ANSWERS TO CORRESPONDENTS

Radio Record, Volume I, Issue 12, 7 October 1927, Page 5

ANSWERS TO CORRESPONDENTS

(By ‘

Megohm

An inquiry from Nelson district asks for information regarding ‘adding onc stage of neutralised R.F. to a three-coil regenerative set." ‘This is not a very practicable proposition, aud in these days the three-coil is scarcely worth hanging on to when the more sectional Browning-Drake can so easily be coustructed, using the same andio stages if desired. Apart from giving better results, the properly neutralised Brown-ing-Drake will always win the appreciation of neighbours when it replaces a three-coil tuner. ‘the same correspondent is troubled with harsh tone, and has been endeavouring to improve it by utilising a three-to-one ratio transformer between set and speaker, taking output from the primary as a step-down, which las made an improvement in toue. Of course the obvious remedy is to replace the audio transformers in the set with more cfficient ones, try a fixed condenser of .001 m.f.d. capacity or larger across the ontput, and also across the primary of first audio transformer. The sinaliness of these condengers or absence of them will often canse harsh) to1ie. , W.T.H. (North Auckland) has a Browning-Drake set, number of valves" not stated, but does not affect the first question much. He is unable to tune in 2YA when 1VA is on the air and wishes to know the reason. Your set is rather unselective for a esl | ing-Drake, and probably has closelywound coils instead of the more selective ‘low-loss’ or space-wound coils, Decreasing the value of the small condenser in the aerial circuit makes _ the set more sclective, but too great. a reduction is inclined to make the. set unstable. The Browning-Drake of which you have read the description gets Auckland at two miles from | QYA without a waye-trap, only a neglivible background of 2YA being heard. Situated where you are, you should easily get 2YA without more than a trace of 1YA at Teast. Careful tuning counts too in such a case. In answer to your second query as to whether you should | be able to get Dunedin or Adelaide with the set much dependsupon the number of valves. Dunedin, at your distance, would not be more than ’ploné strength on four valves, except, perhaps, on odd occasions. Four valyes will bring in Adelaide at very good speaker strength on occasions, but other times only on phones. You will find that skill in tuning-in soom comes with practice. A.I3t, (Reefion) writes asking 1f the short-wave adapter cau be used on a reflex set employing crystal detector. This is a case where the adapter will not suit, as there is no valve detector socket to which the adapter can be connected. A request is also’ made for a short-wave adapter to be desigued for use with a valve reflex set. he short-wave adapter is really only a detector unit to be coupled to an audio amplifier, and by doing away with the old valve-base plug the three flex wires can be connected to the proper battery, and other leads of any type of amplifier, assisted by reference to the original diagram, Although Megohm’? will always give all assistance possible, it takes too much time to design special additions of valyes to suit any circuit diagram that may be sent along. J.W.C. (Puponga).--The 20’s_ wire for the crystal sect coil is intended to be S.W:G., but, although B. and S. gauge is slightly thinntr than S.W.G., it would answer in this case. The equivalent would he 19’s B and S. EI. (Wellington).-You would not be wise to increase the capacity of variable condensers in the set mentioncd, as the capacity should not be too large. Why not take out’ two or three of the moving plates? ‘The fixed ones can be left, and the moving ones replaced when the set is dismantled. ‘This is the hest way out of the difficulty. It is much better than altering cuil values in this case. HLA.R. (ITavelock).-As you find a difficulty in getting reception of lower wave-lengths, it is necessary for you to bring your set down a little to cover the usual range. The wave-iengths as now atranged appear to be giving general satisfaction since the recent alterations were made. You give no particulars whatever, beyond the information that you have a set, so the only thing I can suggest is to take a few turns off the tuning coils, so that the range of the set will be lowered. If our correspondent cares to supply details as to tuning arrangements in the set, further particulars can be giyen as to what should be doue, . 4