1. BITX20@groups.io
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Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Jerry Gaffke
 

Ah, very nice that you were able to do all of this, and document it so well.
See my comments inline with your original text below
 
On Sat, Feb 3, 2018 at 09:50 pm, John wrote:
Further tests and head scratching.
 
Since I replaced the Arduino and mounted it on female headers I decided to do more tests to try to answer some of the leads and questions in the thread.
 
I used some 20cm (8 inch) female-male connectors and connected the Arduino remotely from the Radiuno so that I had access to the 12Mhz crystal next to the CH340G chip underneath the Arduino board.
 
The radio has been re-calibrated and shows a difference of less than 10Hz on a 10M beacon and on an 80m CW training transmission from our WIA here in Sydney, so I suspect it is pretty accurate in frequency. 
 
I then re-did a BFO adjustment both on the factory side (low side) of the 12Mhz filter and on the other side. By observing the audio spectrum I adjusted the BFO so that the passband was as close as I could tell 500Hz to 2400Hz.
 
I then in each case moved the first and 2nd VFO to shift the alignment of the two crystal filters and noted the change in signal strength between the factory default and the peak.
 
Results:
 
1. Factory side of BFO adjustment results in a BFO frequency of 11,996.6Khz while the opposite side of the pass band results in a BFO of 11,999.5Khz. So as expected there is a difference of around 3KHz between a low side and high side BFO. And the centre of the filter appears to be at around 11,998Khz which I suspect is pretty normal. Please comment if you think it is not.
The exact frequencies you report seem reasonable, others may find their rig to 
be using 12mhz crystals that are a khz or two off from what you report.
Crystals are sorted by frequency at hfsignals, different rigs get slightly different freq crystals.
 
 
2. The tuning clicks and tones within the pass band have definitely disappeared as mentioned in a previous post.
So by moving the Raduino 8 inches away from the uBitx, the radio no longer hears these interfering signals
on either low or high side BFO settings.  Suggests we could deal with it using shielding. 
 
 
3. The tones outside of the passband are still there for some values of the BFO and shift by 550Hz for each change of 100Hz of the BFO. Note that the receiver is usable as the tone free BFO values result in a passband that is more or less 500-2400Hz.
Our assumption has been that it is the 4x harmonic of the BFO (4*12=48mhz) beating with the 3x harmonic of the Nano (3*16=48mhz).
Any chance the tones shift by 400hz per 100hz of BFO, not 550hz?   550hz would be difficult to explain, that's a very funny number.

 
 
4. Going with the BFO on the high side of the filter produces similar results. I just noted that the passband seems less steep on the low audio frequencies when in this configuration. Of course in that case LSB becomes USB and vice-versa.
Typical of a crystal ladder filter that one side is less steep, the skirts are not symmetrical.
 
 
5. Now the part I can't understand: while listening to a fixed signal (the CW training transmission on 80M) AND positioning the BFO frequency so that strong tones would be heard and seen on the spectrum at 13,379Hz, I touched the three crystals in turn: the 16Mhz Arduino one, the 12Mhz CH340G one, and the 25Mhz VFO one. 
 
The first two did not produce any difference in Rx signal or tones. Touching the 25Mhz one produced a shift in the received signal audio frequency BUT NOT in the tones frequency. 
 
This does not make sense to me as if the si5351a clock was to shift, any beat of harmonics should produce a shift in frequency.
 
And yet if I adjust either the BFO frequency OR the 1st and 2nd oscillators frequencies I get a shift in tones frequency.
 
So if the tones were geneated after the filter or in the audio circuit I can't see how they would shift in frequency when I change some oscillators frequencies. And if they were generated before the 12Mhz filter they should shift and the 25Mhz crystal shifts!
 
Any idea why that is?
Indeed, this is unexpected.
Perhaps the 12mhz and 16mhz crystals are insensitive enough to not vary much when interfered with.
(But wasn't there a previous report of tones changing when a finger was near the 16mhz crystal?)
And perhaps the 12mhz and 16mhz crystals are somehow beating against each other?
Or there is some totally different source for these tones, apparently coming from the Raduino?

