2N2-20

20 Meter CW Transceiver

This is another of Jim Kortge's fine CW transceivers. I was fortunate enough to have been at Pacificon in October 2004 and met Jim. He was one of several people who presented their project at the QRP conference. Jim had his prototype there and everyone had an opportunity to "play" with the rig. Jim is a master of Manhattan style of building and the 2N2-20 was no exception. I was anxious to build the transceiver but it took me a couple of months to gather up most of the parts, I still need to get some matched crystals for the filter and LO.

Several of my ham friends as well as some non-hams have asked how I make the round pads used in this style of building. I thought I would start out showing how I make the pads. This isn't the only way they can be made but this works for me. The first picture below shows the Harbor Freight punch I use. The second picture shows the larger of the two sizes I usually make. These pads measure 3/16" across and the smaller ones, not shown here, measure 2/16". I normally will use one of the larger pads when there are more than 2 components to be soldered to it.

The board for this transceiver is the same size as that for the 2N2-40+, 5" X 7". I got started by drawing the lines that mark out each section of the rig. I began building the transceiver with the receiver T/R switch. The batteries in my camera were dead so I didn't get a picture of just that section. Below are three views of the T/R switch and the receiver input filter.

 

I was looking at the pictures on Jim's website and noticed that T1 was on the opposite side of where I had intended to put it. I exchanged emails with Jim and he explained that he considered this a better place for T1 because it is closer to the mixer and didn't require running signals "all over" the place. Jim suggested that my method would probably work just fine but that he had built several of these circuits, using this layout and they all had worked just fine. I decided that if it's good enough for Jim, it's good enough for me. The following pictures show the receiver RF amp, receiver input filter and the receiver T/R switch.

You can see the copper shield between the receiver RF amp and the space where the VFO will reside. I haven't tested the EMS-1 mixers I got off of ebay so until I have the pin outs, I'll continue building with the VFO.

The hardest part of Manhattan building is trying to figure out the parts placement. I studied the pictures on Jim's site and also used Larry, K3PEG's, VFO layout guide. I ended up using both of them to some degree. I'm always worried that I will run out of room, so I started the VFO fairly close to the copper shield, a little too close as it turns out. I'm going to have trouble getting the RG178 coax solder to the Rx VFO pad but I'll worry about that later. Below are three views of the VFO, I didn't have a MV109 variactor diode for the RIT circuit, so you won't see it in the pictures, it will be added later.

I will be checking out the operation of the VFO in the next couple of days. (1-03-05)

Well, I got a bit behind updating the website because I was having too much fun building the rig. I finished checking out the VFO and after a couple of false starts got it going without too much trouble. After a phone consultation with Wayne, NB6M, I found I didn't really have a problem and everything was working properly. Lesson learned was, you must terminate the VFO while taking measurements, thanks Wayne.

There isn't much to the receiver mixer section so it went really fast. I didn't have an ADE-1 so I used a EMS-1 mixer which is the same as a SBL-1. I didn't have the pin out for the EMS-1 and found where others had asked about this mixer on various reflectors. I got these mixers from John, N6PLR and he provided me with the necessary info to get it working. In case others have these mixer I have provided the pinout below. The numbers are for reference only.

 

Pin 1 and 8 RF and return Pin 2 and 7 IF (must be connected together) Pin 3 and 6 IF return (These two pins must be connected together or the mixer won't work.) Pin 4 and 5 LO and return

 

 

Rx Mixer

I haven't gotten around to matching crystals for the filter section so I built up the final audio amp section.

Final audio Amp

I finally got around to matching crystals but I didn't get around to taking pictures. I'll include a couple of picture that I snapped after the rig was completed.

Ashot of the final amp and driver.

 

 

 

 

 

 

 

The completed board.

 

 

 

The finished 2N2/20

This was another fun project and all-in-all it went together without too may problems. I'm getting almost 100khz frequency spread and about 4 watts output. I believe I should be getting more like 6-7 watts out but I didn't try to tweak anything to bring the power up. I'm trying to clear my work bench of this project so that I can start another, I'll be working on the R2Pro receiver soon!