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2N2/40+ - A 40 Meter, Discrete Component CW Transceiver Built Manhattan-style
Designed by: Jim Kortge, K8IQY
The original configuration of the 2N2/40+ incorporated essentially the same main circuitry as my original 2N2/40, but on a larger footprint, 5X7 inches instead of the original 4X5 inches. This change was made to encourage other builders to try building the design.
When the 2N2/40 article in the winter 1998 issue of QRPp was published, this was the rig used in that article. The only difference between my original 2N2/40 and this rig was the RIT circuitry that was added.
However, shortly after the article ran, I started making additional changes to the rig in several areas that I thought could be improved.
The first change made, or more accurately, the series of changes made were to improve the audio muting. A couple of interations of bipolar circuits were tried to reduce thump on the receive to transmit change. Each was better than its predecessor, but not "world class". Next a 2N7000 MOSFET was tried. This was markedly better than the PN2222 bipolar versions, but still not as good as I thought it could be. Finally, a J176 JFET circuit was installed, and that worked like I wanted; clean transistions from receive to transmit, and back.
Next, another stage of audio amplification was added. Since the original design was just a tad shy on audio gain, with this change one could copy much weaker signals than before.
I also changed the RF amplifier in the front-end to a Norton "Noiseless Feedback" design to improve the strong signal handling capabilities of the rig. While the original switchable gain amplifier worked well, most of my operating was at the 10 dB gain setting. The Norton Amplifier provides 12 dB and can handle a lot more input signal before going into compression.
The variable bandwidth crystal filter also was changed because the original varicap tuning diodes, MV2115s, became impossible to find. One could purchase MV1662 varicaps from Hosfelt Electronics at 3 for a dollar, so the circuitry was updated and redesigned to use that part. That varicap can also be used in the VFO with minor changes. Of course, with the change from a bipolar transistor to the JFET, the Rx/Tx Switch had to be changed to make everything work correctly.
|Block Diagram - A simplified view of the rig.
|Substrate Layout - How the blank PCB is partitioned to fit all of the needed sections.
|Schematics - a complete "road map" for the project Note: You can download a .pdf file containing
all of the schematics here.
|Pictures - details that show how this rig was constructed.
|Parts List - everything you will need to buy or scrounge to build the rig,
(provided by Kenyon Cox, WD8INS, one of the Flying Pig Group builders in 2003).
|1998 Winter QRPp Article written by Jim Kortge, K8IQY and illustrated by Paul Harden, NA5N.
|Reported Errors and Omissions in above article.