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I had just finished building the Norcal SMK-1 40m QRP transceiver kit when a consulting client was throwing away a whole box of unused plastic cases... I just needed to shear some sheet aluminum to make a bunch of appropriately sized panels, and find some long 4-40 screws to hold the case halves together.
As you can see with the top cover removed, this medium to small transceiver case (5.25"x5"x2.25" or 133x127x57 mm) is mostly empty space! That's just fine with me, it's still small and I have plenty of room to work on it.
I created a power circuit on the interior of the rear panel. A bridge rectifier, 7809 regulator, and capacitors it allow to be fed with 10 to 15 volts AC or DC. Just give it electricity and it runs.
This was my first surface-mount transceiver project. But it's not too hard with the relatively large 1206 surface-mount devices (0.12 x 0.06 inches).
The Norcal QRP club's point in making this kit was to provide an SMT (surface-mount technology) construction trainer.
The transceiver circuit board mounts to the front panel by the three pots controlling the receive gain and the receive and transmit frequency. I did the "high-power modification" to boost power from about 360 mW to 650 mW. So, the final amplifier transistor is up off the board with a finned heat sink.
I added a TiCK Morse code keyer chip. It's also a surface-mount chip on its own small board attached to the interior of the front panel, as see at left. A surplus piezo-electric sounder provides external audio feedback on keying, if it is switched in. See it just beyond the power transistor in the two pictures above, or at the lower left corner in the image at left here. It isn't really needed given the way the QSK full break-in works on this design.
For TiCK and NorCal keyer chips see Jackson Harbor Press.
Best DX (so far!) has been WA3BKD, operating from a houseboat on the Ohio River near Weirton, West Virginia. That's about 540 km from here in north-central Indiana. Most of the way across Indiana and all the way across Ohio. Now bad for 650 milliwatts to a quarterwave monopole thrown off the balcony and across the top of a small tree.
The SMK-1 was a kit sold by the Norcal QRP Club. It's no longer offered, but for details see the American QRP Club's page. For a good presentation of the construction, see WB8RCR's page.
The NorCal 2030 is a nice design by Dan Tayloe, N7VE, an I/Q quadrature direct conversion transceiver.
It can be built for either the 20m or 30m band. I chose to build mine for 30m as I didn't have a QRP radio for that band!
It uses almost entirely surface mount technology. The US $0.01 coin (19.05 mm diameter, 1.55 mm thick) provides scale.
There are a few toroids, and the long solenoidal inductor of the permiability-tuned oscillator, plus two 8-pin DIP chips. However, the bulk of the work is surface mount. The hardest parts for me were the 3-terminal transistors and dual diode packages with their tiny tabs.
The NC2030 was a much bigger project than the other radios shown here, so it has its own page. Click here to see the NC2030 in detail.
I then built the SW20+ 20m transceiver.
Yes, I put everything in those cases.
The front panel is just a Postscript file printed out and photocopied onto colored cardstock. There's more inside than in the SMK-1.
I added a larger heat sink to the final amplifier, and added a power filter capacitor.
Toward the left side of the right-hand image you see a switch (blue-green), RG-174 coax (black backwards "C" shape), and the two tuning pots, joined by resistors with purple wire insulation pulled over their leads. These make up the frequency coverage modification described below.
Best DX (so far!) was S5VK, in Slovenia, in a contest. Wow, those Slovenians have good receivers and good hearing....
The SW+ series of transceivers are designed and sold as kits
by Dave Benson, K1SWL.
See:
his Small Wonder Labs website.
First, replace C8 with a 47 pF NPO/C0G capacitor.
Second, replace C7 with a short piece of RG-174 coax running to a SPDT switch selecting between two capacitors:
15 pF
high | |
O---------| |----------+
/ | | |
switch/ |
+------O |
| 27 pF |
| | | |
| O---------| |----------+
| low | | |
| |
| +---------------------------+
| |
| | RG-174 to original
| | C7 position
| |
O --O--
---
-
Third, replace the VCO tuning potentiometer. The original design uses a 50-100 kohm potentiometer from regulated +8V to ground, with the VCO input taken from the wiper. Replace that with this:
regulated <---+------------------+
+8V DC | |
[ ] |
100 kohm [ ] |
[ ] |
| |
| |
300 kohm [ ] [ ] 100 kohm
fine tuning[ ]<-------+------>[ ]coarse tuning
pot [ ] | [ ] pot
| | |
| | |
[ ] | -----
100 kohm [ ] | ---
[ ] | -
| |
| +---------------> to VCO input
-----
---
-
My result was a range of 13990 - 14059 kHz in the low range, and 14039 - 14110 in the high range, with fine tuning available across the total frequency range.
| Straight Key | Paddle |
This military surplus J-38 has been cleaned up and put back into operation. It's fully adjustable for travel and tension. |
Norcal also put out a mechanical construction kit. The heavy steel base was ready to go, but the brass and plexiglass parts all took some finishing work. It's adjustable for travel, and the tension is magnetic. I had some minor issues with contact oxidation on both of these, and tried burnishing the contacts and then rubbing on some Ox-Gard conductive grease. Not enough to call it a layer, more that I rubbed it onto the surface and wiped it off, leaving only a very thin film. That seems to have fixed the problem. |
Click here for Morse Code tables
Cut a hole in an Altoids tin with a Dremel tool and install a BNC jack so the lid can still close. A screw in the bottom floor holds a wire lug connected to about 2 meters of wire with an alligator clip. The BNC center conductor goes to a quarter-wavelength of wire, the far end of which is tied in a small loop around a large nut. Attach the alligator clip to some handy ground or counterpoise. Throw the other end into a tree or over some shrubbery. Here are separate models for 7040, 10106, and 14060 kHz, flavor-coded by frequency.
This can make for a very high performance HF system. Rick Campbell, KK7B, has written a series of articles in QST magazine starting in the early 1990s, see below for a bibliography.
More recently, Dan Tayloe, N7VE, has designed some systems that do I/Q quadrature conversion using switching rather than traditional mixers. See the NC2030 design above.
Also see some articles describing the technology as an "H-mode mixer", named after the circuit topology. Sergio Cartoceti, IK4AUY, wrote an article in QEX.
Siniša Tasić, YU1LM, has also used it in some interesting designs that combine sample-and-hold quadrature modulation and demodulation with software-defined radio technology. See his web page for the details.
Here's one way of doing it digitally. Use a VFO running at 4 times the desired LO frequency, and use high-speed D flip-flops to generate the quadrature signals:
+--------------------------- Q ( 90 degrees)
| _
| +------------------------ Q (270 degrees)
| |
+-------+ | | +-------+
+-----+ +---+D Q+--+-)|(-----+D Q+--------- I ( 0 degrees)
| | | | _| | | _| _
| VFO +--+--)|(--+clk Q+-----+ +--+clk Q+---+----- I (180 degrees)
| | | | +-------+ | +-------+ |
+-----+ | | | |
| +--------------------)|(-------------+
| |
+-------------------------+
The resulting four LO signals will be square waves, which are in fact preferred assuming (as with everything else) you do it right and provide:
This approach is used in the designs by Dan Tayloe, N7VE. See:
A bibliography on the topic includes:
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| © Bob Cromwell Sep 2010. Created with /bin/vi and ImageMagick, hosted on OpenBSD with Apache. Root password available here, privacy policy here. |
