Archive for the Electronics Category

IC-7300: more antenna connectors with Arduino!

Posted in Electronics, VHF with tags , , , , on 12 April 2017 by iw0ffk

I wish to use the IC-7300 on all my bands, but the problem with this rig it’s always the same: too much frequencies for a single antenna connector and I don’t want to swap the coax all the time. On the market there are manual coax switches, but there are not so handy for a remote use…and this one is cheaper.

So, in a rainy Sunday I have built this 1×3 antenna switch controlled by Arduino. I already done something similar in 2009 with a PIC, this time I choose Arduino because it does not need of any programmer to write the code on it, just the USB cable. In the past several OMs have sent their empty PICs to me and I have sent them back programmed. A single project usually don’t worth the cost of a PIC programmer.

This should stops the foot traffic, everyone can load the code in the IDE and write it into the chip with a click.

This 1×3 ant switch is made with few generic electronic components around a “Nano” (ATMEGA328), but the code can be adapted to any ucontroller. It is powered by the transceiver (pins 2 and 8 of the ACC connector) and reads the frequency from the “Remote” jack. It can be fixed directly on the antenna’s connector by using a male-male PL259 adapter. Into the RF box there are three Finder relays model with gold plated contacts. The values of attenuation and isolation between the ports are good:

28 MHz – att. 0.11 dB – isol. 40 dB
50 MHz – att. 0.11 dB – isol.35 dB
70 MHz – att. 0.12 dB – isol. 32 dB

The microcontroller and the rest of the parts are in a separate box to avoid interferences.

The IC-7300’s range of frequency 30-74800 kHz is divided in 24 sub-bands, every sub-band can have associated one of the three antennas output. The right antenna is selected automatically. Simply it remembers the last selection.


Ask me the source code to my address. does not permits to upload zip files.

Icom IC-7300 RX Antenna mod

Posted in Electronics with tags on 11 March 2017 by iw0ffk

I like this transceiver, good receiver, fantastic DSP filtering and NR, excellent GUI and many goodies like the automatic record of QSOs triggered by ptt/key or the RS-BA1 software that shows the waterfall on the PC screen (it works ok also in Linux wine).

Probably Icom has decided to limit some capability of this model for market reasons. The IC-7300 has only one TXRX antenna connector and no RX input, but it’s easy to add a connector on the back and, inside, there is enough room to place a coax relay.

The relay can be mounted on a shaped aluminium bracket fixed to the transceiver by two screws that fix the RF-UNIT board to the chassis.

The adapter has been made with a female TMP connector and a SMA-M to SMA-F transition (used as a wear protection for the connectors of the instruments).

The external ATU supply connector can be moved away, like on the IC-756, and replaced by two pieces of copper pcb board that holds the switch and the coaxial connector.
The orange wire of the ATU is used to energize the relay.

This mod is fully reversible and the transceiver can return in his original status in few minutes.

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Now the IC-7300 can be used also as a second receiver for the 6m or for monitoring the IF of the FT-817, connected to the 3cm transverter.

Hacking the Spectrum Analyzer Siglent SSA 3021X

Posted in Electronics on 29 January 2017 by iw0ffk

ssa3021Last year  in the laboratory where I work we bought two Siglent SSA 3021X 2.1 GHz Spectrum Analyzer for generic/every day use. It’s a nice cheap object with all the functions of a modern digital instrument: colors, memory and math for traces, ethernet access, usb drive support etc.
After a while I found some bug in the software (v 7.03), as example if a screenshot image is saved in the internal memory with spaces in the filename, then it’s impossible to delete….
So I googled for a firmware update and casually found a thread on EEVBlog’s Forum where a guy shared the root’s user/password to log in the instrument with a telnet client. :-)

The big brother of the SSA3021X is the SSA3032X 3.2 GHz SA that has the same hardware of the SSA3021X. The instrument works on Linux, Busybox is running, and it’s an easy job to edit a configuration file and upgrade the SSA3021X to SS3032X with all the options enabled (tracking generator included) and extra BW filters 1Hz and 3MHz (!!!)

This works with installed firmware version 7.07, probably Siglent has corrected this bug on the newer firmware releases, but for sure I don’t need further updates on these units…


Kenwood TS-590 official ALC mod

Posted in Electronics with tags on 12 September 2016 by iw0ffk


Thanks to the yahoogroup of this transceiver, finally is available the mod to eliminate the dangerous power spike generated at the start of every transmission. The power spike can reach two times the power selected for few milliseconds, in the best-case this can trigger the input protections of several linear amplifiers.

Kenwood performs the mod for free also on the units out of warranty, but here in Italy the official Kenwood lab has asked me the purchase bill. I don’t have that bill because my rig was bought used from another OM and it already was out of warranty.

Here the doc: ts590-alc-fix

Picture from DK5TX website



Another USB controlled 230V socket

Posted in Electronics on 16 May 2016 by iw0ffk

The easiest way to switch on-off a 230V socket using an USB port is to buy an already made device, but if one has some hardware in the drawer and some spare time in a rainy Sunday, he can try to build it by himself.

The scope of this job is remotely switch on and off some instrument in the hamradio shack when I’m away, using the USB port of  an always-powered pc server.

Disclaimer: be careful, here we play with the main voltage. Proceed at your own risk and try to don’t kill anyone or burn something.

I used an USB-TTL adapter with the PL2303 chip, 0.65 euro included shipping on a web store (how they can do that?).


The pins on the right side are +3.3V, +5V,  TXData,  RXData, Ground.
TXData and RXData are useless for this project, but their tracks on the PCB can be used to route different signals, on their path there are also two surface mounted bonus leds to monitor the status of the lines.
A little mod is needed. By using a magnifying glass and a cutter, the TXD and RXD pins have to be cut on the PL2303 chip. I have cut them from the top, keeping the blade close to the body of the chip then, with the soldering iron, it’s easy to remove the pins from the pads and connect 1-2 and 3-5.


