QRP Frontend 02

QRP Frontend 02

Final test with the Arduino Mega controlling the i2C buss(select Filter and set attenuator Tx/Rx, turn Rx amplifier on/off.

QRP Frontend 02 is a BP filter board with RX preamplifier MAR-6 or a discreet PIN-diode attenuator, controlled by a dac. The same BP filter and the attenuator is used in Tx and is driving a amplifier SGA-3486Z as driver for the QRP PA earlier described. All BP filter is controlled from I2C bus. BP filter is from YU1LM i i think it is rely good result, no alignment.

I has started working on a front panel board, the latest before putting all this together to a QRP Transceiver. Stay tuned!

QRP LP filter and SWR board

QRP LP filter and SWR board

Here is the LP-Filter mounted on the earlier described PA.

QRP LP-SWR 01 is a LP filter board 1.8MHz - 52MHz and added SWR Meter, all relay for filter is controlled from I2C bus. The filter is design from GQRP Club Datasheet W3NQN, Filter PDF. I have rely problem to get low insertion loss, so I think it was the toroid was the problem. Now I know it is the capacitor I firs used has really bad Q value. I has change to SMD GC0 500V capacitor and they has much higher Q value than the hole mounted capacitor I bayed first. The SWR was presented in QRP-Quarterly January 2018, SWR Meter. I lock for different diodes then 1N60 and tried a few types and get god result with HSMS2800. Her is the result. 

Exemple 80m and 10m.

Backside off the filter.

Part off shematic

I have a few PCB left, e-mail if you ar intrested xxx@gmail.com.

Signal generator for short wave 0.1 – 30 MHz

I have an old test set Schlumberger 4022 I don’t need longer. This was one reason to build this generator. The generator is a kit from QRP Labs   it uses Si5131 from Silicon Labs. I used 2 attenuator  Weinschel  0-63.75 dB. The insertion loss @ 0dB atten was around 7 dB so I need a Amplifier and one more attenuator to compensate for that. I adjusted the attenuator to get 10 dBm output. A high isolation switch on output to turn on/off RF, typical 75dB isolation. A rotary encoder and Arduino mini pro drive the attenuator and isolator directly and one I2c OLED display, really simple solution, sw 100 row of code.

RF Power Meter

It started with that the Anritsu power meter ML2438 brakes when i turn on the meter. The fault is in the power supply part. I lock around on internet and found this from Elektor.  link RF Power Meter

I ordered  the boards and build it. Get a problem with the software note a few liens in a forum and get a updated version in a few days. Added battery voltage reading on the display. It is really handy to only have one connection the RF port, that’s the reason I build in Lipo-battery 7,4V.

Data• RF power meter
• Bandwidth 1 MHz to 10 GHz
• Dynamic range 55 dB
• Compact: approx. 95 × 36 × 30 mm
It has 20 calibration points in frequency, so it is possibility to get accurate measuring result.

Fox receiver for 2019

Fox receiver

Prototyp

It starts in the spring this year, I help Bo SM5CJW to do some small receiver board he work with.  I save some boards for own use and later I get updated info from Bo. So I will give it a try.  I build the HF board and an LF board, the  Lo Si5351 i was familiar with earlier, it was also published in Swedish ham magazine QTC. After some change of mixer it works grate with excellent  sensitivity  and low noise level. Bo also have same example on different antennas, and I start to try with loop antennas . I really like the result. I build prototypes with both loop and ferrite antenna and as I see it the loop is the winner, 1 more shape on minimum signal, 2 more quiet, ferrite  has a small noise I didn’t  here in loop, 3 a little bit higher signal level.

I decide to try this receiver build together with my earlier built electronic compass. This was the hardest bit to put in 3.3V cpu together with an sensitivity receiver (around 0.5 uV) many filters and try and error to get all thing to work.

I start to merge the code to one cpu but I couldn’t  get it small enough, so way not run the Lo with Bos code on Attiny85 and do the rest with an Adafruit board Pro Trinket 3V. So this Fox receiver has 2 cpu!

Here is the result.

Sensitive receiver.

Excellent Front back or side decision.

Integrated compass direction  in display and calibration status .

Frequency information in display.

Battery voltage in display.

Signal strange meter in display.

Attenuator 0-80 dB info in display.

Look forward to test signal strange in practise, difference so far  95dB 1m from Fox compared to 3.5 km from fox.

I am relay glad I start this work has learn a lot.

Thanks to Bo SM5CJW for the receiver part.

QRP PA

QRP PA

QRP PA

See earlier work in December 2017. After that I made a PCB and have now mounted and tested the first board. It is inspired from K5BCQ and from  DK1HE QRP-PA.

Not as god as I hope, but working.

+10dBm iN,

OUT  @ 1.8 MHz  41,3 dBm

          @  7,1 MHz 43,3 dBm

          @ 28,4 MHz 41,0 dBm

          @ 52 MHz 39,2 dBm

RL < -15 1,8 – 52 MHz

Current 2,5 +/- 02A

I hope it will be in one more QRP transceiver  I have ides for, we will se!

There  is also an USB to serial board on the back panel.

I have some PCB over if you are interested e-mail.

Minima PA

Minima PA

I by  the Minima complete all mounted component in February, but i didn’t receive any so i by a new in April a kit 100W, after build it, i burn two transistor MRF 9120 so no idea to go on. Change to use IRF530 and skip 50MHz. And this works. After a try to made and measure on LP filter, all have high insertion loss  more then 1 dB. I decide to by one and to get ready with the PA. I found this on ebay

So a small board  with diode to fix the band select, and a regulator for the relays had to be done .

I already have an old led driver  LM3916 to monitor the power,  useful to monitor when struggling with the SDR parts!

Link to PA description Example Minima pa

Link to Filter

Result PA 1.8 – 30 MHz Output 45 – 75W ( drive max 5W) SWR 1.1 in 3.5 – 30 MHZ 1.2 @ 1.8MHz.

Hope to use it more in 2019!