EA8/LA3ZA April 2023

This was a fun holiday operation from the island of Tenerife with 2.5 - 4 Watts running digital modes, mostly FT8 and some FT4 using a low-band and a high-band QDX.

The best bands were 30 m (29%) and in particular 10 m (65%) with a lot of contacts across the Atlantic ocean as the picture shows. In total 62 different entities/countries were contacted. 

QSL via Logbook of the World.

3 tips for not blowing the finals of the QDX transceiver

I have now used both the low- and the high-band QDXes daily as EA8/LA3ZA for a period of two weeks without destroying the four BS170 final transistors. Here are some procedures and tips.

But first, I do actually have experience in blowing the finals. That happended under testing prior to leaving, and all it took was 9.5 Volts for my 9 V build and what I thought was a dummy load, but which might have been an open circuit load. One BS170 developed a short between drain and gate with the result that 9.5 Volts was passed directly into the outputs of the driver IC5, 74ACT08, so IC5 blew as well.

My three tips for avoiding such failures are:

Clock cycles through chemical elements

The latest addition to the Multi-face GPS Clock is a clock face that for hour, minute, and second cycles through the corresponding chemical element in the periodic table. This is shown in the image to the right.

This is screen number 39 for this clock, all of them selectable by rotating a rotary encoder. The project, with Arduino Mega hardware and software is documented on Github, where the current release is v.1.6.0 (2023-04-14).

The display also shows  the full name for the element corresponding to the second, as shown above for element 3 which is Lithium. It is located in group (column) 1 and period (row) 2.

QDX Twins 80-10 m

My QDX twins from QRPLabs: 

1. On top, the high-band version, 20-10 m, with a revision 4 PCB
2. In the bottom, the original 80-20 m version with a revision 3a PCB

Both have been assembled for 9 Volts operation nominally.

My wife and I have identical twins in real life and at times one of the ways to distinguish between them was by different colors. Here it is the same, so the high-band QDX has a yellow LED and the low-band one has a green LED.

Audio delay - the unspecified parameter for ham radio transceivers

Elecraft K3: Upper trace is start of sidetone and
lower trace is start of RF ~15 ms later.

An amateur radio transceiver is not a precision measurement device. This is apparent when it comes to measuring time for your own round-the-world signal or when characterizing Long-Delayed Echos (LDE). One cannot just substitute onset of sidetone for the actual start of transmission of RF. Similarly there may be an unspecified delay between received RF and start of audio output on the receiver side.  

The main specification for ham radio transceivers is that the sidetone is synchronized with the keying. The delay to start of RF is only of secondary importance. All numbers should therefore be judged against the length of a dot which for instance at a morse code speed of 30 WPM is 40 ms. 

Here are some measurements for the Elecraft K3 and K2 that I did in 2021 for a presentation on LDEs at the HamSci 2021 conference. A video of the presentation is also available: Long delayed radio echoes – the illusive secret of the ionosphere