Low pass filter for Minima

I need a Lp filter to put after the PA-2008. I made a copy of the original design and add 2 pcs. off 5v regulator. My relay is 5V. I made simulation of the filter in ELSIE program. The result from Elsie is to optimistically. Perhaps I should have use heavier wire in the inductor. If more stop attenuation is wonted, I think better layout and more shielding is needed.

Here is the ELSIE simulation.

Her is the real result only filter on PCB.

Here is the measurment, in - out of the PCB.

I hope it has been better but here is the result.

I have run a first QSO, but Murphy is with me, i will come bake, stay tuned.

Minima QRP Transceiver Setup

I won’t to describe a little off the process to get this Minima up and running. Early in the spring I set up this pc board to put main board and digital board connected, and to check tx and rx.

BFO.

First problem I could not hear any station clear SSB, I figured out that the bfo. was on the wrong side,  lo is over  f0, see BFO wrong. This is now changed so it is working.

Filter.

Next problem was filter 15-30 MHz didn’t switch in when move to 18MHz. I think it was hw problem check agene now fault. Time to lock at sw. and there it was, I added this line,

pinMode(BAND_HI, OUTPUT); ?

and now it works , original from Radiono - The Minima's Main Arduino Sketch.

Modulation.

The rx. woks fine listening on 80m. But tricky to get power out. I try to put out mic signal and ston, to modulate. The level at modulator is low. I have build Bitex or more exactly MKARS80 and it works grate from beginning, the difference is a emitter-follower. I build this on my board, it dossent effect rx level much.

Now I can have a grate signal on modulator.

Next the ston. is a bit low for monitoring, change R41 10 ohm to 22 ohm value sounds ok. But for modulation docent work. Try signal from T13 collector its much higher, but impedance in mic stage is to low so one possibility is to connect at mic input, I will fine tune later. I also change emitter resistor 220 ohm to a trim pot, 500 ohm, to adjust mic level

Button.

The SW. WA0UWH has made locks grate so I decided to install 7 buttons for the final setup.

I am now working hard to get the LP-Filter after the PA to work,

Theoretical loss and loss in practical. Stay tuned I will be back.

Minima PA Driver and Rx Preamplifier

Minima PA Driver and Rx Preamplifier.

I start at locking in the book Experimental Methods in RF Design, page 2.32. There was a good example on a amplifier for higher Pout then I need, so I lower the current. I do a test and find it working. I add a Rx preamp switchable in/out amplifier, copy from a QRP station.

Made a PCB and it is now finished.

The Result, gain 1.8 MHz 32 dB, 30 MHz 29 dB.

Pa for the Minima Transceiver  QRP Pa 2008

I make a decision to by this kit instead for doing the RF386 pa for Minima. After build, I put the transistor on a sheet  of aluminum. Adjust bias and start test.

Power in +10dBm.  Vin = 13,5 V.

Frequency       Power                Current

3,5 MHz             12W                    1,53A  

7,1 MHz             13,2W                1,57A

14,2 MHz          13,2W                1,43A

21,2 MHz          8,5W                   1,31A

28,5 MHz          7,9 W                  1,27A

I bye the kit here.

Excellent Measurements. Here by IN3OTD.

Si5351

Si5351

I lock so much at info about this module so i order one from Adafruit.

Breakout Board

After that I came over this really inspired, QRP homebuilding transceiver from qrparci, presented in Januari number, and here . So I play around with it, couldn’t get the code to compile so I change to the AdafruitRSGBLcd display I have. The performance locks ok for QRP, lots of info here   NT7S .

8 kHz – 160 MHz , I measure around -2 dBm out @ 50ohm on f0.

I really like VFO + BFO on this small board. I will try it in one of my project later on.

TFT Display 2.4”

#include "SPI.h"

#include "Adafruit_GFX.h"

#include "Adafruit_ILI9340.h"

ADS7846 Touch-Controller

One day in summer i tested the TFT display 2,4” 240*320. I tested different library. The best I tested was this Adafruit_ILI9340 and the library Adafruit_GFX.h. Just convert signal I/O from 5V to 3,3V change the pin number and all works. Tested some writing. The Code did as in this video TFT video if I remember correct. Also weird up SD card and wives the parrot and sunset.bmp. Tested a simple code for touch screen, ADS7846 Touch-Controller. This will be the display for next QRP station.

Fox Transmitter 80M now Working

 

This work started in Januari 80m Fox it has now came to the end.

The Fox-Transmitter fail in the beginning of the same week that i wont to use them for a competition her in Sweden. Two of the foxes burn up the FET IRF510 after a few minutes. I have a older board off this type and it has run for several years.  As I understand the problem is the high capacitance between terminals on this FET. It was not possible to load the gate more (1k ohm). So I tried to change the FET to a NPN transistor BC139 and it looks promising. I change 2 components R to C and put in R on not used pads. 5 Foxes has now been working for several hours, and in a small competitions W31. But it was a hard fight against  Murphy. I will build 2 more this winter. Stay tuned.  My son has also updated the SW with more Features. I f you won more info please contact me.