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TDA2822 Audio problem
#ubitx
#tda2822
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Assembled my ubitx last week and after a demonstration last night in front of some boy scouts one of the parents complained of a loud tone coming from the speaker.? So I busted out my cell phone and fired up the Spectroid app mentioned in another post.? There is definitely a 9khz tone coming out of the speaker.? Its does change intensity when changing volume but it is a good 3 times the volume of all other audio coming out of the speaker. I have the MX TDA2822 chip. I rerouted the wires going to the volume control pot and to speaker without any positive changes. Any suggestions on how to clear this up or just swap the chip or build an alternate audio amp circuit or filter it out?? Just looking for some recommendations on how to attack this problem.
Jason Schlager KM6AUS |
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Here's an old thread on it:
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? ??/g/BITX20/message/40038 Here's a summary: The uBitx 11.9965mhz BFO can have harmonics that can beat with harmonics of the 16mhz oscillator on the Raduino.? There's also a 12mhz oscillator on the Raduino for the USB port to the host that may be causing trouble.? Those with this issue have found that swapping to a new Nano seemed to cure it. In your case, you could instead add a low pass audio filter in there somewhere. The Nano's use a resonator, not a quartz crystal, something like this: ? ? Can be some variation between Nano's. Ideally, we would either move the 12mhz IF to some other frequency, or build a custom Nano/Raduino that does not have 16mhz and 12mhz oscillators. The work-around for now is to keep the BFO below the 12mhz filter, swapping sidebands by moving the second local oscillator (clk1) between high side and low side.? This works fine on most rigs. Jerry ? On Tue, Mar 13, 2018 at 10:31 am, Jason Schlager wrote:
Assembled my ubitx last week and after a demonstration last night in front of some boy scouts one of the parents complained of a loud tone coming from the speaker.? So I busted out my cell phone and fired up the Spectroid app mentioned in another post.? There is definitely a 9khz tone coming out of the speaker.? Its does change intensity when changing volume but it is a good 3 times the volume of all other audio coming out of the speaker. I have the MX TDA2822 chip. I rerouted the wires going to the volume control pot and to speaker without any positive changes. Any suggestions on how to clear this up or just swap the chip or build an alternate audio amp circuit or filter it out?? Just looking for some recommendations on how to attack this problem. |
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I didn't notice it too much myself until someone pointed it out.? Now it drives me crazy.? Was thinking if I am going to build an audio filter I might as well socket the MX TDA2822 and mount the IC to board with a voltage regulator and a bandpass filter. May try to make it a plug in module that fits into the DIP socket.
-- Jason Schlager KM6AUS |
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Joe Puma
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John
Hello Jason,
On mine, I noticed that the tone frequency would change the most when I adjusted the BFO frequency. If you re-calibrate the BFO to a slightly different frequency, does you tone move as well? A more complete test would be to try Ian Lee's software version 1.61 and use the IF Shift function to see if that moves your tone. If it does, you could try to shift the IF so that the lower frequencies are emphasised and continue in the same direction until you have reversed the sideband. If in that position, after swapping the sideband in the menu you can receive signal properly without an audible tone, then we can look at swapping them in software. If this does not work, you could try to move the first IF instead.? You could load the test version I uploaded in the files section in the? "Software based IF attenuation" folder and through the menu change the first IF and see if your tone moves in frequency. Then we can it from there. Good luck. This issue drove me nuts...lol. 73, John (VK2ETA) |
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What we need is a scratch built Raduino board that takes an ATMega328P chip,
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an si5351, regulators for 5.0 and 3.3 volts, and has a carefully chosen?frequency on the oscillator for the processor.? ?Or at least a randomly chosen frequency. No USB interface, just some pins to hook an FTDI USB-UART cable (or similar) up to the host. Another possibility is to hang a cap across that 16mhz resonator by the ATMega328P on your stock Nano to bring the frequency down, hopefully by a few tens of khz. But the resonator is ridiculously small, I can't really recommend that hack to thousands of ubitx owners with nothing but blunt instruments for soldering with. Also, the Nano has that USB interface with a 12mhz resonator, could also be wreaking havoc with our 12mhz BFO.? Unfortunately that's on the backside of the Nano, no chance of putting a cap across that 12mhz resonator unless you first clip the Nano free from your Raduino. Once the Raduino is certified free of 12 and 16mhz, we can go back to Farhan's original plan of moving the BFO above or below the 12mhz crystal passband to select LSB/USB.? And CLK1 can remain stuck at 45+12mhz, which should avoid some some of the extra birdies we get when it's at 45-12mhz for LSB. Jerry, KE7ER On Mon, Apr 9, 2018 at 03:46 pm, John wrote:
Hello Jason, |
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Vince Vielhaber
Another solution would be to separate the Si5351 from the raduino. Put it on its own board that plugs into the uB. Pins 10-16 pass thru to another connector. Another connector connects the I2C to the raduino. Then you can put the UNO part of the raduino (or use something else entirely) wherever you want where the Xtal won't be an issue. That also gives more options for boxes and mounting.
