A REALLY Cheap Receiving Rig

Wow, lots of ingenuity in this 1921 receiver.

-- Has anyone actually made a diode out of a light bulb in the way described? 

-- The antenna coupler on the table leg is not much different from the tuner that I have attached to the wall of my car port. 

-- Note that when our hero finishes the receiver, he is able to pick up signals from Mars!  FB OM. 

Who will be the first to recreate this 1921 receiver? 

Aladdin's Lamp == The Vacuum Tube (aka The Thermatron) (Video)

After our posting of the video about 1957 transistor production, our friend Peter O'Connell VK2EMU asked for some equal time for vacuum tubes.  He sent me this 1940 Western Electric video.  It is quite interesting. 

-- I like the Aladdin's lamp metaphor.  When I was out in the Azores I thought of my homebrew 17 meter DSB rig as my "magic carpet." 

-- Lowell Thomas was brought in to narrate.  His voice sounds a lot more natural than that used to narrate the transistor film. 

-- To explain the effectiveness of transcontinental telephony with vacuum tube repeaters, they compared the system that of a relay of "hog callers" claiming that it would take 100,000 hog callers to carry a signal from New York to San Francisco.  So perhaps this could be a rival to db?   100,000 hc? 

-- Arlington to Paris 1915 caught my eye -- Arlington Va. is right down the road. 

-- The film of Edison in his lab was good to see.  And note the importance of his lab notebooks. 

-- The explanation of thermionic emission was quite good.  But of course too much credit was given to Lee DeForest. 

-- The breathless description of the amazing uses of tube technology was for me a reminder of how recent this technology is.  My father started as New York City cop in the 1950s.  He always referred to his police car as a "radio car." 

Hey, are any radio amateurs out there using one of those big water-cooled tubes?  If not, why not? 

A Homebrewer

 

That is Homer Price, the lead character in two books by Robert McCloskey, published in 1943 and 1951.  The thing in the valise is Homer's pet skunk.  Of course. 

More info here: 

https://en.wikipedia.org/wiki/Homer_Price?fbclid=IwAR2cRUCurQBXaP-m4LdPFBOnBU4nvgZwtOZqrAzF8MaGvS4Xb_eTWHSWE2E

Homer is clearly a fellow we need to know more about.  I have ordered the book. 

Making Transistors in 1957

Thanks to Thomas K4SWL for alerting us to this video -- he had it on his excellent SWLing Post blog. 

Many things crossed my mind as I watched this video: 

-- Pocket protectors!  Pete recently noted that this was a common fashion accessory among electronic techs and engineers back in the day. 

-- HP test gear. 

-- "Extreme cleanliness" that doesn't seem quite so clean.  

-- 550 transistors per hour.  Now we have upwards of 50 billion on a single chip. 

-- The Germanium salami that Pete mentioned in our last podcast. 

-- Hints of Silicon's impending replacement of Germanium. 

-- A transistor factory in Spring City, Pa. that "hums with excitement" (seemed kind of sleepy). 

-- The 1957 assumption that Philco transistors would be in the first orbiting satellite.  Then came Sputnik.

-- The transistor that moves like a "Gulliver through Lilliputian lands."  

-- Our voices or accents seem to have changed, at least the voice used in products like this.  No one talks that way today. 

-- As I watched, I tried to remember if Pete's CK722 was made by these folks.   But no, that was a Raytheon product.   Here is a nice short description of the early days of the CK722:   https://en.wikipedia.org/wiki/CK722   We need to learn more about the hobbyist Carl Todd.

The Secret Life of LEDs -- A new Tim Hunkins Video

Thanks to Tony G4WIF for alerting us to this really nice video from the fellow who made all those great "Secret Life of Machines" videos.   This video on LED's makes me want to improve the lighting in my work shop.  And I think I need some more high wattage resistors.   I'm really glad Tim Hunkins is making more videos.  His look at the Secret Life of  Radio was a real masterpiece. 

