Re: uBITx v5 - with mods

Ashhar Farhan
 

ravi,
which firmware version are you using? it might help to trace a signal. inject a 100mv signal and trace it with a scope on the rx path..
- f

On Sun, Jun 9, 2019 at 11:35 AM MVS Sarma <mvssarma@...> wrote:
Ravi jee, 
Just use kd8cec , select the lcd type in ubitx.h, select ver5 on main file, just compile. 

Later pwer on Nd while calibrating  change bfo to 1105550 and click ptt and save. Also power cycle.
Later select wwv and complete calibration.if needed few steps of bfo.

You should succeed. Atb
Sarma vu3 zmv



On Sat, 8 Jun 2019, 8:14 pm Ravi Miranda <ravimiranda@... wrote:
Hi All,

Apologies for the long post.

Background
I built a V5 using the circuit here:
http://www.hfsignals.com/wp-content/uploads/2019/02/ubitx_v5.pdf

I have also included the mods (BFR106) and changed the resistors as
specified. Only the RX stage has been enabled.
For the stages I used :
http://w7zoi.net/bidirectional_matched_amplifier.pdf keeping the
original values intact

The ladder crystal filter has been built with 11.0592 Mhz Crystals.

The voltages for the RX side (only) transistors are as follows:
Q10 [C] (9.33)     [B] (2.02)      [E] (1.31)
Q11 [C] (11.69)    [B] (9.33)     [E] (8.62)
Q12 [C] (11.69)    [B] (8.62)     [E] (7.89)


Q30 [C] (9.12)     [B] (2.06)      [E] (1.38)
Q31 [C] (11.69)    [B] (9.12)     [E] (8.45)
Q32 [C] (11.69)    [B] (8.45)     [E] (7.75)

I have not used the AGC circuit as given in the original V5 but opted
for the LM324 version. However, this is not  enabled.

I have taken the Panadapter out from just before the ladder filter
(post the stage 2 TIA). This is connected to SDRSharp to check signals

For the software, I used the V1.2  with frequencies calculated based on KD8CEC:
http://www.hamskey.com/2019/02/whats-new-with-ubitx-v5-1-changed-if.html

I  used the following values:
#define SECOND_OSC_USB (56054200l)
#define SECOND_OSC_LSB (33940800l)

#define INIT_USB_FREQ (11059250l)

According to the notes in KD8CEC's blog the firstIF has been set to
45005000L due to L7 and L5 pulling the crystal filter by 5KHz

Using the PanAdapter tap point that has been provided for I can see
that the signal passes through at just about 45.000.000 MHz, but at
times (start up) the signal can be heard on SDR# on 44.993.400.


Going backwards, I have used a signal injector from the input of the
audio amp to the output of the crystal stage and have a good noise
injection level at the speaker. If I use the signal injector at the
input side of crystal filter there is no sound.

I am using a local MW station on 1458KHz as this is the only station
that I can hear via SDR# (AM). The beat seems correct.

I can hear this station on the uBITx speaker very faintly (if I put my
ear next to it).

I am unable to copy any Ham stations or WWV or any other HF broadcast stations.

On start up I can hear a slight crackling noise through the speaker,
but have no clue where this is being generated.

To ensure that the SI5351 was calibrated correctly I used :
https://groups.io/g/BITX20/wiki/Si5351-Calibration-Sketch

and saved the value in the program

I have a RF milivoltmeter (homebrew) using a AD8307 and LM358
(uncalibrated), this is showing signal levels at testpoints. I haven't
done a thorough test at all points yet.

I have injected a 20mV(approx) using a AD9851 into the antenna input I
can hear the zero beat (14.150). With a stronger signal injection the
speaker jumps around quite a bit :-)

I have the following few questions ( few)
1. How do I know that the uBITx is tuned correctly
2. The volume level through the speaker is very poor.
3. Are the voltage levels on the transistors correct?
4. Shouldn't the Pandadapter (RTL dongle + SDR#) show the spectrum of
a larger bandwidth rather than just the tuned frequency at 45MHz?
5. Are the stages amplifying correctly?
6. How do I locate the source of the crackling? This dies down in a few mins.

I have access to a DSO, what checks can I do to verify the working and
improve the sound level?

Thoughts suggestions and comments welcome.

Sorry once again for the long post and thanks for reading. Have a great weekend.

Best 73,

Ravi/M0RVI










--
I'm here to add more value to the world than I'm using up.



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