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Sunday, September 21, 2014

Inducted Into Shortwave Rogues' Gallery

Jeff Murray, K1NSS, has done me the honor of placing me in his VERY ELITE Friends of Shortwave "Rogue's Gallery."  Check it out:
Kind of ironic that I should be recognized for my work on regens! 

Thanks Jeff! 

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"First Smoke" from Antananarivo, Madagascar

Here in Northern Virginia, it is not all that unusual to run into friends and have them say things like, "We're moving to Antananarivo."  Here is a report from Jack, AI4SV on his new location. That garage seems to have real potential as a workshop Jack.   

Greetings from Antananarivo, Madagascar!

I thought I'd turn the tables and give you a bit of travelogue and radio news.

The only radio-related item in our air freight was my toolbox, which I thought was justified. I lugged along the rest of the station in my carry on, an FT817 (with post-market Collins mechanical filter), magnetic palm paddles, a winkeyer, and the 40/20/10 end-fed LNR halfwave dipole, plus some mason line. I also brought a very compact 240V recharger that I had picked up in Sweden. 

The day after I got here, the dipole was hung using the time respected coke bottle on a string method, which greatly entertained the guard assigned to the house. A couple days later, I clambered up on the roof to raise the feed end another ten feet. Since then, I've worked about 240 stations with my QRP rig (all but three CW). I don't have any way to upload to LOTW right now, but my rough estimate is that I have worked something like 45 DXCC entities.

The location is probably not as ideal as Azores in terms of having a nearby salt water ground plane, as we're 100 miles to either east or west coast, and the local noise here can be very high in our tightly packed appliance-heavy diplomatic neighborhood. On the other hand, we're on the central highlands, almost a mile up and Madagascar is a very desirable DX location. When propagation smiles on me, I can work runs of 30+ stations before I disappear again into the ionospheric mist.

Before I got here, I talked with a bunch of US, UK, and German hams who had held 5R callsigns, and they gave me the lay of the land. Phil, G3SWH became my QSL manager and put me in touch with Albert, 5R8GZ, who has been a huge help. Prior to arrival, Albert was able to put through my paperwork with OMERT, the local equivalent of the FCC, so I could get on the air as soon as I arrived. He has similarly assisted quite a number of visiting hams and dxpeditions and is a big proponent of ham radio in scouting here. 

There's no ham club here, but there are so few active hams that in my three weeks here, I've either met or been introduced by email to about half of them.

It will be another month before our main shipment hits the docks here, and meanwhile management has given me the thumbs up to install a tower in the backyard to support a hexbeam. Between the K3 and the hexbeam, I think I'll be in good shape to do some serious operating, although I think that a couple months of operating QRP has been not only a character-building experience, but has given me a much better understanding of propagation patterns.

We have a large, empty garage and I think it's destined to become the workshop. I am curious about how dry it will stay in the rainy season and how many mosquitos will visit me there, but it has electrical power and plenty of wall space for shelving. Packing out my workshop took me about as much time as the rest of the house combined. So many little parts...

My toolbox arrived last week and the soldering iron was put to immediate use to build a dipole for six and then 15 meters. I've captured the moment of "first smoke" in the new location for your viewing pleasure.

So, please look for me on the air in future months and point your moxon over here when you can.  I'm putting updates about the station's status on its qrz page.

Keep up the podcasts! I've enjoyed the series with Pete Juliano - kind of a return to the original format. Also, I've listened to the icq podcast for years, so it was great to hear the "very special crossover episode" with you and Martin.



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Saturday, September 20, 2014

Kiwi Lunchbox Sideband: The Tucker Tin Two

Pete Eaton sent us links to an old article from the New Zealand magazine "Break-In."   So many good, simple rigs come to us from New Zealand!  Who can forget ZL2BMI's DSB rig?  This one is the work of Fred Johnson ZL2AMJ.  It is especially interesting and is in some ways similar to Peter Parker's "Knobless Wonder."

It uses the phasing method of sideband generation.  No crystal filters in this one.  You need TWO balanced modulators.  You have a 90 degree phase shift network for the RF (from the carrier oscillator) and a second 90 degree phase shift network for the AF from the mic amplifier.  When you combine the signals from the two balanced modulators -- viola! -- one of the sidebands disappears.  The balanced modulators take care of the carrier, and an SSB signal is launched.  That is how my old HT-37 works, and similar ideas seem to be at work in modern SDR rigs.  

