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.

A history lesson from call signs

World empires and colonies in 1914, also at
the time of the 1. Int. Radiotelegraphic Convention.
Source Wikipedia Commons, user Andrew0921

There's a lot of history to read out from amateur radio call signs. Being interested in history as well as amateur radio I found that for some countries you can actually figure out which time period it got independence just by looking at the prefixes of the call sign. But on the other hand the history of the international conferences and the call sign allocations is as complex as politics can be so this short blog post can only scratch the surface of this complicated topic.

I have always been envious of those radio amateurs who have a call sign starting with a letter that reflects their country's name. This seems to be the privilege of big and powerful nations, or countries that were just lucky in having names that didn't overlap too much with those of other nations. Among the 1913 call signs one can find:

CQ DX Marathon and 2011 Activity

I just submitted data for all my radio contacts for 2011 to CQ DX Marathon. My log program is UcxLog by DL7UCX and I started by exporting the ADIF-log and then analyzing it with the recommended analysis program by AD1C.

In the process of doing the conversation I also happened to find the Contact Map tool from NS6T which generated this map from my 2000+ contacts in 2011. What it shows below it not so surprising - from my location in the south of Norway it is easiest to work Europe, Russia and the East Coast of the US, but it is nice anyway.

2011 contacts from LA3ZA, open in separate window for larger map.

My CQ DX Marathon result was 167 countries (165 real DXCC countries), 35 zones giving a total of 202 points which is a result I was very happy with. It was actually my highest country count in a single year since I got my license in 2001. Much of it must be attributed to the renewed activity of the sun last year which gave a lot of new opportunities on the 10 m band. All countries except one are CW (morse) contacts with a 100 W Elecraft K3. Antennas are a 75 m long horizontal loop for the lower bands up to and including 21 MHz, and a 5 m half wave wire vertical for 24 and 28 MHz. The length of the wire loop exceeds that for the Formula Class, so I had to submit my score in the Unlimited Class.

Now I am only looking for a software tool which can analyze my ADIF-file for US states and Russian oblasts, but so far I haven't been able to find any.