Once you tune the radio and can observe these tones, see if you can disable the 12mhz and 16mhz crystals
by shorting one end to ground.  See if shutting down one or the other somehow gets rid of the tones.
The 12mhz crystal is only needed when downloading new firmware.
The 16mhz crystal is needed to tune the rig, but once the si5351 is programmed the 16mhz can go to sleep.
You may need to reset the Nano to get it back on the rails after re-enabling the 16mhz crystal.

 
 
6. I used the code below to shift the alignment of the first xtal filter and the 12Mhz xtal filter. I noted improvements in signal level (I assume the Rx amplification chain is more or less linear) of 3 to 6dB. So less that the 8dB I reported before but still not negligible.
 
I'm not sure I totally understand all of this.
Some change in signal strength is expected if as you use different parts of the 45mhz crystal,
the passband isn't all that flat.


 
The peak seems with a first and second VFO about 2 to 3Khz above their default values.
 
The shift is reset to zero each time the Arduino is reset and is not saved in EEPROM at present.
 
It would be interesting to see if some other units show the same changes in signal strength.

I noted that some shifts would produce tones and these tones would shift in frequency too, and by 4,000Hz for each change of 1,000Hz of first and second VFO
frequencies. (as opposed to 550Hz for each 100Hz of the BFO). 
The four to one ratio (4000 to 1000) here is consistent with our assumption that it is the 4'th harmonic of the 12mhz BFO involved, at 48mhz.
But I would think the BFO is not moving when you hear these tones move, is that the case?
If the BFO is not moving, this is quite puzzling, and perhaps the tones are due to some fourth harmonic of either the first or second oscillator.
I assume that as you move one, you also move the other by an equal amount, you might try only moving one of the two
local oscillators, see which one causes the tones to vary.  I haven't totally grok'd your new code yet.

Jerry, KE7ER 
Re: BitX40 v1.27.7 SPOT mode

Vic WA4THR
 

OK, great! One other question...what is the relationship between the "PPM" calibration value and the "CAL VALUE" in line 43?

=Vic=
Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Jerry Gaffke
 

So, moving the Nano 8" away did away with tones in the crystal filter passband, 
which would be the ones of most concern to folks here in the forum
But you still see tones coming through the demodulator, up around 13khz. 

Can you give some idea of how strong these 13khz tones are?
I assume they are relatively weak.

You said that a finger on the 16mhz crystal does not affect these tones.
Did a finger on the 16mhz crystal affect the the tones you heard within the passband
back before the 8" move?

There's all sorts of weird things that can happen around mixers.
Always have some unwanted products that come out the IF port.
We have a filter there (45mhz or 12mhz) to only select the signal of interest,
those other signals are not getting terminated and so reflect back into the mixer
to mix again, creating all sorts of unexpected havoc.
Could be this 13khz stuff has nothing to do with the Nano.

Jerry


On Sun, Feb 4, 2018 at 09:19 am, Jerry Gaffke wrote:
Ah, very nice that you were able to do all of this, and document it so well.
See my comments inline with your original text below
 
Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Jerry Gaffke
 

Bingo!
See this ceramic resonator on Mouser:  pnum  81-CSTCE16M0VH3L99R0
Same physical size as what's on the Nano, I didn't see any quartz crystals that small.
Tolerance of those Murata parts is 0.07%, so could be off by as much as plus or minus 16mhz*0.0007=11.2khz 
Whatever they stuff on a $2 Nano is probably not Murata, unless they are Murata rejects.

This internal oscillator capacitance thing, is though only in the interest of accuracy?
Or is it a matter of the oscillator not working at all?

Regardless, anybody with tones, I suggest you pack some capacitance across pins 7 and 8 
of the ATMega328P chip (hard to get at those signals on the very small ceramic resonator).
I have no idea how much, perhaps hundreds of pF, if the Raduino display no longer works then that's too much.
This might be something best done at hfsignals on new units, as those 328P pins are pretty small

And if that doesn't help, try shorting out one end of the 12mhz resonator to ground.
Found on the back of the Nano, unfortunately.



