Date   
Re: TDA2822 Audio problem #ubitx #tda2822

Jerry Gaffke
 

The USB-to-UART cables sold for use by Arduino hobbyists generally have 0-5v logic levels,
not RS232.   That thing on Oddwires I suggested in a previous post:
    http://www.oddwires.com/cp2102-serial-adapter-module-usb-to-rs232-with-jumper-wires/
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,
    http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf
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:
    http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232RG_CABLES.pdf

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:
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.

Re: Variation on Ian's KD8CEC uBitx software (based on his 1.04 release for now) and ATU sketch. #ubitx

Tim Gorman
 

I think you have it nailed. It's why the mjkdz backpacks need a
different software initialization. Based on what I have read the mjkdz
backpacks wire to the lcd pinouts differently than the other backpacks.
The software apparently needs to know about that difference.

tim ab0wre

On Tue, 10 Apr 2018 09:02:23 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

I think that list of pins describes the interface between the PCF8574
i2c chip on the backpack into the parallel interface of the LCD
display. Nothing to do with pins on our Nano, all the Nano sees is
the SDA and SCL pins for the i2c bus that is shared between the i2c
display and the si5351.

The parallel interface into an lcd requires 4 parallel data lines,
and they are used for both read and write.

On Tue, Apr 10, 2018 at 08:56 am, Jack Purdum wrote:


It appears that most of those extra pins are for read/write
capability, and most of the BITX displays don't use software that
reads the display. Also, since most of those use pins 2 and 3, they
would kill the ability to use external interrupts on the rig. Since
I use external interrupts for tuning, such an I2C display for my
projects would be a bad choice. They probably are fine for projects
that don't use external interrupts. Personally, I'd look for
displays that only require the device address and the row/column
specs.

Re: AGC circuit to try?

Tim Gorman
 

Jerry,

I've ordered four BAP64Q units for when my second ubitx gets here. I'm
going to stick it in the rf path somewhere as we discussed earlier.
Maybe between R17 and C12?

tim ab0wr

On Tue, 10 Apr 2018 08:05:57 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

It was just a thought, getting an AGC scheme to work well is not
trivial. I'm still thinking a BAP64Q at R17 might be best.

Base of Q70 could work.  It might do better on the other side of C50,
where that weak incoming audio is centered on ground. 
Though as we have seen here, have to think about what happens when
you have strong audio from the mike amp during transmit, potentially
going through the intrinsic diode in that FET. 

You're on your own!

Jerry

On Tue, Apr 10, 2018 at 07:32 am, Tim Gorman wrote:


I have mine connected in the receive line before the first mixer.
Your idea might work better. I assume you would put it at the base
of Q70 in the ubitx?

Re: AGC circuit to try?

Tim Gorman
 

So you think the BAP64 would be better placed before the audio pre-amp
rather than in the IF? Before C50 maybe?

tim ab0wr

On Tue, 10 Apr 2018 09:23:34 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

Yup.
Getting AGC right however you do it is not trivial.
And not something I am able to fully analyze.
For example, Henning Weddig pointed out some time ago that
delays through the crystal filter can cause instability when you
close the loop.

He also pointed out that it is our audio pre-amp that limits the 
total dynamic range of the rig, and thus an attenuator prior to 
that pre-amp is preferred if you might be dealing with really strong
signals.

On Tue, Apr 10, 2018 at 09:10 am, Sandy T wrote:


At least the BAP64Q at Q70 would only cost $0.56 but proper biasing
to work "as expected AGC" might be a trick.

Re: AGC circuit to try?

Jerry Gaffke
 

The half-life of the charge carriers in a PIN diode is only around a microsecond,
so won't work at all at audio frequencies, must be prior to D5 pin 3.

Most of the AGC schemes we see here suppress the audio after the audio pre-amp.
And they work well enough.
But we should get more dynamic range (be able to receive strong signals) if the AGC
attenuator is somewhere between C50 and the antenna port.



On Tue, Apr 10, 2018 at 10:19 am, Tim Gorman wrote:
So you think the BAP64 would be better placed before the audio pre-amp
rather than in the IF? Before C50 maybe?

