Arecibo Birthday

Thanks to Bob Crane for this birthday alert:

The Arecibo Observatory opened on this date in 1963. At a diameter of a thousand feet, it's the largest single-aperture telescope ever built. It's also got the largest focusing dish in the world, which gathers electromagnetic waves from space. Located near the city of Arecibo in Puerto Rico, it's close to the equator, which enables it to "see" (via radio waves) all the planets in the solar system; within six months of its opening, it enabled scientists to study the rotation rate of Mercury and determine that it rotated every 59 days, rather than 88 as was previously thought. It's also been used for military purposes like locating Soviet radar installations by tracking their signals as they were reflected off the moon. It's provided the first full imaging of an asteroid and also led to the first discovery of planets outside our solar system.

In 1999, it began collecting data for the SETI Institute; SETI stands for "search for extraterrestrial intelligence," and the organization looks for deliberate radio or optical signals from other planets. The Arecibo Observatory also sends data over broadband to the home and office computers of 250,000 volunteers, who, through the Einstein@Home program, donate their computers to be used for data analysis during periods when they would otherwise be idle. A year ago, three such volunteers in Iowa and Germany discovered a previously unknown pulsar, 17,000 light years from Earth.

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Brooklyn Bike Generator -- Want one!

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The New "Gold Standard" in QRSS Grabbers

Bill 

I just discovered Scott Harden's "QRSS Plus" grabber aggregator...

http://swharden.com/qrss/plus/

Check it out - it is the new "Gold Standard".

73, Paul

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An Interesting Idea for Checking Crystal Filter Passbands

Today at 9:37 AM

Hi Bill,

Just listened to your last soldersmoke blog with reference to xtal filter checking using a DDS and scope. What do think of this idea to check filter performance?

http://www.qsl.net/7n3wvm/Fil_Meas.html

 Logical, relatively easy to build and NO digital electronics to deal with. 

Best 73

Rick G6AKG

PS keep up the great work, love the Blogs.

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Slide Show of BITX 17 Build

As I was building this rig, I periodically stopped and took a picture of the board.  I think the resulting slide show is kind of fun.  Check it out:  There is a button to launch the slide show.

http://www.flickr.com/photos/106886073@N04/sets/72157637045750216/

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Book Review: "Bunch of Amateurs" by Jack Hitt

The title held a lot of promise, but the subtitle ("A Search for the American Character") hinted at the main problem that I had with the book:  the author (perhaps driven by his editor) seemed to be struggling to prove that there is some uniquely American elements to amateur science and technology.  Early on, Mr. Hitt, makes the preposterous claim that "the rest of the world doesn't have amateurs."  He goes on to write that "In Europe and on other continents, the word hints at class warfare... Amateurs may be taken seriously, but, almost by the power of the word, are kept in their place: isolated outside some pre-existing professional class, some long-standing nobility.  In America, amateurs don't stay in their place or keep to themselves."   

What a load of rubbish!  This claim directly contradicts what many of us have been finding out in the quintessentially amateur world of amateur radio:  as we travel around the world (in person, or via the ionosphere) we find, all around the globe,  guys who have followed shockingly similar paths to ham radio.  From Sudan to Switzerland, from India to Indiana, the story is much the same.  And I'll bet you'll find similar similarities in just about every serious sci-tech hobby (astronomy, photography, etc.).  To claim that there is something fundamentally exceptional about amateurism in the U.S. is, I think, ridiculous.  Mr. Hitt should have spent some time looking at the amazingly diverse and vibrant world of British amateur science and technology.  That alone would have prevented him from straying into these silly claims of American amateur exceptionalism. 

But, all that aside, there is a lot of interesting material in the book.  I liked his description of John Dobson and the amateur telescope builders.  And, somewhat surprisingly, Hitt's description of the DIY Biology movement (these guys are playing with genetics and cooking up new organisms) seemed to capture very well the creative joy and satisfaction that amateurs find when working (just for fun) on their projects.  I was kind of surprised when I found myself identifying with the DIY Biology folks. Their basement labs sounded a lot like our radio shacks.   

