Saturday, November 19, 2022

High voltage supply for tube/valve tester

 A power supply for a future tube/valve tester


Main circuit for the positive side is similar to the one bellow (the top section),


 The filament circuit is similar to the bottom section.

 The negative supply is similar to the diagram bellow("Standard") with small adaptations to allow 2 different ranges:




 There's a separate transformer for each of the supplies; the filament the positive and the negative, also other separate on to power the voltage meters.

Was added a small relay controlled high voltage supply output so I don't get accidentally zapped, you need to constantly press enable button to have high voltage output at the terminals.

The internals:


 Finished here:


 
Working during testing:


Now I still need the tube socket and metering part for the full valve/tube test set, eventually something like this (only the top section):


Have a nice day!




Monday, October 03, 2022

Arduino bootloader burner

I have some spare ATmega328 chips that are not programed and can be used in some projects specially now the prices Arduino boards got some inflation.

In order to upload the program to the IC's you will need to burn first the bootloader, at least so that later you then upload via de Arduino IDE. 

Schematic and instruction are from here: https://docs.arduino.cc/built-in-examples/arduino-isp/ArduinoISP

End result:


Bottom Arduino is the programmer where you upload the ArduinoISP.ino code, it connects to the Arduino on top (target) that is going to have the chip to be programmed/burn.
The zif socket on the target Arduino just facilitates the insertion of the ATmega IC.

Another view:


For uploading: select the Arduino programmer USB port and then the programmer type "Arduino as ISP", in the end just "burn bootloader".


After bootloader burn:

Have a great day!







Monday, March 21, 2022

External PLL reference for Redline WL-2 Twin LNB

 As part of the construction of a QO-100 station decided to try and convert a common satellite LNB from internal PLL crystal reference to an external one.

 

On the image, during testing after the convertion was still drifting a bit since the Wavetek signal generator used was still warming up.

 This is the inside of the LNB after plastic and metal cover removed:

Another view bellow. The crystal oscillator is on the other side of the PCB so it's needed to de-solder the F plugs terminals (top left and right):

After completion of the operation I can confirm It does work, still need to do more testing with different input signal reference, at the moment it accepts/works from around -10dbm to 0 dbm. Also tried to inject different reference besides the 25Mhz to shift the IF and works with ref. higher than the 25Mhz, bellow testing with 25.787Mhz as the PLL reference

 

The drift is the fine adjust being done on the signal generator, the actual LO LNB frequency is the crystal frequency times 390.

The mod bellow, I also had to remove one cap from the input line to the output filter so that there is no load to the reference signal in.

The jumper wire is from one of the LNB external output plugs to the place where the crystal was (the two big blobs of solder).


 This is the original schematic (it's a RDA3567 chip on the LNB board) with the mods made:

The capacitor used was one of the ones that were connected to the 25Mhz crystal on the original diagram

To remove the original crystal since I don't have SMD tools, I placed the iron with a bit of solder on top of it and waited for warming up the underlying terminals until it could be removed (note: this voids the warranty).

Another view of the LNB inside:


 I also tried injecting on the LNB a parallel signal from the reference oscillator in the ADF4351 generator board to good success. Bellow the part where I took the signal from the ADF4351 reference:

I connected to the terminal normally used for the reference input and bridged the missing place for the 0 ohm resistor case you reference it externally.

Let's see in the future how stable is this internal reference of the AD4351, if good enough it avoids having to build an external TCXO for the LNB.

Have a nice day!



Sunday, February 06, 2022

ADF4351 Signal Generator with frequency select

Another one for the list of projects with the ADF4351, following the ADF4351 Signal Generator and the ADF4351 signal generator with sweep

 This one to be used on a future project, a transverter for QO-100 satellite where a TX and RX frequency will be needed, depending if RX or TX enabled. The original design of the RX for around 50Mhz is that it can be divided by two so that signal will drive the 25Mhz oscillator of the LNB. I'll probably do that way for the LNB but also as full down conversion from 790Mhz.

 Main code is from F1CJN at: https://github.com/F1CJN/ARDUINO-ADF4351-QO-100/blob/master/ADF4351_Dual_251119.ino with small changes for my particular board and needs. 

 

 The end result:


 The diagram:
 

might need a pull down resistor on pin D5 to ground since on open air even a finger touch will make it select the TX frequency. On "0" then default to enable the RX frequency. Added an LED to be on during TX frequency select and blinking 3 times during boot. The MUX out is not needed but could be implemented on the future to check if the lock is on.

