Monday, July 19, 2021

 NEW parts from my

There are some new parts which I made in last month. I do have much more at the table, but I am waiting for enclosures...

Small 3-way RX splitter / combiner board:

The splitter or combiner is a very useful device. It can provide equal voltages, equal current, or equal power to matched or unmatched loads. Like all passive splitters and combiners, this device is less than ideal. Isolation is maximum only when at least one port are properly terminated. In this case isolation between the three splitted/combinated ports is maximum when the main port is properly terminated. This HW is designed only for RX line. Both impedances 50 or 75 Ohm can be selected by the jumper.

Main functions:
- Broadband: 0.1 MHz to 60 MHz
- 3-way Splitter or Combiner
- Low loss
- In to Out is typ. -5,8 dB
- 50/75 ohm impedance - easy jumper switch

PCB size = 50 x 50,4.
Aluminium enclosure size W x H x L = 58 x 24 x 50.

- Impedance 50 or 75 Ohm
- Insert loss: around 1 dB
- Split 4,8 dB, together with IL around 5,8 dB
- Isolation more than 18 dB for middle port and more than 23 dB for 1 and 3
- SWR on splitted ports better than 1:1,15 on HF, resp. 1:1,25 on 6 m
- SWR on main port around 1:1,3 on HF, resp. 1:1,4 on 6 m

- Antennas combiner - 3 el broad side array
- RX signal divider
- 10 MHz signal splitter
- One antenna to three RX

4-way PTT splitter:

This is simply 4-way analog splitter. Designed for no-delay PTT switching. From one input to 4 outputs. You can split PTT signal to 4 independent devices.

Main functions:
- Universal (PTT) switch splitter
- Minimal delay
- Compatible with 5V PTT logic (OM-power)
- 4 x output FET switch - DC 50V 0,5A
- PTT LED indicator.
- RCA connectors.
- PCB size = 50 x 50,4 mm.

Available as:
Assembled board - tested
Assembled in aluminium enclosure (blue)

- Input PTT logic compatible with 5V and more
- Input PTT logic active when grounded
- Input PTT logic current typ. 40mA
- Output FET switch 50V 500mA for each port
- DC power supply 9V to 15V typ. 65mA

- PTT for more PA
- TRX PTT to another RX and TX devices
- PTT to interlock, PA etc.

Decoder BCD to DEC (1 from 8) not only for antenna switch:

This is simply but powerful decoder from BCD data to one of eight. You can use it everywhere you have less wires than you need. You need only 4 wires and control up to 8 outputs. You can supply external relays over the BCD data wires. There is universal output driver. You can drive outputs by switching to GND or + Vcc voltage. BCD inputs include RF and high voltage protection.

Main functions:
- BCD to DEC matrix table
- Outputs 0 to 7 or 1 to 8 (jumper)
- Universal OUTPUT: + or gnd
- No external voltage needed. Up to 0,5 A by BCD wires
- BCD input 9 to 13,8V
- RF and high voltage protections
- Both drivers (ULN and TBD) are included
- PCB size = 90 x 52

- Output current max. 500mA
- Voltage drop for TBD driver typ. 0,2V for +12V input and 0,6V for BCD wires power input
- Voltage drop for ULN driver typ. 0,8V for +12V input and 1,3V for BCD wires power input
- Input voltage > 13V is recommended for 12V relays
- Control voltage for BCD input is 9 to 14V
- Low loss in switching driver
- Universal output switching: to GND or + Vcc
- Output 0 for 0000 BCD or 8 for 0001 - easy by jumper
- Compatible with Ameritron MCS-10
- RF and high voltage input protections

- Universal decoder BCD to DEC
- Compatible with Ameritron switches
- When you miss wires to your tower :)
- Remote Control expander