Re: AGC circuit to try?

Jerry Gaffke
 

Any an attenuator used up front at the uBitx antenna port 
will be dealing with a whole world's worth of RF, 
so any non-linearity in the attenuator could create IMD products 
due to a strong local AM or FM or TV or hairdryer signal.

The situation gets slightly better after the 30mhz low pass filter at L1,2,3,4
Much better after the 45mhz crystal filter.
Much much better after the 12mhz filter.

Though as Tim has pointed out, the 12mhz filter might
be especially sensitive to variations in impedance.

Pick your poison.

Jerry


On Tue, Apr 10, 2018 at 10:36 am, Jerry Gaffke wrote:
The half-life of the charge carriers in a PIN diode is only around a microsecond,
so won't work at all at audio frequencies, must be prior to D5 pin 3.

Most of the AGC schemes we see here suppress the audio after the audio pre-amp.
And they work well enough.
But we should get more dynamic range (be able to receive strong signals) if the AGC
attenuator is somewhere between C50 and the antenna port.

Re: AGC circuit to try?

ajparent1 <kb1gmx@...>
 

That's why the CDS cell and the #49 bulb  worked so well the attack and decay are limited
by filament heating and cooling.

I'm aware of all the various opto isolator, that parts bin has about 15 different parts.
The Jfet based parts might work well.  I've used the 4n25 and 26 parts in attenuators as well.

FYI a common Jfet works well too, generally as a series device.

Allison

Re: AGC circuit to try?

ajparent1 <kb1gmx@...>
 

Yes it would seem that way but it does work very well.

Using the bridged T design from Avago apnote with common 1n4007 worked very well for me
at 6M and the environment was "must still work with 100mW from the antenna".    It is what
you get with a very local ham that can't run a repeater contact at less than 1KW.  Never
minding BC stations 4 miles away, and 7 miles the other way the local Boston TV nexus. 
Bridged T has the feature of near constant 50 ohms and even with 1n4007 50DB range
was easily had.  That went in my 6M SSB contest radio that I called Crunchproof.

Another part that works well is the DBM,  Apply small DC (less than 20mA) to the IF port and
the loss though it is small. Reduce the applied current and 40-60DB of attenuation is had
(depends on balance).

The closer to the antenna the better the result, however it has to be out of the TX path.

With the uBitx/Bitx that easiest to do in the amps. as they are split for RX and TX.  The
switching is already done.

Allison

Re: AGC circuit to try?

Jerry Gaffke
 

By this:
>  Yes it would seem that way but it does work very well.

sounds like you mean that a PIN diode bridge attenuator should have no problem 
with the strong RF signals it might encounter toward the front end of the uBitx.
That's good to know.

I do think your gain control scheme using the 1n400x parts would work fine.
Though one BAP64Q gives more dynamic range, and can be all in one spot.

And is just plain cool.
It's puzzling to me that they can maintain a 50 ohm impedance so well.

Jerry


On Tue, Apr 10, 2018 at 11:16 am, ajparent1 wrote:
Yes it would seem that way but it does work very well.

Re: W0EB/W2CTX Latest uBITX software release #ubitx

youainti@...
 


 Is this software hosted somewhere such as github or bitbucket?

Will   KG7YQB

Re: TDA2822 Audio problem #ubitx #tda2822

Jerry Gaffke
 

Sent an email to Oddwires through their contacts webpage, got a reply within minutes:
  
Hi Jerry, thanks for your inquiry. Board is configurable with a solder junction to 5 or 3.3V. Let me know if you need any more info. Thanks, Ian.


Very nice to have such a quick and concise response.
And he gave his direct line phone number with the response.
I'm sold.

Jerry





On Tue, Apr 10, 2018 at 10:06 am, Jerry Gaffke wrote:
The USB-to-UART cables sold for use by Arduino hobbyists generally have 0-5v logic levels,
not RS232.   That thing on Oddwires I suggested in a previous post:
    http://www.oddwires.com/cp2102-serial-adapter-module-usb-to-rs232-with-jumper-wires/
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.

