Monday, November 21, 2022

 LoRa APRS digi and LoRa Packet Radio experiments

LoRa boards are becoming very popular in the HAM community. Advantage is in price and also incredible sensitivity. With very small power (20-80 mW) you are able to make DX over hundrets of km. 

I have updated my LoRa point in Eagle Mountains to ver. 4.0 :) a few weeks ago. It is solar powered hardware with 4el for DiGi OK2ZAW-17, WX station OK2ZAW-15 (broken wind sensors) and new LoRa Packet Radio experimental 2m APRS RXnode and BBS (OK2ZAW-1 and -7). 

Very nice Tropo ducting came a few days after update. New ODX DF0AP-15 and 707 km!

Inside of the box: LoRa WX station, 2x solar power system (own design), Raspberry pi zero with LoRa module and RTL-SDR for 144,8 MHz APRS RX.

New Packet Radio has LoRa module as a link radio. Raspberry Pi zero works as BBS, node and 2m APRS receiver. All decoded packets from 2m are sent by the LoRa link down to another Raspberry and then to APRS network. Power consumption of the raspberry is 1W + RTL-SDR (running) 1W. Weather station measure temperature, presure, wind (demaged sensor) and voltage of the ACU:

Decoded LoRa packet Radio with APRS packets down at OL7M QTH.

Monday, November 14, 2022

 RX Audite - TRX/SDR splitter and switch

This is my new RX splitter and TRX switch. Including string of protections, optional preamplifier and INBAND RX antenna input. You can find more at: this link.

Main functions:

  • Frequency range: 0,1 to 60 MHz
  • Main TX/RX ANT splitter to two RX
  • RX RF limiter protections for both RX outputs
  • Isolated SDR RX output + Common-Mode filter
  • HPF (> 100kHz), high voltage and current protection at both RX outputs
  • INBAND RX ANT input - works only for SDR output
  • TX-RX switch controlled by the PTT
  • Designed for 2nd RX, WEB-SDR, SKIMMER or Panadapter
  • Controller OFF = TX/RX ANT port to SDR RX out via RF limiter protections Skimmer/web-SDR
  • Controller ON = TX/RX ANT port splitted to TRX and SDR RX out via RF limiter protections
  • TRX TX to main TX/RX ANT = SDR RX out to dummy load or INBAND RX ANT input via RF limiter protections
  • Front panel Switch - SDR RX output to INBAND RX ANT all time
  • Preamplifier (optional): insertion loss compensation, up to 14 dB of additional gain
  • Preamplifier could be ON for SDR even controller is OFF (both by the front panel switches)
  • Very high isolation when TRX TX and SDR to INBAND 100 dB @ 14 MHz and 80 dB @ 50 MHz
  • Please, see also Frequently Asked Questions There FAQ

One black box but many different parts inside:

  • TX / RX switch controlled by PTT signal
  • PTT splitter (IN/OUT) in sniffer mode (IN directly to OUT) or output PTT FET switch picture
  • 2-way RX splitter with low loss
  • 2 x RF limiter RX protections - the best on the market :-)
  • RX switch for INBAND RX antenna (only for SDR output) settings
  • Both antennas with HPF > 100 kHz
  • RX preamplifier (high IP3, 18 dB gain) with variable ATT - OPTIONAL link
  • RX lines with High Voltage protections > 60 V AC
  • RX lines with SuperFuse current protections > 100 mA
  • Very high isolation TX to SDR, between RX ports, INBAND RX and TX/RX ANT port


  • Supply voltage DC + 12 to 14 V (13,8 V recommended), DC plug cable
  • Supply current DC max. 0,7 A with preamp
  • Maximal TX power 250 W, recommended 200 W
  • Very high isolation when TRX TX and SDR to INBAND 100 dB @ 14 MHz and 80 dB @ 50 MHz
  • PTT IN compatible with 5V logic or higher, TX = GND
  • PTT OUT sniffer (IN=OUT) or output FET (max. 35V DC and 0,5 A) picture
  • PTT is not designed for QSK but you can use with right PTT lead/tail/TX delay time: min. 10/10 ms
  • Default configuration SDR to INBAND RX ant input while TRX TX settings
  • Optional Preamp preset to insertion loss + 6 dB (total gain abt 10 dB)
  • Low insertion loss see measurements picture

RF limiters:

  • Limiter for RF signal to + 13 dBm = 20 mW (could be + 17 dBm) @ 50 Ohm
  • Current SuperFuse - the only at market
  • Can survive high input power (current) for long time
  • The soft clipping reduces the IMD products of a classic hard diode clip limiter

Internal Preamplifier module: (OPTION / version with preamp) link

  • Preamplifier could be retrofitted also by you - customer
  • High IP3 preamplifier module with 18 dB gain
  • With 2SC5551 transistor
  • Real OIP3 is +34 dBm
  • Preset to 40 mA @ 13,8 V
  • Low Noise Figure (NF) < 2 dB (60 mA 50 MHz)
  • Variable gain by output ATT
  • Preset to 10 dB for TX/RX ANT to both RX outputs = insertion loss + abt. 6 dB (1S) of gain
  • Bypass relays
  • Could be switched ON even the controller has got power switch OFF - preamp for SDR output.

    FAQ remoteQTH

144 MHz TROPO 11. - 13. Nov 2022

There were nice TROPO duct opening in last days. Thanks to some antenna work at OL7M I can use new 12el G0KSC LFA Yagi. Due my faul when I have overdrived my 150W mosfet PA some weeks ago, I was able to test new antenna only with less than 5W :( When I come home from OL7M and switched remote ON, the big surprise started at the screen. Nice tropo ducting to OZ, SM. Saturday morning started with opening to EU and UA. I was very happy to make some nice QSO over 1000 km at FT8 with only 5W in the antenna. ODX is EW6D from KO55 1149 km.

Worked stations: