Valve Circuits Menu


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Valve Circuits 1

Two amplifiers, five oscillators and one mixer

Valve Circuits 2

Beam deflection balanced modulator and one AF amplifier

Valve Circuits 3

Full break-in techniques including grid block keying, receiver mute and a valve T/R switch

Valve Circuits 4

Grid block keyed VFO, buffer/multiplier stages and a keyed HF PA

Valve Circuits 5

Stabilised valve power supply.

Valve Circuits 6

Beam deflection mixer and band pass filter

This page links to the various valve circuits pages which will be extended as time and inspiration permit.

(N) = New, (U) = Updated, blank = no recent change

1. Indirectly Heated Valves

2. 1.4v Filament Battery Valves



Valve Circuits B1

AF amplifier

Valve Circuits B2

RF amplifier

Valve Circuits B3


Valve Circuits B4


Valve Circuits B5

Active detectors

Scope Probes

Some issues with conventional scope probes and suggested solutions when used with very high impedance tuned amplifiers and oscillators

Constructors and designers should be aware of important differences between low power battery operated directly heated valves and conventional indirectly heated valves:

1. The directly heated filaments are very fragile and completely intolerant of excessive voltages so over-voltage protection is required.

2. The average slope (gm) is lower so expect lower gain compared to indirectly heated valves.

3. The typical anode currents are much lower so much higher anode load impedances are required to obtain adequate gain. This means higher resistor value anode loads in AF amplifiers and higher L/C ratio tuned circuits in RF applications.