Hodgepodge: Moving the Carrier Oscillator Frequency (and a Flashback to 2002) (Video)

As explained in the video, in the course of using my RTL-SDR dongle I noticed that the signal being put out by my Hodgepodge rig had some problems.  There was poor opposite sideband rejection, and in terms of audio quality I has putting out too many lows and too few highs.  I figured the problem was the result of the carrier oscillator frequency being a bit too low, a bit too close to the flat portion of the crystal filter passband.   I needed to move that carrier oscillator frequency up a bit. 

BITX40 Module BFO 

In the actual BITX40 Modules, L5 was replaced by just a jumper wire, and the C103 trimmer was not on the board.  Farhan and his team instead selected X5 crystals to match the passband of the 12 MHz crystal filter. Mine was originally at 11.998653 MHz.  But I wanted to tweak mine a bit -- I wanted to move it up about 500 Hz.  Reducing the capacitance would move the frequency up. Putting capacitance in series with C102 would have the effect of reducing the capacitance in the circuit.  I just removed the jumper wire and used the holes for L5.  First I put in a single 30pf capacitor.  This dropped the capacitance between X5 and ground to 18 pf.  That resulted in too large a shift.  So I added another 30 pf cap in parallel with the first one.  This resulted in a total capacitance from X5 to ground of 26 pf.  This was about right -- the carrier oscillator/BFO frequency was now 11.9991 Mhz.  I had moved the carrier oscillator frequency up by 447 Hz -- just about what I was hoping for.  

This was a very satisfying fix.  it was a chance to put to use experience with other SSB rigs, to make use of the RTL-SDR dongle as a diagnostic tool, and to tinker with the BITX40 Module in the way that Farhan had intended for it to be tinkered with.  

I'd done this kind of adjustment before, but without the benefit of an SDR display.  Below is the story of one such adjustment. 

---------------------------------

A Flashback to 2001-2002

(From my book "SolderSmoke -- Global Adventures in Wireless Electronics")

Now it was time for some debugging and fine tuning.  I needed to make sure that the frequency of the carrier oscillator was in the right spot relative to the passband of the crystal filter.  If it was set too high, the filter would be chopping off high notes in my voice that were needed for communications clarity, and it would allow too much of what remained of the carrier (residuals from the balance modulator) through. If it was set too low, the voice signal transmitted would be lacking needed base notes.  I didn’t have the test gear needed to perform this adjustment properly, but my friend Rolf, SM4FQW, up in Sweden came to my aid.

One night, during a conversation with Rolf, I explained my problem and he offered to help me make the adjustments… by ear.  Performing an electronic version of open-heart surgery, with power on and Rolf on frequency, I opened the case of the new transmitter.  The carrier oscillator has a small capacitor that allows the frequency of the crystal to be moved slightly.  With Rolf listening carefully, I would take my screwdriver and give that little capacitor a quarter turn to the right.  “Better or worse?” I would ask. 

I think this little adjustment session captures much of the allure of ham radio.  There I was, out in the North Atlantic, late at night hunched over a transmitter that had been forged from old Swans and Heathkits, from cell phone chips, and from bits of design from distant members of the fraternity of solder smoke.  Pericles, the source of many of the key parts, was gone.  So was Frank Lee, the amateur whose SPRAT article had inspired the project.  But Rolf and I carried on with the core tradition of the radio fraternity: hams help their fellow hams overcome technical difficulties.  

Straight Key Night 2021 at SA2CLC in Sweden

Wow, check out the FB gear of Tommy SA2CLC in Sweden, in use on Straight Key Night 2021. There is some German WWII gear,  a BC-348,  a homebrew transmitter, and some FB QRP kits. 

More on Tommy SA2CLC here: https://www.qrz.com/db/SA2CLC 

The culvert under the road for coax to the antennas is very cool. 

FB Tommy!  A belated HNY to you OM.