Topics

Ubitx alignment


Bruce Morrell
 

I just spent several several days to get the best possible calibration using an oscilloscope, my Ears and Ashhar's audio spectrum analyzer.  The radio has been modified with KD8CEC firmware with 3.2 Nextion display.  The first observation I want to make is that Ashhar and Dr. Lee are geniuses.  This radio does so much with so little.  That being said, what I wish for is better signal to noise ratio.  I compare this radio to my kenwood side by side, where the kenwood picks up weak signals that I have to strain to hear on the ubit.  Before this conversation goes off the rails, I completely understand this is a QRP kit and I should not have high expectations.  That being said, with in the limits of the radio and its current design, how to achieve the best SNR.  

I tuned the LO using an Oscilliscope to precisely 10mhz, and when I hit the PTT turned the radio off then back on it was 18kHZ higher.  It still zero beat WWV at 10mhz with the  BFO is tuned to 11.0562mhz.

So can anyone tell why the calibration freg changes like that?  If I continue to play with it to get a a better calibration will it change my SNR??  Just asking... Bruce KB8MW


Curt
 

Bruce

Great topics. Strain to hear what? Was it a cw signal, and were you using a narrower filter? Or was this ssb? In the same bandwidth,  the ubitx should only be slightly less sensitive,  and you should mostly notice this in upper HF where noise coming in the antenna port is more than the receiver makes.

Frequency calibration. If calibrated to wwv or a similar frequency reference,  the carrier will be at 0 Hertz. Keep in mind none of us can hear 0 Hz. When we listen to cw we hear around 700 Hz or whatever is your favorite pitch. When we listen to ssb speech,  maybe around 100 to 2400 Hz give or take. 18  kHz off? Maybe your calibration isn't taking into firmware.

Taste and see again, there's a wonderful rig there that more around the globe can afford.

73 Curt wb8yyy


Rubens Kamimura
 

Olá todos, 

Tenho uBITX v4, seria um problema de alinhamento a falta de potência RF de 10 a 15m? Na frequência de 7074kHz a potência de saída oscila aproximadamente 5 W. Mesmo ativando "fake It" no JTDX. O circuito LPF 10m e o relé KT1, estão ok.
73
Rubens
py2pvb

Em qua, 20 de jan de 2021 12:48, Bruce Morrell <bmorrelltx@...> escreveu:

I just spent several several days to get the best possible calibration using an oscilloscope, my Ears and Ashhar's audio spectrum analyzer.  The radio has been modified with KD8CEC firmware with 3.2 Nextion display.  The first observation I want to make is that Ashhar and Dr. Lee are geniuses.  This radio does so much with so little.  That being said, what I wish for is better signal to noise ratio.  I compare this radio to my kenwood side by side, where the kenwood picks up weak signals that I have to strain to hear on the ubit.  Before this conversation goes off the rails, I completely understand this is a QRP kit and I should not have high expectations.  That being said, with in the limits of the radio and its current design, how to achieve the best SNR.  

I tuned the LO using an Oscilliscope to precisely 10mhz, and when I hit the PTT turned the radio off then back on it was 18kHZ higher.  It still zero beat WWV at 10mhz with the  BFO is tuned to 11.0562mhz.

So can anyone tell why the calibration freg changes like that?  If I continue to play with it to get a a better calibration will it change my SNR??  Just asking... Bruce KB8MW


Bruce Morrell
 

Thanks for the reply Curt,
I tuned to 40 meters ssb and only heard one faint conversation.  It was not a great signal on the Kenwood but understandable.  
The radio has both IF and RCV shift which should suffice for basic reception,  no other filters. 
So my objective is to increase SNR to get equivalent reception.  The holy grail of any radio.. 

I am trying to understand if the radio is working at maximum sensitivity.  I have to order an attenuator for testing with my frequency counter, It only goes down to 1mv.  I suspect the radio does not have full sensitivity.   I would like to get the most by focusing first on the LO, BFO.  Then trouble shoot the electronics.  

There is not much traffic on 40 meters and at least what my crummy antenna, a 40-10 dipole in the attic allows.  


