A simple 40 meter DC receiver that’s inexpensive and fun to build!
The TinEar is a simple DC receiver designed by Wayne McFee, NB6M that covers approximately 400 kHz of the 40 Meter band. This receiver has a stable VFO, and is quite pleasant and fun to operate. The kit is easy to build, and uses all through hole components. Everything is included in the kit, even the straw that is used to wind the tuning coil!! It tunes by means of a simple PTO (permeability tuned oscillator) and uses a 9V battery for power. The receiver uses common earbud or walkman headphones and has controls for Tuning and RF Gain. The battery even fits inside the case!
A neat feature of the kit is the great custom metal enclosure that is the exact same size as the BLT tuner. It is 3″ x 3″ x 1.625″ and is made from .063″ aluminum. All parts are included – case, AmQRP quality soldermasked, silkscreened, plated-through pc board, knobs, connectors, hardware, etc.
The kit ships with an extensive manual on CD-ROM that will also be downloadable from this web page.
The TinEar – What It Is Not
The latest kit offering from AmQRP, the TinEar receiver, is definitely not a “superfine superhet”. It is not a receiver that has such refinements as a narrow CW filter, or single-signal selectivity. It is also not the usual NE602/LM386 integrated circuit type of receiver that we are all used to in such offerings as the “Sudden”, the MRX40 and the receiver in the SMK-1.
The TinEar is a simple design that uses all discrete parts, fostering greater learning possibilities about the inner workings of basic receivers. It incorporates a simple, but quite stable, VFO that provides for 400 KHz or more of tuning range.
Even without narrow filtering the TinEar is able to cleanly deliver the sounds of all of the modes available on the 40 Meter band and beyond. If one wants to listen to CW, tune up the band and scout out some SSB, tune in a little AM Foreign broadcast, or even listen to the Canadian time-hack station (CHU) above the upper end of the band, one can do so.
If so desired, the output can be routed to a computer sound card so as to decipher PSK-31, MFSK16, or other digital modes, as well as SSTV or whatever.
The point is that the TinEar is not limited by crystal control to a very narrow frequency range. Nor is it limited by a narrow CW type filter in its reception capabilities. It does allow one to tune in whatever is desired, in whatever portion of the band the signal of interest lies.
In those ways, the TinEar points to the deficiencies of the type of superhet receiver we are used to listening to in almost all of the CW transceiver kits. They are typically very limited in frequency range, and their narrow IF filters preclude the reception of anything other than CW or narrow bandwidth digital signals. In some, the filters are so narrow that the superhet drastically reduces the audio quality of even CW reception.
Think of the TinEar as the kind of easy listening receiver that you can use to casually tune in anything. Further, you can learn more about what makes a receiver work by perusing its design and building the kit.
Should you want to go on even further, a companion transmitter can be used to make many a QSO. The basic design can be placed on any of the lower HF bands – 160, 80, 40, or 30 – with just a very few simple changes. The entire board, or the entire receiver, can even be used as the product detector and audio section of a more complex receiver!
Give it a shot – you just might be more than pleasantly surprised! If you don’t, you will be sorry you missed it.