that the build is most likely OK.? Hans Summers has written a post that describes what some of the causes might be for low or no power output.
/g/QRPLabs/message/74132

Based on your symptoms, I would suspect that the USB audio connection is being interfered with.? Look at the?"TX" signal and "RX" signal?section of the post.??

Note that there are two conditions to get power out as stated in the post.? The one is being met: The CAT command to set the rig in transmit mode is being received.? I suspect the other one, a valid tone from the PC, is not.? The most likely cause of this is that there is RF blocking the USB audio when it first keys up and quickly knocks out the USB connection for long enough to drop out the TX signal.? The CAt command is still active, so it appears to be in transmit mode.? This is supported by the current draw NOT going high as it does on 40 meters.? One possible way to verify might be to try transmitting into a shielded dummy load and see if you get power on all bands.

Hans indicated steps to take to address this issue.? My suggestion is snap-on ferrites, as that worked for me with my other RF-sensitive rig to computer connection.? In trying to find out the cause of my low power issue I have blown the BS170s and need to replace them before I can verify that the ferrites work for me with the QDX.

Out of curiosity, what are you using for an antenna?

Good luck and happy hunting (for the bug).
73
Evan
AC9TU

Thanks Evan
?? I put the QDX in its case. The USB cable has ferrites on both ends. I also coiled the excess length and tied it together.
For these tests I'm transmitting into a dummy load and using 9 volts power, so I only have 2.4 watts out (T1 is 3:2).
? I still saw the same behavior. Flashing led with power output on 40 and flashing led but no RF out on 20, 30 and 80 with no current draw on those bands above receive.
? My low band antenna is a lazy (drunken?) sorta vertical 57' long that runs from the remote tuner at the corner of my garage to the top of a nearby tree. There is a buried radial field of wires out to the edges of the yard. Since I use a remote tuner there is close to 1:1 on the coax leading in, but I also have several turns of coax through 6 FT240-43 torroids. There's also a box with relays that switch in a loading coil for 160 m so the antenna can be tuned easily and it disconnects and grounds the antenna when power is off.

? Good luck with your low power problem.

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? 73
??? KD8CGH

Bob,

Maybe try another PC if you have one.? As my posts in other threads have stated I am having issues with one of my Windows PC.? The Raspberry Pi seems to work fine.

The lack of current draw when in TX mode to me is an indication that the tone is not getting to the MPU.? Do you have the power setting in WSJT-X all the way up?? You cannot overdrive the audio, as it is only looking at the frequency.

73
Evan
AC9TU

Evan
? You were right on with the power setting. I had set it up on 40 but it was still down at mid-level on the other bands. I was sure that I had set them all.
? I found something unexpected about WSJT-X. If you set the power level when you're not transmitting, the next time you transmit it reverts back to the old level. If you're paying attention to something else, like your power/SWR meter, you might not notice.
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? 73
??? KD8CGH