LOTW unconfirmed FT8 QSOs [SOLVED]

Posted in VHF on 17 March 2023 by iw0ffk

LOTW is the well known ARRL log online useful to match and confirm contacts between the radio operators without the need to exchange paper cards.

JTDX is one of the most used weak signal decoder/encoder software in use by the HAM radio community. JTDX saves QSO in ADIF format to the wsjtx_log.adi file. This file or a part of it, is periodically sent to LOTW, automatically or manually.

JTDX records, for each QSO, the start and ending GMT hours formatted as example

<time_on:6>120802 <time_off:6>120944

It may happen, during the normal activity, that you start calling a station and keep calling for a long time or stop calling him and continue after a pause. This often happens with OM of rare countries, rare squares or DXpeditions.
When finally the rare DX answers, 73, QSO logged and time_on differs from time_off of several minutes (hours?).

The rare DX station, on the contrary, saves your QSO in his log with time_on reasonably very close to time_off.

When both upload the log on LOTW, the QSO will be validated only if the two time_on values differ of maximum 30 minutes.

Kudos to Sergio IK0FTA who discovered the flaw.

I don’t know why LOTW use time_on instead the more logical time_off to match the QSO, there will be a reason for sure, I hope. However the solution is simple: edit the file wsjtx_log.adi and modify the time_on of QSOs that last more than 30 minutes to make them shorter.
Too many QSO to check ? There is a script :-)

#!/usr/bin/env python2
# coding=utf-8

import time
import sys
import os

def printfound(line):
    print "\nLong QSO detected!"
    print "##################"
    print line
    print "##################\n"

with open("./wsjtx_log.adi", "r") as myfile:
    with open("./fixed_qso.adi", "w") as outfile:
        outfile.write("Time_on fix for LOTW - IW0FFK 2022\n<EOH>\n")
        print "> Log found"
        for line in myfile:
            if "<time_on:6>" in line:
                rawtimeon = line[line.index('<time_on:6>')+11:line.index('<time_on:6>')+18]
                rawtimeoff = line[line.index('<time_off:6>')+12:line.index('<time_off:6>')+19]
                hh_on = int(rawtimeon[:2])
                hh_off = int(rawtimeoff[:2])
                mm_on = int(rawtimeon[2:4])
                mm_off = int(rawtimeoff[2:4])
                ss_on = int(rawtimeon[4:])
                ss_off = int(rawtimeoff[4:])

                if hh_on == hh_off:
                    if (mm_off - mm_on) > 25:
                        outfile.write(line[:line.index('<time_on:6>')+11] + str(hh_off).zfill(2) + str(mm_off-1).zfill(2) + \
                        str(ss_off).zfill(2) + line[line.index('<time_on:6>')+17:] + '\n')
                elif (hh_off - hh_on) == 1:
                    if ((mm_off + 60) - mm_on) > 25:
                        outfile.write(line[:line.index('<time_on:6>')+11] + str(hh_off).zfill(2) + str(mm_off-1).zfill(2) + \
                        str(ss_off).zfill(2) + line[line.index('<time_on:6>')+17:] + '\n')

                    print "Very long QSO or data inconsistencies"
                    print line
                    outfile.write(line[:line.index('<time_on:6>')+11] + str(hh_off).zfill(2) + str(mm_off-1).zfill(2) + \
                    str(ss_off).zfill(2) + line[line.index('<time_on:6>')+17:] + '\n')

Copy and paste the code above into an empty text file and save as adif4lotw.py.

Copy adif4lotw.py file into the JTDX log folder and run the command

python2 adif4lotw.py

A new file named fixed_qso.adi is created containing the suspicious QSO with the time_on value corrected and set close to time_off.

This file can be uploaded to LOTW.

If you use Python3 instead of Python2, it should be easy to modify the script to make it work.

I tested this script in Linux and works fine, probably it works also in Windows or OSX with Python installed.

Using the script I recovered about 15 QSO confirmation and three new squares ^_^

I don’t know if also WSJT-X has this problem, worth to check.


Magic night on the magic band

Posted in VHF on 8 March 2023 by iw0ffk

Rome 8 March 2023

I am writing this post just to fix this date for future reading.

In these days with the solar activity growing in its cycle, we are experiencing strong TEP/F2 openings on 50 MHz.

Almost everyday there are paths to 3B8, 3B9, FR, ZS, V5 and the afternoon/evening with PY/LU.

Some lucky italian station worked also FK, 3D2, VK. Here in Rome just three decodes of FK8CP, not enough to complete a QSO.

Last night around 23z I was sleeping, and my 24/7 QRV SDR receiver started sending messages to my Telegram account.
The phone was ringing loud and finally I woke up. What I witnessed was a JTDX screen full of Japanese stations calling and my beam was directed to South America! The possibility of contacts with the Japan Long Path is well known, in Rome it was already happened before for three days in October 2000, October 2001 and March 2002.

During about 1 hour long opening with QSB signals I completed about 10 JA QSOs plus PY6BK and PY6ZL in new field HH.

The JA lines in the screenshot below have been wrongly traced short path, the Pskreporter software don’t know how magic the six meters band is.

ES Season 2021

Posted in VHF on 7 November 2021 by iw0ffk

It’s a bit late to write about the last VHF ES season, but it was the best of the last 30 years and over and it is not possible not to write about it on my blog.

On 6m we had several openings with North and South America, not only the usual countries facing the Atlantic.

We (me and some other lucky OM in Rome) worked a miracle QSO with KL7HBK (Alaska) that worth the whole season…
KL7HBK was monitoring 50.313 while suddenly has received some decode from a station in Rome working EU stations.
Immediately he started to call him, but no QSO. Everyone on the KST chat got their feelers out and the first in JN61 who completed the QSO was Tony I0JX….thanks Tony for the wake-up call!!!
This is a screenshot of the KL7HBK landing zone in South Europe.

A big surprise was Nepal, I was drinking my coffee in the early morning and looking the tablet with the FT8 screen when I’ve seen a decoded text in the “new country” color, so I clicked without reading the callsign…

Other remarkable QSOs are with Australia, in three days worked VK4MA – VK2EFM – VK3BD – VK3DUT – VK3WE and the new ODX 16320 km VK2WJ

To complete this amazing 6m season must to mention the great openings with the US West Coast with about 15 contacts in DN DM and CM fields.

To sum up the new countries worked on ES 2021:

AP2HA Pakistan #202 CW + 11 FT8

9N1DX Nepal #202 CW + 12 FT8

HC2DR Ecuador #202 CW + 13 FT8

KL7HBK Alaska #202 CW + 14 FT8

TI5CDA Costa Rica #202 CW + 15 FT8

V31MA Belize #202 CW + 16 FT8

YI1SAL Iraq #202 CW + 17 FT8

On 144 MHz great fun too with frequent and long openings to the Middle East. Israel worked several times and finally a new country: OD Lebanon.

To the West, after several years Madeira finally arrived in Rome on 144 MHz. I’ve already worked that country in 2006 SSB and it was a pleasure to do it again in FT8.

Another new country worked on 2m band has been Albania. It’s not so far from Rome but it’s covered by the mountains. Worked during a very strong and short ES opening.

OD5KU Lebanon #71 2m

ZA/IW2JOP Albania #72 2m

That’s all for now

Almost universal panadapter with Malachite SDR

Posted in Electronics, VHF on 25 July 2021 by iw0ffk

I bought a Malachite SDR with the main purpose to find the noise sources all around my antenna like faulty led bulbs, neon lamps, battery chargers etc. but I discovered that it can have a more valuable use.

When the little receiver is connected via its USB port to a personal computer, a new serial port appears.
In Linux/Raspberry it’s mapped to /dev/ttyACM0
Sending Kenwood CAT commands through this port permits, among other things, to set the tuned frequency so it was an easy task to write a minimal Python script that reads the transceiver’s frequency and writes it to the Malachite periodically. The effect is that the Malachite follows the transceiver’s QRG, like a real panadapter.

The RF is sampled in the transceiver’s RX path just after the preamplifier and before the first mixer, usually there is a ready-to-use connector on the pcb designed for the alignment procedure.

Instead to use the serial port where the transceiver is connected to, I choose to interface it with the Hamlib rigtctld utility.
Rigctld permits to control via CAT almost any transceiver with a socket connection over the network instead of the serial port. This is a big advantage because the serial port can be opened only by one application at time. With rigctld there is no the single app limit and, as example, the python script can run simultaneously to WSJTX and/or a log program that need the CAT connection to the rig.

This is the command line I use to start the rigctl daemon:
rigctld -v -m 214 -r /dev/ttyKNW2000 -s 9600 C serial_handshake=None -t 4532

  • -v means “be verbose”
  • -m 214 is the rig model, Kenwood TS-2000 in this case (see the rigctl man page)
  • -r /dev/ttyKNW2000 is the serial port physically connected to the rig
  • -s 9600 is the baudrate
  • -C no handshake needed
  • – t 4532 is the TCP port where the daemon accepts the connections

In order to test if the rigctl daemon is running, just connect it via telnet and send the command “f” (lowercase and without quotes), if the reply will be the tuned frequency in Hertz, the daemon is working.

The following videos show how it works

Below the Python2 script code, probably it works in Python3 too but I haven’t tested. Copy and paste it to a text file and save to panadapter.py then run python panadapter.py

import socket
import serial
import sys
import time

RIG_PORT = 4532

MESSAGE = "f\n"

rig_freq = 0
old_rig_freq = 0

serMAL = serial.Serial()
serMAL.baudrate = 19200
serMAL.timeout  = 0.1

except serial.SerialException, e:
    print("Can't open serial port %s: %s" % (serMAL.portstr, e))

def getfreq(TCP,PORT):
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 
    server_address = (TCP, PORT)
    amount_received = 0
    amount_expected = 8 #len(message)
    while amount_received < amount_expected:
        data = sock.recv(16)
        amount_received += len(data)
    return data

def setfreq(freq):
    serMAL.write("FA" + freq.zfill(10) + ";\n")

while True:
    rig_freq = getfreq(TCP_IP_RIG, RIG_PORT) 
    #print "TS2000 freq:" + rig_freq

    if int(rig_freq) != int(old_rig_freq):
        #print "MALACHITE freq set to: " + str(rig_freq)
        old_rig_freq = rig_freq

Antenna rotator voice control with Alexa

Posted in Electronics on 27 September 2020 by iw0ffk

This is a simple Node-Red application to use Amazon Alexa as a voice interface to set and get the beam direction.

The same thing could be made without the use of Node-Red, but thanks to the node-red-contrib-alexa-remote2 the implementation is a whole lot easier.

The rotator controller, described in a previous post, is connected to the same WLAN of the echo device.

It’s worth to say that there is no a special Alexa skill activated. Node-Red catches the voice commands, take decisions and sends to the echo device the appropriate text to be pronounced.
Alexa doesn’t know the command “Antenna”, indeed the first Alexa reply is the error sound (dong…) and this can’t be avoided.

Here a short video (in Italian language) to show how it works:

2020 VHF Es season in JN61

Posted in VHF with tags , , , , , , on 14 September 2020 by iw0ffk

I’m writing in the first week of September 2020 and I can say that the ES season just ended, was the best one since I started to follow the ES openings on 144 MHz and multihop ES openings on 50 MHz.
Here in Rome, and probably in the whole northern emisphere, we had strong and sometime unexpected openings never seen also by OMs older than me in over 30 years of constant activity on air.

Probably half of the credit is of the FT8 digital mode that was extensively used by the whole VHF DX Enthousiast community on both the bands.
As said before, the fact of being all tuned on the same frequency, 50313 and 144174 kHz and the real time map offered by PSKREPORTER.INFO permits to detect and sometime to predict the ES openings.The system works even if no one is answering to our CQ because the “spot” to Pskreporter is automatic.
In light of the above, the old way to check the various beacons to know the opening landing zone, is today obsolete. The VHF beacons themselves become obsolete, but they are still useful for local tests.

The season started early this year, on 6m the first logged European was the last week of March, the first multihop the mid-April. In End-April, during the Italian Covid19 lockdown,  the middle East was seen almost every day with a new country worked on 6m 7Z1SJ (Saudi Arabia) in FT8 and CW  #202 CW + 8 FT8
Early ES also on 144 MHz on May the 1st CT1BYM in IM68 then the same day in the late afternoon, HK4SAN (Colombia) on 50 MHz #202 CW + 9 FT82020_05_01_hk4san_covid19
With a crescendo on 50 MHz worked before the May endPuerto Rico, Guadeloupe, Cayman Island, Barbados, Brazil, Trinidad & Tobago, Kazakhstan, Bahrain, Japan, Taiwan, Hong Kong, Oman, West Malaysia, Western Sahara, USA, Canada, Vietnam, China, Dominican Republic, Anguilla, Haiti, Aruba and Mexico.
Just a note, K0GU in Colorado was the first US contact worked on 17 May and he was also the latest US contact on 16 August when everyone thought the season were already over, and Colorado is not the easiest State of the US to work from Europe!

The greater surprise of May was an exceptional QSO (ES + Sea duct I think) with D4VHF (Cape Verde) on 144 MHz >4500km ODX and DXCC #70
I was driving home from work and I received the alert via Telegram: my transceiver at home was receiving Cape Verde on 144 MHz !!!
I tried to be faster than ever and reached the shack after 15 minutes with the feeling to have lost the chance for the QSO. Fortunately after about 1 hour I received again the D4VHF CQ and this time I was ready to answer and complete the contact :-)

The day after this event, the 29 May 2020, will be remembered as the biggest and largest and longer 2m ES opening in Europe of last 30 years. It lasted more than three hours and every “single hop country” was heard or worked. I have deliberately avoided to answer stations already worked in the past, to avoid QRM and permit the newcomers to work them. It seemed to be tuned on the shortwaves. Amazing.
Here the report on MMMonVHF website .

50 MHz on June was full of JA openings in the morning, hundreds of Japanese stations in the log, over 40 JA stations decoded in a single receiving period!!!


Unfortunately the first days of June I damaged my 400 Watts solid state PA that I use when I work remotely. So I transmitted with 100 Watts for the rest of the season. On 7 June worked Indonesia, YB0IR was the first of five Indonesian OM worked in the following days #202 CW + 10 FT8
Indonesia was never heard in Rome for 30+ years and it was a new country also for some BIG nearby.
The same day I have in the log Australia VK8AW in JT65 mode, 13200 km.
On 15/06 worked Arizona, DM32 DM42 DM33 and DM43 squares then finally the long awaited California opening on 22/06, CM95, CM98, DM03, DM04, DM15 with about ten different stations worked during a two hours opening.

To complete the report, must mention Sergio IK0FTA that discovered an important and useful correlation: when we receive the French station F8DBF in IN78, North-West of France, Brittany, there is a very high probability to cross the Atlantic and have QSO with USA from Rome. The curious thing is that if F8DBF works Europe only and has no contacts with USA stations, we have good chances to work USA, BUT if we receive F8DBF working USA, there is no way for us to work USA too.
This event has been noted a number of times on 2019 and 2020 and we consider it as a fact.

Improved WiFi rotator & actuator controller

Posted in Electronics on 14 May 2020 by iw0ffk


During the recent lockdown for the COVID19 pandemic, I had the time to learn the HTML5-CSS3-JavaScript basics with the purpose to enhance the interfaces look of the various Internet of things around.

I’ve played with the vectorial graphic that permits to draw and animate objects in a web page. The great advantage is that there is no need to have a dedicated client program to control the things, just a modern browser and everything works indifferently on PCs and mobile devices.

As training I’ve tried to replicate the YAESU G400/G650 graphic because I feel it very confortable and easy to read, after years on the desk.


With this approach the WiFi microcontroller ESP8266 hosts a simple web server and a websock server for telemetries and commands.
To control the rotator, it’s possible to use the web interface with the browser or the websock only, one can write a command translator to make it compatible with the common rotator protocols e.g. GS232A, GS232B etc. An example is the Telegram bot I use for mobile operations.

The following video shows the Telegram Bot functioning:

The microcontroller is the D1 mini version board, the one with the  “external antenna” option.


Make sure the 0 Ohm resistor is connected to the right path to the external antenna instead of the internal one, as specified in a previous post


On the same line I’ve updated also the WiFi controller for the dish linear actuator “Superjack HARL” or similar. The controller counts the reed pulses during the movement and reads the absolute tilt degree from an AD345XL module

Microcap 12 is free

Posted in Electronics on 21 February 2020 by iw0ffk


The Spectrum Software, a company that produce the well-known electrical simulator “Microcap” since the 1980s, is shutting down and now their product became free. Thanks!

