Building a DC20B 20m CW Transceiver kit.

[gil]

The DCxxB from qrpkits.com fits in a box the size of a pack of cigarettes and allows you to make contact all around the world! For $30, how can you go wrong... I thought the best emergency radio is the one you will take with you. The DC20B (there are other bands available) certainly fits that bill. I also ordered a frequency counter kit from N3ZI to help setting it up.

The circuit board it small: 3.5"x2.5". All the components come with the kit, with the exception of plugs needed to mount the PCB in a box. Actually, the kit was missing an integrated circuit socket (I found one at Radio Shack), and had two extra transistors..

It had been a long time (27 years) since I had finished electronics school. I had never soldered on a double-sided circuit board, but it turned out to be fairly easy. I just made sure I had a nice solder joint on both sides. The resistors went in first, then diodes, and so on, mounting the shortest components first, finishing with the talents. This way, you can use a piece of foam to press the components side onto it while you solder on the other side. This keeps the components near the board. One exception is the transistors. You don't want to overheat them, so it is better to mount them a little further out. The final output transistor is not put in until the kit is finished and tuned. Transmitting without a tuned antenna could destroy that component. Winding the coils was a pain. You need to make sure you count the turns carefully. One turn is every time the wire goes through the center. The parts are so small, I needed to wear reading glasses!

When all the components were in, I cut off the plug from old headphones and soldered them in. I also soldered a long wire as an antenna to test reception. It worked! I did hear faint morse code and SSB voices when tuning. The oscillator frequency however seems to be wrong: 14,063.2 Mhz instead of 14,060. I am not sure if there is a problem with the frequency counter, or I am that far off. The morse code keyed works too, so I have a working radio, except for the output frequency. I will need to find someone with an HF ham radio to check my tuning. I am investigating a way to fix the frequency problem and measure it accurately for sure. My progress will be posted here soon, as well as the mounting of the project in a box. Now I just need to learn morse code; darn, why didn't I think of that?

Update (May 27^th): I think I am going to ditch the DC20B. I have a box for it, and should complete the build, but after that, it's going away. I can't get it on frequency, and I am not the only one... The Rock-Mite kit should arrive this week. I can't wait to build it. Look for the article!

Update (May 30^th): Well, I gave it one last try.. Changed C36 to a 100pF, and C29 to 47pF. It worked! Now I get 14,059.72 on transmit. Receive goes from 14,060.16 to 14,060.32, a perfect 600Hz offset. The problem is the receiver, which has no selectivity. I receive Chinese, French and Spanish commercial radio stations, but little, faint CW signals. Maybe the problem comes from the wire I use as an antenna, which isn't tuned. I will try a tuned dipole during the day and see if I can get clear CW (morse code). I boxed up the DC20B in a nice Hammond cast aluminum box. I made a hole in the cover to tune CT1 and glued a piece of coax outer insulation so that I can't touch anything with my screwdriver upon insertion.. The box is a little big, but it looks good and as though it would survive being run over by a semi-truck.. I might make another hole for access to CT2 and add an RCA plug for a frequency counter (for tuning).

Still waiting for the Rock-Mite (shipped today).
Elecraft K1 arrives tomorrow (June 7th).

[Raymond Buehler]

The DCxxB from <a href="http://qrpkits.com" title="QRP Kits" target="_blank">qrpkits.com</a> fits in a box the size of a pack of cigarettes and allows you to make contact all around the world! For $30, how can you go wrong... I thought the best emergency radio is the one you will take with you. The DC20B (there are other bands available) certainly fits that bill. I also ordered a frequency counter kit from <a href="http://www.pongrance.com" title="Pongrance" target="_blank">N3ZI</a> to help setting it up.
<P>
The circuit board it small: 3.5"x2.5". All the components come with the kit, with the exception of plugs needed to mount the PCB in a box. Actually, the kit was missing an integrated circuit socket (I found one at Radio Shack), and had two extra transistors..
<P>
It had been a long time (27 years) since I had finished electronics school. I had never soldered on a double-sided circuit board, but it turned out to be fairly easy. I just made sure I had a nice solder joint on both sides. The resistors went in first, then diodes, and so on, mounting the shortest components first, finishing with the talents. This way, you can use a piece of foam to press the components side onto it while you solder on the other side. This keeps the components near the board. One exception is the transistors. You don't want to overheat them, so it is better to mount them a little further out. The final output transistor is not put in until the kit is finished and tuned. Transmitting without a tuned antenna could destroy that component. Winding the coils was a pain. You need to make sure you count the turns carefully. One turn is every time the wire goes through the center. The parts are so small, I needed to wear reading glasses!
<P>
When all the components were in, I cut off the plug from old headphones and soldered them in. I also soldered a long wire as an antenna to test reception. It worked! I did hear faint morse code and SSB voices when tuning. The oscillator frequency however seems to be wrong: 14,063.2 Mhz instead of 14,060. I am not sure if there is a problem with the frequency counter, or I am that far off. The morse code keyed works too, so I have a working radio, except for the output frequency. I will need to find someone with an HF ham radio to check my tuning.

I am investigating a way to fix the frequency problem and measure it accurately for sure. My progress will be posted here soon, as well as the mounting of the project in a box. Now I just need to learn morse code; darn, why didn't I think of that?
<P>
<font COLOR=red>Update (May 27^th):</font> I think I am going to ditch the DC20B. I have a box for it, and should complete the build, but after that, it's going away. I can't get it on frequency, and I am <a href="http://blog.g4ilo.com/2009/10/dc20b-osc-mod-failure.html" title="DC20B osc mod failure" target="_blank">not the only one</a>... The Rock-Mite kit should arrive this week. I can't wait to build it. Look for the article!
<P>
<font COLOR=red>Update (May 30^th):</font> Well, I gave it one last try.. Changed C36 to a 100pF, and C29 to 47pF. It worked! Now I get 14,059.72 on transmit. Receive goes from 14,060.16 to 14,060.32, a perfect 600Hz offset. The problem is the receiver, which has no selectivity. I receive Chinese, French and Spanish commercial radio stations, but little, faint CW signals. Maybe the problem comes from the wire I use as an antenna, which isn't tuned. I will try a tuned dipole during the day and see if I can get clear CW (morse code). I boxed up the DC20B in a nice Hammond cast aluminum box. I made a hole in the cover to tune CT1 and glued a piece of coax outer insulation so that I can't touch anything with my screwdriver upon insertion.. The box is a little big, but it looks good and as though it would survive being run over by a semi-truck.. I might make another hole for access to CT2 and add an RCA plug for a frequency counter (for tuning).
<P>
Still waiting for the Rock-Mite (shipped today).


Elecraft K1 arrives tomorrow (June 7th).

It think it is a scam company..Even I placed an order a while ago and still their is no delivery yet..I have sent them so many messages but without any reply

[Rob_ma]

It think it is a scam company

Nope, from their website:

Hendricks QRP Kits Closed
July 1 - August 15

- Rob