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Tuesday, March 30, 2010
AA1TJ on Polyakov, Scrounging Parts from a Wehrmacht Tank, QRPp Success

Labels:
AA1TJ,
mixer theory,
Polyakov--Vladimir,
Russia
Sunday, March 28, 2010
Building W3PM's Colpitts Oscillator

I took a break from all the computer stuff and decided to melt some solder this weekend.
W3PM has a neat WSPR rig on his site. I decided to build at least parts of it. Today I put together the Colpitts oscillator. I really like this circuit -- it produces enough power to drive a diode ring mixer directly. Mine went together very smoothly. Sure enough, mine produces about 10 mW.
It was good to get back to solder melting. I used circular pads sent to me by Jerry NR5A. And parts sent by Jim AL7RV, and by Mike AA1TJ. EMRFD provided very useful background info on the circuit. I powered the prototype up with my Kempton Park power supply with the current limiting chip provided by Tony G4WIF. So it was a like a team effort. Thanks to all!
I'll try to get the next podcast out mid-week.
73
Labels:
WSPR
Saturday, March 27, 2010
Polyakov Plus! Dual-band Receiver with Subharmonic Mixer

You'll see in the comments attached to my last blog post that our man on the left coast, Steve Smith, gave that cute little Doug DeMaw/Vlad Polyakov receiver a name that might set American-Russian hamrelations back a bit: He called it "Vlad The Inhaler." Good one Steve! (But you might want to stay out of the diplo game!)
Check out "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm
Labels:
mixer theory,
Polyakov--Vladimir,
SPRAT
Thursday, March 25, 2010
Sunspot 1057 Doing Good Work for US!


IZ0PEC de AA1TJ/QRPp
Dear Fabio,
Thank you for your patience in copying my signal on 20m CW this evening. I had been calling DX stations for several hours but you were the only one to answer. My homebrew rig has an output power of only 10mW (0.010 watts). The distance between us is 8793km; nearly one million km per Watt!. The antenna here is simply an end-fed wire.
I am amazed that you heard my 10mW signal in Rome. It's fantastic!
Again, thank you for patiently listening for my weak signal, OM. It would not have been possible without your very kind efforts.
Ciao,
Mike, AA1TJ
Thank you for your patience in copying my signal on 20m CW this evening. I had been calling DX stations for several hours but you were the only one to answer. My homebrew rig has an output power of only 10mW (0.010 watts). The distance between us is 8793km; nearly one million km per Watt!. The antenna here is simply an end-fed wire.
I am amazed that you heard my 10mW signal in Rome. It's fantastic!
Again, thank you for patiently listening for my weak signal, OM. It would not have been possible without your very kind efforts.
Ciao,
Mike, AA1TJ
Labels:
AA1TJ,
astronomy,
Brazil,
Italy,
propagation,
solar cycle,
WSPR
Polyakov's Russian Mixer

Of course, the big question is what mixer circuit I should use. I'll probably go with an SBL diode ring, but while perusing the literature, I again came across "The Russian Mixer" of Vladimir Polyakov, RA3AAE. Michael, AA1TJ, is a big fan of this circuit, and has been talking about it on Radio Havana Cuba. What a cool circuit it is! Just two diodes in parallel, cathode to anode. RF from the antenna goes in one side, and the local oscillator signal is placed at the other end. The LO signal causes the diodes to turn on and off on voltage peaks, effectively chopping up the incoming signal, producing sum and difference frequencies. LA8AK's drawing of one version of this circuit appears above. (Obviously OM AK didn't like this configuration, but it gives you the idea.)
The really cool part is that because you have two diodes, the "chopping" takes place at TWICE the LO frequency. This happens because on a positive LO peak one of the diodes conducts, and then, on the negative peak, the other conducts. So it is as if the mixer gate is opening twice each LO cycle. This allows you to run the oscillator at half the operating frequency, with advantages for stability and for the effort to eliminate common mode hum.
A while back I saw (somewhere!) a clever use of this circuit. LO was running at around 3.5 Mhz. With the two diodes in the circuit, it was a 40 meter receiver. They had a switch that could remove the second diode from the circuit. By throwing this switch, the RX went to 80 meters.
Does anyone remember this circuit? Where did it appear? SPRAT? QQ? Tech Topics? I can't find it.
I had the impression that OM Polyakov was active in the early days of radio. But some Googling shows that he is of much more recent vintage, still active and listed on QRZ.com. Here he is:

Labels:
mixer theory,
Polyakov--Vladimir,
Rainey -- Michael,
Russia
Wednesday, March 24, 2010
Was Marconi the First Radio Amateur?
Steve, WG0AT, posed this question in the title line of his latest (excellent) video. I really liked the recordings of Marconi speaking in English. (I'd heard him in Italian, but never in English.)
So, was he one of us? I say yes. Definitely. Why? Because he very clearly had what we would call a shack. This is discussed in SolderSmoke -- The Book. When his mom saw that his tinkering with electricity had some potential (!), she had an attic room in the family home near Bologna configured as a workshop for her Knack-afflicted son. And there he tinkered. Just as we do.
Labels:
Marconi-Guglielmo,
radio history
Tuesday, March 23, 2010
Dino's Awesome Workbench

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Ok, can't stand it anymore....had to show off my workbench as well. BTW, will be making a presentation at Dayton Hamvention in May on "Building Your Ham Radio Workbench." So if guys have any great ideas to pass along would love to hear them and include as possible. Am gearing this toward the beginner and focusing on basics, soldering equipment, tools, safety, the bench, parts accumulation, etc. Over the past two years have made pitches at Hamvention on Test Equipment and Station Engineering Manuals....always lots of fun.
73 -- Dino KL0S
Labels:
workbench
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