On Sun, Feb 4, 2018 at 09:15 am, Arv Evans wrote:
Not 100% sure but popular thinking indicates the "crystals" on smaller Arduino boards are actually ceramic resonators.  If this is true then it should be possible to use capacitence to pull them further than would be possible with a real crystal.  This also lends credibility to the caution about possibile need to change AVR internal oscilator capacitence if changing resonator or crystal device.
 
Re: ubitx receive audio troubleshooting

Gordon Gibby <ggibby@...>
 

Where do you have a TPA 2016 chip?
The uBitx does not use that.

image1.png


On Feb 4, 2018, at 11:12, radiodoc43 <Monsen.Craig@...> wrote:

I am still trying to identify the cause of an audio "squeal" which makes receiver unusable.

Audio is ok at lowest volume setting. As I turn up volume, a "squeal" begins and gets louder obliterating any other signals. The TPA2016 chip gets extremely hot if left in this state for any length of time. I suspect that something is causing the audio stage to oscillate at higher volume levels.

I have tried "cleaner" power supplies, created a ground plane for my front panel, and substituted shielded cable for the volume control leads, all without any improvement.

Any suggestions as to getting to the bottom of this problem?

Btw, the radio is able to receive strong signals at the lowest setting.

Craig
KC2LFI

Re: ubitx receive audio troubleshooting

radiodoc43
 

My mistake. I meant TDA2822 chip.

Craig
KC2LFI
Re: Second batch of uBITX shipping? #ubitx

KM4TRT
 

Where did mine December 15th and got it about a week ago
Andy KM4TRT
whistles in receive

Leland Lannoye
 

I am sitting here reading some of this information and studying the new technology.  When I was young (at leas 50 years ago), solid state technologies were either in their infancy or still a dream.  Our rigs were two pieces of equipment, a receiver and a transmitter with a variety of accessories.

Most of our receivers for those of us who were not well heeld in the financial area were of the single conversion genre with an if frequency of 455 kHz.  With little preselection capability, this relegated the ham bands 20 mtrs and above useless with hetrodyne images from frequencies 910 kHz either above or below the desired reception point. There, in that day, were three remedies to fix this. The first two were:

    1.)  add a really selective high gain preselector to tune the offending images out

    2.)  raise the if to something on the order of 1600 kHz which left bandpass selectivity at a substantial disadvantage.

The third option, and the most expensive in its day was double (or, even triple) conversion.  If  you were able to pay the 1958 price of over $300, you were in and there were few difficulties thereafter until the receiver aged and developed some bad shield grounds or worse.  The second or third conversion local oscillator would provide a cornu copia of birdies of one type or another. These included signals that were always there, I know the newer designs with balanced mixers and the like have few of these problems, but, it is worth considering.

An aging ham from way back.


Lee, WA9AOE


---
This email has been checked for viruses by AVG.
http://www.avg.com
Re: ubitx receive audio troubleshooting

Gordon Gibby <ggibby@...>
 

So in order to have an oscillation, you have to have a closed loop with a gain greater than one at the oscillation frequency

Since your squeal begins when you turn the vine control up, and then input of the loop that Apparently exists is earlier in the system.  

My guess would be via the power supply lines.  That would suggest adding additional filtering in Decoupling capacitance in parallel with the lowest inductance (short leads ) as possible as near to the chips involved as possible.   Probably the audio Amp chip & its preamp should have additional filtering on the power supply lines.  You can test this by  merely touching capacitance to the proper places temporarily.


On Feb 4, 2018, at 13:21, radiodoc43 <Monsen.Craig@...> wrote:

My mistake. I meant TDA2822 chip.

Craig
KC2LFI

Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Joe Puma
 

I’ve been following this post. What does this all mean for a beginner who is waiting on a uBitx? Is there a problem with original design? Are these strong audio tones noticeable or interfering with when using the ubitx straight away? 

