The power supply should not be neglected when designing a high performance communications receiver. High-efficiency full-wave rectification should be used if possible, coupled with double regulation and adequate filtering. It is not uncommon to find two series regulators feeding each other in a high-performance power supply as shown in Fig. 1. Switching power supplies should be avoided because of the noise generated that can easily pollute the receiver's sensitive circuitry.
I am against a single power supply in a communications receiver, because of the FM-like phenomenon resulting from it. Many low-cost communications receivers power their audio amplifiers as well as their variable tuning oscillators from the same power supply. Because of inefficient design in the power supply, the output voltage to these elements will vary as peak current is required for audio signal reproduction. The result is pulling of the variable tuning oscillator which is actually frequency modulated by the sound of the receiver.
This phenomenon is very annoying and can only be eliminated by rebuilding the power supply. When designing a receiver, use separate power supplies for the Vfo and i-f amplifiers. The audio amplifier should have its own power supply. Digital counters should also be powered from a separate supply, reducing the chance of digital noise feedback into the rf circuits.
Ground loops are also a consideration. When designing with multi power supplies, there is no known way of predicting ground loops in a communications receiver, and they can be the final obstacle in achieving high performance. They manifest themselves by introducing severe amounts of hum in the output of the receiver. Good grounding techniques may or may not solve the problem. Although theoretically understood, ground loops will almost invariably impact the performance of a newly designed receiver. Removing them has always proved to be a time consuming trial and error process.
Fig. 1. Doubly-regulated power supply is used to insure superior
performance in a communications receiver.