When 5 Watts is TOO MUCH!

Hi gang, 

The bands have been absolute garbage for most of this weekend. Lot's of state QSO parties going on and virtually all of Saturday and Saturday night, I was hearing nothing. I got a chance to get back on the air Sunday night (May the 4th be with you!) and instead of breaking out the Elecraft radios, I decided to dig out an old monoband kit rig I built in 2001.  

The Norcal SMK-1 Transceiver - Designed by Dave Fifield AD6A -  April 2000

I built this radio in 2001 and decided to take it to the QRP gathering know as Four Days in May over near Dayton Ohio.  I entered it in the show-n-tell competition and was awarded "Honorable Mention - Best Attempt at Bribing Judges with Food".  

The following is an excerpt from the SMK-1 construction manual:

This little radio was capable of about 350 milliwatts on 40m.  It was one of the first kits to be primarily surface mount.  Norcal put this together to see if a hobby builder, like me for instance, would be able to build a kit that was constructed of surface mount parts.  It's a very cool kit.  

The SMK-1 circuit is basically a modified Tuna Tin 2 transmitter integrated with a modified MRX-40 receiver. It is a further modification of the modified TT2/MRX-40 that I built for the indoor foxhunt at Pacificon 1999.

All this is fitted onto a small 2.475” x 2.25” PCB. The transmitter consists basically of the two 2N2222A transistor lineup of the original TT2 but with electronic keying. A key-switched crystal oscillator that has some degree of VXO feeds a medium power packaged version of the 2N2222A as a final in class A mode. 

After harmonic filtering, the result is about 350mW of fairly clean transmit power on 7.040MHz (+/- a bit). The RX front end uses the ubiquitous NE602 mixer/oscillator with a crystal VXO. The RX is a direct conversion receiver, so you will hear both sidebands as you tune through a station. 

The input stage of the NE602 has been biased a bit harder than normal by R1, a 22K resistor (this resistor may need tweaking, if your receiver is overdriven, increase the value of this resistor. Try 27K or 39K). This gives the device more conversion gain. 

The audio output of the NE602 direct conversion front end goes through a FET switch that serves to mute the audio to an acceptable sidetone level during TX and then on to a standard LM386 audio power amplifier running as much gain as it can. 

End of excerpt from the SMK-1 Construction Manual

Here is a shot of the front knobs.  I mounted this in a plastic food storage container. 

This is a shot of my finished circuit board.  Even though it was almost a quarter century ago when I built this, I remember it very well.  It was super fun but man did you need a magnifying glass to make sure the parts got in the right place. 

Here's how I wired it up:

Here it is, all ready to go.  The round thing on top is a speaker, I also had a WM-2 Wattmeter connected and set on the ONE WATT setting. 

So I started listening.  The SST contest was in full force so I heard a LOT of stations.  The one I heard the loudest was Mike AD9CA over in Newton Illinois, which is about 125 miles due west of me.  He gave me a signal report of 449, I gave him a 579.  The frequency was 7039.6 Khz. This is what my signal looked like on the Kiwi Receiver in Edinburgh Indiana (about 30 miles south).  This receiver is owned and operated by Bob WA8VZY and he allows people to connect over the internet and use it to listen to the bands. 

Mike AD9CA was the red signal, I am the Green signal

One last picture, my wattmeter showing about 300 milliwatts of output.  I think the most I ever got on this little radio was about 340 milliwatts.  My battery may not be totally charged.   My contact with Mike 125 miles away is equal to about 500 miles per watt!! 

WM2 Wattmeter showing right at 300 Milliwatts on the 1W Scale

Just goes to show, when the band is open, you don't need mega power to make a CW contact!! Try milliwatting sometime, it's a hoot! A Giant THANK YOU to Mike AD9CA for taking the time to tune me in and pull me out of the ether!! It absolutely made my weekend. 

73 de KB9BVN

Brian