Colin, G0NQE continues his description of the Willow transceiver.

The receiver was designed by John, G4LOS with a front end consisting of a three pole band pass filter and a J310 RF amplifier.

The inductors used for the band pass filter were 8.2uH axial chokes with a low impedance link winding wound over the middle of the choke at the input and output of the filter. This gave 50ohm in for the aerial and 50ohms out for the first mixer.

The two mixers used in the receiver were both home made ring diode mixers, accordingly the strong signal handling qualities of this receiver are excellent.
The output from the band pass filter is mixed with the VFO to give the 10Mhz IF Frequency.

Output from the mixer is then amplified using a 2N2222 broadband amplifier, the output of which is then transformer coupled to the 10Mhz six pole crystal ladder filter.

The filter crystals were 30p each from a well known emporium; we achieved a bandwidth of about 2.6Khz with this filter. Once the signal is filtered it is then amplified by the MC1350 IF amplifier chip with AGC facility.

The second ring diode mixer is used as the product detector; output from the MC1350 is mixed with the CIO to give us the required audio signal out from the mixer, it is then amplified by an audio pre amp consisting of two BC184 transistors, output from the audio pre amp is then fed into a BC546B.
The resulting amplified audio is then connected to the audio PA an LM386 and a small amount is fed back to the AGC amplifier.

John managed to get one FET a BS170 to do four jobs i.e. AGC detector, AGC amplifier, S meter driver, plus an IF gain control, not bad value for one FET and it works to great effect.

The output from the AGC amp is fed to pin 5 of the MC1350 and the resulting AGC action is quite smooth.

The last thing to mention is the CIO which consists of a single BC546B plus 10MHz crystal and a 60pf trimmer, the output is filtered by a low pass filter.
The whole receiver was made on two boards, one for the front end, first mixer and broadband amplifier. The other board consisted of the crystal filter, IF amp, product detector, AGC amp, CIO, audio preamp and PA.
The Willow was originally designed for 40 Metres but we have built different versions for other bands and it works just as well.