Monday, December 26, 2022

Please visit our new e-shop :)

Saturday, December 3, 2022

Extra Virgin Can 70 - cavity filter for 70cm :)

Vodafone build new GSM site here at the roof in my job. There are three antenna systems for 800 and 900 MHz and this killed my experiments with LoRa at 433 and 868 MHz. I have found very nice cavity filter for 868 MHz at Aliexpress which works great but I need something also for 433 MHz.

I found 5 l can in my stock with drilled holes and N connectors. Marek OK2DL drilled it many years ago when I ordered these cans for 50 Ohm oil dummy loads :) I have decided to try it. 3D printed part helped with mechanical stability and works also as a nut holder. Tunning screw is metal, what is a bad idea but I do not have better now... The result is not so bad! I focused to very low Insertion Loss where the result is lower stopband and also higher BW. There, the IL is around 0,7 dB and 3 dB BW 9MHz. By the moving the internal loops from the tunning screw you are able to obtain better stopband but higher IL.

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 RX, node 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

Parameters:

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.

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:

Friday, October 21, 2022

LoRa APRS TROPO condx 20.10. 2022

There were nice TROPO condx on VHF and UHF last days. It is very interesting how well the LoRa modulation with very small power could coverage during the tropo conditions. LoRa DiGi in 1100 m asl with power around 20 mW with 4el 3D printed colinear system made new ODX to JN49xc 482 km.

Best RX ODX in this tropo was 586 km to JO40cb.