CW ok, SSB 0.3W - how come?

[sp5xyz]

TLDR: SSB power way to low, CW power ok, on USB or AC or a battery

Hi everyone,

I am observing relatively peculiar behavior.

- (tr)uSDX bought from UP STORE, LO version, already soldered and in a 3D printed case, with preprogrammed call sign

Scenario:

1. Antenna is measured with nanoVNA showing SWR less than 1.5 for a given frequency
2. (tr)uSDX is connected via USB port to the computer. Computer is not connected to a AC power, it's running on battery
3. When i press PTT when i am in CW mode power meter (the one bult in (tr)uSDX) shows power level which is to be expected according to the specs with this voltage (4,5V)
4. But when i choose the LSB or USB mode the power meter shows 0.3 W
5. But, and bear with me, when i connect 12V from a battery, on CW mode it shows power around 5W, even bit higher, but in LSB or USB mode it shows 0.3W, sometimes even 0.2W. Doesn't matter if it's 12V from a lead battery ora 13.8V from a AC adapter - the result is exactly the same.


6. So (with the antenna's SWR measured with nanoVNA) i introduced ATU-10 into the (tr)uSDX - antenna connection, as it is (i hope so) able to measure power. Unfortunately it shows the exact values as (tr)uSDX shows in both described cases.

7. RX works great all the time

Has anyone had similar issues? What am i doing wrong? Did i burnt something? Is there any menu option that can cause such behaviour?

My knowledge about electronics is virtually non-existent unfortunately.

Any info or help will be deeply appreciated

Best

Przemek SP5XYZ

[sp5xyz]

I am replying under my own post as i don't know how to edit the previous one - i am sorry.

I think i found the reason, and the reason is my lack of knowledge.

When i plug the device via USB to a computer with a driver and WSJTX suddenly i saw 3W in TX mode.
And then i struck me - CW is much more "condensed" than SSB, and not only i have to press PTT, but as well do something to "drive" the transceiving, ie to call a CQ with my voice...

Sorry i bothered you.

[dl6sez]

Hello OM Przemek,

no problem we all make mistakes
Nice to see it works as expected.
A little hint: be careful with antenna tuning, i use every time the dits in cw (by pressing ptt and cw with iambic mode) and an atu-10 as you use....
So why? Your class-E PA built in the (tr)uSDX is very good in efficiency >75% and therefore reflected power from bad SWR can easily kill the FETs. The PA FETs can't stand the reflected power to dissipate and die.

73 de Chris

[sp5xyz]

Thank you very much for your kind answer and helpful tips.

Yes, after some time of reading this forum I still don't know much about PA FETs but I know I have to take a good care of them and be very aware with SWR.

73 de Przemek