Joe
KD2NFC 



On Feb 4, 2018, at 11:58 AM, Arv Evans <arvid.evans@...> wrote:

Not 100% sure but popular thinking indicates the "crystals" on smaller Arduino boards are actually ceramic resonators.  If this is true then it should be possible to use capacitence to pull them further than would be possible with a real crystal.  This also lends credibility to the caution about possibile need to change AVR internal oscilator capacitence if changing resonator or crystal device.

Recently i purchased some Arduino Pro-mini units that have a standard crystal for the CPU clock.  These are for a frequency counter project where the stability of a crystal is needed.  Search Ebay for "arduino pro mini crystal" for these units.  

The Pro-minii Arduino are also interesting because they do not include built-in USB and thus there is no 12 MHz crystal to interfere with the BITX 12 MHz IF.

Arv. K7HKL
_-_


Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: James Lawrie <lawriejk@...>
Date: 2/3/18 11:15 PM (GMT-07:00)
Subject: Re: [BITX20] #ubitx-help Strong Audio Tones in and outside audio receive passband

I know I'm late to this party but you cannot swap crystals on nano board without first using a atmel programmer to burn the fuse bits that tell what freq it will be using or you will brick your nano.... also if the ftdi or whatever usb chip is using 12mhz, you could get the sparkfunPro 16mhz/8mhz board that does not use usb but instead uses usb to serial cable to upload. Be warned 16mhz board is 5 volt and 8 mhz is 3.3 volt.

I only use the Sparkfun Pro 16 for my projects. Another note if you go with the ATMega32U4 boards they have built in usb....

Maybe this will help someone or maybe not....

James Lawrie

Sent from my Galaxy Tab A

-------- Original message --------
From: Arv Evans <arvid.evans@...>
Date: 2/3/18 09:38 (GMT-06:00)
Subject: Re: [BITX20] #ubitx-help Strong Audio Tones in and outside audio receive passband

Jerry

Interesting observation that the 12 MHz USB clock oscillator is on nearly the same frequency
as the uBITX IF and BFO.  If the BFO is offset to the high side of the IF passband it could well
be within audio range of the USB clock frequency.  If this is the problem then it might be possible
to pull the USB clock crystal down with a small parallel capacitor.  That should not make a
significant change in USB clock timing but could take it out of range of the receiver IF and BFO
frequencies.  Some experimenting is probably necessary to tell how far to pull the crystal.  It
would not be good to accidentally put it within the IF filter passband.

Arv  K7HKL
_._


On Sat, Feb 3, 2018 at 1:47 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
I assume you mean changing the Arduino crystal, not cap.

The 16mhz ATMega328P crystal is about 3mm x 1.5mm, goes to  ATMega328p pins 7 and 8.
It is on the top of the Nano, just above the silk for edge pin D5.
Seeing the actual crystal now, and not just looking at datasheets and schematics, I see that it is
extremely small.   I doubt most of those with uBitx in hand will want to mess with it.

I bought some spare Nano clones, I believe they're identical to what's on the Raduino.
Mine have a CH340G chip on the back of the Nano for the USB interface.
This chip has another 3mm x 1.5mm crystal nearby, this one happens to be 12mhz.
    http://www.datasheet5.com/pdf-local-2195953

Quite possibly it is the 12mhz oscillator for the USB interface that is causing the trouble in at least some cases.
Though in post 40432 it was reported that a finger on the Nano's crystal caused the tones to vary,
which suggests that case was due to the 16mhz crystal since the 12mhz crystal is not usually accessible.

None of this was ever a problem on the Bitx40v3, far as I know.
I'd like to think there will be a simple fix, perhaps soldering in a bit of copper tape somewhere for shielding,
or adding a few caps.    Moving the IF would be pretty disruptive.

Jerry



On Fri, Feb 2, 2018 at 11:55 pm, Ashhar Farhan wrote:
changing the arudino cap is going to be a challenge as the arduino is soldered and you need to access it from the underside to desolder it. we had to resort to solder it in as keep it on a socket was leading to bulge and an additional failure point on the board.
 
