23 May, 2019

50 MHz Doppler shift from planes

This is the first time I have observed Doppler shift in the 6 meter band. It is not so hard to see on the waterfall display of FT8.

The two stations are LA9PJA (1415 Hz) and LB6D (2477 Hz). Both of them are located in the same square as me (JO59). The other weaker signals are British and French. One can see the direct signal which has a constant frequency, and then a time-varying frequency on top of that.

16 May, 2019

Morserino now supports Single Paddle Emulation

Picture credit Morserino-32
I was happy to see the other day that the nice-looking Morserino keyer with its modern display in its latest firmware, version 1.3, now supports a new mode. It is described as follows:
A new mode in addition to Iambic A, Iambic B and Ultimatic: Non-Squeeze. This "simulates" the behavior of a single lever paddle when using a dual lever paddle. 
Operators used to single lever paddles tend to have difficulties using dual-lever paddles, as they sometimes inadvertently squeeze the paddles, especially at higher speeds. The non-squeeze mode just ignores squeezing, making it easier for these operators to use a dual lever paddle.

13 May, 2019

More spurs than I had hoped for

My Just good enough 10 MHz reference based on the direct output of a Neo-7 GPS module, described in detail before on this blog, is good in keeping long-term frequency stability. Short-term stability and phase noise is as expected not so good. When connected to the reference input of my Elecraft K3 and listening to an outdoor antenna, I get quite a substantial amount of spurs around 10 MHz radiating from the GPS module. But since the K3 itself does averaging over a second or so, this is fine from the point of view of keeping accurate frequency.

02 May, 2019

Book rather than Blog

My blog has suffered in recent years and here is the reason. For three years now I have been writing a book entitled "Waves with Power-Law Attenuation". It is now in Springer's catalogue under classical continuum physics and I'm also very happy that it is published in the Acoustical Society of America Press series.

The emphasis is on models for waves that experience attenuation that follows a power-law in frequency. Topic-wise it is more about mechanical than electromagnetic waves, but analogies are drawn between the two fields as many of the models are the same. Power-law models in electromagnetics are in particular useful for waves in biological tissue, which is indeed also the case for acoustic and elastic waves.

24 April, 2019

The Ultimate WSPR Spot

Being spotted by the designer of my WSPR transmitter must be the ultimate WSPR spot! Perhaps only surpassed by being spotted by the designer of the mode himself, K1JT, Joe as I was four years ago.

It is Hans, G0UPL, of QRPLabs who is the designer of both my U3 to the left (turned off) and the U3S to the right. The latter was the active transmitter at the time of the spot below.

By the way, this is a line from VK2TPM, Peter's excellent WSPR Watch app for Ipod.

12 April, 2018

Power regulator works as polarity protection

Step-down converter based on LM2596. Note the damaged chip
Ok, now I've done the test. My QRPLabs U3S runs off a 12 Volt power supply. There are two step-down converters, one for 5 Volts for the processor and another adjustable one for the power amplifier, if one can call 0.2-0.5 Watts a power amplifier. See picture of these voltage converters in this post.

I happened to make a new cable for 12 Volts which had the polarities inverted - and puff - there was a noise and absolutely no response from the U3S. I feared that I had blown the entire circuit. As my power amplifier was turned off, only the 5 Volts supply was affected and upon inspection I found that the voltage converter had a destroyed chip.

Since since these step-down converter modules are so cheap on EBay, I had a spare. Luckily for me, the U3S worked as it should after the replacement. So the LM2596 can take a reversed polarity and sacrifices itself in order to protect the rest of the electronics. Nice!

This post first appeared on the LA3ZA Radio & Electronics blog.

04 March, 2018

Deteriorating ceramic filters due to DC

Tandberg Huldra 10
Tasos, SV8YM, has written about "The Mysterious Case of the Withering Filters". This seems to affect not only ham radio transceivers, but FM stereo receivers as well.

Tandberg from the 70's are collectors items and since I actually worked one summer at Tandberg in the early 70's they bring back good memories for me. The latest generation of receivers (2nd version of Huldra 10, Huldra 11, and Huldra 12) had ceramic filters for the 10.7 MHz intermediate frequency for FM. It is also known that these filters deteriorate leading to reduced sensitivity over time.

SV8YM has pointed out that ceramic filters deteriorate due to DC on the terminals, especially the output terminal and that this leads to electromigration. In the Huldra 10, both filters have 7.1 V DC on the input. Filter F1 has 0 V DC on the output, while F2 has 2.1 V on the output.

27 December, 2017

QRSS experiments: FSKCW and Slow Hell

These last few days I've been experimenting with my QRPLabs Ultimate 2 and Ultimate 3s transmitting on 7 MHz. In addition to WSPR, the modes transmitted have been FSKCW with 6 second long dots, and Slow Hell with 17 second long characters. The result as received this morning can be seen on the display from the grabber of Les, G3VYZ in Northumberland, UK. This is a stack of 6 consecutive 10 second frames as can be found on the QRSS grabber site of AJ4VD.

FSKCW and Slow Hell reception of LA3ZA at G3VYZ

My signal is on 7,039.870 kHz and has been set up with a FSK shift of 6 Hz. Power output was 0.2 W and the distance is about 890 km.

It works but the reception is much less reliable than for WSPR, which is not so unexpected. At the same time the WSPR signal was received all around Northern Europe (G, GM, DL, ON, OE, LX, LA, OY, OH, PA, SM) as well as on the Canary Islands, 3930 km away.