Curt
 

Bruce

Good idea to compare a signal with 2 different radios. I do remember using IF shift on my ts140 to improve signal to noise ratio.

Keep in mind that stock ubitx does not have agc. On weak signals we must turn up the volume, maybe close to max depending upon headphones and our ears. (Same is true after installing audio agc in the ubitx).

Yes receive bandwidth is a second factor. I use a tunable SCAF, switched capacitor audio filter, cool to have a bandwidth adjust pot on my ubitx. I am using a NESCAF, I don't know if they are being sold this moment. Others use audio dsp. Something to consider adding, but see what your ubitx does when you increase volume or slightly adjust tuning.

Don't give up on your ubitx or your antenna. If you could sneak an end fed halfwave outside or other hidden vertical, it might help.

73 curt


Rubens Kamimura
 


--
Saudações fraternais, 
73's PY2PVB

Rubens Kamimura
Técnico em Eletrônica e Eletrotécnica - Aposentado
CFT/CRT-SP: 80254934820
Cel. +55 (18) 9-9819-2225 WhatsApp
Hello everyone,

I have uBITX v4, would it be an alignment problem due to the lack of RF power from 10 to 15m? At the frequency of 7074kHz the output power oscillates approximately 5 W. Even activating "fake It" on JTDX. The LPF 10m circuit and the KT1 relay are ok.
73
Rubens
py2pvb

Em qua., 20 de jan. de 2021 às 18:33, Rubens Kamimura via groups.io <rubens.kamimura=gmail.com@groups.io> escreveu:

Olá todos, 

Tenho uBITX v4, seria um problema de alinhamento a falta de potência RF de 10 a 15m? Na frequência de 7074kHz a potência de saída oscila aproximadamente 5 W. Mesmo ativando "fake It" no JTDX. O circuito LPF 10m e o relé KT1, estão ok.
73
Rubens
py2pvb

Em qua, 20 de jan de 2021 12:48, Bruce Morrell <bmorrelltx@...> escreveu:
I just spent several several days to get the best possible calibration using an oscilloscope, my Ears and Ashhar's audio spectrum analyzer.  The radio has been modified with KD8CEC firmware with 3.2 Nextion display.  The first observation I want to make is that Ashhar and Dr. Lee are geniuses.  This radio does so much with so little.  That being said, what I wish for is better signal to noise ratio.  I compare this radio to my kenwood side by side, where the kenwood picks up weak signals that I have to strain to hear on the ubit.  Before this conversation goes off the rails, I completely understand this is a QRP kit and I should not have high expectations.  That being said, with in the limits of the radio and its current design, how to achieve the best SNR.  

I tuned the LO using an Oscilliscope to precisely 10mhz, and when I hit the PTT turned the radio off then back on it was 18kHZ higher.  It still zero beat WWV at 10mhz with the  BFO is tuned to 11.0562mhz.

So can anyone tell why the calibration freg changes like that?  If I continue to play with it to get a a better calibration will it change my SNR??  Just asking... Bruce KB8MW


_Dave_ AD0B
 

Keep in mind that changing the BFO will change the calibration of the VFO. 

I once bought a used v4. The owner was utterly convinced that his uBITX receiver was a dud. Several hams on the group tried helping him. He was on the wrong side of the bfo frequency. I think he had changed the volume rheostat for a beautiful aftermarket unit and it didn't work either. I don't remember the impact on the transmitter. 
--
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys


Bruce Morrell
 

Thank you, yes I have noticed change calibration then before they do interact. I may have to come to grips with the radio having a sensitivity problem. Don't look forward to chasing that down.   Bruce


On Thu, Jan 21, 2021, 9:03 AM _Dave_ AD0B <davesters@...> wrote:
Keep in mind that changing the BFO will change the calibration of the VFO. 

I once bought a used v4. The owner was utterly convinced that his uBITX receiver was a dud. Several hams on the group tried helping him. He was on the wrong side of the bfo frequency. I think he had changed the volume rheostat for a beautiful aftermarket unit and it didn't work either. I don't remember the impact on the transmitter. 
--
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys