What do you use as a AM transmitter to listen to your radios

[Julianh]

Quick question, I'm looking at an AM transmitter to send some suitable music to my radio(s).
I've been looking at the "Spitfire" but it's quite expensive. What would you recommend?

Thanks

Julian

[FRANK.C]

A vote here for the Minimod
https://www.vintage-radio.net/forum/...d.php?t=149604


Frank

[Station X]

Some reviews here:-

https://www.vintage-radio.com/reviews/transmitters.html

I use an SSTRAN fed from a Roberts Internet Radio controlled form the UNDOK app running on my smart phone. I don't think the SSTRAN is available any more though.

[Julianh]

Thanks for that, is there a kit or assembled version I can buy "off the shelf" I particularly like that it's valve driven.

[Bazz4CQJ]

If you can find a suitable crystal, the attached circuit may be of interest, using only cheap and readily available parts. I have not yet tried it, but it's on my 'to do' list.

B

SSTRAN AMT3000, very good but no longer in production.

[PaulR]

Originally Posted by merlinmaxwell

SSTRAN AMT3000, very good but no longer in production.

Same here, fed by a Squeezebox. The Squeezebox remote connects via wi-fi so can be used in any room. There are some good vintage internet radio sites but I have to admit that R4 is the favourite station. There is a huge amount of LW interference here which makes R4 on 198 impossible to use during the evenings but the MW interference is greatly helped by a class X capacitor housed in a plug top.

[paulsherwin]

I use the guts of a Wild Planet Radio DJ, but they don't seem to be available in the UK at a reasonable price now. It was always a bit tricky importing them from the US.

https://www.amazon.com/Radio-Dj-Studio/dp/B00L5YBSZG

[ekjdm14]

This is something I'm interested in too, since there's not great reception here even on VHF & some of my nicer radios only cover AM.

Has anyone built the valve kit on ebay? It looks quite neat and I too like that it uses valves, but if it's got decent sound quality and enough range to receive clearly in more than one room would be the important things to myself.

The spitfire does sound ideal, though the price is quite a chunk of cash & would usually prefer to build something myself.

[paulsherwin]

There are lots of designs on this forum and elsewhere if you want to build something from scratch, everything from a couple of transistors to semiprofessional rigs. Transistor designs are easier to live with than valves because of the power supply requirements, but valve designs tend to be a bit simpler.

A reminder that all pantry transmitters are illegal unless CE marked, so you should ensure that the signal stays within your property and you don't cause any interference.

[petervk2mlg]

I've built various designs, but found the SSTRAN perhaps worked the best.
Last week I built the one on this site:
http://members.iinet.net.au/~cool386...ono%20osc.html
It worked really well actually. I can recommend it.

P

[paulsherwin]

Here is a similar simple valve design that I found on the net years ago, apparently by Bill Jarvis. I keep meaning to build it but have never got around to it. It should work equally well with B9A frequency changers like ECH81s or UCH81s.

[Andrew2]

Remember the range of a MW transmitter will be set by the antenna system in use. Inevitably a pantry transmitter will use a 'pantry antenna' as well, and the efficiency of a short wire will be low and highly dependent on an earth system and being accurately tuned to resonance. An off-tune or badly mis-matched antenna may produce a range of only a few metres, but one 'on song' and working properly will probably reach well beyond your property.
Loops get around the earth problem, but they bring other problems.

[plaka78]

I use this pantry TX that can be switched from Medium Wave to FM.

[Argus25]

I had tried a few commercial pantry Tx's but never been satisfied with the performance.

One of the major problems is very few have automatic amplitude control and soft clipping of the audio and a lot of the time the match to the antenna is poor. So I made my own to work with matched loops or whips. They also contain the NE571 Compander IC and a soft peak clipping circuit. One problem is there is a very wide range of levels from source materials, especially mp3 recordings.

The unit in the photos has three pcb's stacked on each other, only the top one is visible. The lower one holds the output devices, a class A-B linear amplifier with a 50R output impedance. The middle board power supply management and the upper board the Crystal L/O based on an MPF102 (two optional transmission frequencies) an MC1496 modulator IC and the NE571 compander IC and a pre-driver circuit.

In the end I went to loops which are much more effective in the near field if the receiving radio has a ferrite rod. Noise reception is negligible in this case.

Be aware that a ferrite rod & coil can make a reasonable tank coil for a transmitter, but it is useless as an RF energy radiator because its cross sectional area is too small, so it still needs a long wire attached to it and long wires are not as good as loops, unless the receiving radio has a wire antenna (and no ferrite rod) then the long wire for the TX is better as the radio responds better to the electric component of the EM field in that case.