#1820 Aug 11, 2014
I resolved to make a new radio transceiver. It's going to overcome the
overly wide receive bandwidth of my current transceiver and have
several other important features that should allow me to work CW with
a bit more ease.
The basic specs are that it is a 7 MHz transceiver with a crystal IF
filter at 4 MHz. I intend for its receive bandwidth to be less than 1
KHz (It's a CW transceiver) and I may improve the transmit power as
Right now, I only have three stages complete on the receive board;
there's the 9v regulator, the VFO, and crystal-controlled BFO. The BFO
works although I'm not happy with the output waveform. Maybe I will
end up feeding a resonator with it in order to clean it up a bit. The
VFO does not oscillate at all.
Attached is a schematic. The buffer (MPF102 and 2N2222A) might be
changed as I'm sure it was designed to drive TTL loads. As far as the
VFO goes, I'm shooting for a target frequency of 3.0-3.2 MHz and am
getting nothing. I think that the value of the 10 pF capacitor should
be changed but I'm not sure. A lower value would better isolate the
tank circuit from the FET's gate but a higher value would allow more
signal through. Please advise.