Re: W0EB/W2CTX Latest uBITX software release #ubitx

Jim Sheldon
 

The only place it's hosted presently is in the "Files" section of this group.

W0EB

Re: W0EB/W2CTX Latest uBITX software release #ubitx

Jim Sheldon
 

Chris - If the KD8CEC software is working fine for you you should probably continue to use it. 

To use our latest software, you would have to either ADD a key jack and connect the tip terminal of that jack to the orange wire from the Raduino's P1 plug (PTT) line (you can easily just connect it to the PTT (ring) terminal on the MIC connector if you are using the provided 1/8" stereo jack for the microphone jack.  If not, connect the hand key jack's "TIP" contact to whatever contact on the microphone jack you connected to the orange PTT wire.  If you don't want to add another jack, simply wire your key with a plug to match your microphone plug.  The key would connect to the ring and round terminals on that plug with the TIP (microphone wire) left open. Simple as that.

Jim - W0EB

Re: AGC circuit to try? new topic?

ajparent1 <kb1gmx@...>
 

Correct you cannot filter IMD with wide filters unless its outside the crystal filter bandwidth.
For  bitx that is about 2.5khz give or take and for ubitx that's 15khz (45mhz filer is for FM, wide).

However...  Limiting the audio bandwidth to the modulator helps.  A good compressor
can help.  Isolating the tx audio from the RX audio may help.  Why?   The RX preamp
Q70 even unpowered the base emitter junction can look like a diode across the mic amp
(Q6) output teh clipping level is about .5 to .6V P-P and it would be noticeable.  Inserting
an audio low pass filter between C222 and C63.  Then you get a free audio clipper with
lower IMD at that point.  Suggested cutoff is around 3.5Khz.

If the N6DT pop stopper is used that would isolate the RX and TX audio paths, worth a
try and it could help more than the pop.

The next step is insuring the drive from the modulator to the succeeding stages does not 
push the DBMs into compression.  Generally that means staying 10db or more below the
LO for each mixer.  That helps both inband (IMD) and out of band (spectrum).  You trade
that for less power out and lower average power.  You need very little gain from the
modulator to the next mixer and the amp plus filter should have a net gain of maybe
only a few DB otherwise the mixers are being hammered and will compress and
you will hear that.  

Now filtering from the last mixer to the power chain does help the out of band especially out
of ham band products.  The fewer undesired products you feed the amplifier chain with the 
better the result.  The key is only out power to the RF you want even weak spurs and splatter
is lost power.  

Then you have to deal with the amplifier chain itself.  Every stage must have enough current
to insure you do not hit even -1db compression.    Note the output matching may not be
optimal and can have the device in voltage or current limiting.  Underloading and overloading
can be troublesome. That's tricky as what may work well for 80-20M might be really poor at
10M.  If you do not need above 20M then optimize for that, you should be able to get a few DB
improvement.  For example the low pass filter could then have a 3db corner of 16mhz.  The
output low pass filter can be  then for split for 80 through 20M (or 40M). 

A 24 volt battery in the field... 2 8AH gells will do that nicely or 6 series LiPo.  Both cases give
more watt-hours with less current.

However for the ubitx that means protecting the most everything before the pre-driver from 
more than 12V. The TBA2822 seems fragile.

I do know that with the monobanders I have for 80/40/20/15/10/6M that they all perform 
better as they are optimum fot the band rather than trying to be everything for ever where.
Multiband with wide tuning is not easy ad requires some compromise to accomplish at that
uBitx does pretty well.


Allison

Re: AGC circuit to try?

Henning Weddig
 

Jerry and all the other AGC enthusiasts:

first of all I would replace the first audio amp with an amp of higher dynamic range, as this amp firstly limits the dynamic range in the uBITY as in the BITX40.

I am still thinking of using a NE5534 (gain = 20 dB?) and thereafter use a SSM2167 (or MAX9814?) as an audio processor with AGC functionallity.

A PIN diode attenuator can be used either in front of the first xtal filter (IF = 45 MHz) which will not give much distortion  due to the long carrier life time..