Re: BITX QSO Afternoon/Night, Sunday, February 4, 3PM/7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere

Tom VE3THR
 

Get well soon John. Listening to the top end of 40M right now and it's chock full of AM Rally stations all over the place from 7.250 to 300. I'm QRV on 7.240 for traffic and a possible substitute frequency. Open to suggestions.
Re: Toroids winding information #ubitx

Jerry Gaffke
 

My idea would be to divide and conquer.


First step, see if you get proper quiescent currents through the IRF510's.

Put an ammeter in line with 12v supply for the IRF510's,
turn RV2 and RV3 to the minimum setting, all the way clockwise.
Put a 50 ohm dummy load good for at least 5W (intermittent, better if 10W), on the antenna port.

Power up and hit PTT with no attempt to transmit anything, ammeter should be close to zero ma. 
Slowly slowly turn RV2 up, should be able to get 100ma of drain current on Q95 when RV2 has the gate at around 4v.
Then do the same with RV3 till we get an additional 100ma (200ma total on the ammeter) through Q94.

If you now have the ammeter at 200ma, the IRF510's are doing fine, L8 and L9 are passing current,
and traces from the 12v supply through L8 and L9 into the IRF510's are all intact.
Possible that L8 or L9 is shorted and thus zero inductance, but unlikely if not visibly damaged with obvious scorch marks.



Exactly how did he feed 500mv of RF into T10? 
I'll assume you remove R961, add a short across C92, then inject 500mv peak to peak of RF into T10 pin 4. 
If you don't remove R961 you have 12 volts DC in there, could blow out the signal generator.

All those relays and low pass filters are a major complication.
I'd cut the trace from T11 pin 5.  Easiest spot to cut would be on the back of the board, the 1 inch long trace
from the transformer closest to the two IRF510's, cut it near the transformer.  Can be repaired
later by scraping soldermask from the trace and adding a short wire from transformer to trace (or a big solder glob).
Then add a 50 ohm dummy load from T11 pin 5 to ground.
 


Now, with PTT pressed, apply the 500mv pk-pk of 7mhz RF into T10 pin 4.
If that picoScope can see 7mhz, should now see something on the order of 250mv pk-pk of RF centered at around 4v of DC
at the gates of Q94 and Q95.  The drains of Q94 and Q95 should now have about 2 volts of 7mhz RF signal centered on 12v DC.
(Note that the two gates have complementary RF signals, when one is high the other is low.  Same with the two drains.)
And the dummy load should have about 4 volts pk-pk on it.

The 4 volts peak to peak of RF on the dummy load would  have an rms voltage of  (4/2)*.707 = 1.414 volts,
and the power into the dummy load would be   1.414v*1.414v/50ohms = 0.040 Watts.
So the dummy load could be most any 50 ohm resistor, though a small resistor will quickly vaporize if you turn up that signal generator.
 
Those without a picoscope or signal generator could use a simple diode RF probe with a DVM to check the RF voltage levels,
and one of the si5351 outputs through a couple series resistors to generate the 7mhz test signal.
The diode RF probe is not very sensitive, so perhaps double all of the voltages, so 1 volt peak to peak injected into T10.
Not obvious exactly what load T10 will present (due to gate loading by the IRF510), but a couple 50 ohm resistors in series
to ground  from the si5351 should get you into the right ballpark, the junction between the two resistors gets tied to T10 pin 5.

But beware, I haven't actually done any of this.

Jerry


On Sun, Feb 4, 2018 at 12:23 am, Raj vu2zap wrote:
What Cesar has not told us other than he has some great antique guns is that he has
6600 function generator. He also has a pico scope.

I've been trouble shooting via whatsapp which is faster than group emails!

The last test done was to feed 500mv to T10 at 7.15MHz and check output - NIL.
Any ideas Jerry!

Raj
Re: BitX40 v1.27.7 SPOT mode

Allard PE1NWL
 

The CAL VALUE x 100 represents the offset (in Hz) that we need to apply to
the nominal VCOA frequency (875 MHz) in order to get the correct output
frequency.

So the ppm (parts per million) value can be calculated as follows:

ppm = CAL VALUE x 100 / 875,000,000 x 1,000,000

For example, the default CAL value is 1575
so the corresponding default ppm value is
1575 x 100 / 875,000,000 x 1000,000 = 180 ppm

Hope this helps.