The code (will change the TX and RX frequency for my needs in the future): 

 Original at: https://github.com/F1CJN/ARDUINO-ADF4351-QO-100/blob/master/ADF4351_Dual_251119.ino

Bellow with changes:
///// code adf4351_dual_v1.ino
/// look for " PFDRFout=25; // Frequence de reference" if using a 10Mhz reference /// on the board


//   ADF4351 with fixed frequency
//   By Alain Fort F1CJN november 29,2019
//   alain.fort.f1cjn@orange.fr
// 
//
//
//  ****************************************************** FRANCAIS *******************************************************
//  Ce programme permet de programmer un ADF 4351 avec deux fréquences fixes et en utilisant une fréquence de reférence de 10 MHz.
//  La premiére frequence frequence est utilisée avec un convertisseur émission (RX=0 et la seconde avec RX=1.Selection par PIN 5
//  Les fréquence de sortie peuvent être modifiées aux lignes 79 et 80 en conservant le format.
//  La frequence de reference peut être modidiée à la ligne ligne 70  (10MHz par défaut)
//  ********************************************* HARDWARE IMPORTANT *******************************************************
//  Avec un Arduino UN0 : utilise un pont de résistances pour réduire la tension, MOSI (pin 11) vers
//  ADF DATA, SCK (pin13) vers CLK ADF, Select (PIN 3) vers LE
//  Resistances de 560 Ohm avec 1000 Ohm à la masse sur les pins 11, 13 et 3 de l'Arduino UNO pour
//  que les signaux envoyés DATA, CLK et LE vers l'ADF4351 ne depassent pas 3,3 Volt.
//  Pin 2 de l'Arduino (pour la detection de lock) connectee directement à la sortie MUXOUT de la carte ADF4351
//  La carte ADF est alimentée en 5V par la carte Arduino (les pins +5V et GND sont proches de la LED Arduino).
//  ***********************************************************************************************************************
// 
//
//  *************************************************** ENGLISH ***********************************************************
//  This software is used to programm an ADF4351 with Two fixed frequency, using a 10 MHz reference frequency.
//  The frequency can be changed at lines 79 and 80, using the same format.Frequency selection is done with Arduino PIN 5.
//  The reference frequency can be changed at line 70, using the same format (Default 10 MHz)
//  ******************************************** HARDWARE IMPORTANT********************************************************
//  With an Arduino UN0 : uses a resistive divider to reduce the voltage, MOSI (pin 11) to
//  ADF DATA, SCK (pin13) to ADF CLK, Select (PIN 3) to ADF LE
//  Resistive divider 560 Ohm with 1000 Ohm to ground on Arduino pins 11, 13 et 3 to adapt from 5V
//  to 3.3V the digital signals DATA, CLK and LE send by the Arduino.
//  Arduino pin 2 (for lock detection) directly connected to ADF4351 card MUXOUT.
//  The ADF card is 5V powered by the ARDUINO (PINs +5V and GND are closed to the Arduino LED).

#include <SPI.h>
#define ADF4351_LE 3

uint32_t registers[6] =  {0x4580A8, 0x80080C9, 0x4E42, 0x4B3, 0xBC803C, 0x580005} ; // 437 MHz avec ref à 25 MHz
//uint32_t registers[6] =  {0x3D88FA8, 0x8009F41, 0x14E42, 0x4B3, 0x91003C, 0x580005} ; // 1969,501 MHz avec ref à 10 MHz
//uint32_t registers[6] =  {0, 0, 0, 0, 0xBC803C, 0x580005} ; // 437 MHz avec ref à 25 MHz
int address,modif=0;
unsigned int i = 0;
double FreqTX, FreqRX, RFout, REFin, INT, PFDRFout, OutputChannelSpacing, FRACF;
double RFoutMin = 35, RFoutMax = 4400, REFinMax = 250, PDFMax = 32;
unsigned int long RFint,RFintold,INTA,RFcalc,PDRFout, MOD, FRAC;
byte OutputDivider;byte lock=2; byte RX=1;
unsigned int long reg0, reg1;

void WriteRegister32(const uint32_t value)   //Programme un registre 32bits
{
  digitalWrite(ADF4351_LE, LOW);
  for (int i = 3; i >= 0; i--)          // boucle sur 4 x 8bits
  SPI.transfer((value >> 8 * i) & 0xFF); // décalage, masquage de l'octet et envoi via SPI
  digitalWrite(ADF4351_LE, HIGH);
  digitalWrite(ADF4351_LE, LOW);
}

void SetADF4351()  // Programme tous les registres de l'ADF4351
{ for (int i = 5; i >= 0; i--)  // programmation ADF4351 en commencant par R5
    WriteRegister32(registers[i]);
}

