A Bad Day for a New Receiver

Here is the latest picture of my version of the W3PM WSPR receiver. You can see the Ugly Weekender AF amp in the upper left. No front end of any kind yet -- the sig goes right from the antenna jack into the RF pin on the SBL-3 diode ring mixer.
Turns out that this morning was a bad time to test a new receiver. Spaceweather.com reports that a big coronal mass ejection hit earth today, causing havoc in the ionosphere. I'll try it again later today.

G0UPL's Ingenious QRSS Circuit

Just look at that circuit! That's a complete QRSS beacon transmitter, including a multivibrator (the two transistors on the left) to generate a recognizable pattern on the grabber screens. This diagram appears in SPRAT 134. Hans Summers ran this rig with just a couple of volts from his homebrew bleach-based battery system back in 2008. I plan on putting a version of this rig into the solar powered lawn lamp I showed you two posts ago (scroll down).

In other news, I finished building the Ugly Weekender AF amp this morning, and it passed the smoke test. My WSPR system went toes up this morning, so today I am QRSSing on 30 meters. I'm running my usual upside down FSK. Please let me know if you see me.

Colpitts Mania! Two Rigs Under Construction

I'm really into Colpitts oscillators lately. I blame Gene, W3PM. He reminded me of the fact that these little one transistor stages can pump out the 7 dbm needed to drive a diode ring mixer. Gene sent me a note warning that I'd have to take special precautions to ensure stability, but I found that this circuit never strayed more than 20 hertz in the course of a full day of oscillating.

Above you can see my version of the Colpitts circuit that Gene has in his very nice WSPR transceiver. You can see the SBL-3 diode ring mixer above the oscillator in this picture. I still haven't decided on the audio amplifiers.

I'm working on a second Colpitts circuit. This one is for a QRSS transmitter, also for 30 meters. Here I took my inspiration from Michael, AA1TJ, who has been working DX with power levels similar to that of this little oscillator. Long-time blog fans might recognize this board, or at least the device that it was used in. This is the board from my "DaVinci Code" 30 meter frequency standard, so called because I used a paperback copy of the Dan Brown novel as insulation for this weird piece of test gear. With my Kempton Park Frequency counter working, I had no need for the DaVinci device. But the oscillator was a Colpitts, capable of pumping out 10 mW all by itself... I plan on building a Hans Summers-style multivibrator circuit to put a distinctive pattern on my QRSS sig. It should fit nicely on the same board. I have a case and a power source in mind: see below. See if you can figure out where I'm going with this.

Workbench/P! Taking Solder on the Road!

Sure, lots of guys carry rigs with them to the field, on vacations, etc. But how about taking your WORKBENCH with you on trips? Perhaps only truly hardcore homebrewers reach this extreme.

It may be that with summer approaching, guys are getting nervous about being away from their beloved workbenches... This week I got three e-mails related to portable workbench operations:

Jim, AL7RV, sent in a nice shot (above) of his most recent workbench location. Jim says while he does not have racks and racks of sophisticated test gear, he does have lots of fresh air (and a nice view) while working on his projects.

Nicholas, M1HOG, sent me a web page describing the portable bench he put together for use at his country cottage. While out there, he said he had "started to miss the delights of melting solder." We hear you Nicholas! Nice solution:
http://www.m1hog.com/projects/elecraft-kx1-building/elecraft-kx1.html

Finally, Rogier, PA1ZZ & KJ6ETL, reports on some very nice cabinets that seem ideally suited to this kind of work: http://www.gerstnerusa.com/

This is all great, but I think we have to draw the line somewhere. How about this: No soldering while driving!
No soldering while in flight on an airliner!

Soldering Irons to the Field! EXCELSIOR!

Success! Uganda WSPR Station On The Air!