G3TXQ has the complete set of Break-In articles (it includes a VFO):   

Here is a Canadian article on the rig.   A "Tucker Tin" is apparently what the Kiwis call a lunch boxes (shades of Benton Harbor...).  

Thanks Pete!

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Friday, September 19, 2014

Long Delayed Echo on Radio China International

Several people have e-mailed me suggesting that the weird echo I have been hearing on shortwave broadcast stations is in fact one of the fabled "Long Delayed Echoes" that radio amateurs have been hearing intermittently since about 1927.   I was skeptical at first, but -- at least in the case of the Radio China signal -- I think LDE caused by the signal going around the globe several times does explain what I've heard.  Each trip would add a delay of about .133 seconds, and that seems to match what we hear in my recording: 

Compare that with what K9FIK recorded on 10 meter SSB (thanks Stephen!):
(you can listen to the audio on this one). 

It sounds very similar. 

If this is in fact LDE, I'm lucky -- this is pretty rare.   And it is a eerie that I first heard it on on Regen receiver from the 1920s!  Above is a picture of the regen used to study the FIRST LDEs. See:

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Thursday, September 18, 2014

SSB with Just Two Tubes

Here is the two tube SSB transmitter that Pete was telling me about.  This would be a nice companion to the "Mate for the Mighty Midget" receiver that I built a long time ago.  Another Benton Harbor Lunchbox may have to be sacrificed... 

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Wednesday, September 17, 2014

Eclectic Electronics: Powering Arduinos with Tube Filament Voltage

You know that you are dealing with a broad range of technology when you find yourself discussing how to power an Arduino microcontroller from the 12V AC voltage on a vacuum tube filament line. Thanks Pete. 

Hi Bill,
There is only so much that can be said in 1 hour and 19 minutes so maybe here is some stuff for the blog.
The 1st thing on the list when working with the Arduino when it is not connected to the computer is to have a proper power supply. My research as indicated that 9 VDC “raw” is a good starting point to power the Arduino boards so here are two supplies that will provide that power.
I did find that it was necessary to have an isolated supply when working with the “toob” radios and even to isolate the RF into the radio using a ferrite core transformer –some more tribal knowledge.
One supply takes an 8 VDC regulator and boosts its output to 9 VDC. The second uses a switching regulator and the beauty of the second is that the input can be either 12 V AC or DC. This is ideal for use in toob radios where you can sample the 12.6 VAC filament string.

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Tuesday, September 16, 2014

Regen Receivers in Cuba

Hola amigo Bill:

I was able to pick up the podcast with excellent audio quality.
It is quite true that regenerative receivers are very much in use
even today... for example many if not all of the automobile RF
keys opening and closing the cars doors rely on a superregenerative
receiver circuit !!!

The radio that you copied at the blog works very well indeed
but it would be  good idea to include a 5 kilo ohms volume
control.... Very easy to do indeed.

But let me tell you that my favorite regenerative receivers are
the classic ones, using vacuum tubes, and operating them
at voltages not higher than 50 volts... As a matter of fact many
tubes work very well at the 24 volts DC voltage level.
Using the classic Hartley circuit , there is no need for a hard to
find throttle capacitor required by the Armstrong circuit, because
the regeneration control works very well by using a potentiometer
to change the screen grid voltage of the detector.

I agree that using an RF stage ahead of the detector is always
a very good idea.... In my tubes regenerative I use a triode connected
6AK5 clone.... as a grounded grid stage....another 6AK5 clone ( the
6ZHE1P Russian tube ) is the detector and I use another 6AK5 clone
as the first audio amplifier then feeding an audio output pentode
all provided from a very simple basic 70 volts DC power supply.
BTW, using regulated DC on the filaments of the detector stage,
although a luxury by my standards is very helpful to reduce
hum .... 7805 regulator recycled from a bad motherboard, with
one 1N4007 from broken Compact Fluorescent Lightbulb inserted
in series with the regulator ground pin, produces a nice 5.7 volts
regulated DC that with a brand new tube is more than enough... with old
6ZHE1P recycled from Russian TV sets, you add another 1N4007 to obtain
6.4 volts regulated DC....