After this mod, on the output plug  with the labels “TXD” and “RXD”, there will be two RS232 control signals, DTR and RTS, that can be raised/lowered at will.

This project uses only the RTS signal.

A mosfet (BSS138) is used to drive an opto-isolator to energize the 24V coil of a 2×8 amps relay.
The 24V are obtained directly from the mains, well I don’t like it so much, but this voltage is needed only for the relay’s coil, it isn’t worth a transformer, anyway in the little junction box there was not room for anything else…
This circuit is *LIVE*, no one  must be able to touch it when powered, it has to be placed in a plastic box or carefully isolated.Danger-Live-Electrical-equischematic_powusb

Most of the parts (capacitors, zener, resistors etc.) have been recycled from an old steam iron control board.

When connected to my Linux server, the PL2303 adapter is mapped as /dev/ttyUSBx, where x is a number depending the inserting order in the USB hub. I have a number of PL2303 connected to the pc, so it’s  highly recommended to create a static link to the port, whatever be the first PL2303 connected. The file /etc/udev/rules.d/serusb.rules has to be edited/created to contain a string like:

SUBSYSTEMS==”usb”, KERNEL==”ttyUSB*”, KERNELS==”1-2.1″, SYMLINK+=”ttyPOW”

This maps the port always to /dev/ttyPOW .
The number 1-2.1 is the position of the serial adapter on the USB hub. These RS232 converters have all the same serial number, so the only way to identify them is to insert always in the same USB port, easy. The hub position of /dev/ttyUSB0 can be obtained with the command:

udevadm info –attribute-walk –path=/sys/bus/usb-serial/devices/ttyUSB0

To move  DTS and RTS, for now, I use a minimal Python script created to test the signals, I think I will insert it as a cgi in the local webserver to permit any browser  to power on the instruments.
Here the script: dtrrts



KKMoon P2P PTZ cam tips

Posted in Electronics on 15 May 2016 by iw0ffk


A new pan & tilt camera installed on the rooftop to monitor the antennas, it’s a chinese 720p “KKMoon P2P Cam”, hardware version = JH41E-V1.0, firmware version build 2015.06.09 02:51.
I bought it on Ebay and received a partial refund due the several bugs in the firmware which make the object to be used with caution and a number of declared functions does not work at all:

  • Sending email notification when a motion is detected does not work, at least with my SMTP servers.
  • FTP upload of the images does not work. I’ve tried with my local working server, no success.
  • There is not a plugin for Firefox or Chrome, the only browser capable to view the h264 streaming video is MS Internet Explorer with a proprietary plugin. The stream can be reproduced also by VLC but without the pan and tilt controls.
  • There is a security issue, the rtsp stream can be opened without inserting any password even if the password is correctly set.

On the other hand the Android app works quite well and the image have a good quality.
Googling around I’ve found few results about this cam, this one is the most interesting.

Summing up, to view the stream with VLC (without password) the address to open is


To catch a snapshot the http address is


Unfortunately the snapshot image has a very low resolution 320×240.
I like to save an image every some minutes to create a time-lapse video, this resolution is unacceptable, but there is a workaround to obtain snapshots with good quality. This command get some seconds of video then save an image with native resolution 1280×720

cvlc rtsp://user:pass@IPAddress/camera-media/profile0 –video-filter=scene –scene-prefix=$prefix –scene-format=jpg –scene-path=./ –scene-ratio 240 –sout-x264-lookahead=10 –sout-x264-tune=stillimage –vout=dummy –run-time 15 vlc://quit

To rotate the camera the sniffed commands are

Move to the preset x:
where x = 1 to 16, preset number

Move UP:
Move DOWN:
Move LEFT:
Stop Movement:

I prepared a simple Python script to be executed in a terminal ->

$ ptz 3 moves the cam to the preset number 3
$ ptz r 2 moves the cam to the right for 2 seconds



Playing with ESP8266

Posted in Electronics on 1 May 2016 by iw0ffk

I am always been interested in efficient ways to remote control via internet my hamradio station, mainly due to the fact that I’m away from the shack most of the time.
I use my fully controlled remote station since 2006, my first QSO from the workplace was YL2HA in 144MHz during a good E-sporadic opening on 13/06/2006. Over the years several improvements have been added to reduce the bandwidth, the delay of the link and, in the latest years, to be QRV and work some basic QSOs by using the smartphone.

Some months ago I heard about a wifi module that can be controlled via AT commands (like the old modems) and I immediately bought one for few euros. The plan was to give a TCP way to communicate with the world to all the microcontrollers without the need to fill them with the TCP-IP stack.


When I received the module, based on the ESP8266 v12E, I discovered that it can be flashed  with a different firmware that permits to use the onboard microcontroller to control some input/output ports and a 10bit ADC. So there is no need to add another microcontroller to send the AT commands.

The new firmware is called Nodemcu and, when flashed, removes the AT commands  and adds a Lua interpreter. Lua is a programming language used for generic scripting.
I wrote a simple script to connect my access-point and start a basic web-server to control the status of an output pin, this pin drives a relay that switches on-off a 220V socket.
When connected to the access point, a led blinks in Morse code the last number of the ip address, to easily identify the module in a DHCP network.

This “Wifi controlled 220V socket” was built in few hours, I will use it to switch on the power amplifier when needed (instead to leave it always powered on).

I think the ESP8266 can have in the future many interesting applications to the our hobby.
I already have some ideas about it and I ordered a good number of these modules :-)