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.

Incredible projects based on 7400 logic

Last fall there was a competition at DangerousPrototypes with many interesting entries based on the 7400 logic gate family. The ancestry of these circuits goes back to the 60's and early 70's, but they are still popular. I have picked out some of the ham radio related entries here.

They said "The  Open 7400 Logic Competition brings awareness to open hardware and software, and fosters understanding of the building blocks of modern integrated circuits. What can you build with logic chips?"

I think the most interesting and inspiring entries were:

Simple IKEA transmit indicator

IKEA Oleby automatic wardrobe light with passive
infrared sensor upper right and four LEDs in the center.

Passive Infrared (PIR) detectors have the bad habit of being sensitive to radio frequency (RF) radiation. This can be a nuisance for neighbors of radio amateurs. But we can use this property to our advantage as this makes them suitable for transmit indicators next to a feedline.

The IKEA motion activated LED sensor light, which one can get for a few dollars or euros, turns out to be quite simple to hack for this purpose. You can only buy them in pairs so the other one can be put to use in the darkest wardrobe you have.

Whatever happened to the 1 Volt QRP Transceivers?

Output stage of the 1 Volt DL2AVH transmitter
(from http://www.lichtnetzwerk.de/1volttxvr_dkumentation.pdf)

I am intrigued by minimalist transceiver designs like the Pixie 2 which I built some years ago. Therefore the "1 VOLT Challenge" from Dayton 2000 is also something I wish I knew more about. It had these winners:

1. Duncan Walters, G4DFV - The HAMEOBA - A 100 mW Single Cell CW Transceiver (30m)
2. (tied) Helmut Siefert, DL2AVH - A 30m 1V QRP transceiver
2. (tied) Charles Fletcher, G3DXZ - An 80m CW QSK Transceiver
4. Jim Roberts, NC9H - A 20m 1.5V Transceiver

Now, what happened to these designs? I'll try to figure it out from sources on the web.