Re: Si5351 correction question
Hi Jerry,
When I replied with a suggestion he told me he is not using a Bitx40 nor uBitx nor a raduino nor any of the Bitx or uBitx software. -shrug-
73,
Bill KU8H
--
bark less - wag more
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Re: Si5351 correction question
I have not heard of others in the forum voice concern about the si5351 calibration changing.?
Unless you are using different firmware or there is an error in the firmware,
that sounds like the 25mhz crystal reference oscillator at the si5351 has changed a bit.
If you have a good second rig that can receive 25mhz, perhaps bring a short
antenna from it close to your uBitx and listen to the 25mhz oscillator, see if
you can hear it move, perhaps when blowing hot air on the si5351 board.
Assuming your firmware is using the si5351bx routines that Farhan's original release was using,
then the correction factor says how many hertz off from 875mhz the vco internal to the si5351 is.
The clock output frequencies and the rig operating? frequencies will be moved by a factor?
exactly proportional to to that correction factor, assuming your firmware is written correctly.
For example, you report two different correction factors of 15380 and 14210.
So in the first case, the vco was at 875.015380 hz, and in the second case at 875.014210 hz,
and the vco moved by 15380-14210 = 1170 hz, slightly more than a 1ppm difference.
That could be attributed to temperature or power supply differences around the si5351 and crystal.
A rig operating at 3.5mhz would have moved by? ?3.5mhz * (1170/875000000) = 4.68hz
If the rig was operating at 28mhz, it would have moved by 28mhz * (1170/875000000)?= 37.44 hz.?
Unless you are operating in one of the narrow band digital modes, those shifts are not of much consequence.
If you are operating in a narrow band digital mode in a varying temperature environment,
you may need a more stable reference than the 10 cent? 25mhz crystal supplied with your si5351 board.
There are si5351 boards out there with a TCXO (temperature compensated crystal oscillator)?
from QRPLabs and Etherkit.? ?The QRPLabs board can be GPS disciplined.
Or I suppose you could look into rubidium oscillators.? ?;-)?
I don't know if you are experiencing temperature or voltage changes around the si5351,
or exactly how much the frequency would shift if you did.
It could be that you have a more sensitive crystal than most, you might experiment with
swapping it out.? Better yet, get a different si5351 board.? Preferably one with a TCXO.
You might try cleaning the area around the si5351 and 25mhz crystal with alcohol.
Jerry, KE7ER
? ?
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On Sat, Nov 3, 2018 at 07:04 AM, Mark Pilant wrote:
My main puzzler is why, given the same Si5351 and Arduino boards, did the correction
number need to change to get the correct output frequency?
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Hello everyone! Today I played a little with my Ubitx, I made a lot of contacts all over Europe. After a while I decided to listen myself on a SDR located somewhere in Norway because I wanted to play a little with the BFO. By accident I have sellected "Set Calibration" instead of "BFO" and everything was messed up, I couldn't hear or transmit nothing at all. I was lucky because I have a configuration file for backup and now I am back on the ionosphere. I am wondering, is there a website from where we can download this configuration file with the .btx extension? If someone else wants this file with the default settings, leave me a message. Thanks!
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Re: Si5351 correction question
Hi Mark. What firmware are you running? None. The calibration sketch is here: This sketch simply programs the Si5351 as an oscillator, no USB, LSB, offset, etc. Hi Jerry. I'd recommend the algorithm of post /g/BITX20/message/54501
( /g/BITX20/message/54501 ) for calibration. I'm eventually going to be doing something similar to what was mentioned in your post. My main puzzler is why, given the same Si5351 and Arduino boards, did the correction number need to change to get the correct output frequency? 73 - Mark N1VQW
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Sorry for the above message. The audio is there its just very low. I should have checked
the info on the web site re this problem. and? Shall? have to get an amplifier to boost the audio
A Redface Regards
Fred Aunger (G6FJA)
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Re: the cause for the spurs, found!
Correction:
After seeing your results I feel the stage is OK for upto -5 dbm
input output where as the actual input
is -30 to -40 dbm. The output of the stage is max -10 dbm and so
the input will be 15 -20dbm
less (i.e. gain of stage) So your Bidi amp is good to go.
At 03-11-18, you wrote:
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Raj
The input VSWR with that mod increased the input VSWR to around
7:1.? (measured 0-30MHz, my current setup)
I didn't check before the mod but assume its closer to 1:1.
glenn
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Re: the cause for the spurs, found!
Thats a given. The stage becomes a high impedance input.
Try a 470 Ohms parallel with input to compensate the resistors
removed.
We did discuss the notch but I have not tried.
After seeing your results I feel the stage is OK for upto -5 dbm
input where as the actual input
is -30 to -40 dbm. The output of the stage is max -10 dbm and so
the input will be 15 -20dbm
less (i.e. gain of stage) So your Bidi amp is good to go.
So where is the offender, it is the strong harmonics of the final that is
getting coupled from
the relay contact loops and into the input of the Bidi amp which is
getting overloaded !
