Advanced Projects

Halse and Hatch

The emphasis in this phone singe sideband design is ease of construction. The Halse RX can be used on its own but together they form a single band 5 Watt SSB TCVR for any single band of 20, 40 or 80m. The superhet's IF is 9 MHz which gives coverage of the 20 and 80m bands with a single VFO band near 5 MHz; and by just changing the VFO inductor it can work near 2 MHz for the alternative 40m band. Starting at the aerial, the receiver has a double tuned RF filter, followed by the first mixer which is an SA602 having its own discrete IF amp prior to the IF filter which uses four crystals in a ladder formation. The second mixer is also an SA602 which includes the Carrier Insertion Oscillator and can work on either sideband by the addition of an inductor. The first audio stage uses a pair of BS170 MOSFETs driving the AF gain control, which is followed by the audio output stage able to drive a loud speaker or phones. The RX PCB is nearest the front panel in the photo below. You can add the Mini CW kit, the Mini AGC, and or a digital frequency readout - the three digit one is most appropriate.

For transmission, the RX is switched over to produce low level SSB by installation of relays that come with the TX kit.  The microphone speech amplifier output is fed into the RX second mixer which now acts as a balanced modulator. The IF strip is then used in the reverse direction (with relays reversing the mixer inputs and outputs to reverse the signal flow), so that the IF filter removes the unwanted sideband and feeds into the other mixer to get to the desired band frequency. The RF BPF removes the unwanted mixer products so that low level SSB is actually ejected out of the RX aerial terminal! Then follows the TX RF amplifier chain with an IRF510 MOSFET for the RF output stage; this is designed to produce 5W on a nominal 12v supply, but as ever, it is highly dependent on actual supply volts at the output stage! This is followed by a double Pi harmonic filter with the inductors and capacitors adjusted for the chosen band. TR control is by your mic's PTT switch and this also mutes the RX when transmitting.

Prices are GBP 46 for the Halse RX, or GBP 79 for the Halse and the Hatch when ordered together. The Hatch is priced at GBP 36 when ordered on its own later.


Finally! I am still churning ideas for a more advanced new design but the price is not yet right - keep in touch with developments in Hot Iron!

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