Why that all?
About 38 years ago (spring 1980) I was a member of a design team for a main ship´s, communication receiver (10 kHz to 30 MHz) with a first IF of 63.078 MHz. The first mixer was a Mini Cirucuits SRA 3H.  The IF port was terminated with two BF246B in common gate configuration-- unfortunately the P8000 was obsolete even at that time.  Then a PIN diode attenautor (three diodes) was used in front of the rfirst xtal filter followed by a BF910 DG MOSFET gain stage.  Unfortunately the inpurt return loss as a function of the attenaution for the PIN diode attenautor is not constant, which introduced some ripple in the passband.

The second IF was 5 MHz. For the gain stage we used MC1590 (in a TO99 case, wider temperture range as the MC1350).

I designed the "demodulator cassette" (last IF stage with a MC1590, delta gain = 40 dB, with some tricky AGC voltage linearisation; DSB-AM; SSB/CW demodulator with CA3028A, not the famous MC1496 )  including the AGC generation and audio preamp. For the AGC the RF was postamplified and a Plessey SL621 AGC long/short hang derivced circuitry built with opamps was used.
There was one problem: the feedthrough of te BFO voltage did introduce some AGC voltage even under no RF, but at that time did not matter much...
MC1350 users: please read the old app note for the MC1590, input and output iompedances must fullfill scertain conditions in order that the amp will not oscillate.

A High Gain Integrated Circuit RF-IF Amplifier with wide Range AGC


The "famous" G6LBQ clone of the BITX20 using this MC1350 chip showed on my build this self oscillation problem!!

The gain reduction scheme was as follows: the gain reduction started at -107 dBm (SSB bandwidth; 20 dB SINAD) and for my cassette ended at a gain reduction of 40 dB. Then the gain stages on the first and second mixers together gave an extra 80 dB gain reduction.
As the AGC performance was measured from the 20 dB SINAD point on (+30 dB) we never tested how the receiver behaves if 30 dB steps were introduced which will affect the gain stages (first and second mixer) in front of the filter bank. May be that also there problems can occur due to delays in the filter bank. 

Concering the pregvious mentioned AGC stability problems:
in the next receiver design the AGC scheme was changed, i.e. the gain control was completely done before the filterbank, the AGC voltage generation still done in the demodualtor dassette (its amp had a fixed gain) and then the problems of an instable AGC started, when using narrow bandwidth (CW) filters which were behind the gain reduction stages. The reason is the "long delay" due to the narrow bandwidth of the filter. 
 The remedy was a so called "lead-lag" compensation-- EE´s may remember the associated control theory!
I am not a control theory specialist, so I can not defenitely say that the SSB filter in the UBITX will intorduce such a long delay in the step response if a PIN diode attenautor is uesed in the first IF, that the control loop must go unstable.

BTW: the four PIN diode attenautor originally comes from Hewlett Packard -- when they were in the semiconductor business, then taken over from other companies...
There must be a lot of variations concerning the control voltage range and component values, I remember that even on Microwaves & RF there was an article about it. 

I remember that I also built a four diode PIN Diode attenautor, and ran into problems of not -constant return loss (S11). In addion I introduced a linearisation circuitry using opamps for the control voltage range to make it more "dB-linear". But as ohte rnoted, the inserteion losse even at minimum attanuationnis in the range of 2 to 3 dB.

73
Henning Weddig
DK5LV  

Am 10.04.2018 um 20:29 schrieb Jerry Gaffke via Groups.Io:

By this:
>  Yes it would seem that way but it does work very well.

sounds like you mean that a PIN diode bridge attenuator should have no problem 
with the strong RF signals it might encounter toward the front end of the uBitx.
That's good to know.

I do think your gain control scheme using the 1n400x parts would work fine.
Though one BAP64Q gives more dynamic range, and can be all in one spot.

And is just plain cool.
It's puzzling to me that they can maintain a 50 ohm impedance so well.

Jerry


On Tue, Apr 10, 2018 at 11:16 am, ajparent1 wrote:
Yes it would seem that way but it does work very well.

