These articles are scanned and OCRed from
old editions of The Wireless World
I finally managed to get an early edition of The Wireless World magazine
for a reasonable price on a eBay auction. Now I will be able to post a few of those
articles from the UK to compliment those from some of the American magazines. This
particular edition is from March 9th, 1932. My next target is to get a few from
the World War II era which although it began on December 7, 1941 from America's
perspective, it officially began on September 1, 1939 for Europe.
Warning for the weak of heart - epochal words like "niggardly" and "parsimonious"
are used herein, and therefore adult supervision should be employed if ignorance
might cause an objection to at least one of the aforementioned.
Practical Hints and Tips
Simplified Aids to Better Reception
When a receiver is fed with H.T. current from the mains, there is no particular
need to be niggardly in the matter of consumption; a few milliamps. here or there
make practically no difference to the cost of upkeep. But it is a different matter
when dry batteries are employed; in this case, all possible sources of waste should
be rigorously avoided, and it may be helpful to enumerate some of the more common
causes of excessively high anode current.
As often as not, a valve takes more anode current than it should because an insufficient
amount of negative bias is applied to its grid. Of course, the same thing happens
if the grid is totally unbiased, but then an audible indication that something is
wrong is generally given. Further, it is not enough that merely the bias battery
itself should be in order, and where there arc grounds for suspicion, it is advisable
to test the entire circuit for continuity to make sure that a negative voltage is
actually impressed on the grid.
A "soft" valve will generally pass a high anode current ; if this defect is not
made obvious by the presence of a blue glow around the electrodes of the valve.
it may generally be detected fairly easily by short circuiting the grid circuit
resistance, and noticing whether this brings about an appreciable change in anode
current. If it does, the valve will definitely be "soft." It should be remembered
that if there is not already a resistance of sufficiently high value in the grid
circuit, this test will not be conclusive, but a resistance may be temporarily inserted.
Other faults that may occasionally be responsible for excessive anode current
consumption in battery-operated sets are short-circuited anode feed resistances,
or leakages. or more or less complete "shorts" in the anode circuits; the bypass
condensers may be suspected.
Users of D.C. mains supplies are always handicapped by the fact that the H.T.
voltage available is inevitably fixed at a considerably lower value than that obtainable
from the majority of A.C. rectifiers. This limitation is particularly annoying when
one is trying to devise means for supplying a power grid detector with sufficient
anode pressure; even if initial difficulties are overcome the detector decoupling
must always be designed on almost parsimonious lines. Even if actual "motor-boating"
is not present, there is always an uneasy feeling that too much stray L.F. reaction
for really good quality is taking place. The final result is that we generally arrive
at a compromise - something like a "semi-power grid" detector, in which the usual
anode circuit limitations may possibly become evident, due to insufficient H.T.
voltage. At the best, we can hardly hope to use, as a coup-ling between the detector
and succeeding L.F. valve, an arrangement which will produce anything approaching
the maximum attain-able magnification.
The type of diode detector discussed in The Wireless World of February 3rd suffers
from none of these limitations, and, apart from providing almost perfect detection,
has the additional advantage that it does not impose any serious damping on the
tuned circuit which immediately precedes it. The arrangement, therefore, is one
that should be particularly attractive to D.C. mains users, who may accordingly
be interested in the skeleton circuit diagram given in Fig. 1. This shows the
nucleus of a diode - a L.F. set suitable for high-quality reproduction of local
broadcasting, and in which indirectly heated D.C. valves are used throughout. Where
greater range is necessary, an H.F. stage may be added in' the usual way.
In the suggested circuit diagram a pentode output valve is shown, but, of course,
there is. no reason why this should not be replaced by a triode, or where large
outputs are required, by a pair of triodes push-pull.
A set on these lines, with an H.F. amplifier. is definitely capable of long-distance
reception, and there is always the possibility of improved sensitivity by using
the diode anode - which in the simpler form of circuit is unemployed-for purposes
of reaction in the manner suggested in The Wireless World of June 10th, 1931.
People old and young enjoy waxing nostalgic about and learning some of the history
of early electronics. The Wireless World was published in Great Britain
from April 1913 through March 1922. Thereafter it ran under the name The Radio
Review, and then finally Electronics and Wireless World. For all of
the articles posted a page is created with a cover image and the table of contents.
As time permits, I will be glad to scan articles for you. All copyrights are
Vintage "The Wireless World" Magazine Articles
Posted October 11, 2021(original 4/4/2011)