Medium Wave Modulator for FM, DAB etc on old radios

[Mark R]

I must say I have re-read Stef's article Joe posted. It seems a worthwhile build.

cheers Mark

[Yorkie]

Stef has recently had a valved 'micro-transmitter' (the unlicensable RF type) in Radio Bygones, but Im not at home just now so can't recall which issue it is in. My son has a 'Spitfire' (also illegal to use anywhere in the EU), which I recently saw in use. I must say that they're excellent, with a very good range from top to bottom of a three story house. He plays his i-pod through it to his Ecko A22. I was surprised to see how very small the 'Spitfire' is - it fits in the palm of the hand. The original 'modulator' (rather than transmitter) that I mentioned at the start of this thread that I built to Stef's design continues to give good service. When I get home, I'll re-attach the pics to my post.

[Skywave]

To inject an RF signal into a radio that does not have an external aerial socket: it might be worthwhile trying the following approach.

Since a socket for an external aerial is not available, there must be an internal loop of some description to provide an aerial for the set. So, if a wire loop, consisting of about 3 to 4 turns of wire is made and attached physically, not electrically, to the existing loop aerial, then the ends of this coupling loop can be brought out of the set as 'aerial' and 'earth' connections for the external device. This approach has the added advantage that it is suitable for a.c. / d.c. wireless sets, since the loop makes no electrical connection to the set. In the event of a set with a ferrite rod, same concept: a few turns on the end of the rod.

It will probably be necessary to adjust the number of turns of the loop and certainly the distance the loop is from the aerial coil, otherwise the loop will almost upset the tuning calibration & tracking of the set, since the aerial loop often carries a winding for the local oscillator. As a guess, I would start with something like a one inch seperation from a frame aerial; for ferrite rod, position it as mentioned above.

Just a thought.

Al.

[Joe]

That makes sense and doesn't compromise either safety or originality.

- Joe