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Friday, May 14, 2010
The Death of a 2N3904: Captured on Grabber Video!
Hope everyone is having fun at Dayton. I caught G3RJV's talk yesterday via streaming video. As always, inspiring stuff! And I really liked a word he used: socketry. You know, "the PC board, and the box will all the associated SOCKETRY."
Wednesday, May 12, 2010
Schematic for QRSS Transmitter
It was a lot of fun to take this thing very quickly from LTSpice, to the workbench, then to the antenna, with Johan's grabber providing instant feedback. This started out as a one-stage Colpitts oscillator transmitter. But I needed more stability. Indeed, the separate oscillator with the source-follower buffer makes it much more stable. Before, any adjustment to the antenna tuner shifted the frequency. At one point I even suspected that wind blowing the antenna was shifting the frequency -- we are talking about a band that is 100 HERTZ wide, so even a few hz of instability is noticeable. But I find that crystal ovens and other extraordinary measures are not really necessary.
I had one unusual problem with this little rig: As I was doing my initial tests, I noticed that the output signal was sort of jumping up and down. The problem was in the PA. I isolated the problem to the base circuit. At first I thought that some small blob of solder was intermittently messing up the bias voltage (that's quite possible here in the N2CQR lab!). But no! It was that 4700 ohm resistor. It was bad, and kind of intermittently bad! I never had a resistor go south on me like this. It is an ordinary 1/4 resistor. It is not dissipating a lot of power.
I'll keep it around 10140010 today. Check it out on Johan's grabber:
http://www.on5ex.be/grabber/grabber.html
Look for a horizontal lines with little bumps (about 4-5 per minute). That's me.
Tuesday, May 11, 2010
The DaVinci Altoids LED 30 Meter Multi-vibrator MEPT Transmitter
This rig has evolved quite a bit. It started out as a frequency standard for QRSS and was mounted inside a paperback copy of Dan Brown's book. Then I matched the oscillator up with the multi-vibrator pattern generator from one of Hans Summers' rigs. This week I decided that I really needed a buffer and a PA -- I needed a bit more stability. I'll try to post a schematic tomorrow. In the meantime, watch for my little signal on the ON5EX grabber (off to the right). The pattern is small (3 Hz) bumps, about 4-5 per minute.
Saturday, May 8, 2010
First Transatlantic Transistorized QSO
The online Transistor Museum has a wonderful new article about this historic event, with details on the rig and the operators. Check it out:
http://semiconductormuseum.com/HistoricProfiles/Raytheon_TransAtlantic_Transmitter_Profile_Index.htm
Thanks to AA1TJ for alerting us to this.
The Limerick Revolution
Today G-QRP club announced the release of a Limerick kit version of G3RJV's Sudden receiver.
Take a look at the final product and the boards:
Very nice. Read more about this wonderful kit here: http://www.gqrp.com/sudden.htm
Go Limerick! Go Sudden!
Thursday, May 6, 2010
QRSS LED FSK Experiments: More Blue vs. Red
Just to make Hans happy, I switched from a forward biased blue to a reverse biased (upward pointing) red diode. The resulting pattern (below) looks a lot like the pattern shown in the picture in Hans' excellent SPRAT article. This is clearly FSK. The positive voltage from the multivibrator increases revers bias on the LED, DECREASING capacitance and RAISING the oscillator frequency. In the curve of the leading endge of the pattern you can see the voltage from the multivibrator slowly rising. FSK here is "right side up."
Finally I tired a little 1N914 diode forward biased. I was hoping to see some cleaner switching action, but even with this little diode you can see quite a bit of varactor action at work:
I think the switiching would be a lot cleaner and more complete if the voltage from the multivibrator wasn't coming through a 1 meg resistor. But when you put a lower resistance in place of the 1 meg ohm part, you start to mess up the frequency of the multivibrator.
I have to say, my favorite pattern is that from the Blue diode forward biased. Sorry Hans. To each his own...
Wednesday, May 5, 2010
Altoids to the Max!
http://blog.makezine.com/archive/altoids_and_tin_cases/ The first one that appears seems to belong somewhere else -- just scroll down to find the tins.
Wiki provides background info:
Altoids are a brand of breath mints that have existed since the turn of the 19th century. Altoids are less widely available in Britain—their country of origin—than in the regions to which they are exported, the standard peppermint mints being the only flavour available and only stocked in relatively few stores. Callard & Bowser-Suchard manufacture and produce Altoids at a plant in Bridgend, Wales, although Wrigley, the brand's owner, announced in mid 2005 they planned to move Altoids' production to an existing plant in Chattanooga, Tennessee, in order to manufacture its products closer to where they are sold.
The history of Altoids dates back to the reign of King George III. The brand was created by a London-based Smith & Company in the 1780s but eventually became part of the Callard & Bowser company in the 1800s. Their advertising slogan has been "The Original Celebrated Curiously Strong (insert flavour here) Mints" for a number of years, referring to the high concentration of peppermint oil used in the original flavour lozenge. The "Story of Altoids" text is printed on the paper liner inside certain tins.
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Monday, May 3, 2010
Soldersmoke Podcast #124
May 3, 2010
Oprah follow-up: On to Martha Stewart and Dr. Phil?
Fencing on a Roman piazza
Breaking an important cable
My WSPR Direct Conversion receiver
Roger Hayward's wonderful ugly AF amp circuit
The beauty of SBL mixers
My DaVinci Code Oscillator goes on the air!
Making my own 555 timer chip (sort of)
LEDs as varactors (or are they colorful switches?)
Black Holes in workshops -- is the LHC to blame?
Altoids: now made in TENNESSEE!
G3RJV's wonderful video
MAILBAG
Saturday, May 1, 2010
Down For Maintenance
I hope to get the next podcast out as soon as I can. Maybe tomorrow. I will try to spare you all the gory details. Back to the radios! I've had a very interesting e-mail exchanges with Hans Summers G0UPL about LEDs as varactor diodes and their use in QRSS FSK systems. I'll talk about this in the next podcast.
Tuesday, April 27, 2010
Red vs. Blue. (Diodes)
Hans: Live and let live OM! Some people like their diodes up and red, others down and blue!
Any little diode would, of course, work as a switch, regardless of its possible varactor properties. When the diode is not conducting, that 5 pf cap in your SPRAT 134 circuit has one end floating. When the +2 volts comes in from the multivibrator, that little cap is fully across your 22 pf trimmer, and the frequency shifts.
I did some additional Googling this morning and found that Alan, VK2ZAY used this diode as a switch scheme in his early QRSS design. See:
http://www.vk2zay.net/article/180 Alan wrote "A small trimmer in the oscillator circuit is diode switched by the beacon controller to pull the oscillator an adjustable amount." (He later went RED on us with upward pointing varactors!)
I did the test you asked for (shorting out the diode). Before I shorted it out, my freq counter shows the transmitter shifting from 10140020 to around 10140030. Shorting out the diode with a bit of wire puts the freq at 10140010, and it stays there.
The switching scheme has a side benefit: You get a cool-looking LED that turns on and off with your keying.
73 Bill
--- On Mon, 4/26/10, Hans Summers
From: Hans Summers
Subject: Re: [Knightsqrss] FSK LEDs: Red or Blue, Switches or Varicaps?
To: "Bill Meara"
Cc: knightsqrss@cnts.be, "g3zjo"
Date: Monday, April 26, 2010, 1:18 PM
Hi Bill
Currently it's still offending my sense of correctness, having that
diode upside-down!
And also I'm still not convinced it's behaving as a switch.
Even when reversed (i.e. Forward biased), the diode can still show a
variable capacitance effect, seemingly.
Please can you try shorting the LED and tell me what FSK
that produced? 73 Hans
On 4/26/10, Bill Meara
wrote:
I'm thinking that both configurations might work:
Perhaps with Red LED working in reverse bias mode, the diode serves as a
varicap, with the voltage from the multivibrator varying the capacity
and causing the FSK. I guess we'd call this the "diode as varicap" mode.
