The value of a Simple Project.
Several years ago I found in my stash of parts a bag of Motorola MC1496 Double Balanced Mixers. I think I purchased a dozen from a reputable US Supplier and the cost was $6. No Alibaba stuff here.
I
hit upon an idea to build an SSB transceiver using nothing but the
MC1496's in all the major pieces like the Rx and Tx mixers the Balanced
Modulator and the Product Detector. (4 pieces out of the 12.) The IF
Stage would be built using Dual Gate MOSFET's, the 40673.
But
I thought it might be wise to build a test circuit first to assure all
of the MC1496 devices worked and perhaps cherry pick the best of the 12
for the circuit modules.
The DCR Board with the MC1496, 2N3904, LM380N-8
Underside of the DCR
What
better way to test the MC1496's than to build a simple Direct
Conversion Receiver using a socket to cycle the devices under test and
my go to 2N3904/LM380 audio amp.
While
under construction I thought about an RF amp stage and wanted to try a
2N3906 PNP transistor just to piss off those who only use the 2N3904.
What
resulted astonished me! Of course no Analog VFO crap so I used the
Arduino/Si5351 for the LO. It was so good that I wrote an article for
the GQR-P Club SPRAT on the DCR project.
To
my surprise this project hit a nerve and I have received about 160
requests world wide for the Arduino sketch and know many of these were
actually built. Along the way I got help from two UK hams who built the
project and they too published data on their MC1496 project efforts. I
have been told that this was one of the most popular projects published
by the G-QRP Club.
Just
today I received an email, some several years later, that another
MC1496 is inhaling RF. Of note this build used a different Audio Amp and
RF Amp plus he got some benefit from his son, a software guy, who
programmed his Arduino Uno.
So in my response back to him was that there were 4 hidden benefits to his completing the project.
1) He had some fits and starts but didn't give up.
2) He learned from the ground up how the Direct Conversion Receiver worked
3) He made substitutions based on what he could find. (A different Audio Amp IC and different RF Amp.)
4) He had a real sense of accomplishment in being able to say "I built that rig".
I
have challenged him to get his son to program the Arduino so on demand
the LO signal shifts 700 hertz and with a few more inexpensive parts has
a CW transceiver.
This afternoon the UK Ham who emailed me early this morning shared a photo of his final build. He had a defunct computer switching power supply and repurposed the case into an enclosure for his DCR. Bravo and Bellissimo!
So, you couch potato heads who never build nothing hams -- get off your butt and get started!
BTW
I did go on to actually build that MC1496 SSB transceiver and the 40673
IF stage came from SSDRA. I shared the MC1496 project with W7ZOI and he
in turn shared that with the original builder of the IF stage. The
Circle is complete.
73's
Pete N6QW