Isn't it beautiful? Like an RF palm tree rising out of Uganda. That's a map display of the stations that have received the WSPR signals of 5X7JD in the last 24 hours. Not bad considering that Jack's rig is running one watt and that we are in the midst of a pretty massive geomagnetic storm.
This is a beautiful story for several reasons: Technically, the rig is very elegant. But even more appealing is the human aspect of this operation: This is a real "International Brotherhood of Electronic Wizards" story. First, Jack Dunigan goes to Kampala to help kids who are struggling with AIDS. Then Gernot, OE1FM, jumps in and designs and builds an ingenious rig that will allow Jack to run a WSPR beacon from Uganda. For more details, check out Jack's web site: http://hamradiosafari.com/ I got a kick out of his mention of a certain station in Rome that is running a 200 mW WSPR beacon. (And I'm looking forward to Jack's article on Kampala's "Radio Row" -- I suspect it will be a lot like Santo Domingo's.) Three cheers for Jack! Three cheers for Gernot! Three cheers for Joe Taylor! Three cheers for the International Brotherhood of Electronic Wizards!

SolderSmoke Book Helps With License Upgrade SAVE 10%!

Thanks to all those who are helping to get the word out about "SolderSmoke -- The Book." I put together a web page about the book:
http://soldersmoke.com/book.htm Lulu is running a sale: 10% off during April. Coupon Code: SHOWERS

I got a very gratifying e-mail from OM Walter. I was very pleased to hear that the technical portions of the book helped him in his license upgrade efforts:

Bill,

Just thought I would drop you a note to let you how much your podcasts and book have influenced my life (for better or worse). I have been listening to you podcast since last summer and have all of them on CD and have listened to them all. Living in Florida for the past 10 years I have not been active because I thought I could not get a proper station and antenna setup here (HOA restrictions). Boy was I wrong. Late last year I bit the bullet and bought a Icom 703+ QRP rig and hooked it to my computer for digital modes. Antenna of choice? A PAC12 vertical antenna kit. The antenna is indoors sitting on a small photo tripod.

With this setup using PSK and RTTY I have over 1/2 of the US confirmed and 8 countries including England and Germany. I am having a ball. My wife calls it "Playing with Radio's". At least she knows where I am...

Next steps is to get my code speed up and I have a couple of kits on order (QRP of course).

Your book was instrumental in me ugrading from General (N2LTB) to Extra (AJ4UM) in Dec 2009. Read your book and used the ARRL study guide. Your explanations hit home and I believe made studing for the test easier. Also very entertaining.

Thanks again for all you do for the Ham community and keep it up.

Walter

AJ4UM

Geo-Magnetic Storm! Aurora as seen from orbit

Batten down the hatches my friends. The solar wind is blowing, and we're in a geo-magnetic storm. Well, we were anyway, yesterday. Astronaut Soichi took this amazing picture of the resulting aurora.
No WSPR spots of my little signal this morning -- I blame it on the storm.
You can see some interesting discussion of the storm conditions on the WSPR live-chat system. Here is a sample of last night's commentary:

How much AF amplification needed between diode ring and a sound card?

Progress continues on my WSPR direct conversion receiver. The Colpitts oscillator is working nicely and is very stable. Yesterday I glued an SBL-3 diode ring to the board and hooked it up. With my 'scope and sig generator I can see it turning 30 meter RF into audio. So far so good.

Now it is time to build the AF amp. Here's my question: How many db do I need? The standard 100 db DC RX AF Amp seems like a bit of overkill -- this thing won't drive a speaker or a headphone, but instead, a computer soundcard. What do you guys think? How many db?

SolderSmoke Podcast #123

Listen at: http://www.soldersmoke.com

SolderSmoke #123
4/1/2010
Spring! Equinox! Sap in Vermont! Aurora in Norway! Birds singing in Rome!

SolderSmoke on Oprah. Program Schedule:http://www.soldersmoke.com/oprah.html

Special Report from MASSCON QRP Convention by Mark, NX1K
Propagation improvingWSPR as a personal sunspot detector
Building the W3PM WSPR rig
Colpitts oscillators
Polyakov's "Russian Mixer" BANDSWEEP: A low-frequency sweep by Chris, KD4PBJ
EMRFD on Direct Conversion and Direct Aversion
Faraday's toroid diagram
NA5N's ISBN
MAILBAG
SolderSmoke--THE BOOK:
http://stores.lulu.com/store.php?fAcctID=3999032
SolderSmoke--THE STORE:
http://www.cafepress.com/SolderSmoke

