Antenna switch for SDR (5)

The technical specifications of Airspy HF+ says;
+10 dBm Maximum RF input.

Since the maximum RF output power of IC-7410 is 100W, we need the attenuation of 40dB or more with an antenna switch.

A very rough experiment shows that with the TX RF output power of 35dBm at 7MHz the leak to the RX port is around -6dBm (=S9+67dB), which means the attenuation of 41dB.

FT8 decode with IC-7410 and Airspy HF+

A 5m long wire antenna is connected to two receiving systems:
(1) IC-7410, WSJT-X on Raspberry Pi 3 Model B
(2) Airspy HF+, WSJT-X on Mac mini

The decoding results that appear in the Band Activity window is almost the same for the two systems.

Airspy HF+, IC-7410, and Raspberry Pi 3

Running two instances of WSJT-X with:

% wsjtx --rig-name=IC7410 &
% wsjtx --rig-name=AirspyHF &

pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 7/7
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 2: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
pi@raspberrypi:~ $ arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 2: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

WSJT-X and GridTracker

GridTracker is a companion program for WSJT-X.

You may find that the program offers some information not provided by PSKreporter.

In this case the two programs, WSJT-X and GridTracker, are running on the same machine.

And this is when the programs are on different machines.

Raspbian Stretch and systemd-timesyncd

pi@raspberrypi:~ $ lsb_release -a
No LSB modules are available.
Distributor ID:	Raspbian
Description:	Raspbian GNU/Linux 9.4 (stretch)
Release:	9.4
Codename:	stretch

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.14.34-v7+ #1110 SMP Mon Apr 16 15:18:51 BST 2018 armv7l GNU/Linux

pi@raspberrypi:~ $ ps aux | grep time
systemd+   276  0.0  0.4  17276  4012 ?        Ssl  Jun18   0:00 /lib/systemd/systemd-timesyncd

pi@raspberrypi:~ $ timedatectl status
      Local time: Tue 2018-06-19 01:55:55 UTC
  Universal time: Tue 2018-06-19 01:55:55 UTC
        RTC time: n/a
       Time zone: Etc/UTC (UTC, +0000)
 Network time on: yes
NTP synchronized: yes
 RTC in local TZ: no

pi@raspberrypi:~ $ cat /etc/systemd/timesyncd.conf
# Entries in this file show the compile time defaults.
# You can change settings by editing this file.
# Defaults can be restored by simply deleting this file.
#
# See timesyncd.conf(5) for details.

[Time]
#NTP=
#FallbackNTP=0.debian.pool.ntp.org 1.debian.pool.ntp.org 2.debian.pool.ntp.org 3.debian.pool.ntp.org

pi@raspberrypi:~ $ ls -l /var/lib/systemd/clock
-rw-r--r-- 1 systemd-timesync systemd-timesync 0 Jun 19 01:59 /var/lib/systemd/clock

Airspy HF+ and Raspberry Pi 3

A very small system to decode FT8 signals.

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.14.34-v7+ #1110 SMP Mon Apr 16 15:18:51 BST 2018 armv7l GNU/Linux

pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 7/7
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 7/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7

pi@raspberrypi:~ $ arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: Loopback [Loopback], device 0: Loopback PCM [Loopback PCM]
  Subdevices: 7/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: Loopback [Loopback], device 1: Loopback PCM [Loopback PCM]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7

pi@raspberrypi:~ $ cat /etc/modules
snd-aloop
pi@raspberrypi:~ $ sudo modprobe snd_aloop
pi@raspberrypi:~ $ lsmod
Module                  Size  Used by
snd_aloop              24576  4

WSJT-X Transmitter Audio Level (FT8)

Note: The USB MOD Level (Menu 39 of IC-7410) is set to 100%, and the RF output power level is minimum (around 1 watt) in all the following cases.

The output volume of Linux sound system is far bellow the maximum.



WSJT-X Transmitter Audio Leve: -30dB.




WSJT-X Transmitter Audio Leve: -20dB.




WSJT-X Transmitter Audio Leve: -10dB.




WSJT-X Transmitter Audio Leve: -6dB.




WSJT-X Transmitter Audio Leve: -3dB.




WSJT-X Transmitter Audio Leve: -1dB.




WSJT-X Transmitter Audio Leve: 0dB.



It seems that the signal suffers from some clipping when the Transmitter Audio Level is set to 0dB.

From the top, the Transmitter Audio Levels are; 0dB, -1dB, -3dB, -6dB, -10dB, -20dB, -30dB, -40dB, and -45dB.

IC-7410 USB Audio Level

Injecting a digital full scale single tone (440Hz) audio signal through the USB I/F of IC-7410. The USB MOD Level (Menu 39) is set to 100%, and the RF output power to minimum which is around 1 watt.

A dummy load is being used.