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BITX BUILD UPDATE #17 Arv's Discrete AF AMP

I've been kind of cheating with the audio output from my BITX17:  I've been using one of those little battery-powered computer speakers.   It sounded fine, but hey, this is supposed to be a homebrew project right?  I've already noted my ideological objections to the use of the LM386 CHIP.  The files of the BITX20 yahoo group provided a very promising and completely discrete AF amp circuit by Arv Evans, K7HKL.  I used a 2N3906 and a 2N3904, with a 2N2222 driving them. It works like a charm.    Not a bit of feedback or motor-boating.  It sounds great.  I've already had a contact with it:  Jack, W7YUM is a builder of big amplifiers out in Salt Lake City.  He seemed very impressed with the BITX concept so we may have a Utah BITX in the works. 

 book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Words of Wisdom (on Amplifier Stability)

From "A Simple SSB Transceiver"  by Ashhar Farhan:

"What if your transmitter is unstable?  Don't curse your fate.  All transmitters start out as unstable beasts. Relax."   Farhan goes on to provide some good pointers on how to tame the beast.  

I've had very good luck with the PA in the BITX  -- very little cursing of fate on this project. 

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BITX BUILD UPDATE #16 -- FIRST QSO!!!!!!!!!!!

 

Wow, it is very clear that the radio gods are pleased with my BITX efforts!  I had my first QSO on the new rig today.  And it was with a station in my old home, the place where I got my start in 17 meter homebrew phone:  THE AZORES!  CU7MD.  Very cool.

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BITX Build Update #15 -- Necessary Mic Amp Mod

I was having trouble with the mic amp on my new Manhattan Discrete BITX 17.  I had it wired as per the schematic, but it just wasn't working right -- I was getting very little DSB out of the balanced nodulator, but everything worked fine if I 1) unbalanced the bal mod or 2) injected audio (from a sig generator) directly into the audio in port of the balancec modulator.  Clearly something was wrong in the mic amp circuit.  I noticed the collector voltage seemed quite low.

Some quick Googling revealed that others had struggled a bit with this problem also.  Nicolae's note was especially illuminating and useful: 
http://users.tpg.com.au/nfieraru/Electronics/BitX20_Mic_Preamp.htm

As Nicolae noted, the 10K value may have worked with lower gain transistors.  We must remember that BITX was (very admirably) designed for minimal cost and maximum use of scrounged parts.

I swapped the 10K resistor for a 39K and all is right with the world.  The band is not yet open here, but I bravely called a European aeronautical mobile station, hoping that he would be my first QSO on this rig.  I think he heard me, but no QSO (yet!).

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

BITX Build Update #14 -- STABILITY!

Good news on the BITX.  I think I have solved the low frequency oscillation problem in the power amplifier.  I tried running the PA off a separate power supply -- the oscillations disappeared leading me to conclude that the feedback was taking place via the power supply lines.   I put a 22 uF cap to ground from the top of the PA's RF choke.  With this cap in place I can dispense with the separate supply kludge. The amp is stable.

This morning I also resolved a different stability problem.  I'm using a relay for T/R switching.  One set of contacts controls the DC power, the other set was supposed to disconnect the receiver input from the antenna/lowpass filter when on receive.  But I had positioned the relay too far from the LP filter and RX input, so I ended up with this long piece of coax that was hanging off the PA output terminal and carrying lots of RF on transmit.  Yes, this led to oscillations.  I thought about repositioning the relay, but I think part of the problem is that even if optimally positioned, the long unshielded contact levers inside this relay would be radiating a lot of RF and causing stability problems.   So instead I put a small reed relay very close to the PA out and RX in connections.  It carries the signal to the receiver when in R mode, and disconnects the RX when in T mode, without any long coax lines or unshielded relay levers.   It works.

I still have a few things to do:
-- I need to build a proper speaker amplifier so that I can dispense with the amplified computer speakers KLUDGE.
-- I need to get a 3 pole double throw switch and some crystal sockets so that I can switch crystals from the front panel.  Three rocks will cover all of 17 meter phone.
-- I have to build a case for this rig.  I'm thinking wood, with tin or aluminum sheeting glued to the inside (for shielding).  


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From Bits to Atoms -- Software vs. Hardware

I thought this was pretty good.  On Hack-A-Day.

http://hackaday.com/2013/10/18/guest-rant-from-bits-to-atoms/#more-105097

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20