73 Allard PE1NWL

On Sun, February 4, 2018 18:51, Vic WA4THR via Groups.Io wrote:
OK, great! One other question...what is the relationship between the "PPM"
calibration value and the "CAL VALUE" in line 43?

=Vic=
Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Jerry Gaffke
 

For anything this complicated, a few units will fail in the field, if only due to rough handling through the mails.
The uBitx count is now up in the thousands.
Most uBitx's just work as delivered, no offending tones.

We're still trying to figure out how it is that a handful of rigs are misbehaving,  and how best to fix them.   
The initial complaint of audio tones in the audio passband on a couple rigs would be distracting, but the rig might still be usable.
The 13khz tones that John mentions are outside the audio passband, easily filtered if they ever get as far as the headphones.

Jerry


On Sun, Feb 4, 2018 at 10:43 am, Joe Puma wrote:
I’ve been following this post. What does this all mean for a beginner who is waiting on a uBitx? Is there a problem with original design? Are these strong audio tones noticeable or interfering with when using the ubitx straight away? 
 
Re: Toroids winding information #ubitx

César EA3IAV
 

Hi! I have checking with a magnifying loupe looking for broken copper tracks or any strange looking components. I have unsoldered and redone t11 and t10

i have resoldered all bits that looked poor soldered

still no advance. I get 0.7amps when ptt but no power output.

inyecting 7.150 400mV on t10 before mounting the t10 showed some activity but i guess it shoukd be higher right Raj?
Re: BITX QSO Afternoon/Night, Sunday, February 4, 3PM/7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere

N8DAH
 

7.222 seems clr. Listening for a few then I will call some.
--
David

 N8DAH
Kit-Projects.com
Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

Joe Puma
 

Thank you for the clarifications. I’m all in for mods, changes and improvements to this kit radio because that’s where the fun is. But this post is cringe worthy if it affected the radios on a global scale. Glad it’s just a strange anomaly in some of the radios.  

Joe
KD2NFC 



On Feb 4, 2018, at 2:37 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

For anything this complicated, a few units will fail in the field, if only due to rough handling through the mails.
The uBitx count is now up in the thousands.
Most uBitx's just work as delivered, no offending tones.

We're still trying to figure out how it is that a handful of rigs are misbehaving,  and how best to fix them.   
The initial complaint of audio tones in the audio passband on a couple rigs would be distracting, but the rig might still be usable.
The 13khz tones that John mentions are outside the audio passband, easily filtered if they ever get as far as the headphones.

Jerry

On Sun, Feb 4, 2018 at 10:43 am, Joe Puma wrote:
I’ve been following this post. What does this all mean for a beginner who is waiting on a uBitx? Is there a problem with original design? Are these strong audio tones noticeable or interfering with when using the ubitx straight away? 
 
Re: BITX QSO Afternoon/Night, Sunday, February 4, 3PM/7PM Local Time, 7277 kHz in North America, 7177 kHz elsewhere

ekelley
 

I tried 7222 and it sounded like there was a station way down
in the mud. I also tried to listen for myself on a number of SDR
radios around the country and nothing. I will try back later.
Ed W0OIC

On 2/4/2018 2:08 PM, N8DAH wrote:
7.222 seems clr. Listening for a few then I will call some.
--
David

 N8DAH
Kit-Projects.com
Re: uBITX woes, feeling disheartened. #ubitx

rlawson695@...
 

hello; ok I'm getting no 12 volts at D7 with ptt on and vom leads one on both des. sure do appicate all the help. so with no power at d7,where do I check next 73's de AC8XZ
uBITX: Convert LCD to I2C

kb1oiq@...
 

Hi Everybody,

I just posted a file: kb1oiq_i2c_mod.pdf

The document describes a hardware and software modification that I performed on my uBITX.  It converts the LCD to use the I2C bus, thus freeing 6 Arduino digital pins for other uses.  I hope you find it useful.

Have a lot of fun, and 73,

Andy
KB1OIQ