Battery decals

Batteries for valve portable radios are sadly no longer available. In fact, not since about 1973! However, it is possible to build your own HT or combined HT/LT battery by placing sufficient PP3 batteries in series (10 required for 90 volts). If you want LT supplies too, best to use large 'D' cells, perhaps two in parallel, held in suitable holders. Holders and PP3 clips are freely available from component suppliers. The battery should be assembled in a lightweight wooden box. Thin MDF or 6mm plywood should suit. To add the finishing touch, battery decals can be added. Click on the links above to find good quality scans of a standard Ever Ready B136, as used in 'Sky Queen' and other larger portables. Ensure that the scans are printed to the correct size - see instructions on the page.

Looking for high resolution scans of battery cases? Click on one of the above tabs

Disclaimer

This design is offered in good faith. It is the responsibility of the constructor to ensure his personal safety, and that of others, when building and using the device.  Bear in mind that mains-powered items must be constructed to a high standard of safety. If you are in doubt about your knowledge and ability to construct and use safely, you are advised not to attempt the work.

Safety Lamp

This simple design is extremely useful to the restorer. It allows power to be fed to an 'unknown' radio in order to test for potential problems with mains transformers, smoothing capacitors or rectifier short-circuits. The device works like this:

The power is applied to the set under test in series with a 60W lamp*. Once satisfied that no danger of burn-out or catastrophic failure is likely, the switch is thrown to short out the lamp and apply power directly. It's that simple - and that useful.

Do NOT attempt to build this device unless you are sure of your ability to do so safely.

*Never apply power through lamp limiter or direct until you have ensured no obvious short-circuit or other power supply fault exists. 

LIST OF COMPONENTS AND MATERIALS

1 X 60W mains lamp. 1 X batten holder to suit above lamp. 1 X one-way mains-type surface mounting light switch and pattress box, plastic. 1 X surface mounting switched 13A socket and pattress box, plastic. 1 X choc-bloc, at least 3 way @ 13A, for facilitating lamp wiring. Quantity of timber. Original uses a 9mm ply top panel with 15mm MDF side rails. Woodscrews, fixing clips for cables, PVA adhesive, Danish Oil or varnish.

Dummy Aerial for signal generator

This simple little device is built into a felt-tip pen and uses a short length of plain brass rod as a probe. It is suitable for use in the alignment of most valve radio sets.

Why a dummy aerial? Well, radio sets are intended to work with an aerial of some kind: valve portables usually have frame aerials, which are, in effect, the aerial coils would onto a large former. This, by the way, is the reason why the cases of portable receivers often need turning, as best reception occurs when the axis of the frame aerial is in line with the transmitting station. The same sort of process gives the principle behind radio direction-finding. Portables should always, therefore, have their frame aerials in place when alignment is carried out. Such sets need the generator to be linked to the aerial by means of a inductively-coupled coil when RF stages are being aligned. Inductively means, in practice, that no electrical connection is made - ideally, a radiating coil, shielded and constructed to the Radio Manufacturers Association standard, should be used, connected to the generator AF output by means of a shielded cable and placed about a foot from the radio set's frame aerial.  However, here's an alternative  for battery portables. Construct a loop consisting of about four turns of - preferably - stiff insulated wire on a former about the size of the set's frame aerial. Connect the loop ends to the generator output and set the aerial about 2 feet from the receiver. Initial setting-up might require the generator leads to be placed near the frequency-changer grid for inductive coupling, to roughly align, before proceeding with the loop.

With mains radios, it is easier and quicker to have a suitable dummy aerial built up as shown. This design is very basic, using no inductances, but is fine for general use.

It is not suitable for alignment of short waveband RF stages.

Construction is simple. The components should be mounted on veroboard. The cable should be fed through a hole drilled in the base of an empty thick felt pen case and soldered into place on the board. A plastic strap should be fitted to prevent strain on the cable. This should fit inside the end of the assembled case. A hole to suit the brass rod should be drilled in the nozzle (cap) end and the rod bonded with Araldite resin adhesive so that about an inch sticks into the case body when the cap is replaced. 

 The rod should be notched with a file to help the Araldite resin glue hold it firmly in place. If the cap is too loose, a turn of adhesive tape around the body top should help. The probe may be insulated by sliding some plastic sleeving over it, leaving just a small tip exposed. The sleeving can be obtained by stripping heavy duty electric wiring cable.

LIST OF COMPONENTS AND MATERIALS

One felt-tip marker pen, about 0.75" diameter by 4" overall length.

One brass rod, about 3mm diameter by 3" in length

One 300pF capacitor

One 390 ohm resistor (ideally a non-inductive type)

One length of flexible screened or co-ax cable

One plug to suit RF output socket of signal generator

One short section of matrix board or veroboard