Tuning the Crystal Receiver

Radio Record, Volume I, Issue 42, 4 May 1928, Page 12

Tuning the Crystal Receiver

GETTING THE BEST POSSIBLE RESULT

_--- PHL operation of setting the cat’swhisker and finding the correct wavelength for broadcast reception on a crystal set has always been looked upon as of so simple a nature that uo cne has thought it worth while to give the ‘matter serious thought. We find, therefore, that whilst constructors and users of valve sets are given full and adequate advice on the correct method of procedure, the crystal user has been pomewhat neglected on this pasticular point. It is the purpose of this article tu rectify this omission. I suppose we all realise that any increase or decrease of strength, however slight, is much more readily discernible on a weak signal than ou a strong one, and yet how many of us act on the knowledge of this simpie fact? ‘We push the slider, turn the knob, plug in the basket coil (or whatever is necessaty to find the correct wavelength on our particular set) to what we know from experience to be tlie best point fot bringing in our local station, and then proceed to juggle with the cat’swhisker until we get what we think are the loudest possible ‘signals.

WORKING ON WEAK SIGNALS. O we not always have an uneasy feeling at the back of our mind, spoiling our enjoyment of the progranine or our pride in showing off our set to a pal, that what we believe to be the ‘"‘Joudest possible" is not really the very best of which our little receiver is capable? When next you are preparing to enjoy your local station, employ the following method, and I venture to think that uncomfortable fecling of wncertainty will be entirely absent. Start off as nsual, but after having fontid the station required so place your -eal’s-whisker that only the very faiilest signals are coming through. Now alter /your wavelength finder up and down; if yon find a better spot agam adjust your cat’s-whisker until the signals — are otily just discernible, and then try again for tle best position of the tuner. In this way the exact spot can he found at which the loudest possible sigtials are discernible so far as the wavelength tuning is concerned. Now we come to the setting of the cat’s-whisker: Having carefully marked the exact position for the wavelength as found ahove, set the cat's-whiskcr ta the loudest position which can be fourd, then "detune" the wavelength sintil the signals are at the very faintest point; next try for a better adjustment of the cal’s-whisker, and when this is found, ‘de-tune" again’ for the faintest signals, and so on until the very best setting of the cat's whisker has been fount, Jf sou then savitel

back to the point previously ntarked fot the best possible wavelength, you may feel confident that you have reached the "best possible’ setting and can sf down to ’enjoy the programme knowing that no amount of extra ‘‘fidcling". will bring better results. HIS method of working on the weak~- . est possible signal strength will be found the most advantageous one when testing the relative merits of various inakes of crystal, and. also for testing the best combination of crystal and cat’s-whisxer, and whilst on the subject of testing cat’s-whiskets, here 1» 4 hint which nas been found very useful. Say. you wish to find out .whether a gold, silver, or copper. whiske1 gives the best result with any .particular. crystal, fix all three whiskers into the der tector in such a.manner tliat. they. stick .out. at various angles. .It is then only a matter. of seconds to test gach one in tury (using. the weakest possible signals as outlined above) to ascertain which gives:the best results:

Lastly, there is the, annovance of getting "shaken. off" by the banging. of a door or. the. thoughtless steps, of those members of the family who do not share our enthusiasm for wireless. After trying many gadgets, an ellthusiast has found that by using a piece of silver wire (obtained from a jewel: ler) slightly thicker than the ordinary cat’s-whisker (about 26 $.W.G.), and two inches long, tapering the end to a fine point with a fije, and ‘making up with a coil of large diameter ‘(about twice a& large as that in the usual cat’s whisker), a very ftne aml. stable adjustment is obtained. .