//************************************ Setup ****************************************
  void setup() {
  Serial.begin (9600); //  Serial to the PC via Arduino "Serial Monitor"  at 9600
 
  pinMode(2, INPUT);  // PIN 2 en entree pour lock
  pinMode(5, INPUT);  // Pin 5 for TX/RX
  pinMode(ADF4351_LE, OUTPUT);          // Setup pins
  digitalWrite(ADF4351_LE, HIGH);
  SPI.begin();                          // Init SPI bus
  SPI.setDataMode(SPI_MODE0);           // CPHA = 0 et Clock positive
  SPI.setBitOrder(MSBFIRST);            // poids forts en tête

  PFDRFout=25; // Frequence de reference
  RFintold=1234;//pour que RFintold soit different de RFout lors de l'init
  RFout = RFint/100 ; // fréquence de sortie
  OutputChannelSpacing = 0.005; // Pas de fréquence min
  //******************************************************
  FreqTX=1969.501;
  FreqRX=51.8462;
  //******************************************************
  RX=1; //

// ct2gqv
  pinMode(6, OUTPUT);          // PIN 6 for display if on tx and blink 3 times during boot.
  digitalWrite(6, HIGH); delay(500); digitalWrite(6, LOW); delay(500);
  digitalWrite(6, HIGH); delay(500); digitalWrite(6, LOW); delay(500);
  digitalWrite(6, HIGH); delay(500); digitalWrite(6, LOW);
} // Fin setup

void loop()
{
 //**********************************************
  RX = digitalRead(5);   // reading RX/TX
  if (RX==0){RFout=FreqTX; digitalWrite(6, HIGH);}  // output frequency selection // ct2gqv put out 6 high to display we are in tx
  if (RX==1){RFout=FreqRX; digitalWrite(6, LOW);}  // output frequency selection  // ct2gqv put out 6 high to low since we are in rx
  RFint=RFout;
 //********************************************
  if (RFint != RFintold) {
    if (RFout >= 2200) {
      OutputDivider = 1;
      bitWrite (registers[4], 22, 0);
      bitWrite (registers[4], 21, 0);
      bitWrite (registers[4], 20, 0);
    }
    if (RFout < 2200) {
      OutputDivider = 2;
      bitWrite (registers[4], 22, 0);
      bitWrite (registers[4], 21, 0);
      bitWrite (registers[4], 20, 1);
    }
    if (RFout < 1100) {
      OutputDivider = 4;
      bitWrite (registers[4], 22, 0);
      bitWrite (registers[4], 21, 1);
      bitWrite (registers[4], 20, 0);
    }
    if (RFout < 550)  {
      OutputDivider = 8;
      bitWrite (registers[4], 22, 0);
      bitWrite (registers[4], 21, 1);
      bitWrite (registers[4], 20, 1);
    }
    if (RFout < 275)  {
      OutputDivider = 16;
      bitWrite (registers[4], 22, 1);
      bitWrite (registers[4], 21, 0);
      bitWrite (registers[4], 20, 0);
    }
    if (RFout < 137.5) {
      OutputDivider = 32;
      bitWrite (registers[4], 22, 1);
      bitWrite (registers[4], 21, 0);
      bitWrite (registers[4], 20, 1);
    }
    if (RFout < 68.75) {
      OutputDivider = 64;
      bitWrite (registers[4], 22, 1);
      bitWrite (registers[4], 21, 1);
      bitWrite (registers[4], 20, 0);
    }

    INTA = (RFout * OutputDivider) / PFDRFout; 
    MOD = (PFDRFout / OutputChannelSpacing);
    FRACF = (((RFout * OutputDivider) / PFDRFout) - INTA) * MOD;
    FRAC = round(FRACF); // On arrondit le résultat

    registers[0] = 0;
    registers[0] = INTA << 15; // OK
    FRAC = FRAC << 3;
    registers[0] = registers[0] + FRAC;

    registers[1] = 0;
    registers[1] = MOD << 3;
    registers[1] = registers[1] + 1 ; // ajout de l'adresse "001"
    bitSet (registers[1], 27); // Prescaler sur 8/9

    bitSet (registers[2], 28); // Digital lock == "110" sur b28 b27 b26
    bitSet (registers[2], 27); // digital lock
    bitClear (registers[2], 26); // digital lock
  
    SetADF4351();  // Programme tous les registres de l'ADF4351
    RFintold=RFint;//modif=0;
 
  }
}   // fin loop

//// end code


Have a nice day!


