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.

Fox Receiver 2m

Sam weeks ago i found that the ARDF resources from G3ZOI was updated. URL fox description I like this design wary good. So I ordered one bored and this arrived a few days later, PCB + 2 potentiometers, 3.5 mm jack for earphone and 2 Led, soldered and aligned. Order a box from Elfa 10-431-36 Aluminium 115 x 64 x 30 mm 1550B. I won’t little different setup see picture, possible to operate attenuator and pejel with one hand. Already use a old antenna. Fox Antenna Is made after this info. Use Isolated SMA connector and can easy change antenna.

Testing on Lab bench.

 

Current 13.6 mA.

Frequency 143,6 – 145,0 MHz

 

Input            RSSI pin 7.

-100 dBm    0,98V

-90                1,16

-80                1,40

-70                1.66

-60                1,84

-50                2,0

-40                2,23

-30                2,45

-26                2,5 max.

 

MinDetectebelSignal  around -120dBm

 

To turn on led1 red it needs maximum signal -30 dBm.

I measure Led1 Vforward around 1.8V if I remember correct.

I use one Elfa 75-036-76 it turns on 1,6V with the same current. Now Led1 turns on earlier.

 

Practice at home 3 Km away strong signals excellent reception.

Red diode lightning 100 - 150m before Fox.

2015-04-24 First Competition. Bad result, but excellent receiver especial I like the pitch it helps to determine the exact direction, When Red diode on, take exact bearing and catch the fox.

 

It is my third 2m Fox receiver and the best I have.

Minima Input-filter

This is the 15 MHz filter RF OUT - C13

This is the 30 MHz filter RF OUT - C8

This is the notch L7, CT3, L9, CT2, L11, CT1

This is the 30 MHz filter RF OUT - C8 and notch.

This is the 30 MHz filter RF OUT - C8 and notch and K1.

First comment  L1, L5 is 0,68uH and L2, L3, L4 is 0,82uH. Notch L7, L9, L11 is 3,3uH I check in filter-program Elsie before I order inductor and the effect was small.

I think the vna-plot says more than a lot of data or word. The notch is not so selective so it effect the 21MHz band, perhaps it is possible to compensate with preamplifier. Locking at the plot it can be possible to change IF to 16 MHz -1,65 to 14MHz and + 2,68 MHz to 18 MHz band. Chang lo-filter to 10 to 12 MHz cut off.

I think it is better to have tow small relays in sted of one, the K1 on this solution I work with (pp2kr pcb). I think this is the reason way there is les attenuations in the last plot. K1 serves out and in of the filters.

  Here is the result a finished board.

Next step is to load original sw and start playing with it the receiver. I will be back in May stay tuned.