Topics

New uBitX - Start up Questions...

Steven
 

Hi All! I'm Steven KM4WIP. I have just completed assembly of a uBitX. It was my reward for passing the Extra Class exam last month.

The rig is built on a metal baking pan. When I plug in the 12v line, it lights up right away, that is good news. The on/off switch seems to only work with volume - is this correct? Volume does work.The VFO push button works, I can get to menu choices. I heard some garbled SSB and some clear CW on 40m. It won't transmit. And there is no CW sig at key down.

So here's my most obvious question. With the mike plugged in the VFO just sits on (I think ) 7.500 MHz. When I unplug the mike I can tune the VFO. Any clues?

Also is there an initial set up I need to run, or should this rig be able to plug in, tune in, and transmit?

Thanks!!!
Steven KM4WIP

_Dave_ K0MBT
 

Congrats on the upgrade.

Definitely odd behavior. Is the radio going into transmit when you plug in the mic/ptt? That is what it sounds like to me. Check the wiring make sure that the resistor is across to the ptt.

Doug Hall
 

Hi Steven,

Congrats on the upgrade to Extra Class. 

It sounds like you didn't wire the switch contacts in series with your +12V power, but instead you have the +12V power and ground going directly to P1 on the board. If you want the on/off switch to turn the radio on and off then you'll need to run the +12V leads from the rear panel power jack to one side of the pot-mounted switch and then another wire back from the other side of the switch to the +12V connections on P1. The connection diagram shows a switch in series with the power lead - that switch is the one that is part of the volume control.

As far as not being able to tune when the mic is plugged in, it definitely sounds like the radio is going into transmit mode when you plug in the mic. You can't change frequency while the rig is in TX mode. Remove the mic and check between the ground of the mic plug and the ring connector. I'm betting your ohmmeter will show a short there.

As far as initial setup - I had to do the BFO frequency adjustment on my radio when I built it. This involves putting the radio into setup mode and then selecting BFO adjustment from the menu. Then you turn the VFO knob until the audio passband is in the right place - basically until a sideband signal "sounds" right. If it's too far in one direction the audio will sound very tinny with no low frequency response. If it's too far in the other direction it'll sound muffled. When you're happy with the setting you press the PTT button once to save it. So you're gonna have to fix that mic short before you do this part since you need a working PTT button.

Good luck,
Doug K4DSP

Steven
 

Thank so much Doug and Dave.  Will let you know the results this weekend when I have time to mess with projects.

Steven-KM4WIP

Christopher Ryan
 

Does anyone know the LO Drive level being used with the double balanced mixers off-hand? I suppose I could look it up on the data sheet for the synthesizer, but not in a place to do that at the moment.
Christopher

Jerry Gaffke
 

The uBitx mixers use schottky diodes, they are level 7 mixers.
They don't quite see 7dBm from the LO though, they get several dB down from that.
So the receiver loses a few dB of dynamic range at the top end, not a major issue.

Jerry, KE7ER


On Thu, Aug 1, 2019 at 03:43 PM, Christopher Ryan wrote:
Does anyone know the LO Drive level being used with the double balanced mixers off-hand? I suppose I could look it up on the data sheet for the synthesizer, but not in a place to do that at the moment.
Christopher