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I have it partially finished in KiCAD but other things have gotten in the way so it's on hold. I tried to get Mike Hagen to do it but he didn't seem interested. Vince. On 04/09/2018 09:46 PM, Jerry Gaffke via Groups.Io wrote:
What we need is a scratch built Raduino board that takes an ATMega328P chip, --
Michigan VHF Corp. |
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We could mount an si5351 the Adafruit si5351 breakout board to the back of the uBitx:
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? ? ? ? ? ? ? ? ? I'm thinking some duct tape on the back for insulation, then solder wires from breakout grounds to uBitx groundplane securing it mechanically. Steal the old clk0,1,2 lines going into the uBtix for use as i2c? SDA, SCL lines. Hans of qrp-labs.com is active in this forum. Nik is successfully using that Adafruit board on his Raduino replacement: ? ??/g/BITX20/message/41676 And we were initially using the Etherkit si5351 library on the Bitx40. All good choices. Jerry, KE7ER On Mon, Apr 9, 2018 at 06:56 pm, Vince Vielhaber wrote:
Another solution would be to separate the Si5351 from the raduino. Put it on its own board that plugs into the uB. Pins 10-16 pass thru to another connector. Another connector connects the I2C to the raduino. Then you can put the UNO part of the raduino (or use something else entirely) wherever you want where the Xtal won't be an issue. That also gives more options for boxes and mounting. |
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Vince Vielhaber
For all that matter, I'm using one of the Adafruit boards in my CB-to-10 conversion. It works well. Only using one clock tho, but your si5351 routines.
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Vince. On 04/09/2018 10:26 PM, Jerry Gaffke via Groups.Io wrote:
We could mount an si5351 the Adafruit si5351 breakout board to the back --
Michigan VHF Corp. |
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Jerry:
12 MHz is necessary for ANY USB interface. The 12 MHz xtal on the radiuno drives the CH340 chip. It cannot be disabled (or changed very much) and have USB work anynore. Similarly, any other chip connected, FTDI or whatever, has to have the 12 MHz to operate. It is easy to build a Si5351 board with an Adafruit board or whatever, and drive it with a bread-boarded ATMega328P which does not have a USB interface. Then only the mcu xtal would possibly be a source of interference. Generally, I do not think this is the case. In any event, almost any xtal up to about 20 MHz could be substituted and the mcu would work. If it is the source of birdies (or whatever) they should shift substantially. It could very well be that the 12 MHz xtal is the source of some birdies, but the proper method is to isolate and possibley ground the output of the CH340 chip under some conditions. It is always active, even when a USB connection is not being used. john AD5YE |
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Given all the different Raduino's getting built, seems reasonable to?
