Minima QRP the BiDirection IF Amplifier

This is no build and tested.

RX  

R24 0,4mA, 

R26 8,17V 2k2 -> 3,7 mA

R27 7,47 V 220 ohm  -> 34 mA

Total current R22 0,39V 10 ohm -> 39 mA.

Put in 10,4 mV 20 MHz from generator 50 ohm to C34.

Get 40,8 mV out @ C38 this means 11,9 dB ?, but in Z is not 50 ohm.

More then -25 dBm in @ C34 is clipping in T11

TX

R13 1,28V 220 ohm -> 0,6mA

R17 8,8V 2k2 -> 4 mA

R18 8,13V 220 ohm -> 37 mA

Total current R10 0,48 V 10 ohm 48mA.

Put in 32 mV 20 MHz from generator 50 ohm to C29.

Get 56 mV out @ C33 this means 4,9 dB ?, but in Z is not 50 ohm.

50 mV 1kHz to MIC in measure @ C33 with 50 ohm power meter -23 dBm.

100 mV 1kHz to MIC in measure @ C33 with 50 ohm power meter -16 dBm.

172 mV 1kHz to MIC in measure @ C33 with 50 ohm power meter -10 dBm.

It start clipping at higher inputs!

After this i test Rx put generator to C34 -107 dBm. 20,001 MHz.

Give me a audio around 12 dB SINAD, i can clear hear a toggle on/off generator @ -120 dBm.

For me it seems that this part is working, better then expected.

Next time i start with the X-tal filter lock forward to test the 30 X-tal i have in my box.

Fox Hunting Transmitter for 80m

As i mention in this blog Fox transmitter 2m that this work has start.

After Christmas i received this PCB to start work with. Most work left is to set output level and make the tuning to the short vertical antenna to optimal. There is also little sw upgrade to do.

I will put info here when working.  

Minima QRP BFO and Mixer

I started with the BFO, put in an inductor 3,3 uH with one trimmer CT5 to minimum c, frequencies was 20,003 MHz, I tray to put in 2N7000 to connect the other trimmer CT4 butt F go 2-3 kHz lower without fet switched on. I try BA482 in serie to ground it only lower the frequency a few hundred Hz. Turning on the diod i found a value 2,2k to 4,7k will be fine, frequency is 19,995 MHz.

Dc is  T5:e = 5,6V T6:e = 5,2V it means 11 mA to the BFO. I winding the T3 6.5 turn trifilare on BN43–2402. Then time to do diode matching. see Diode... i think 2,2k to 12V is to mutch current 6mA, it take to long time to stabelesise.

The BFO gives 1,5Vp-p on C27 with no load. 600 mVp-p @ 50 ohm. I can now hare a IF 20MHz 1mV in to C38 also see 20MHz signal on osciloscope when tx and audio to mic amplifier.

Next its time for Bi-direction-amplifier.

Marry Christmas and a Good New Year, 

de SM4HNG Leif.

Minima QRP Transceiver The Audio part.

AF Amp

After reading on the freelists i decide to test the audio amplifier, because there was lot of ides to change the design i have LM380 and LM386 in the box. The original amplifier could give around 600mV rms over 8 ohm before clipping. The LM386 could give 2,8V rms over 8 ohm P = U*U/R = 2,8*2,8/8 ~ 1W, LM380 give less power.

47 uF out. -3dB @ 200 Hz, 0 dB @ 100 kHz

5 mA no input signal.

135 mA @ 1 W out.

input 150 mVrms  @ 2,8Vrms  out.

Pre Amplifier

Max out 940 mV rms before clipping. Around 1 mV in. T16:c = 11V.

T15:c = 8,2V , T15:e = 6,4V, Around 2 mA current.

Mic Amplifier

30 mV in around 40 mV rms out.  -3dB @ 20 Hz  -3 dB @ 10 kHz. there is a little maxi-ma @ 200 Hz around + 5-6 dB. T13.e = 1.5V T13:c = 5.1 V must be 7 mA.

Side Tone

Wen tone on gives around 100mV @ max volym on speaker output, Tx monitoring.

Around 1 mV @ C28 modulator. T17:c = 6,7V T17:e = 0,27V.