Tuesday, May 25, 2021

 6 and 4m MSK144 and FT8 skimmer OK2ZAW/2

There is new Es season starting on VHF bands. I have seen interesting DK8NE 6m skimmer (link) for more modes. I do have Proxmox virtual server under the roof in 40m above the ground. Why not to run one more VM, add 4m dipole with filter and LNA for RTL-SDR (70MHz) and RSP1 (6m). There are some photos. You can find spots at:

3D printed insulator for 70MHz dipole


Thursday, May 20, 2021

 Outstanding opening on 6m to NA 19th May 2021

I had big luck to be on air during the afternoon 19th  May 2021. I were able to work NA until 1 am in the morning. Big surprise was John W7CD from WA. Quick QSO with strong signal. He played for more than 1,5 hours around -10 dB signal.

I totaly made 80 NA stations during evening!

It was very nice to meet some friends. First QSO to NA this year was with Pat W5VY. Thanks for email PAt :) 

Hello Jan,

I was great to work you on 6M FT8 today!  Your Four to One QRO switch was in-line….with very little attenuation!!

73, Pat, W5VY

Thanks also to Gary K9RX and Mark K4SO.

Tuesday, February 16, 2021

OL57ZW - in memory of our friend Zdeno-san OK2ZW - CQ WPX RTTY 2021

OL57ZW is special callsign dedicated to the memory and honouring Zdeno OK2ZW (ex.OK2PZW), who unexpectedly left us on 4th January 2021, at the age of only 57 years. For Zdeno, the radioamateur hobby was everything and his greatest passion. He was an excellent DX-man, HF and VHF contest operator, who achieved many excellent world results. He was active from Accra as 9G5ZW and Ankara as TA2ZW in the past. He was also participated in several DX expeditions, where he was a brilliant operator.  Zdeno took part in more than 10 contests with us from our OL7M club.

He was also active with contest teams OL2R and OK5W.

He was our great friend and buddy, whose departure hit us hard. Please, recollect all the great memories you had with Zdeno. We will surely do the same thing...


Call: OL57ZW
Station: OL7M

Class: M/S HP
QTH: Policko
Operating Time (hrs): 48
Location: Northern Europe

Summary:   Compare Scores
Band QSOs
80: 564
40: 1306
20: 1065
Total: 2935 Prefixes 1087 Total Score 12,258,099

Thanks for QSOs - All stations will automatically receive a special QSL via the bureau.

R.I.P. Zdeno

Pavel OK1MU on behalf OL7M gang

Photos by Olda OK1YM:

Saturday, December 26, 2020

LoRa APRS - part 3: Raspberry PI (3 or 4) image - ready to use with LoRa & 2m APRS and OpenWeb RX ( RTL-SDR )

Project description
It is exactly one year from my first LoRa APRS test. Thanks to Ondra OK1CDJ who sent me first device for testing. I have opened Facebook room about LoRa APRS a few weeks ago. Thanks this more and more people are interested to try it. That's why I have decided to prepare Raspberry PI (3 or 4) SD card image for PnP - you need to change your station data. You can use this image for LoRa APRS iGate based on IOT4pi project, also 2m (70cm) classic APRS based on RTL-SDR and OpenWeb RX.

All of my LoRa APRS blog posts here.

Download image and upload it to the SD card
At first you need to download image and upload it to SD card. You need 32 GB 8 GB (rev. 3) or bigger one. I recommend to use Samsung EVO or some similar higher quality card.

You can find last image here.
Download image from the link on this page and unZip it.

Then you need to copy it to the SD card. This is for windows users :) So please download and install this software: Win 32 disk Imager

Now you can insert SD card to PC, start Win32DiskImager and open UnZipped image. Select right Device (microSD card) and press Write. If you see error, eject and insert SD card again.

After that you can insert microSD card to Raspberry PI and start it. If the Raspberry is connected to LAN you need to find its IP address. You can find it in your router (DHCP clients), using some LAN IP scanner or connect HDMI monitor.

If you use LAN connection, download and run Putty.
Write right IP address and press Open. You will see information about certificate - do agree.
Write username: pi and password: raspberry 
Now you should be logged in:

It is highly recommended to change password by: passwd
Write current one: raspberry and write your new one.

