Vintage Tektronix oscilloscopes

I first encountered this generation of Tektronix oscilloscopes in my first job at the Electronics Lab of SINTEF, Trondheim, Norway in 1978. Already at that time the main use for them was as heaters in the offices. That is, only if you wanted to work in the break between Christmas and New Year when the central heating was turned down.

Since then I have come across the two oscilloscopes shown here, and the collector (or is it hoarder?) in me has not been able to say no to them. They are really advanced for their time: regulated power supplies with tubes, ceramic stand-offs and lots and lots of tubes.

The  oscilloscopes are 541A and 543, from 1959 and 1964 respectively, it seems. The plug-in units are 1A1, L, M, and 53/54K plus the cart. The 1A1 actually seems even to have FET-transistors, not only tubes like the others. The units work, but how well they work I am not sure about as they have been in storage for the last 5-10 years.

The 10 biggest lies in audio

Quad II Tube amplifier. (Wikipedia Commons, user Harumphy)

In the fall of 2000 The Audio Critic had an article listing the 10 biggest lies in audio.

The article is well worth reading even today although the scene has changed a little since it was written. It for sure makes you think.

Peter Aczel's points were:

Medium delayed echoes

Medium Delayed Echoes or Magnetospherically Ducted Echoes (both MDE) are radio echoes delayed from 0.14-0.3 seconds. They represent a subset of Long Delayed Echoes (LDE) and is the only one of the five LDE effects discussed in "The Five Most Likely Explanations for Long Delayed Echoes" which is fairly well understood.

Here is a fascinating report of such echoes from G3ZRJ. His report is different from those of many others in two unique and very interesting ways.

More long delayed echoes

4.5 metre high UK acoustic mirror used as early warning system
during WW1. Not so relevant for Long Delayed Echos, but something
which definitely reflects well. Wikipedia Commons, Paul Glazzard

The mystery of Long delayed echoes is still without a scientific solution. With that I mean an explanation in terms of an effect which is testable, i.e. where one can predict the value of the delay and under what conditions it occurs.

It is likely that there isn't just one explanation, but several. I found it helpful some years ago to list all 15 possible hypotheses and then narrow them down to The Five Most Likely Explanations for Long Delayed Echoes. This list is now being referenced on the RSGB site for Long-delayed echoes (LDE) as well as in the Wikipedia article on the subject.

In this blog post there are examples of multisecond echoes on 21 and 27 MHz.

Will I ever complete "Worked All States"?

Here's my map of confirmed US states as it has slowly been filling over the last 10 years. 41 states have been confirmed on CW on Logbook of the World, while 9 are still missing.

In recent years progress has been very slow so I don't see my WAS being finished any time soon. Perhaps there is some resource on the web that could assist me with arrangements for the remaining states, or even some readers in these states who would help me?

Unusual HF Propagation Phenomena

Earthrise from Apollo 8 (NASA)

My blog has just been updated by migrating posts from my old web site containing a collection of audio samples from unusual HF propagation phenomena. They range from round-the-world propagation (delay 138 ms) to ducted transmission in the magnetosphere (delay ~140-300 ms) ending with moonbounced 7 MHz signals (delay 2.39 sec).

The posts are:

• Magnetospherically ducted echo
• Three paths from Japan to Norway along the grayline
• Propagation via aurora reflection
• Polar flutter
• Moonbounced echoes on 6792.5 and 7407.5 kHz

Passive Crossfeed for iPhone

Some records just have too much stereo separation. This makes them kind of artificial to listen to with earplugs or headphones as the sound in the two ears is too different. This is where a crossfeed circuit has a role to play as it is designed to mimic the blending of the two channels that takes place when listening through loudspeakers.

As the head is smaller relative to the wavelength at lower frequencies than at higher, the shadowing is also smaller. Therefore there should be more blending of right and left below 1 kHz than at higher frequencies.

Reliable auto-detect for keyer for Elecraft K2

The Elecraft K2 has an autodetect feature for the keyer input. When enabled, and when the DASH and the DOT lines are keyed at exactly the same instant in time, the K2 will detect that this is a hand key or an external keyer. I and several other K2 owners have however experienced erratic action of the autodetect with seemingly random keying.

My problem only occurred when keying was done from an external keyer. This could happen when keying from e.g. the WinKeyer.