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Editorial

Doug Parfitt

We are sure that all club members will join us in expressing very sincere sympathy to Doug’s family following his death on April 19th from cerebral haemorrhage.

Doug was 54 when he died and his club membership number of 750 belies the fact that he has been associated with the club for many years.  He was one of those rare and useful people who could always be relied upon to work quietly away in the background and it is to people like Doug that we owe so much of what we enjoy today on Mendip.  His skill as an electrician was always at the club’s disposal and the ease with which we got our electricity back so soon after the fire, and subsequently into the present Belfry was due to his, and his son-in-law Brian Prewer’s efforts.  At one time, Doug and Brian spent every Monday evening at the Belfry working on the lighting, power and plumbing.  His last job was to install the night storage heaters.

Open Air Caving

Our main feature this month is a series of articles on the delights of gorges, collected for us by that stalwart contributor to the B.B., ‘Kangy’ King.  With the summer months coming on, it is as well to remember that we are an exploration club and the traversing of gorges forms a nice summer link between caving and climbing.

Electronics For Caving

From time to time, as in last month's B.B., we read of the part which electronics can, or could, play in caving.  Since my personal experience of things electronic puts me somewhere in that no-man’s-land between the layman and the expert.  It might be of interest for me to play Devil’s Advocate on this subject and to ask just what electronics has really done for us and whether we are really interested?

Taking the three main headings of the article of last month, we have COMMUNICATION between caves and the surface; PINPOINTING of underground places with respect to the surface and finally CAVE FINDING from the surface to unknown caves.  Our record on Mendip of these three activities over the last thirty years has not been good.

We once had a telephone from the Dining Room in Cuthbert’s to the Belfry, but it packed up and was finally abandoned.  There was some success at pinpointing places in Cuthbert’s, but a record of unreliability on the same sort of exercise in Wookey.  As far as cave finding is concerned, not a single instance of success has ever been recorded on Mendip to the editor's knowledge.

Now why should this be? Over the period in question the state of the art in electronics has improved out of all recognition.  Most of our present-day electronic engineers have never seen an ordinary radio valve, yet alone handled one.  What is the trouble?

Taking telephonic communication first, it is true that the conditions met with in a cave are a little worse than those of the average living room but, compared to the conditions in a rocket; missile; satellite; atomic reactor etc. they are mild.  It should be well within our capabilities, if we were so minded, to build handsets which would stand being in a cave if necessary for years without attention.

Cables should no longer be a problem.  The old ex-army 'Don 8' cable, with its rubber insulation is now a thing of the past. Modern insulation can readily cope with any thing a cave can offer, and with transistor amplification a few ohms here or there cease to matter.  Single line and earth return should be possible even in dry caves.

Radio communication is, admittedly, a more difficult subject because the limitation here is more fundamental that transmitters are very inefficient at the low frequencies which have to be used.  The answer would thus appear to be that of making sure that receivers are as sensitive as possible to overcome the deficiencies of the transmitters.  When I was first employed as an electronic engineer, a communication receiver which could receive very weak signals of the order of a microvolt per metre were large, heavy boxes weighing as much as 40 or 50 lbs and containing perhaps as many as twenty or thirty radio valves. Maybe transistors still cannot cope with the very low signal levels that valves can sort out, but if they still lag behind valves in this respect, I am sure that it won’t be for much longer and we shall be able to build small, lightweight receivers as sensitive as were the old communication sets.

Turning now to pinpointing, much the same arguments apply.  The transmitter ideally needs a large loop aerial, laid horizontally on the cave floor for preference and fed with relatively large currents.  However, the receiver is on the surface and can be relatively big if that is the price of extreme sensitivity.  Maybe the transmitter should be fed in pulses to enable large currents to be used without flattening the batteries too quickly. Reliability of equipment should be no problem.

As for cave finding, the odd exercises involving resistance measurements which have taken place from time to time seem to me to be a waste of time.  We hear rumours of a possible gravimeter but, to show what can at least be postulated, it might be as well to consider the scheme that a B.E.C. member known as 'Monty' proposed way back in 1949.  The method was a seismic one and depended on being able to borrow one of those machines which thump up and down for tamping down odd holes in the road surface - also a number of seismic microphones, nether of which Monty was able to get his hands on to at the time.  Monty designed all the rest of the device round radio valves, and with modern equipment it should be a doddle.  The idea was that each 'thump' should start up a time base.  A variable time delay narrow band (in time) gate was then manually adjusted until the time interval coincided with the time delay of a particular echo.  Since the whole thing was repetitive, the signal from the echo could be summed and displayed on an ordinary meter.  One would then log the various echoes as a function of time delay, checking one microphone after another and plotting the echo depth.  By this method, general effects, such as changes in rock structure could be separated from local effects due to cave passage.

Perhaps I have been a little harsh with all this, but again perhaps not.  Could any of our current (note clever pun) electronics types put us wise on all this?

“Alfie”