This unholy mix of signals is causing spurs.
Replacing the stock top contact relays with bottom contact AXICOM of Mike
Doty relays reduces
the loop size and so the coupling to L5. I noticed if the stock 45MHz
filter is mounted high by 3mm
then the spurs increase, it needs to be close to the board. That gave me
the clue!
The harmonics are also getting picked up by L1/2/3/4 !
1: Change the relays and you will see major relief. DO NOT mount in
sockets, they add to the loop.
additionally but may not be needed for your board.
2: Change L5/7 will make a small change only if the relay is
changed.
3: Change L1/2/3/4, one of my boards became unstable if any wires or
finger was near.
4: Add another 45MHz filter at the Bidi out to clean up after the Bidi
but with a big power loss.
5: Do't over drive on higher bands. Drive settting that gives 10W on 40M
is fine on all bands
with only relay change. We need a audio clipper / hard limiter for the
next board.
Raj
At 03-11-18, you wrote:
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Raj
The input VSWR with that mod increased the input VSWR to around
7:1.? (measured 0-30MHz, my current setup)
I didn't check before the mod but assume its closer to 1:1.
glenn
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Re: the cause for the spurs, found!
Glenn,
pleas keep in mind to check the output of Your signal generator,
mostly the ahrmonics are in the same range i.e. about -30 dBc to
the main cyarrier. So to make sure You do not make false
measurements, place a low pass fitler between the output of Your
sig gen and DUT.
Henning
Am 03.11.2018 um 10:33 schrieb Glenn:
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Not much change really Raj, I used 39k.
At -10dBm input, there is a slight improvement by maybe 2-3dB
At -20 & -30dBm in, virtually same result.
I wonder if a notch could be added for the 2nd Harmonic..... Did
you do any sums on the 3rd harmonic? It may also contribute.
glenn
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Re: uBitxr4 audio distortion fix
Dear Raj, No heat in the final Audio Transistor , It is cool including my self?
Thanks & regards sudanthiram vu2nsk
Sundar,
It should be best sound around half. Just check if final audio tr's are too hot!
Raj
At 03-11-18, you wrote:
>Dear Raj,
>I? added one 100 ohms preset (not trimmer) in between the diode d15 and D16 (after cut the track) the audio is ok and volume is increased.
>
>Good result.
>vu2nsk?
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Re: Tone on Nextion LCD Dimming
Thank-you for the reply.? I did try wrapping the 5 v lead through a toroid I? had, though at 300 hz, even if a square wave, I would not expect much attenuation.? I will try a larger inductance.
On Fri, Nov 2, 2018 at 8:47 PM Glenn < glennp@...> wrote: Evan It's almost certain the dimming is done by PWM, ie chopping the LED supply.?? Did you try adding some series inductance to the display supply along with your extra capacitors.?
vk3pe
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Re: the cause for the spurs, found!
Raj
The input VSWR with that mod increased the input VSWR to around 7:1.? (measured 0-30MHz, my current setup)
I didn't check before the mod but assume its closer to 1:1.
glenn
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Re: the cause for the spurs, found!
Not much change really Raj, I used 39k.
At -10dBm input, there is a slight improvement by maybe 2-3dB
At -20 & -30dBm in, virtually same result.
I wonder if a notch could be added for the 2nd Harmonic..... Did you do any sums on the 3rd harmonic? It may also contribute.
glenn
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Re: the cause for the spurs, found!
Ashar,
I always had a lot of doubts that the first mixer should be the
culprit but suspected taht the first BiDi amp must be the reason
in producing harmonics. But now You and Raj confirmed my
suspicion. This findings also explain why putting another xtal
filter between the output of the BiDI amp (in TX direction) and
mixer.
My proposal: first of all put a diplexer on the IF output of the
mixer and the following stage. THen use two 90 deg hybrids and in
between tho identical xtal fitlers, i.e. split the 45 MHz IF
signal into two path, filter them within two identicla filters
(gain and phase) and combine. Both dipexer and 90 deg hybrids with
the xtal filters will attenuate harmonics.
I am also thinking of another diplexer (LP - Hp ) at the
RF-In/Out of the mixer, the high frequency path be treminated into
50 ohms. In TX mode the image (LO+IF) will then be terminated and
not be reflected into the mixer.?
In addition do a good leveling of all stages in the TX path, but
keep in mind that the balanced modulator has a limited LO
suppression, so the carrier suppression (and image band) must be
taken into account.
Henning Weddig
DK5LV? ?
Am 03.11.2018 um 03:39 schrieb Ashhar
Farhan:
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the 45 mhz if amplifier is distorting and
producing a second harmonic at 90 mhz. this mixes with the
local oscillator to produce a spur at 90 mhz - local
oscillator.
here is how it happens :
the spur moves down as you tune up.
when the radio is tuned to 28 mhz, the spur is
at 17 mhz. when the ubitx is tuned to 28.150 mhz, the spur
is on 16.850 mhz.?
at 28 mhz, the local oscillator? is at 73 mhz.
there is a signal X such that :
X - local oscillator = 17 mhz
local oscillator is 73Mhz.