Next it is time to do the BFO, stay tuned SM4HNG, I relay like this building the Minima

1.8" TFT LCD Display module ST7735S 128x160

The color on the TFT i not correct on this photo for same reason, sorry for that.

Just use level converter 5V -> 3,3 V 5 wires, CS, RESET, D/C, SCK and SDA.

Try the TFT sw in aurdino library Guide/TFT.

Next time i must find out if it is fast enough for S-meter update in next radio.

I am glad it works fine.

Minima main board started

The T/R switch is done. 5mA in Rx mode 45mA in Tx mode.

CW-Gen is done. 1mA when it is turned on. Output 10mV 720 Hz.

Tx/Rx, low = Tx  high = Rx, It is working ok if I/O is 3,3V.

CW-Gen if I/O is 3,3V R37 must be a lower value 47k > 27k, check T17c 6V.

Not much more to say about this.
The audio was to low for driving a speaker 140 m. So i must find a modification, i order some IC to tray. Next modification is to skip K2 LSB/USB relay.

The rest of the board will be the original design.

QRP MINIMA DIGITAL BOARD

 

A complete logic to a all-band sw transceiver.

55 cm2   115 mA       Lo included  10 MHz - 260 MHz   around +16 dBm out.
I use a Spark-Fun Breakout board, i do not have RS232 on my computers.
I don't think the the pcb was aimed for adapt directly back of the lcd, but i find it possibility to do that, no wires just connectors.

I am really glad i came in to this project, Minima.
I used the test for LCD and I/O from AE5PH a few minutes after ended the soldering all is completed tested. I program in 10MHz, 3,75+20, 17.2 +20?   and 28.4+20 MHz for test.

I spend last weekend to measure the spurious, output level, and later phase noise.
I started this blog with the DDS-60 so i compared this to the Si570 unit.

Si 570 was around +16 dBm from 10MHz - 260 MHz. (10 dB atten to instrument)
DDS60 was 8.5 - 6 dBm out, 10 - 48.4 MHz

I use my home-breve spectrum analyzer.

And here is some phase nose measurements.

Si570  f = 10 MHz, Fnoise = 149dBc @ 10 kHz offset.

Si570  f = 23,75 MHz, Fnoise = 145dBc @ 10 kHz offset.

Si570  f = 37,2 MHz, Fnoise = 138dBc @ 10 kHz offset.

Si570  f = 48.4 MHz, Fnoise = 138dBc @ 10 kHz offset.

Si570  f = 144,3 MHz, Fnoise = 129dBc @ 10 kHz offset.

i think it is a relay good value.

DDS60 f = 23,75 MHz , Fnoise = 123 dBc @ 200-300kHz offset.

Here is the spurious list for Si570 @ 23.75 MHz

374665,-105.567

2.97076e+006,-105.015

3.30659e+006,-84.054

3.48848e+006,-105.268

4.47881e+006,-101.74

Nice values.

Here is the spurious list for DDS60 @ 23.75 MHz

432.174,-104.615

651.559,-105.865

866.931,-107.598

8217.29,-106.33

16483.7,-91.9783

19704.9,-94.6973

33065.9,-91.1369

38828.2,-93.0068

40964.1,-98.8106

48969.1,-78.3117

65155.9,-91.3816

83652.8,-84.6034

100000,-81.2614

115349,-84.2683

148096,-82.02

180225,-83.4377

197049,-79.2568

227295,-80.9892

248513,-71.561

297076,-77.092

342676,-72.7429

395275,-80.2696

424529,-80.6772

447881,-75.4794

545047,-80.7331

712382,-75.0742

738273,-74.7648

836528,-76.63

1.23886e+006,-75.5836

I also check the Output Z.

Si570 was 13 ohm  from 10MHz - 150MHz.

DDS60 was close to 50 ohm at 10 MHz and little higher @ 48.4 MHz.

I have never test so mutch on a LO signal, i enjoy to build and measure. 

No i lock forward to start with the main board next weekend.

This is the schematic for this PCB.

Thanks to Ashhar Farhan the designer.  

Thomas Sarlandie driver for Si570.

PP2KR Kleibe PCB-Maker, tanks a lot.