If you have bigger SD card than 32 GB you should resize partition. 
You can check free space by: df -h
Resize card: sudo raspi-config

(EDIT 10-2021:)
Change your  Time zone: dpkq-reconfigure tzdata 

You can run Midnight Commander: mc

RTL-SDR device: test and calibration
Test if you can see RTL-SDR(s): sudo lsusb
You can see my two devices connected:

Calibration: sudo kal -d 0 -s 900
Means -d 0 is first RTL-SDR, -d 1 is the second one. -s 900 means calibration on 900 MHz GSM

Calibration using one of the scanned chanels: kal -d 0 -c 45

You can see my RTL-SDR frequency mistake. This one has internal TCXO, so it is very stable compare to cheaper plastic one. You can use this value to 2m APRS and OpenWEB RX.

LoRa APRS 70 cm based on IOT4pi
More about this project is here.
Tested with Raspberry PI daughterboard by Ondra OK1CDJ - , with RFM-96 (433MHz) You can use also I2C oled display + buttons.

Configuration file is located in: /home/pi/iot4pi
File is: sudo nano APRS.conf 

You can start IOT4pi with output to screen by: sudo ./iot4pi_LoraGW_01 (end CTRL + C)

APRS (2m or 70cm) with the PYMULTIMONAPRS
You can test RTL-SDR with raw decoding to screen: 
sudo rtl_fm -f 144.800M -s 22050 - | multimon-ng -a AFSK1200 -A -t raw -  (end CTRL + C)

Configuration file is located in: /home/pi/rtl/pymultimonaprs 
File is: sudo nano pymultimonaprs.json 

You have to change: 
 - callsign: yourcall-10 (can have different number)
 - ppm: more in calibration info
 - gain: check gain you need with OpenWeb RX
 - device_index: number of RTL-SDR - 1st is 0, 2nd device is 1 etc. There can be two RTL-SDR, one for 2m APRS and second for OpenWeb RX. 
 - lat, lng position: click on map and add point - this will show you position
 - comment and text is up to you

Save configuration by CTRL + O (enter) and CTRL + X. 
Copy config file to /etc by: sudo cp pymultimonaprs.json /etc/pymultimonaprs.json

Manual start with output on screen:  
sudo pymultimonaprs -v (close with CRTL + C, later could start after boot)

Some more info at: this link

OpenWeb RX - web based receiver (RTL-SDR)
OpenWeb RX allows you to use RTL-SDR as web based receiver. You can have more frequency profiles, you can use also internal decoders like: WSJT-X, DMR, D-STAR, FreeDV, Packet Radio (can works as APRS iGw too) etc. 

Configuration file is located in: /home/pi/rtl/openwebrx file is: (open with F4)

Configuration instructions are here.
If you use more RTL-SDR in one Raspberry PI, then select different device index (-d 0 or 1) for 2m APRS and OpenWeb RX. I recommend to use first for OpenWeb RX and second for PYMULTIMONAPRS.

Manual start with output on screen: (close with CRTL + C, later could start after boot)

You can open your browser: raspberry_IP:8073    example:

Automatic start after the boot:
There is file where you can uncomment what do you like to start after the boot automatically:
File: sudo nano /etc/rc.local
Example for IOT4pi auto start

Example for 2m APRS and LoRa Igate

All together :

My instalations:


- Raspberry PI with LoRa APRS, RTL-SDR for 2m APRS and RTL-SDR for OpenWeb RX
- Wideband LNA + FM notch filter + 3-way CATV splitter. Lora has 433MHz BPF.
- Antenna is dualband X-30

OK2ZAW-2 & OK2ZAW-4 Cottage

- Raspberry PI with LoRa APRS and RTL-SDR for 2m APRS.
- Wideband LNA  + 2-way CATV splitter. Lora has 433MHz BPF.
- Antenna is dualband X-30