Furlough 40 First Contact

It has been nearly a month since the completion of the receiver beginning to build the transmit modules.  I am super excited that this morning I had my first two confirmed QSOs.  I was putting out just over 2 watts of RF magic and confirmed two contacts in Ontario - about 400 miles from here. 

Furlough 40 First Contact - Thanks to Garry VE3XN! 

In the last month I have built the three final modules to enable the transmitter.  The second stage amplifier / TX Driver, the IRF 510 based final amplifier and the 40 meter low pass filter. Note the fancy brass home-brew heat sink on the TX Driver, courtesy of the plumbing department at Home Depot.  As a reminder, this is my build of N6QW, Pete Juliano's Simple SSB Transceiver and inspired by N2CQR, Bill Meara and Pete's Soldersmoke Podcast. 

Furlough 40 TX Driver, Final Amp and Low Pass Filter

There is a tremendous amount of tribal knowledge in Pete's design and I'm really please I went with it for my first transceiver project, because I really, really needed that tribal knowledge to get the rig built.  There are things that a first-time homebrewer like me would never think about, like cutting the drain pin off the IRF 510 and using the tab to connect.  And using the entire PCB as the heat sink for the transistor. And Pete has been an amazing Elmer, coach, nag and grief counselor when things didn't go quite right - like when I sacrificed the IRF 510 while over exuberantly trying to coax an extra watt out of the not-quite-ready-for-prime-time-rig. The good news was, due to Pete's excellent circuit layout, it only took about 10 minutes to replace the dead transistor.

The sacrificial IRF 510 - IRF, I hardly knew ye!

I didn't get to video of the first few contacts but I will make one in the next few days so you can see the performance.   In the meantime, here is the final pre-air transmit test.

The trace shows flat-topping which means I needed to back off on the microphone gain.  After I made that adjustment the output dropped to about one watt. I tried to compensate by increasing the bias on the final and I pushed just a little too hard - at about 4.75V DC on the bias, the IRF 510 gave up the ghost.  With a little more advice from Pete I managed to get everything more-or-less aligned and am now getting 2-3 watts of output pretty consistently.  

Next step will be optimizing each module to see if I can get the output up to the 5 watt design spec.

73 from Great Falls

Dean

KK4DAS