Re: uBitx just started transmitting a loud hum #ubitx-help

James
 

Raj, just to clarify, that scope was on the collector of q6 with the 4v wave form. The base had only shown much less voltage. The collector had DC voltage as well (somewhere around 10v but I forgot to measure it exactly last night) which is about what I would expect.

The mic input to the base of q6 does have DC of around 1 or 2V again I didn't measure it exactly as it looked about right for the voltage divider bias made up of r61 and r62.

As pointed out, there may well be a grounding issue elsewhere, which would/may explain hearing audio on transmit at the beginning, but at least the culprit for the hum was related to the electret mic.

Just to clarify, haven't measured current of rig yet on tx but it is less than 3A as my fuse is intact.

#uBITX polyfuse? #ubitx

Keith VE7GDH
 

Anyone using polyfuses with a uBITX instead of a fuse? I have some here, but have never played with them before. Would they react quick enough to provide any real protection, or would they be just too slow?

--
73 Keith VE7GDH

compiling KB8CEC version 1.07

Ross Bell
 

Hello: Bitxers:
I have trouble compiling Ians lasted version 1.07 keep receiving the following error message:
C:\Users\Ross\Documents\Arduino\ubitx-1.07\ubitx_20\ubitx_menu.ino: In function 'void menuBand(int)':
ubitx_menu:71: error: 'printLine2ClearAndUpdate' was not declared in this scope
       printLine2ClearAndUpdate();                            ^
ubitx_menu:120: error: 'updateDisplay' was not declared in this scope
       updateDisplay();
                    ^
 
C:\Users\Ross\Documents\Arduino\ubitx-1.07\ubitx_20\ubitx_menu.ino: In function 'void menuCWAutoKey(int)':
ubitx_menu:500: error: 'updateDisplay' was not declared in this scope
     updateDisplay();
 
                   ^
 
C:\Users\Ross\Documents\Arduino\ubitx-1.07\ubitx_20\ubitx_menu.ino: In function 'void setDialLock(byte, byte)':
ubitx_menu:1148: error: 'printLine2ClearAndUpdate' was not declared in this scope
   printLine2ClearAndUpdate();
                           ^
 
C:\Users\Ross\Documents\Arduino\ubitx-1.07\ubitx_20\ubitx_menu.ino: In function 'void doMenu()':
ubitx_menu:1223: error: 'printLine2ClearAndUpdate' was not declared in this scope
 
     printLine2ClearAndUpdate();
 
                              ^
 
C:\Users\Ross\Documents\Arduino\ubitx-1.07\ubitx_20\ubitx_menu.ino: In function 'void factoryCalibration(int)':
 
ubitx_menu:1478: error: 'updateDisplay' was not declared in this scope
 
   updateDisplay();
 
                 ^
 
Using library Wire at version 1.0 in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\Wire 
Using library EEPROM at version 2.0 in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr\libraries\EEPROM 
exit status 1
'updateDisplay' was not declared in this scope
Hoping someone can tell where I went wrong! 
 Thanks and 73 Ross Bell K7RSB

New file uploaded to BITX20@groups.io

BITX20@groups.io Notification <BITX20+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the BITX20@groups.io group.

File: ubitx_I2C_V4_00R.zip

Uploaded By: Jim Sheldon

Description:
W0EB/W2CTX I2C software Version 4.00R for I2C enabled uBITX Raduino cards and the W0EB/W2CTX/N5IB RadI2CIno cards. This software will NOT run on a stock standard Raduino card unless it has been modified to operate with an I2C display This version is for an I2C enabled 2 X 16 LCD display. (The 4 line x 20 character version will be released later). Jim Sheldon - W0EB

You can access this file at the URL:
https://groups.io/g/BITX20/files/ubitx_I2C_V4_00R.zip

Cheers,
The Groups.io Team

Re: TDA2822 Audio problem #ubitx #tda2822

RCBoatGuy
 

I strongly advise against using any kind of tape on a daughterboard containing a silicon IC. Tape can store a lot of charge, and the stickier the tape the worse the charge build up.  You risk zapping the Si5351 due to ESD if you use tape on the board.

73,

Carl, K0MWC