MW Micro-Transmitter

[Joe]

When you lot were coming after me with the pitch-forks and burning torches a few weeks ago because I'd suggested adding a Gram socket to a Bush AC91 the up-shot was a recommendation to make or buy a micro-transmitter.

I easily found some circuits but getting the bits has been a bit more problematical. However, I finally made this one tonight.

http://www.youtube.com/user/Stefan0719?blend=23&ob=5#p/u/0/f42W9jNHMZ0

It was straight-forward enough and worked first try.

       

The sound quality is very good and as can be seen in the photo I'd got the tranny I was playing about with plugged into the hi-fi so as to see just how good it was.

The range seemed very short, which is no bad thing, but I haven't yet added the transistor RF amp.

The only slight disappointment is it needs a minimum of 6V which precludes the hijacking of an LT supply (put that pitch-fork down!) as by the time that's rectified and smoothed it's down to 5.8V.

All told its highly satisfactory and if anybody else wants to have a pop and has any questions then please ask.

- Joe

[tiv48]

now thats one i have not come across before but i like it
rob t

[ppppenguin]

I can't prove it without building it and looking with a spectrum analyser but it does look as if it's going to generate lots of harmonics into the short wave band. Frequency stability is also likely to be poor.

[Shaman]

I C Yuck.....Alan.

[Joe]

I know, Alan. I'd prefer to do that one of yours with a valve but haven't got the bits. At least I put the IC and transistor in sockets for the sake of tradition. Actually, these multiple valves in one envelope things are quite like ICs

I've got the computer playing 6 Music into it at present and am listening on a Vidor portable and it sounds damned good. I'd expected it to be all over the dial but it isn't and as it's range is only a couple of feet it isn't going to bother anybody else.

It's odd but I feel as happy with valves after a few weeks as I am with transistors which I've been messing about with for my whole life. Granted my knowledge of both is still minimal but I think it's our glowing friends for me in future.

All the best
- Joe

[glowinganode]

Does the TL072 use a Mazda Octal base, or International?
Rob.

[Joe]

Even with the transistor amplifier added the range is only about four feet - it's usable to around three - which is handy from an interference point of view. Without the amplifier the radio had to be right next to the transmitter and as I was using a pocket-sized thing wrapped the transmitter aerial around it.

All the best
- Joe

[tiv48]

my attempt at mw micro transmitter on strip board like others i prefer perferated board and pins ,this worked second time ,first try i connected pin 4 to the wrong track
rob t