Trf receiver


Joined Dec 26, 2010
The obvious advantage is simplicity. This may be seen as largely redundant now, apart from as an aid to teaching about radio.
In the earlier development of valve (electron tube) radios this was a more significant advantage, although to some extent it was simply that better methods were invented later, and took time to become adopted.

There are however a few genuine technical advantages we could mention for the TRF receiver. One is the relative absence of the spurious responses such as image frequencies and "birdies" (beat notes) which can arise in a superheterodyne. The absence of a local oscillator can avoid interference to other users*: at one time at least this might have been thought useful from a security aspect. Equally, the TRF does not have the problem of failure of synchronisation that can affect a homodyne (direct conversion) receiver.

At one time, a simple TRF with a relatively wide passband might also have been recommended for giving more faithful reproduction of AM broadcasts, but this was really only relevant before the advent of superior FM transmissions, and also before crowded wavebands enforced the passband to be strictly curtailed at the transmitters.

*Always provided that the TRF remains stable. This may well not be so, especially if positive feedback is used to increase the gain as it often was in the early days of radio.