 

Saturday, December 18, 2021

HP 3312A small repair

 No big troubleshooting here, the HP3312A function generator had been developing small fault over time, the last time I used it was not outputting signal or with the wrong shape, so decided to see what could be done.

This was the "sinusoidal" output:

 


Not good! Also the frequency was not in line with the bezel markings.

Here's the offending component on top board near the front panel.

I just guessed it was the one causing the issue, the crack was easy to spot.

The reference marked in the capacitor, if needed:

TRW 8508
HEW-331
.5MF +/- 10%
50 VDC

Better now after replacement, I didn't had 0.5MF as originally so by mistake placed a 2.2uF, got better but still some distortion seen:

 


 I then replaced by a 1uF one and now it's perfect, in the future I will probably try to find the right value (0.5uF) and replace.


Have a nice day!

Wednesday, December 15, 2021

PGA103+ Ultra Linear Low Noise Monolithic Amplifier

Had this little device for some time, an offer from a fellow ham some time ago (thank you Allan).

Schematic used is similar to the datasheet at: https://www.minicircuits.com/pdfs/PGA-103+.pdf


with small changes (similar to https://vu2bfo.in/pga-103-lna/), in the implementation I didn't included the front end diodes:


  The PCB was done with very few resources so it had to be tinned.

Basically made with a mix of vinegar and oxygenated water
 

On the sweep on the spectrum analyzer this is what you get.


 Will try this further on as fronted for a VHF/UHF radio.

 Other sources of information with more comprehensive details here:

http://www.g4ddk.com/PGA103amp.pdf 

(includes an HPF design for 130Mhz)

https://vu2bfo.in/pga-103-lna/

https://www.w6pql.com/LNAs%20(preamps)%20and%20MMICs.htm


Have a great day!



Sunday, December 05, 2021

10Ghz downconverter for 1.5Ghz spectrum Analyser

Had this build for some time, now it's time to show. 

 


 I was doing some experiments on the 10Ghz band and wanted a way of looking at the signals. Because the spectrum analyser I have only good to 1.5Ghz had to find a cheap way of doing it to get this:


Here looking at the third harmonic from an ADF4351 on 3.3Ghz after a pipe cap 10Ghz filter experiment.
 

The diagram explanation: a dbm mixer (Watkins-Johnson M80LCA) with a local oscillator based on a FVC99 10Ghz oscillator module (cheapest VCO I could find for 10Ghz). Some preamps on the input and output using 2Ghz preamp modules and replacing the MMIC amplifiers for the ones like Corvo NLB300 or ERA-1 that are good to 10Ghz.



The basic design:


 To this diagram I added a 6db directional coupler inline with the FVC99 VCO (used a Omni Spectra PN2023, good from 8 12.4Ghz) so I could measure the LO frequency and PLL it.

There is no stability control on the FVC99 oscillator, still working on a PLL system (maybe one of these days) but in my case I have two select positions, one: VCO is controlled by a single pot (like on the diagram) and the other position controlled by an EIP371 frequency counter (from the Lo Out via directional coupler) that makes the PLL loop. With EIP371 and since the output voltage of the loop is very small the control range seats near 9.5Ghz, there is an option of extending the range like on the EIP manual:

Or with a similar diagram, a multiply by 10 of the PLL voltage out of the EIP371, that would be enough to use the full range of the FVC99.

For now I use 9.5 Ghz if using the EIP371 for more stability and around 10Ghz set by the pot ("Flo" on the panel) if it's just a quick test.

Here the EIP working as external PLL controling the FVC99 so the LO gets more stable.



On the Rigol DSA815 spectrum analyser you can set the input offset to get the display right on the band of interest

Displaying here a 10Ghz signal using the 9.5Ghz Lo frequency

If you want to just check if the signal is around there, no need to use external PLL control to the FVC99, the "stability" with a simple potentiomenter  is enough.

Inside view:

The VCO adjust pot (top right in blue) is glued directly to the front panel

Some other images during prototype development:



Here one of the firsts tests, just an input amplifier, the mixer, the VCO and VCO amplifier and the mixer IF output directly to the spectrum analyser.

Testing during early days of the prototype with a 10Ghz homemade flange to SMA adapter and a pipe cap filter:

 



 

Anyhow, not a measuring device but it serves the purpose of checking if you have any signal around the 10Ghz band and for experiments, still very happy with the outcome and sensitivity.


Have a nice day!