AA1TJ on Polyakov, Scrounging Parts from a Wehrmacht Tank, QRPp Success

Caro Bill, FB on your 20mW DSB WSPR DX! I've never actually been on the air during the upside of a solar cycle. This is wicked exciting! Thank you for the nice write-up on your Soldersmoke Blog, OM. I heard back from Fabio this morning; he seems to be as excited as I am (please see his message below). Italy is my fourth DX contact and third country with 10mW. Two weeks ago I worked F5NBX twice and FM5LD once. Again, all great fun... I'm glad to hear of your interest in the Vladimir Polyakov's mixer. I can attest to Vlad's claim about its resistance to SWBCI. So far, I've used silicon and germanium diodes, MOSFETS, and even a saturating inductor for the subharmonic, commutating switches. I haven't mentioned it till now, but leading up to my Gigi regenerodyne receiver, I built Polyakov reflexed 40m receiver that was lots of fun. The RF input signal first passed through a simple BPF on its way to the cathode of a triode, grounded-grid RF amplifer. The amplified signal next passed through the Polyakov anti-parallel diodes. The resulting AF signal was then re-injected into the grid of the same triode (now working as a common-cathode amplifier). In typical "reflex' fashion, the same tube amplifies first at RF and again at AF. Looking at my notebook entry, I was able to "plainly hear" a 1.0uVrms signal and in a week of operation I hadn't noticed any SWBC breakthrough. Actually, the subharmonic mixer was well-known by 1976, but I'd never seen it used by hams at HF until Polyakov popularized the idea. Our Eastern European comadres took a liking to it right away but it took some time before it finally caught on in the West. By the way, I had a short email exchange with Vladimir a few months ago. I'm pleased to report he's a really nice fellow. He happened to mention that his first amateur radio transmitter was built using parts that he salvaged from an abandoned Wehrmacht tank. It seems radio components were extraordinarily hard to come by in those days. Amazing... Have fun, Bill! Mike, AA1TJ ---------- Forwarded message ---------- From: Fabio Ventrone Date: Sat, Mar 27, 2010 at 9:16 AM Subject: Re: IZ0PEC de AA1TJ/QRPp To: Michael Rainey Dear Michael, Many many compliments for your qrpp station! Really exciting to have qso in this conditions... It's actually the first time I can connect qrpp oversea... Unbelievable, something we can tell our friends forever!!! I was transmitting with 4 el antenna and something more than 100w. I will have to take back my 817 and try to call dx as you bravely did!!! Best 73 qsl Fabio de IZ0PEC 2010/3/26, Michael Rainey > 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

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

Polyakov Plus! Dual-band Receiver with Subharmonic Mixer

I found it! SPRAT 110, Spring 2002, page 5. A short article by OM Rudi Burse, DK2RS. This is the variation on the Polyakov Russian Mixer that I mentioned a couple of days ago. I'd been digging through piles of books and old magazines looking for this. My wife thought I'd gone nuts. (Well, nuttier than usual, actually.) It didn't help that I responded "The Polyakov Russian sub-harmonic mixer circuit with two band application!" when she asked what I was looking for. Of course, I should have known that it was in SPRAT. It just happened that the issue with this article was piled under a lot of junk on the workbench. I really like this circuit. Ingenious. And now that I have come to understand mixers a bit better, I can appreciate this one more. Here's how I'd explain it: With the switch closed, the signal from the LO "opens" one of the diodes on the positive peak, and it opens the other diode on the negative peak. So that RF signal from the antenna is getting sampled and mixed twice each cycle of the LO. The resulting complex waveform has sum and difference frequencies of RF+2LO and RF-2LO. With the switch open, you only have one diode sampling the RF, and it opens only ONCE each LO cycle. So the complex waveform that comes out of this single diode had frequencies of RF+LO and RF-LO. This opens the possiblity of DC receivers for 80/40, 40/20, 20/10 meters, etc. I guess a key adjustment in this circuit would be getting the LO level just right. Thanks SPRAT! Thanks Rudi! Thanks Vladimir Polyakov!

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