X - 73 = 17, X must be 90 MHz.
after checking the spur on a number of
frequencies between 15 MHz and 30 MHz, it was confirmed that
the above formula works consistently to predict the spur.?
what is th cure?
there are three solutions
1. decrease the distortion of the if amp by
modifying or replacing the IF amp (the tx side at least)
2. add a low pass or bandpass filter between
the final mixer and the if amp.
3. move to 60 mhz or 70 mhz IF insteead of 45
mhz. a double or triple bandpass should do it.
this is a result of joint investigation
between Raj and I.
- f
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Re: uBitxr4 audio distortion fix
Sundar,
It should be best sound around half. Just check if final audio tr's are too hot!
Raj
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At 03-11-18, you wrote: Dear Raj,
I added one 100 ohms preset (not trimmer) in between the diode d15 and D16 (after cut the track) the audio is ok and volume is increased.
Good result.
vu2nsk
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Re: the cause for the spurs, found!
Glenn,
Please try a mod..
Remove first transistor's base bias resistors uBitx = 1K and
2.2K
Connect a 39K or 47K resistor from first base to last emitter.? The
emitter voltage will be around 5-7v.
I used 44K and voltage was 6.8 half of my supply.
repeat the test below. I want to see if the feedback improves the
distortion in any way.
Cheers & Thanks
Raj
At 03-11-18, you wrote:
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Interesting, I had built the
uBITX bi-amp stage only, on a small pcb some time ago.
I just measured the 2nd and 3rd harmonics as shown below, with -30, -20
and -10dBm input from an HP8640B sig gen and monitored the output on an
SA.
The other 'grass' is local fm stations and shack stuff but the 2nd and
3rd harmonics have markers 2 and 3 on them. 45MHz is marker 1.
![[]](/g/BITX20/attachment/61266/)
![[]](/g/BITX20/attachment/61266/1)
![[]](/g/BITX20/attachment/61266/2)
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Re: uBitxr4 audio distortion fix
Dear Raj,
I? added one 100 ohms preset (not trimmer) in between the diode d15 and D16 (after cut the track) the audio is ok and volume is increased.
Good result.
vu2nsk?
|
Re: the cause for the spurs, found!
Interesting, I had built the uBITX bi-amp stage only, on a small pcb some time ago. I just measured the 2nd and 3rd harmonics as shown below, with -30, -20 and -10dBm input from an HP8640B sig gen and monitored the output on an SA. The other 'grass' is local fm stations and shack stuff but the 2nd and 3rd harmonics have markers 2 and 3 on them. 45MHz is marker 1.   
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Re: the cause for the spurs, found!
Which corner frequency for the LPF solution should be used, 50Mhz?
Il 03/nov/2018 08:19, "iz oos" < and2oosiz2@...> ha scritto: Excellent finding! Adding a low pass filter seems the easiest solution. At which impedance should be designed? 50ohm, 500ohm? Where exactly place it, considering the schematics of ver. 3 and ver. 4. I hope it doesn't involve cutting traces on the board.
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Re: the cause for the spurs, found!
Excellent finding! Adding a low pass filter seems the easiest solution. At which impedance should be designed? 50ohm, 500ohm? Where exactly place it, considering the schematics of ver. 3 and ver. 4. I hope it doesn't involve cutting traces on the board.
Il 03/nov/2018 03:39, "Ashhar Farhan" < farhanbox@...> ha scritto: the 45 mhz if amplifier is distorting and producing a second harmonic at 90 mhz. this mixes with the local oscillator to produce a spur at 90 mhz - local oscillator.
here is how it happens :
the spur moves down as you tune up. when the radio is tuned to 28 mhz, the spur is at 17 mhz. when the ubitx is tuned to 28.150 mhz, the spur is on 16.850 mhz.? at 28 mhz, the local oscillator? is at 73 mhz. there is a signal X such that : X - local oscillator = 17 mhz local oscillator is 73Mhz. X - 73 = 17, X must be 90 MHz.
after checking the spur on a number of frequencies between 15 MHz and 30 MHz, it was confirmed that the above formula works consistently to predict the spur.?
what is th cure? there are three solutions 1. decrease the distortion of the if amp by modifying or replacing the IF amp (the tx side at least) 2. add a low pass or bandpass filter between the final mixer and the if amp. 3. move to 60 mhz or 70 mhz IF insteead of 45 mhz. a double or triple bandpass should do it.
this is a result of joint investigation between Raj and I.
- f
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Re: Harmonics and Relay Replacement
I tried EPCOS TDK and it works as well as one marked S+M
This one has it marked R68K , tried and works well.
Raj
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At 02-11-18, you wrote: Hi all.
I was looking for the specs of the L5 and L7 replacement. I cannot find the exact yellow ones on the internet. The NLT on comkey are not there. They have NLV type. Is this a typo??
Please your source for me and some other builders in my club. We found the relays.But are looking for this parts.
Rob PA0RBL
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YO8UFO
Raj vu2zap
