Date   
Small audio amplifiers BC637

ohwenzelph
 

I want  to duplicate the small audio amplifiers at https://ludens.cl/Electron/audioamps/AudioAmps.html
but he uses a BC637 & BC640 pair. They have the BC640 at mouser but NOT the BC637. What should I use instead for the BC637?
Or do you know a reliable place to get real ones?
(Or is there another equivalent complimentary pair that would be ideal to use instead?)

thanks

jerry aa1of

Re: Power curve flattening...a lot more #ubitx

Jerry Gaffke
 

Very clever, and very cool!
Much of what you have figured out could be applied to other attenuation schemes.


On Tue, Apr 10, 2018 at 06:32 pm, John wrote:
Got some pretty good results with limited memory usage to flatten the power curve, but only in voice/digital modes (SSB).

Power curve flattening...a lot more #ubitx

John <passionfruit88@...>
 

Got some pretty good results with limited memory usage to flatten the power curve, but only in voice/digital modes (SSB).

I use the first IF shift to produce a fixed attenuation to keep the output power within the required limits.

The process is two fold, a one off calibration exercise then I have a menu item that selects Low, High or Max power.

For mine I have used 5W and 10W as targets for the Low and High values.

I get the following results (I have modified the final stage with  RD16s plus other changes):

80m to 10M in Low power settings I have variations between 4 and 6 watts. In High setting I get a range between 9 and 11 watts.

I use only 16 bytes of data points (could be stored in EEPROM if desired).

In my ATU I use a spare digital output of the 2nd Arduino to send a 1500Hz tone, low-pass filtered, to the microphone input. The audio filtering plus the 2nd IF filter take care of the audio harmonics and the signal is clean. This could be done in the Raduino if digital lines are freed like with an I2C display.

That way I can tune in low power and more importantly I can transmit digital modes in low power without having to adjust the drive every time I change bands.

I will update the code in the file section so that it can be incorporated elsewhere if desired.

Thanks Jerry for the fixed table idea.

All the best,

73, John (VK2ETA)

Re: AGC circuit to try?

Gordon Gibby <ggibby@...>
 

​fascinating.

Thanks!!


learned a lot.



From: BITX20@groups.io <BITX20@groups.io> on behalf of K9HZ <bill@...>
Sent: Tuesday, April 10, 2018 8:34:47 PM
To: BITX20@groups.io
Subject: Re: [BITX20] AGC circuit to try?
 

So back more years than I care to count, I designed and build my first receiver.  That is when I first learned how to build AGC circuits.  I did a lot of research…  At that time most of the leading edge designs based upon the latest published theory came out of places like Collins, RCA, Hammarlund, etc.  They all had certain things in common… A good RMS detector and voltage amplifier/ follower, a low pass filter, an integrator with variable time constant (variable AGC timing), and a DC offset amplifier (provides a place to put an RF Gain control).  My receiver was transistorized so I had to use what I had gleaned from the tube world in the transistor world.  I did a lot of experimentation, but the attenuating element I used in the end was something quite simple… a dual gate FET.  Everywhere from the first RF amp, through the IF and mixer-amps I used dual gate FETS.  It was quite simple to use the AGC voltage out of the DC offset amplifier (just an op amp) to (essentially) turn the gain up or down on those FETs.  I’ve replaced Q10 with a BF998 and rematched/ rebiased the part.  With just a variable voltage source on G2, it seems to work as you would expect (variable gain).  A little more gain but a little less noise too.  I’ll have to take this to my RF lab to see how the new front end is actually performing.

 

The difference here to the pin diodes is that you won’t have the IMD issue.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

 


Virus-free. www.avg.com

Re: AGC circuit to try?

K9HZ <bill@...>
 

So back more years than I care to count, I designed and build my first receiver.  That is when I first learned how to build AGC circuits.  I did a lot of research…  At that time most of the leading edge designs based upon the latest published theory came out of places like Collins, RCA, Hammarlund, etc.  They all had certain things in common… A good RMS detector and voltage amplifier/ follower, a low pass filter, an integrator with variable time constant (variable AGC timing), and a DC offset amplifier (provides a place to put an RF Gain control).  My receiver was transistorized so I had to use what I had gleaned from the tube world in the transistor world.  I did a lot of experimentation, but the attenuating element I used in the end was something quite simple… a dual gate FET.  Everywhere from the first RF amp, through the IF and mixer-amps I used dual gate FETS.  It was quite simple to use the AGC voltage out of the DC offset amplifier (just an op amp) to (essentially) turn the gain up or down on those FETs.  I’ve replaced Q10 with a BF998 and rematched/ rebiased the part.  With just a variable voltage source on G2, it seems to work as you would expect (variable gain).  A little more gain but a little less noise too.  I’ll have to take this to my RF lab to see how the new front end is actually performing.

 

The difference here to the pin diodes is that you won’t have the IMD issue.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 

 


Virus-free. www.avg.com

VK4PLN's Radrino replacement boards

K9HZ <bill@...>
 

Nick VK4PLN…  your Boards showed up today.  They look very good.  Now to build a couple up.  Thanks again!

