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Ubitx V.5 No Receive

Doug
 

Hi
I have a question I hope someone can help me with. I assembled a Ubitx V.5, and everything seems to work
except no receive.
It transmits cw and  mic. If I hook another transceiver to another antenna, it hears it with 1 watt being transmitted.
When I hook the Ubitx to a receive antenna, it sounds like a receiver with the antenna disconnected.
I can hear some birdies, and some are loud. But, no signals even on 20 meters FT8 frequency.
I checked with an ohm meter from the coax center connector to TP1 and have continuity
I do not have a scope, or RF signal generator or a frequency counter right now.
I know that limits my troubleshooting ability greatly. I used to have all that equipment, but sold it years ago.
I could possibly borrow the equipment.... Any help would be appreciated.... Maybe something simple.
Thanks in advance
Doug.

Edward Reynolds
 

Doug
I’d go thru the setup on the receive side, BFO and SSB,  most likely you are receiving dead air between bands, that’s the only thing that comes to mind. Check some of the V5 setup files on the HF Signals site, mine is setup and working on receive and transmit just fine.
Good luck
Ed N7SNT 


On Mar 27, 2020, at 4:41 PM, Doug <69chevynova@...> wrote:

Hi
I have a question I hope someone can help me with. I assembled a Ubitx V.5, and everything seems to work
except no receive.
It transmits cw and  mic. If I hook another transceiver to another antenna, it hears it with 1 watt being transmitted.
When I hook the Ubitx to a receive antenna, it sounds like a receiver with the antenna disconnected.
I can hear some birdies, and some are loud. But, no signals even on 20 meters FT8 frequency.
I checked with an ohm meter from the coax center connector to TP1 and have continuity
I do not have a scope, or RF signal generator or a frequency counter right now.
I know that limits my troubleshooting ability greatly. I used to have all that equipment, but sold it years ago.
I could possibly borrow the equipment.... Any help would be appreciated.... Maybe something simple.
Thanks in advance
Doug.

Doug
 

Ed
Thanks for your suggestions. I just did the calibration and BFO again. No change. The problem there is that I can not receive any stations
to hear. I heard a tone around 10 mhz. very weakly. Could have been WWV... Not sure.
I'm starting to think I have a defective board....
Again thanks.... If you think of anything else please let me know...
Doug

Curt
 

Check to see if you have a cw sidetone. If you don't have a key, at least carefully put a wire across the key interface. I suggest this as a way to verify receive audio is okay.

Gently tap on your TR relay, mine was stuck once.

One can carefully signal trace a receive chain with your finger, to see where you can couple a signal in. Maybe sounds strange but I have fixed a few receivers this way, except I used a stick on my tube receiver.

Evan Hand
 

How did you calibrate the BFO?  Did you use this page?
https://www.hfsignals.com/index.php/bfo-tuning-aid/

It will work with just about any uBiTx, as all are set up for approximately a 2.7 KHz audio bandwidth between 300 Hz and 3 KHz.  The difference is the BFO frequency.  For the v5 it is around 11.0555 MHz.  You set it up by tuning to a "clear" frequency and adjust the plateau peaks to be between the red lines.  

A simple test to see if the receiver is working, in general, is to verify the change in signal level (static) between an antenna connected and one not connected.  Without an antenna connected it should be very quiet, and get significantly louder when connected.

Most of the receiver signal issues listed on this board are ultimately solved with the BFO and then the frequency calibration process and then back to the BFO, in that order 

NOTE: for the stock v5 uBiTx, the frequency calibration process (non-BFO) will put the rig into transmit mode at 10 MHz.  You need either a frequency counter or another receiver and a dummy load.  You need the dummy load as 10 MHz is not in a legal ham band.  You do not want to send the signal out over the air.

My first dummy load was 4, 2 watt 47 ohm, resistors with 2 sets of 2 parallel resistors connected in series.  Gives you a 47 ohm,  8 watt capable, load.  Good for short transactions with the uBiTx.  You can mix and match whatever you have in your junk box.

My experience with both the v4 and v5 uBiTx is that when calibrated (and an audio amp for the v4) they are very close to my Icom 7300 in receive sensitivity and selectivity for SSB.  Just does not have all of the filter and other features of the "big" rig.

Good luck, learn,  and have fun! 
73
Evan
AC9TU

Doug
 

Hi Curt
Thanks for your response. I do have a cw sidetone and it is loud with the volume turned up.
I hear the relay click when I transmit. I measured continuity from the coax center connector to TP1 which passes thru the low-pass
filter. I also can tune a couple birdies across the spectrum that are quite loud. So I think the audio circuit is fine.
I have a low level rf noise on receive, but it makes no difference in the level with the antenna connected or not. The rf noise sounds
like a receiver with the antenna disconnected. If I transmit with another transmitter, I can hear the cw tone loud with one or two watts .
It makes no sense to me.
Well Curt, thanks again and if you think of anything else I would appreciate the info.
Doug
 

Doug
 

Hi Evan
Thanks for your response.
No, I did not use the method you suggested but will try it soon. That may be the answer.
I do not notice any difference in the rf level in the receiver with the antenna connected or disconnected.
The rf level is very low. I can transmit with the Ubitx just fine.
I hear a few birdies across the spectrum and they can be quite loud with the volume turned up.
I have continuity from the coax center connector to TP1 which passes thru the low-pass filter.
If I transmit with another transmitter with one or 2 watts I can hear it loudly on the Ubitx receiver.
It makes no sense to me, but I will do the BFO calibration as you suggested. I will let you know the
outcome when I'm done.
Thanks Evan
Doug

_Dave_ AD0B
 

Definitely check the alignment. I have seen very deaf receivers caused by miss alignment.  If that doesn't do it, it should be very straight forward to trace the signal. You don't really need much in the way of test equipment. You might start with a probe on the input of the audio amp.

