EA3GHS and EA3FXF have produced a single IRF510 FET based version of his Mosquito transceiver using a PC as the back end of a software defined radio (SDR). In essence, the FET is used as a regenerative or direct conversion receiver - I think the two are indestinguishable in a single stage RX - with audio coupled to the sound card via a mains transformer which steps up the impedance. The IRF510 is capable of up to about 7W in this application. Coupled with an SDR back-end and this is SOME simple transceiver, especially if the crystal is VXOed.
28 Jan 2010
Mosquito single IRF510 transceiver
EA3GHS and EA3FXF have produced a single IRF510 FET based version of his Mosquito transceiver using a PC as the back end of a software defined radio (SDR). In essence, the FET is used as a regenerative or direct conversion receiver - I think the two are indestinguishable in a single stage RX - with audio coupled to the sound card via a mains transformer which steps up the impedance. The IRF510 is capable of up to about 7W in this application. Coupled with an SDR back-end and this is SOME simple transceiver, especially if the crystal is VXOed.
Howdy,
ReplyDeleteDirect conversion receivers and regenerative direct conversion receivers are distinctly different. A direct conversion receiver has a local oscillator and some form of non-linear circuit element acting as a frequency mixer. Selectivity is provided by interstage filtering.
A regenerative receiver is an oscillator running at the edge of oscillation with positive feedback. The positive feedback in the regenerative circuit creates inherent gain and selectivity in the receiver.
For SSB and CW reception you set the regenerator into oscillation, for AM reception you set the regenerator below the oscillation point. Regenerative receivers are rather difficult to "tune" as two highly interactive reactive elements (typically capacitors) must be adjusted at the same time for optimum reception. One to tune the frequency and one to adjust the level of positive feedback. A direct conversion non-regenerative receiver has nothing like this.
73's David WB4ONA
Hi Roger,
ReplyDeleteAlthough the differences pointed by David get thin when the regen oscillates still there is the quench interruption which isn't present in the DC receiver which is part of the basic work of the regen.
72 de Pedro LU7HZ.
Not sure I agree about the difference when we are talking about a single stage self-oscillating detector: a self oscillating mixer can be thought of as a regenerative detector OR a direct conversion mixer.
ReplyDelete