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

Moderator – North American QRO Group at Groups.IO.

 

email:  bill@...

 

 


Virus-free. www.avg.com

Re: #uBITX polyfuse? #ubitx

Doug W
 


If you access the list from https://groups.io/g/BITX20/topics there is a search function.  Here's the last discussion https://groups.io/g/BITX20/topic/7489182 regarding polyfuses and other things.

Re: #uBITX polyfuse? #ubitx

K9HZ <bill@...>
 

Depends what you are trying to protect... It's as good as a slo blow fuse.


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
Like us on Facebook!

Moderator – North American QRO Group at Groups.IO.

email: @Doc_Bill

-----Original Message-----
From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Keith VE7GDH
Sent: Tuesday, April 10, 2018 3:28 PM
To: BITX20@groups.io
Subject: [BITX20] #uBITX polyfuse?

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




---
This email has been checked for viruses by AVG.
http://www.avg.com

Re: SI5351 simultaneous clock changes #ubitx-help

John <passionfruit88@...>
 

Hello Jerry,

Tried both methods and came back to your idea..hihi

The lookup table (four frequency points, plus interpolation) does the job better.

For info about the si5351 clock updates, the chip waits for the 8th register to be written to effect the frequency change.

I wrote a method to do as you said changing both clocks first 7 registers then quickly writing the 8th ones. It reduces the clicks but not 100%. Plus the FWD power reading gets messed up when the ATU tunes.

So now I have low, medium and high power dialled up in the menu. Neat.

Thanks for your help.

73, John (VK2ETA)

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

John <passionfruit88@...>
 

Fine and useful research Jerry. Thanks.

73, John (VK2ETA)

Re: POP fix

Rick Price
 

Tried to open the new uploaded .sch file in Eagle. Message says start
missing. Is Eagle the correct program to open this in or was another program
used. Thanks

Rick
KN4AIE

Re: AGC circuit to try?

ajparent1/kb1gmx
 

On Tue, Apr 10, 2018 at 11:29 am, Jerry Gaffke wrote:
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.
They are better at higher frequencies.  However at lower HF it may be problematic.
The 1N4007 is fairly slow and makes a terrible rectifier at 10KHz, I tried them years
ago for a LVSMPS to go from 24V down to 5V.  Schottky was a must.

And is just plain cool.
It's puzzling to me that they can maintain a 50 ohm impedance so well.
There are several designs that as the diode goes to high resistance its complement
is going to low resistance into a resistor.  With care this works well to the Ghz and
higher range.  Check page 9 of the attached PDF.

I'll put the Microsemi hand book in the files area.

Allison

Re: POP fix

ve7hcw@...
 

Thanks to Don ND6T and Gary AG5TX on the insight of why there is a feed back thump on receive when the condenser mike is bumped. I have added an extra resistor and a 2n7002 MOSFET  to clean up the noise. using the KISS principle  to keep every thing simple as possible to procure  and using one value of resistors , capacitor and transistors . I have posted in the file section.

Re: Erratic tuning with my new uBitx

Chris Clarke G3SQU
 

Hi Ian
Just to let you know that my straight key behaviour has now improved out of sight with v1.061, which is fantastic. I was finding that different keys behaved differently and could be unreliable, my favourite Speedex in particular, so I'm really pleased about that.

Also my receiver is now performing far better for CW operation than with v1.01: I had been wondering if there was a problem that the SSB passband was being used for CW, as when I was tuning to zero-beat at 600Hz, where my passive audio filter peaks, the signal would not just be getting weaker but there was so little of it left I could barely hear it! The only benefit of using my filter was that I didn't hear so much QRM either. Now this doesn't happen, I'm gad to say so it's improved my operating experience immeasurably. I took part in the SP-DX competition at the weekend without being able to use my audio filter and was just swamped by all the competing stations. I did manage 34 QSOs, but again I was struck that those powerful signals, that were so strong when 2-3 KHz off tune, were barely audible once I'd tuned them to my 600Hz offset/RIT - the band was so busy there was always QRM from 2-3 KHz off frequency. Not being an SSB operator, nor having ever owned a good SSB-capable rig, I had never come across this particular 'feature' ... seems obvious now!

However, it has left me with another question! I am using CWL because it 'feels' better: I tune above the signal carrier and my RIT offset is subtracted and so my signal has the same frequency as the signal I have tuned in, but as it is below my listening frequency I feel that I am operating with the USB and therefore it should be called CWU! Is my logic faulty or have I got my rig configured all wrong?

Hope you are not pulling your hair out with my naive questions pre-digital age questions ... I'm not sure if I dare start asking about the BFO configuration!

Despite the queries I am having a fascinating and very rewarding time with this rig and your enhanced software, and I am extremely grateful that you have put in so much time and effort.


Best 73 Chris
G3SQU

PS I don't have a microphone so I'm basically staying away from all SSB-related issues if I can!

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

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

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

#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

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.

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.