ANSWERS TO CORRESPONDENTS

Radio Record, Volume I, Issue 13, 14 October 1927, Page 14

ANSWERS TO CORRESPONDENTS

(By

Megohm

D.B. has‘a five-valve neutrodyne and . would like an article on how to add. four stages of radio frequency on the one side, and the addition of a power valve to follow the present two stages of audio. Most people are fairly well satisfied with the output of a five-valve neutrodyne if it is behaving efliciently. One would be inclined to think that ia our correspondent’s case he is not get- & ting the results from his set that he: has a right to expect. If that is the case, it would be far better to make the best of the present set, experimenting continually to bring it to a state of high efficiency. ‘This shonld be done before additions are made to any set. Adding a number of radio stages as proposed would not be a simple matter, even with instructions, as R.I. is not easily handled in successive stages, and would probably need the extra complication of screening each valve. Two stages of audio transformer coupling is looked upon as the limit at the present time, though some sets are being specially designed to carry three stages. But the amateur ‘s advised to stop at two, so that cur correspondent should replace his last valve by a power-valve to give a greater output than that at present in use. ‘The introduction of a super power valve often imports a further problem in the shape of much increased high-tension voltage and a grid bias of anything up to 40 volts. It is not essential to run a power valve to the limit of voltage allowable, and niuch increased volume and _ quality may be obtained by striking a happy mediunt. F.R.C. (North Auckland) wishes to’ know if the remaining vyoltage of a 45-volt dry B battery, that has gone down to half, may be utilised to charge a 6-volt battery, and thus recover the remaining voltage. Theoretically this is possible, but in practice the 25 volts > remaining in the B battery has such: small amperage that ils impression on the G-yolt battery would be practically nil.