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Ubitx V3 Rx problems #ubitx #ubitx-help

Impulsive.force@...
 

My uBitx v3 has been working fine and I added a usb audio card and 2 port hub with a separate PSU, this has also been working very well.

I was experimenting with FLDIGI and attempted to change the frequency by clicking in the 'present freq' window and typing in a value. This immediately resulted in strange behaviour from the Ubitx, clicks, pops, jumping frequency.

Now I have very low audio and 'whistles' as I tune through bands. I have changed the audio amp and its the same, supplies are ok, the Tx appears ok (CW, FT8, SSB audio). The Rx has lost volume and sensitivity and there is more noise but less signal - although FT8 still 'works' it is clearly much worse. The basic Rx does not get any better if I fully disconnect the USB sound card.

I am on the original software as supplied.

Doesd anyone have any idea why the Rx should have got much worse?
Blown relay drives?
Arduino/Osc problem?

Thanks for any help given
Bob

_Dave_ K0MBT
 

What have you found out. Perhaps a loose wire on the audio jack where it leaves the main board. Wiggle it. I doubt if it is serious.

I had a low whine on one used radio and vfo was off about 2kc. I could hear the stations but the whine was persistent. Perhaps you mods are pulling the voltage too low or worse injecting some power into the ubitx.

Impulsive.force@...
 

I have removed all modifications (which were only to speaker and mic via capacitors) - no change
I have replaced the audio amp - no change
I have reloaded the original software - no change

My scope is not very good (only 20MHz) but checking the clocks CLK#0 is at 12MHz about 1v p-p on main boad
Using my frequency counter I get CLK#1 switching between 33MHz and 57MHz (USB/LSB)
and CLK#0 at 59.1 MHz when tuned to 14.1MHz which is the correct 45MHz tuning and the frequency changes with tuning
So although I cant check the waveshape and amplitude (dont know what amplitude is should be but si5351 datasheet indicates 0.6 VOL to 3.3-0.6 VOH)

Something has definately changed on the board and I can hear soft 'clicks' as I tune the frequency, the audio signal is very quiet but I can tune signals. There are now whistles at some specific frequencies where as I tune the tone chages with each 100Hz tuning step. e.g.
14,180.7 audio tone perhaps 5Khz
14,180.6 audio tone perhaps 2KHz
14,180.5 audio tone perhaps 1Khz
14,180.4 audio tone perhaps 500hz

Any help with what to test would be a great
Thanks to all - Bob


So something is wrong

Curt
 

I am thinking it is something simple.  check raduino connection to main board - is it firm or flopping around?  Possibly you could have lost some I/O signal.  Same for seating the wire bundle connectors. 

Give unit a good shake in case you have a strand of wire someplace. 

See if you really have a path from antenna to the board.  If this has opened up or shorted out, you would hear some of the clocks and things that used to be below the noise.  I would check DC continuity for the whole path until we reach a blocking capacitor.  or on receive only, bypass stuff to take a clipped wire from antenna to close to the 45 MHz input. 

Although its annoying, its part of the journey.  Put your DVM and scope to use -- most of us have only simple test equipment also - and can debug just fine. 

Curt

Ian Reeve
 

On both my unit,(v3 unmodded and v4 modded with Mention screen) I find that the antenna changeover relays (tx to rx)give problems making on receive signals fade out or are very quiet.A few presses on the pot will restore normal receive for a while.May be worth a look.  Regards. Ian M0IDR


From: BITX20@groups.io <BITX20@groups.io> on behalf of Curt via Groups.Io <wb8yyy@...>
Sent: Friday, May 24, 2019 5:39:15 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Ubitx V3 Rx problems #ubitx #ubitx-help
 
I am thinking it is something simple.  check raduino connection to main board - is it firm or flopping around?  Possibly you could have lost some I/O signal.  Same for seating the wire bundle connectors. 

Give unit a good shake in case you have a strand of wire someplace. 

See if you really have a path from antenna to the board.  If this has opened up or shorted out, you would hear some of the clocks and things that used to be below the noise.  I would check DC continuity for the whole path until we reach a blocking capacitor.  or on receive only, bypass stuff to take a clipped wire from antenna to close to the 45 MHz input. 

Although its annoying, its part of the journey.  Put your DVM and scope to use -- most of us have only simple test equipment also - and can debug just fine. 

Curt

Impulsive.force@...
 

Firstly, thank you all for your help and encouragement.

Then I found that the Rx worked better when the coax shield was not connected at the tuner... so the cable could then work as an antenna... trace cable back to base of vertical and I find the coax core has broken!!..

Normal service has been restored - just got to re-assemble the unit and another lesson has been learned!
:-)
Thanks again