Looking at options for an AM transmitter to feed various audio sources to radios.

Seen attractive kits from USA (Ramsey) and from UK (a 2-valve tx) but each of them would cost close to $100 once international freight is included.

I've been looking at a few circuits online and they vary from extremely basic to pretty complex. Although I'm atracted to the idea of a valve circuit, I think the lower voltages of solid state is probably more practical.

The main differences seem to be in the oscillator generation and control, and there are many ways to do it. Some use integrated circuit counting chips, others use crystals, others use multiple coils you would need to wind yourself.

Wondering if anyone here has built something like this or has recommendations on circuits or kits?

Maven

Hi Maven,

Considering going down this path also.

Either Brad or Marc have recommended a valve set on this site previously; I don't have the reference.

An alternative valve transmitter on ebay http://www.ebay.com.au/itm/171104980078

I have a couple of solid state circuits and other info I could email if you unhide your email address. I haven't studied these circuits in any detail as yet, but when time permits, I would probably try to build something similar from old radio parts etc..

Cheers,
Ian

That is the bloke I bought mine off. The design has changed slightly but the principle is much the same.

I'll unhide email now.

From what I have been reading, I'm hoping it might be possible to build a solid-state transmitter in the case of an old mid-size transistor radio - using as much as possible of the tuning setup, volume control, telescopic antenna, power connectors and maybe other components. Then plug the external program source into re-purposed earphone socket. A vintage James Bond stealth transmitter.

Maven

I looked at that english one. It's pretty, but ~$70 + ~$18 postage +$?? batteries or 90vPSU = $100+.

Maven

A number of US manufacturers have them. For example, here's one from Ramsey:

http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=AM1C

Locally, here's an old project from Silicon Chip 2006:

http://archive.siliconchip.com.au/cms/A_105705/article.html.

I looked at the Ramsey one - it looks like a neat package but they only offer UPS courier freight - at $120 on top of $40 price!

The Silicon Chip "Little Jim" looks about the right scale and I would be able to use some salvaged components. But I can't see how to get access to the schematic. The archived website is closed.

I'd probably prefer a design without IC chips in it, but could work with something like the Jim if necessary

Maven

I looked at the Ramsey one - it looks like a neat package but they only offer UPS courier freight - at $120 on top of $40 price!

I've bought stuff from them before. They will also send by air mail. Email them and they'll quote you for that.

Maven
I have a copy of the article as this is the one I built. I will send it to you on the weekend.
Pcb is available from SC Shop
Ben

There is also the solid state mini TX as described in the HRSA magazine for Jan and April 2010.

I built it from the kit available and it is BRILLIANT!

Harold

Maven,

Files sent.

Cheers,
Ian

Ben and Harold,

If you have (or can make) a digital copy of the circuit diagram of the transmitters you built .... could I have a copy please?

Thanks,
Ian

Are HRSA kits available to non-members? I feel like a kid with his nose pressed to the lollyshop window, but no penny to spend (actually, I've got the pennies, but don't know how to open the relevant doors).

I'll leave my email addr open in hopes some circuits are put forward.

Still looking at some from internet DIY circuit sites. 2-3 transistors seem to be fairly common - one for source amp, one for oscillation, optional one for power amp.

So far I've seen circuits with parts counts from about 10 parts up to about 40 parts. I don't really need super hi-fi for this application, so I'll probably go somewhere in the middle. Still like the idea of building into a plastic tranny case.

Maven

Are HRSA kits available to non-members?

My guess at this stage is no, as they keep themselves to themselves on most other things.

Hey Maven,

A few years back I built a kit from Antique tubes supply in the US , They still do the kit and it was a one valve unit.

Cheers
Vic