APPRECIATION

Radio Record, Volume I, Issue 52, 13 July 1928, Page 13

APPRECIATION

CONCERNING EARTH CON-| NECTION & B ACCUMULATOR THD following appreciative letter has been received from Wanganui by "Megohm" :-""I know you like to hear the results obtained by those listeners who try out the ideas published in the ‘Radio Record.’ I was a bit sceptical as to theimprovementthat might result by using a car radiator as an earth connection, but as an old Ford radiator (all copper and brass) came into my hands,-I thought I might as well give it a ‘trial. "Previously I had three din, galvanised pipes set in the form of an equilateral triangle with six-foot sides, each driven about 3ft. Gin. into pure sand, and with the earth lead soldered to these; with this I got quite average good results on my five-valve neutrodyne, "T attached the radiator about the centre of the triangle, and filled the hole in which it was placed with wood and coke ashes. There certainly has been an improvement of reception of DX stations. My best performance with the set since then was to bring in 2FC broadcasting an Anglican service on Sunday, June 24, at 1 pm, New Zealand standard time. Of-course, the volume was not of the crockery-rattling variety, but I could clearly hear the words of the lesson being read fifteen feet from the loudspeaker. Previously my best on this station at that time of day, was weak phone strength. I have found, as did the originator of the idea, that the tuning has been considerably sharpened-in fact, the tuning is almost too sharp, as the dials (vernier) require very gentle handling. "I use another idea in my set which possibly may be of usé to someone else. When I got the set (second-hand), I found it very tricky to neutralise. If O.KK. on the longer waves-it was inclined to howl aud distort on the lower

band. and vice versa. I got a competent service man to haye a try at it, but no improvemert was effected. I then had a brain-waye to fit outside controls to the neutralising condensers. This was very easily and cheaply done by attaching two long thin xylonite knitting needles to the sliding portion of the neutralisers, which are of the home-made Baleon type. This has given perfect control of the set, and the yalves can be kept just below oscillation point over the whole of the broadeast band. Another control, but -who eares, when efficiency is concerned? You may be interested to hear that the B accumulator built last year more or less to your specifications in the "Radio Record," about which I wrote when completed, is still giving perfect satisfaction. I have had as much as a fortnight’s use out of one charge, but I usually give it a charge of six hours once a week. I can certainly recom-| mend anyone who wants a dependable B:.battery at low cost not to hesitate about making one,-yYours, etc.,

H.M.

V.

Keep R.F. Out of Audio. THE presence of radio-frequency in the audio side of a receiver should always be avoided as much as possible. Such unwanted rf. voltage can affect quality of reproduction to a considerable extent. One of the most effective methods of by-passing r.f. to earth is by "cabling" or binding together all battery leads, under the baseboard in the receiver, and outside it by keeping A and B leads cabled for as far a length as possible. By this means the wiring acts as a continuous condenser, the 1r.f. voltage passing from other wires to the earthed battery wire and so to earth. The most effective way of carrying this out is to let all receiver battery wiring continue to the batteries without a break, dispensing with the usual array of terminals. In the rf. stages also it is a recognised principle to run all r.f. to earth at the first convenient point after its work has been done. This is effected through by-pass condensers of suitable capacity.