In the configuration that I am using, (which I guess we could call the
"diode as a switch" mode) the diode is FORWARD biased
by the voltage from the multivibrator. Then that output terminal goes
positive (mine goes up to about 2.35 Volts), the diode conducts, and the 5 pf
cap is effectively added to the circuitry between the crystal and ground. And
the LED glows (even with current severely constrained by the 1 Meg
resistor between the multivibrator and the diode. When the voltage from
the multivibrator goes below around .6 volts, the diode stops conducting, and
that 5 pf cap is in effect taken out of the circuit.
You can see what I'm talking about in the hand-drawn
schematic here:
http://soldersmoke.blogspot.com/2008/10/i-shift-to-fsk-on-30-meter-qrss.html
This is from the QRSS rig I built back in 2008. You can see in this circuit
I use only 220 ohms between the keyer and the switiching cap.
I plan on putting a 220 ohm resistor in this latest rig (just to make the
blue diode glow brighter!)
One bit of kind of strange electronic serendipity: I turned Hans's diode
upside down, and used it as a switch. But the 5 pf cap that he had in his
original circuit was just right to produce an 8 Hz freq shift.
73 Bill
> >
On 4/25/10, Bill Meara
wrote:
Eddy: But Hans's circuit has it fed through
a 1 Meg resistor. So even if
it glows, that diode is QRP! 73 Bill
--- On Sun, 4/25/10, g3zjo
wrote:
From: g3zjo
Subject: [Knightsqrss] FW: New beacon
To: knightsqrss@cnts.be
Date: Sunday, April 25, 2010, 2:59 AM
Hi Hans, Bill/Group
Its funny how this simple subject can get confusing, brought about
sometimes by people (me) not caring which way up the LED is sketched in
a circuit, because when it comes to building we know what
to do. However sometimes I have seen the LED
deliberate forward biased for a 2
level code and used as a switch to merely
add the extra capacitance in
circuit.
For the QRPp purist though, you could get
around the world on the current that is flowing in the LED :-)
Eddie G3ZJO
-----Original Message-----
From: knightsqrss-bounces@cnts.be
[mailto:knightsqrss-bounces@cnts.be]
On Behalf Of Hans Summers
Sent: 24 April 2010 22:52
To: Bill Meara
Cc: Knightsqrss@cnts.be
Subject: Re: [Knightsqrss] New beacon
Hi Bill
Congrats on getting your multivibrator
working and the success on air!
One thing interested me particularly: not
the use of a blue LED
specifically, but that you mentioned
you'd seen actual light come out
of it? Really? That isn't supposed to
happen! Are you sure you have
the LED connected correctly? It is
supposed to be reverse biased.
Which would mean it shouldn't light up.
See my varicap diodes page
http://www.hanssummers.com/varicap .
On the other hand: there's a good
argument which I refer to daily,
which says: if it ain't broke don't fix
it. Diodes do seem to exhibit
a variable capacitance even when forward
biased, though this probably
has other undesirable side effects such
as lowering the Q.But that
won't matter much in this non-critical
application anyway.
73 de Hans G0UPL
On Thu, Apr 22, 2010 at 7:06 PM, Bill
Meara
wrote:
I just finished my version of Hans
Summers' ultra
simple QRSS beacon (I mean, uh, MEPT). I've been
discussing it on http://soldersmoke.blogspot.com
I got some instant gratification. My QRO
20mw rig was still making it
into Johan's grabber at around 1840
tonight. So I figured the new 10 mW
rig would also be visible. Sure enough --
there it was, rocking along at
10140030. Square wave FSK from an
astable multivibrator.
I confirmed it was me by turning it off at 1850. Right
on cue, it disappeared from the
ON5EX screen. Very cool.
I'll leave it on for awhile tonight,
but the band seems to be shutting
down. Please keep an eye out for it
tomorrow.
73 Bill I0/N2CQR