The latest release can be downloaded on their website: https://www.spectrum-soft.com/download/download.shtm

Microcap 12 is written for Windows but works fine also in Linux and macOS (wine)

The small Polish 10GHz transverter

Posted in Electronics on 22 September 2019 by iw0ffk

In 2018 with Pino IK0SMG, Emilio IK0OKY, Andrea IW0EAC, Giuseppe IK8XFR and other local microwave enthousiasts, we bought a set of 11 GHz transceivers from a Polish surplus seller on Ebay for about 50 eu each. The objective was to use them in the 3cm HAM band, 10368 MHz.

We didn’t found much infos about it on internet, so we started to draw a schematic in order to know what the values of the various supply voltage were needed and the remaining parts to buy, in order to complete the transverter. This task was pretty easy because many precious infos are written on the pcb serigrafy or on the single components datasheet. A bit more complicated was the mapping of the supply connector. At first sight many different voltages are needed but after some test (and staying whitin the specs), +5V, -5V, 10.5V and -1.5V are effectively required. Only +5V and +10.5V have to been designed to delivery a continuous current of 2-3 amps.
I decided to do not use DCDC converters for the high current voltages, I had bad experience with them for a final stage supply…
Below the PSU schematic that includes the power-on and the TX-RX sequencers.
The signal TX INHIBIT is intended to be connected to the Yaesu FT817 pin with the same name, but also to any other transceiver equipped with the new type of sequencer, object of a previous post.
I had to add an extra board to drive the latching coaxial relays I had available.
Finally this summer everything has been assembled, I used an old graphic board heatsink that fits perfectly with the device.

The input LNA and the mixers of LO +13dBm, bodes well for a good receiver perfomances, the output is something over 2 Watts, enough to have fun in RS and TR field day operations.

Some other detail and measurement in this PDF document: xverter_polacco

Yesterday the whole portable station has been assembled and completed the first QSO from the balcony (Fabio I0NLK in SSB).

UPDATE 29/09/2019:
Added a simple power monitor and a temperature meter that use the sensors already made inside the transverter.
Below the power monitor schematic and a short video.

HAM AC rotator on a dish

Posted in Electronics on 21 September 2019 by iw0ffk

A dish has a much bigger gain compared to a Yagi consequently the beam width is very narrow, only few degrees. This can be a problem if one wants to use a classic terrestrial antenna rotator for Tropo/Rain Scatter activity because the rotation speed is too fast and the fine tracking becomes imprecise and annoying.
In my case the procedure is further hampered by the use of a three keys rotator: CDE HAM II.

With this type of rotators, one has to press and keep pressed the central key (brake release) before and during the pressing of the left or the right key. In case of a dish fine tracking, the central key must be kept pressed while tapping fast on the direction key….it’s not comfortable but I must say that in these two years I acquired a some degree of skill and an onset of tendinitis.
So the objective was to have an electronic circuit to slow down the speed rotation or at least that does the same effect of my finger tapping on the key.

A DC motor speed can be easily slowed down reducing the average voltage on the windings, a PWM on the supply is perfect.  The AC motor works in a different way and a simple supply voltage reduction maintans the same speed but with less torque.
The solution foundt was to do the same action of the finger, I used three Omron solid state relays of 50 cents each and three transient suppressors to protect the relays against the overvoltage that is generated when the windings current is chopped.

Any microcontroller with three output and input ports can do the job. The three keys are connected at the input ports of the microcontroller, the outputs are connected to optoisolators that drive the relay connected to the wires previously soldered on the keys.
The firmware is basic:

if left key is pressed:
  release brake
  pause 10ms
  turn left

if left AND center keys are pressed:
  release brake
  pause 10ms
  turn left
  pause 50ms
  stop rotation
  pause 500ms

There is no need anymore to press the brake key, just hit the direction and the rotator starts at full speed, but if the brake key is pressed the global speed is reduced and the dish turns with pulses of 50 milliseconds every half second.
The speed reduction example starts at the second 0:16 of the video below.

2019 Summer on VUSHF

Posted in VHF on 23 August 2019 by iw0ffk

Also this year the 6m activity has been focused on the FT8 frequency.
The whole 6m DXer community nowaday is tuned on 50.313, and one has to decide if play this game or move to another (higher) band still not affected by this new and controversial way of dxing.

I’ve made my choice and my rig is tuned on 6m FT8 pratically H24, I am not so happy but trying to make the best out of this.