Ashhar has kindly put in many test points that you can test from.  More or less follow the yellow brick road back to the antenna.

This drawing outlines both the transmit and receive signal paths
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys

Edward Reynolds
 

Doug
 With no change in air noise volume connecting antenna I’d look at the antenna connector soldered joints to the board and pl259/BNC connector. Going from no antenna to a antenna you should hear a increase in air noise volume. So look for a cold/bad solder joint and verify the correct wiring of antenna board and back of case BNC/PL259 connector, they could be switched. Just a thought! 
Ed


On Mar 28, 2020, at 5:30 AM, Doug <69chevynova@...> wrote:

Hi Curt
Thanks for your response. I do have a cw sidetone and it is loud with the volume turned up.
I hear the relay click when I transmit. I measured continuity from the coax center connector to TP1 which passes thru the low-pass
filter. I also can tune a couple birdies across the spectrum that are quite loud. So I think the audio circuit is fine.
I have a low level rf noise on receive, but it makes no difference in the level with the antenna connected or not. The rf noise sounds
like a receiver with the antenna disconnected. If I transmit with another transmitter, I can hear the cw tone loud with one or two watts .
It makes no sense to me.
Well Curt, thanks again and if you think of anything else I would appreciate the info.
Doug
 

David Nelson
 

look back in the group. They had a problem with some of the bnc
 connectors shipped with the kits. The center hole being to big for
the pin on the mating connector. I know mine was like that.I just bent
the pin slightly and it worked fine.  Dave  kc2ipx

Doug
 

Hi Evan
I have a question. You said that the BFO frequency for V.5 is around 11.0555 mhz. Mine is at 11.995 mhz. That is a long way off. A lot of turning.
Doug

Doug
 

Hi Dave
Thanks for the PDF. Very helpful.
Doug

 

Wrong firmware Dough! that BFO frequency is for V3 if I remember right.

Raj

28/03/2020, you wrote:

Hi Evan
I have a question. You said that the BFO frequency for V.5 is around 11.0555 mhz. Mine is at 11.995 mhz. That is a long way off. A lot of turning.
Doug

Doug
 

Hi Ed
I checked with an ohm meter from the center connector of the coax to TP1 on the printed board. That is thru the low pass filter. I have continuity.
I could possibly have a cold soldier joint on the pcb. If nothing else seems to works, I will pull the PCB out of the case
and start reheating connections on that path. Thanks for the suggestion.
Doug

Doug
 

Hi Raj
Thanks for that info. Saved me a lot of turning...
Do you know what the approximate frequency of V.5 should be?
Doug

Evan Hand
 

Doug,

Are you sure it is a v5?  That would be closer to a v4. There are two ways to tell:
1 - There is a version # printed on the board
2 - Check the crystal filter crystal frequency stamped on the top of one of the 12 crystals that are all in a line. A v5 is 11.059, a v4 is 12.000 

Another way is to check the audio circuit. The v4 uses discrete transistors, the v5 has an lm386 ic for audio output. 

If a v5 OR v6 bfo were set to that frequency, it would be deaf. 

The BFO needs to be set approximately 3.5 KHz below the crystal frequency, with final adjustments for each board. 


Check the version number and then go to the BFO calibration page 

Hope this helps,
73
Evan
AC9TU

 

Should be 11.055,5 It's close enough.

At 28/03/2020, you wrote:
Hi Raj
Thanks for that info. Saved me a lot of turning...
Do you know what the approximate frequency of V.5 should be?
Doug

Doug
 

Hi Evan
I checked.... It is a V.5.. Printed on the pcb.. It has an IM 386 ic and the crystals are 11.059...
So, when I go to BFO frequency, the frequency should be 11.0555 mhz? I have a lot of turning to do.
It is at 11.995 mhz.....
I will wait till you verify before I start to adjust it.
Thanks again Evan...
Doug

Evan Hand
 

Doug,
11.05550 as Raj stated is the correct frequency for a v5 board.  Before you go adjusting things, can you verify that the stock v5 code is in the Raduino nano?  Have you or anyone else uploaded a new version of the code?

If the answer to the question is that it is still stock, then go ahead and adjust the BFO through the settings process.  There will not be a lot of turning on the original code, as every time you go into BFO Calibration the value gets set back to the stock setting of 11.055500 MHz.

It is very important that we know what software is installed, as clock 1 is different (and constant) depending on the board version.  This makes sense as the target frequency for the filter is now lower, the two values for USB and LSB need to be adjusted so that the signal through the 45 MHz roofing filter is in the sweet spot of the crystal filter.

Again, I hope it helps.
73
Evan
AC9TU

Joe Puma
 

If you have the right firmware I think you can reset to factory defaults first.  I’ll let Evan call it because he is more familiar. 

Joe
KD2NFC 



On Mar 28, 2020, at 12:01 PM, Doug <69chevynova@...> wrote:

Hi Evan
I checked.... It is a V.5.. Printed on the pcb.. It has an IM 386 ic and the crystals are 11.059...
So, when I go to BFO frequency, the frequency should be 11.0555 mhz? I have a lot of turning to do.
It is at 11.995 mhz.....
I will wait till you verify before I start to adjust it.
Thanks again Evan...
Doug