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just build one without the 12mhz and 16mhz oscillators. This could be plug and play, an easy solution for the now thousands of uBitx's out in the field. Some digital modes will want a USB interface while operating the radio. But much easier to get rid of 12mhz nasties if the radio only sees 9600 baud UART lines from an FTDI/CH340? ?UART-to-USB? ?cable assembly. ? Jerry On Mon, Apr 9, 2018 at 09:50 pm, John Backo wrote:
Jerry: |
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The baud rate is the effective data rate. It still has to have some kind
of frequency driving it. Perhaps the most effective solution is to switch the supply voltage to the CH340 chip. That is 3.3v at pin 19, I believe. The chip is tolerant of 5v from the USB connection, but ordinarily operates at 3.3v. There is no serial converter chip (as shown in the "normal" configuration in the datasheet. The TXD and RXD lines connect directly to the ATMega chip. It would be a delicate operation to switch and thus disable the power input line, but it could be done. Has anyone investigated that the USB connection might be a source? It has an internal frequency control in the computer. But it is an unlikely source, especially when disconnected. john AD5YE |
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Could be that different rigs exhibiting obnoxious audio tones
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are due either or both oscillators.?? Luck of the draw as to where those ceramic resonators land. Could tell which one by varying the BFO, if 100hz shift in the BFO causes a 100hz? shift in the audio tone, then it's the 12mhz osc. If a 100hz shift in the BFO causes a 400hz shift in the audio tone, then it's the 16mhz osc (since 12mhz*4 = 16mhz*3 = 48mhz). A 9600 baud rate can be generated from any osc above 1mhz by using the appropriate divide factor. The CH340 takes 5v in, the internal 3.3v regulator supplies the si5351. And it's on the backside of the Nano. Good luck hacking that. Jerry On Mon, Apr 9, 2018 at 11:03 pm, John Backo wrote: The baud rate is the effective data rate. It still has to have some kind |
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The Arduino already does UART, digital pins 0 and 1 get tied to the CH340 usb chip on the Nano.
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That chip converts the usb interface on your host into UART TX and RX that the ATMega328P can deal with. I'm just proposing that we do away with the CH340 chip on the Nano, and use a cable assembly? that includes a CH340 chip or similar, typically only needed when we download firmware. Though since the 9600 baud interface is so slow it is easy to filter before going into the rig if you wish to have that USB connection while using the rig for digital modes. Here's a nice cheap USB-to-UART converter.?? ?? On Tue, Apr 10, 2018 at 08:45 am, Dexter N Muir wrote:
I like it! UART to the rig - could do high-rate given logic-level, UART<->USB remote to take the place of the old RS232 (remember them ol' D9 and D25 cables and connectors?). What sort of cost? |
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Dex ZL2DEX Beauty of using the built-in UART and built-in USB interface on an Arduino NANO is that you don't have to mess with voltage level conversion between RS-232 and TTL. This is also convenient because many modern PC do not have built-in RS-232 ports. The Arduino Pro-Mini is an alternative to the NANO that does not include the USB interface.? With this board you only need to do the voltage level conversion in order to use it with your RS232 PC port.? Arv? K7HKL _._ On Tue, Apr 10, 2018 at 9:57 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: The Arduino already does UART, digital pins 0 and 1 get tied to the CH340 usb chip on the Nano. |
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The USB-to-UART cables sold for use by Arduino hobbyists generally have 0-5v logic levels,
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not RS232.? ?That thing on Oddwires I suggested in a previous post: ? ?? claims to be "USB to RS232", but I seriously doubt it.? All I see is the SiLabs chip on it, no level translators.? Could be 5v logic levels, could be 3.3v, or could be configurable. Claims to be suitable for use with both the Rasberry Pi (3.3v) or Arduino (5v). These are nasty hardware details that everyone in the Arduino universe is oblivious to. I have an old TTL-232R-3V3 FTDI cable I use, ? ? since 3.3v and less is what most of electronics have gone for the last couple decades. For use with the Nano, we should have the 5v logic level version, the TTL-232R-5v FTDI is kind of the industry standard, note that the true Arduinos have the same FTDI chips. Better yet, here's a newer FTDI cable that can be configured for either 5v or 3.3v: ? ?? Those FTDI cables are around $20. FTDI clones and alternatives are now out there for $2 or $3. If that's a real SiLabs chip on the Oddwires device it probably works fine, though Oddwires hasn't bothered to fully describe what the logic levels are.? ?? Jerry, KE7ER On Tue, Apr 10, 2018 at 09:18 am, Arv Evans wrote:
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Jason Schlager
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