First to all the use of this mode permits to be QRV all the day without unstick the attention from the main activity and second, you’ll never miss an opening!
I wrote a Telegram bot that automatically sends me a private message when an interesting DX callsign is decoded. Thanks to this alert I successfully worked two new countries on 50 MHz band, VR2XYL (Hong Kong) and 9M6NA (East Malaysia) #200 + 8


In this new world of lazy Dxers, no skill no thrill etc. an outstanding surprise comes from the DXpedition CY9C (St. Paul Island) that has taken place on Jul 31 -Aug 8. Usually in August the VHF ES season is pratically ended and the intercontinental openings are rare and short. But not this time. The CY9C operator, when he noticed the ongoing 6m opening with Eu, started to call in phone SSB, while the European sixers were waiting him on FT8. This was a lucky choice and has permitted to about 30 Italians to work a new country in a traditional mode! #201 + 8

On 144 MHz very little activity this year, by me of course, and I participated only in a couple of ES openings, mainly to test how works the FT8 on 2m ES. The result was acceptable with about 40 QSOs completed. I think the FT4 will be much better for this type of operations, will try next year.
A remarkable QSO between  IK0SMG and D41CV in FT8 mode shows that whatever seemed impossible before, become feasible with this low skill mode.

On 10 GHz great fun with Rain Scatter and Sea Tropo, my terrestrial ODX has been updated to 1155 km thanks to Maxi EA5CV in IM98TJ worked in SSB.


On 3cm band there were very good contacts between I8/IT9 area and the south-east of Spain with QRB > 1150 km (IT9LTA), 1530km (IW9ARO) and the new Spain QRB record of 1599 km on that band between EA5JF/EA5DOM and IK8XFR. Congrats to all!!

WEMOS D1 Mini Pro, external antenna doesn’t work, but….

Posted in Electronics on 2 May 2019 by iw0ffk


I am using the D1 Mini Pro for the ongoing projects. The choice fell on this version because it has an external antenna, so it’s perfect to be inserted inside a metal box. The following picture is of the Yaesu G650 control box with the wireless remote controller GS232A/B compatible. I will write about this project in a future post.


During the tests with the external antenna connected, I noticed that the WiFi signal was lower that the D1 Mini “non Pro”, the one with the antenna printed on the PCB.
So I examinated it closely and discovered that the board comes with the onboard antenna enabled by default and if one needs to use the external connector, a very small size 0 Ohm resistor has to be removed then soldered to the other pad, toward the external connector.


Hope this helps someone to understand why the external antenna seems to work worse than the internal one.

Tx inhibit: how to simplify the TX/RX sequencing

Posted in Electronics, VHF on 21 September 2018 by iw0ffk

When I started to prepare my home 10 GHz station, the designated transceiver for this band was the Yaesu FT-817, because I knew that many microwavers uses it as IF for their transverters but mostly because I already had it and pratically unused.
The little Yaesu has the input signal “TX Inhibit” on one of the ACC pins, so I used it in my Eyal-Gal TX-RX sequencer of a previous post.
The TX INH operation is simple, if you put a voltage on this pin (12V), the transceiver will never transmits radiofrequency even if keyed.
So it was enough to use a couple of wires that bring the PTT and the TXINH signals from the transverter on the rooftop down to the FT-817 in the shack.
When the PTT gets closed, the transverter starts the RX->TX sequence, the TXINH remains to +12V and no RF power comes out from the RTX. At the end of the sequence, the TXINH is switched to GND and the transmission can start safely. Same story for a mast mounted preamplifier instead of a transverter. Also a linear amplifier can be keyed in that way, in order to assure a cold switch (doesn’t work on CW full-break-in of course).

Why this approach is MUCH better than the common sequencers?
The answers are:

  1. there is no need to wire the microphone, Morse key or PC PTT to the sequencer box anymore: the sequence starts when the transceiver closes the PTT, so everything has to be connected on the transceiver in the usual way. No wiring differences with or without sequencer.
  2. one can safely use the features of the transceiver like voice keyer, cw keyer and memories, rtty macros, auto tuning etc. without damaging the device on the rooftop.
  3. because it’s “fail-safe”. For example, with the usual sequencers one can accidentally press the key “SEND” on the transceiver’s front panel and the mast mounted preamplifier is fried in a millisecond.

