Navigation Protractor and Scale Rule (1/2 mill and 1/4 mill)

        Extra-flexible;  Lightweight;  Large figures;  Encapsulated print - can't rub-off;  Inexpensive

        Protractors 5" (125mm) square.   £1 each;   p&p 50p.     Five or more post free.
        Scale rule (26cm long) reads to 35nm and 70nm;      2 for £1.50 including p&p.  

        Details and downloadable PDF to make your own.

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R/T Practice Intercom Project

A simple audio amplifier project adapted to practise radio calls etc, like the units used to do the practical radio exams.  Comprises two stations connected by wire.  Cost of components about £25 for everything needed including computer-style headsets.  Requires simple construction and soldering skills.  Suitable for 10 yrs up with appropriate supervision.  Details below.

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Navigation Protractor and Scale Rule:-

These were developed for training youngsters in navigation planning as an inexpensive alternative to the rigid square protractor and scaling ruler.

If you wish, you can print and laminate your own using the PDF which can be downloaded from the link.  The document is printed out on transparency film, then laminated to produce an accurate square protractor and scale rule for plotting courses on maps.  There are two protractors and two scale rules to an A4 sheet.

Tips:-    For best results, use a laser printer with laser transparency film, as some ink-jet transparency films leave bubbles when laminated.  
            The scale rule is better printed on paper or thin card, so the scales show up clearly on the map.  
            The 160 micron (2 x 80 micron) lamination pockets are adequate, but if your laminator works with 250 micron that might be a little better.  
            The 160 micron sandwich cuts on a normal trimmer with a reasonably sharp blade.  

Note:-  The scale rule is not really stiff enough with the lighter laminating pouch to use to draw a straight line; a separate straight edge is helpful.        

Download Protractor and rule PDF

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  Intercom details:-

Great for practising your radio calls 

Based on a simple amplifier kit, available from Rapid Electronics

 Cost (2010) is £25 + £5 p&p for two amplifier kits, circuit boards, boxes, mike headsets, 
connecting wires and the extra components needed.    Ready-built units are £39 + £5 p&p.

Download PDF Flyer

The circuit needs some simple modification*, with PTT switch instead of the on-off switch, a couple of different resistors, an extra capacitor and a miniature 3.5mm stereo jack socket for the headphone.   The build instructions give all the details.

You will also need a box and the nuts and bolts to fit the bits in, plus some connecting wire to link the two units. The unit could be developed further to allow for radio channel selection and a Mayday and/or PAN emergency button/light to be included.

This would be a very suitable project for groups of air-minded youngsters – the amount of assembly is enough to need some care, but reasonably simple, and there is a comprehensive project leaflet of the basic amplifier kit on the Rapid Electronics site.

*  Mods needed (each station):-  one of each 4.7KΩ and 10KΩ resistor, 0.1 µF Poly or ceramic cap, PTT switch (momentarily closed switch), 3.5mm stereo chassis jack socket, headset with electret boom mike, suitable case and hardware, twin speaker wire, 9V battery.

Amplifier kits are sold in sets of 5, and are available from:- 
Rapid Electronics Ltd., Severalls Lane, Colchester, Essex CO4 5JS.  
Tel: 01206 751166     Fax: 01206 751188    Email:sales@rapidelec.co.uk

Intercom Quick-Build Kit Instructions Download
(This would need some work for the housing and drilling requirements) 

Download PDF Flyer

Dave Hall,     01761-490653