As said in the podcast, it is very important to do a very good
mechanical engineering job, place the main and bandspread tuning capacitors
away from the front panel, use isolated shafts between the capacitors
and the dial mechanism and make the front panel of a a thick steel
plate if possible.

There is a Dutch Cascode Regenerative radio that several Cuban radio
amateurs have built... it was designed with the amateur bands in mind so
the information about the tuning coils and capacitors lets you
obtain a very excellent bandspread on the ham bands.
I can send you that circuit that uses very common 12AT7-ECC81
and Russian equivalent double triodes.

Keep up the good work amigo and always tell us when the next
podcast is available. BTW it lasted for almost an hour !!!

73 and DX

Your amigo en La Habana, Cuba
Arnie Coro
Host of Dxers Unlimited radio hobby program
Radio Havana Cuba

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Saturday, September 13, 2014

SolderSmoke Podcast #165 Arduinos!

SolderSmoke Podcast #165 is available:

September 13, 2014

Workbench Update:  Bill's "Off the Shelf" Regen,  Pete's Boatanchors
Mysterious Echos on Shortwave Signals.  Solve the Mystery.  Please. 
Microcontrollers -- What they can do for you.
Small world:  As a kid, Pete was neighbor of "Digital Dial" N3ZI 
NEWS FLASH: Arduino creator Massimo Banzi was a ham!  
Born in a bar, cheaper than pizza:  The Italian origins of Arduino
Arduino CW generators
No coding skills needed
Arduino + AD9850 = Signal Generator or VFO
Arduinos in the Minma
What the heck is a Shield?
SolderSmoke Mailbag

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Friday, September 12, 2014

Schematic for "Off the Shelf" Regen

Tony, VE7JUL, wrote in asking for a schematic on the "Off the Shelf" regen.  Here you go Tony.  Nothing fancy or new here.  All the credit goes to Howard Armstrong, Charles Kitchin and Jay Rusgrove! 

Even though they seem much simpler than other receivers, I think regens are in fact more of a challenge than, say, a Direct Conversion receiver.  Be prepared to do a lot of fiddling around with the coil and the tuning and regen capacitors.  Think of that detector stage as a VFO, a VFO that you want to be able to smoothly take out of oscillation. 

Here's a tip on regen debugging:  Once you have it built, hang a high impedance 'scope probe off the drain of the FET and watch the scope/counter as you move the main tuning cap and the regen control.  This will give you a visible indication of where (on the regen control) the stage is going into oscillation.  A freq counter (I have one inside my Rigol 'scope) will let you know what frequency range you are operating on.  You may end up having to make adjustments to the coil, adding or taking away turns to get into the proper frequency range, or to the desired level of feedback.  Pay attention to the phasing of the coil turns.  You may also find yourself adding capacitance in series with the regen and main tuning controls (to reduce their tuning range) or adding capacitance in parallel with the main tuning cap (to lower the entire tuning range if necessary).  

Build it solid and strong!  It is, after all, an oscillator.  Be prepared to do a lot of "noodling"   

Hi Bill,
This receiver with just 4 transistors and no chips looks really interesting to me.  Do you have a schematic that you could either flip to me or point me to?  Getting my hands on some air variable caps may be a challenge, but I can 'noodle' something out on that.
Love the podcast, blog and really enjoyed the SolderSmoke book - thanks for your continuing efforts to share with the amateur radio community.
the little red dot at Coquitlam, British Columbia on what used to be the Clustr map (but is now a Revolver map)

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Thursday, September 11, 2014

Shortwave Echo Mystery on Yet Another SW Station. What is this?

A few weeks ago I noticed a strange echo on Radio China International's signal.  If you scroll down a bit you can see my YouTube recording of the problem.  On one of the SWL lists, there was speculation that this problem was the result of a flaw in the RCI digital studio gear.  But then a few days ago I heard it again on RCI -- surely the tech-savvy Chinese would not have let this kind of problem persist for weeks.  

Today I heard the same effect on a very different SW station -- this one an the 24/7 fire and brimstone broadcast that appears at many points on the dial.  The effect is very similar to what I heard on RCI.  

So OK all your shortwave gurus:  What is going on here?

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