Really I don’t know why Kenwood and Icom doesn’t have on their rigs this great feature that helps who uses preamplifiers and/or transverters and/or linear amplifiers. Anyway it’s easy to add an external circuit to obtain the same result. This schematic is for my 10GHz transverter that works with 70 cm IF, it’s just an example.tx_inh

In a few words a negative voltage is sent to the transceiver’s ALC input to inhibit the RF output until the device on the rooftop is fully switched to TX.
I tested this circuit on a Kenwood TS2000 that needs an ALC voltage of about -7V to completely cut off the RF output. The Icom rigs need about -3V, in this case the 68k resistor and the trimmer have to be sized to meet the ALC limits. The DC-DC converter can be replaced by a 9V battery. The calibration is very easy: connect the transceiver to a dummy load, transmit in FM and turn the trimmer until the RF output power is completely choked.

The video below shows the TX inhibit intervention at every RX to TX, the ALC indicator goes to full scale (no RF output) then it’s released and the RF can get out. In CW one has to send a “dot” before transmitting the message, like a conventional sequencer.

New SDR receiver in the shack

Posted in Electronics, VHF on 3 September 2018 by iw0ffk


Recently I bought an SDR receiver in a dongle form to replace the old RTL-SDR in use on the IF of the transceivers, in order to have a panoramic view of the band.

The dongle is Airspy mini that has a good balance of quality and price, 12 bit ADC, samplerate up to 6 MSPS and an acceptable dynamic range.

My purpose is to have a detailed view of the noise floor on the 10GHz band to detect any change when a cloud usable for rain scatter is pointed with the dish.

The previous RTL-SDR was connected to the intermediate frequency of the transceiver, just after the first mixer. This time, thanks to the suggestion of Pino IK0SMG, I moved the RF tap to the input, after the front-end and the filter.

Actually I use a Kenwood TS-2000 with the 3cm/23cm transverters that are placed on the rooftop. The transceiver is tuned to 432 MHz and 144 MHz respectively on the converted frequencies of the two microwave bands.

Fortunately the TS-2000 has a TMP connector already mounted on the TX-RX 2 board, where the VHF and UHF paths are joined before to enter in the first mixer. This connector (CN15) is used in the factory for the band pass filter adjustment and it’s perfect to tap off the signal for the SDR without desensitize the main receiver.


I’ve done some test and the spectrum can be zoomed-in down to a dB per division.
I taken a short video of the 2m IW0FFK/B beacon. The beacon is controlled via Telegram messages, first it was set to “CONTINUOUS CARRIER MODE”, then different RF attenuators have been inserted. The SDR measured amplitude match the values of the attenuators! FB

If you want to send commands to the beacon, join the beacon’s Telegram group by clicking this link.

2018 6m ES season

Posted in VHF on 20 August 2018 by iw0ffk

In 2017 we had the first signs of change in 6m dx activity with the intensive use of JT65 mode during the e-sporadic season.

This year the JT65 has been almost totally replaced by the faster FT8 mode that permits to complete a PC QSO in about 60 seconds.

We had days of strong and long openings with JA/BA and US, sometime till late night. Tens of FT8 DX stations decoded at every period, often with speaker copy.

There are pro and cons of the massive use of WSJT modes on 6m.

– there is only one frequency (50.313) and everyone makes CQ and QSOs there. One can easily check the propagation and the openings simply by monitoring.
– in the past only the CW operators could get some results in 6m DX, now there are much more hams on the Band.
– the WSJT and his clones are connected to pskreporter , a real time propagation map is obtained by the users automatic spots.
– with a minimal remote setup, one can work DX easily with a smartphone

– there is only one frequency (50.313), it’s easy to have a neighbour that calls in the wrong period or work single ES hop stations during the intercontinental openings…or calls for HOURS alone !
– I find this way of dxing very tedious, almost no op skill involved, just make a double click on a callsign and cross your fingers.
– the FT8 on 6m DX is a time consuming activity! One has to follow the decoded text all the time and reply quickly, often the openings are very short and the system is still slow as a snail compared to the CW (but it goes 10dB below)

This year I worked 6 new countries in FT8 mode (PZ, VP9, ZF, HH, KH2,KG6) and 1 in SSB (Z6), so my score now is #200 + 6

I want to keep the DXCC worked in the usual modes separate from those worked on FT8, Although they use the same field of play, they are different sports.