Jeff Duntemann's Contrapositive Diary Rotating Header Image

Odd Lots

  • My Web article on how I designed my workshop has just been aggregated on the Make Blog.
  • Here is the best summary of sunspot-less days I’ve yet seen. We may be coming out of a freakish-high period of solar activity; five of the ten most intense solar cycles ever recorded have occurred in the last 50-odd years.
  • Even NASA admits that our near-record solar minimum may get even deeper. I guess I don’t need to build that 6M vertical any time soon. (Thanks to Mark Moss for the link.)
  • On the other hand, the DX can be had, with some–heh!–effort. In fact, some guys in Germany recently bounced a radio signal off of Venus and heard the echo. They used the same 2.4 GHz radio frequency as Wi-Fi–just with 6 KW of power. No word on antennas or ERP, though the words “big” and “parabolic” come to mind.
  • Print-on-demand meets the magazine business with MagCloud. Basically, the magazine is printed when you order it. All pages are in full color, printed using the HP Indigo technology, with a saddle binding. The price is still steep: 20c per page, giving you a 48 page mag for $9.60. Of course, that’s all content and no ads, so it’s not utterly insane when you consider that a lot of modern magazines are lucky to have 48 pages of Real Stuff. The system works like Lulu for the most part, and if you have the need to publish a short, full-color booklet of some kind it might be worth a look. (Thanks to Jim Dodd for the link.)
  • Pete Albrecht sent a link to some WWII posters, and the interesting one is about not using broadcast receivers. Few people know that nearly all ordinary radio receivers are also very low-level radio transmitters, courtesy of the local oscillator or oscillators in the frequency conversion stages. It’s possible to detect superhet receivers at considerable distance using a good directional antenna, and this was evidently done during the War. The BBC also used to do this (and may still, for all I know) to enforce receiver licensing rules, by sending a truck around towns listening for local oscillators and logging street addresses. (I learned this from the UK pub Meccano Magazine circa 1962.)
  • It’s the not the fat. It’s the high-fructose corn-syrup. Here’s another brick in the edifice of evidence. (Thanks to Frank Glover for the link.)
  • And finally, a food pyramid that I can get behind.


  1. Erbo says:

    The warning against using broadcast receivers is also related to why you’re not supposed to use AM or FM receivers on airplanes in flight; the local oscillators might throw off signals that interfere with the plane’s navigation systems. See this Straight Dope column. (Cecil Adams knows everything.)

  2. Bob Fegert says:

    Truly a tidy workshop Jeff! Mine is a horrible mess.

    I’m also longing for some sunspots… I love 10mtr cw.

    Cool about the Venus bounce…I read some guys used a microwave oven as transmitter for Moon bounce by pulling the freq down from 2.45 gigahertz.

    The local oscillator thing is one of the signals NSA pulls in from geosync orbit with the spindly 150ft dishes up there….can pick up the emanations from a GPS easily if it is way out in some no-man’s land where it is a curiosity. They can also track vessels on the ocean even if they observe radio silence…because few people know of the few milliwatts leaking out of so many electronic devices. They can deform the dishes to cover the entire side of the earth they face, or pull them down to spot beam widths.
    The system can pick up emanations from a great many ‘chipped’ devices. I would imagine a small solar array would be able to store enough of a current pulse and dump the current from a bunch of capacitors to transmit gigawatt level short duration pulses (given the gain of the dish when set for spot beam), enough to activate passive devices on the ground and receive a very short return signal…a very high tech version of an RFID system.
    The gain of those dish antennas would be over 80db, and then there is the super cooled front end receiver components to add yet more gain.
    There might as well be a man in a van full of radio gear next to you because 23,000 miles is nothing with that sort of gain.

  3. Rich, N8UX says:

    The Venus bounce, or EVE experiment was done to clear the ground and command station for use in the AMSAT-DL project to send an amateur space probe to Mars. They sent the traditional “HI” message in morse code – 6kw at 2.4 ghz – using the 20m dish at IUZ Sternwarte observatory. FFT analysis showed the reflected signal after 2 minutes of integration time.

    And weak signal modes on HF have pretty much made the solar (in)activity a non-issue as far as working dx is concerned. I remember watching in amazement several years ago, as I watched solid copy qso’s print across my screen from signals I could not even hear! All I could see was a faint yellow bar on the waterfall display.

    In contrast to that, in 1979 my friend and I hooked an old military 6m rig up to a ground plane *on his bunk bed* and worked a G3 in England that sounded like he was in the next room. This was FM simplex with 10 watts! I think the rig drew 25 amps on transmit, so we had to make it brief…


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