Hi all, Does anyone have a schematic to make a Ipod solid state am transmitter? I built the AES tube kit but want to build a simple solid state transmitter for my radios. I have seen the SSTRAN but money is tight and I am looking t build a "junk box" style.
Thanks!

Here ya go, kiddo;
http://filebay1.home.comcast.net/~fileb ... imple.html

I built one very similar to this back about 1959, using a Vari-loopstick for the coil, and a CK722. It's range was prolly 50 feet or so, with a 30" antenna.

If you use Google for "AM broadcaster transmitter" you will come up with several ideas.



Rich

I think it worth asking why you want a transistor xmitter instead of using the AES you already have. What are the goals/reasons for the new one?

What I am wanting to do is have something that is more portable and compact.

Ah, ok. Well, here's a site with a couple of circuits. http://www.techlib.com/electronics/amxmit.htm

I haven't built one but the basic design looks good and was once on my 'to do' list (even bought the P1811 pot cores) although, IMO, the 'amplifying mixer' isn't really 'optional' as lowering the emitter resistor to get gain is a bad idea. I would also do it differently than he does and use feedback from the 100 ohm to the opamp negative input to reduce distortion more than the simple 100 ohm alone does. That means putting a voltage divider on the plus input to set bias rather than on the transistor's base. I was also going to use a brick oscillator rather than the transistor crystal osc.

As I said, unbuilt, so there may be mistakes, but something like this


Btw, what looks like a transformer is because of the model my spice program uses but it's the same tapped coil he describes and the 'shockingly' different emitter resistor is because of different opamp bias and the fact base emitter drop is removed by negative feedback directly sensing the resistor. Unlabeled components are for simulation and not part of the 'to build' circuit.

Spice indicated it could be simplified by removing the collector to base caps and 22 ohm but they might need to be added back in the 'real world'. The choice of BC550s is simply because I like them, low noise, lots of gain, and, so, have a bunch on hand. They're 45V and circuit dissipation on each is, not surprisingly, roughly 100 mW.

I was going to power it with simple chip regulators off a super cheap transformer from here
http://www.allelectronics.com/make-a-store/item/TX-4025/40-VCT-.25-AMPS-TRANSFORMER/1.html
but you could also use a wallwart.

If you want 'real small' he has a simpler 9V job lower down on the page but, note, the above circuit would only put out about 15 mW on a 9V battery because there would only be 4.5 V across the chopper transistors and current has to be dropped to about 7.5 mA (56 vs 22.1 Ohm), although, it could probably be redesigned to work on 9V. Also, that brick osc pulls 25 mA (max) all on its own, which isn't conducive to battery power.

How about the one even further down the page... "Tunable Phono Oscillator"
http://www.techlib.com/electronics/amxmit.htm#Phono

This looks simple enough that even I could build it... but it uses an oscillator coil from a transistor radio - that part would probably be hard to find in any quantities.

-Sam T.

That's the 'real small' one I mentioned was further down the page and why I noted the posted schematic wouldn't work very well on a 9V battery. But the 15V job is a much better transmitter.

Quantities? Are you going into business? "Playthings of the Past" probably has some. http://www.oldradioparts.com/

Edit>> I thought I had seen them somewhere. I had. http://www.mouser.com/catalog/catalogUSD/644/2427.pdf

Sam wrote: "How about the one even further down the page... "Tunable Phono Oscillator"?

It's an interesting design, but I wouldn't expect to be listening to Patsy Cline with this device.

Not going into business, but if say I wanted to build four or five to give away with vintage radios...
I built the 12AV6/12CS6 and it works very well, but I wouldn't want to build these and hand to relatives, something lightweight & battery-operated with less range would be fine. Something to connect the iPod and play through a vintage radio, without adding a circuit to the radio itself.
And then once a successful build was documented here in the forum I'm sure others would want to build too, that's what I meant by 'quantities'. Finding one of those osc coils would be pretty easy... just select a donor.

EDIT --> Good catch finding that in the Mouser catalog, I searched online and missed it. Thanks!

-Sam T.

Yes the oscillator coil can be found in almost any el cheapo analog AM/FM tuner particularly the cheap Chinese solid state versions of antique radios.

Funny you say that because it's exactly what I built the Twin Triode AM Transmitter for: Christmas presents to siblings. In the converter box with 'Gort' the light bars makes them 'showcase' items to display along with the vintage radios.

Another funny because I missed them too in Mouser. That's where I thought I had seen them but when I did a quick look they didn't turn up. But a Google got me a 'spec sheet', which was cool but where to get them? And then I noticed, these are Mouser part numbers

Here's a really simple one that actually works well if you turn the transformer around and use a parallel LC tank on the antenna.

http://sci-toys.com/scitoys/scitoys/rad ... itter.html

Here's one I whipped up in a few minutes.



With only the ferrite rod as the antenna I get a couple of meters of range. With a 10' wire on the end of the tank I get about 10 meters of range. The led is the tuning aid. Use 6V instead of the 9V. This is cheap and easy to try. Good educational tool if nothing else. If you want junkbox style it doesn't get much junkier than this!

Doug

Thing about that one Doug is the limitation on frequency.
I only know of two in-band frequencies for those oscillator bricks... 1mhz and 1.28mhz I think.
A transmitter with a VFO is one step up, and a little audio processing would be even better.

-Sam T.

I am wanting a very simple and very cheap..... did I mention very cheap.. transmitter and this looks like it will work beautifully. I do have a question about this circuit though. If I don't want to use a ground, or have trouble accessing a good ground, what possible troubles would there be if I either :

1. directly connect the transmitter antenna and ground to the radio antenna and ground.
2. Inductively couple the transmitter to the radio antenna and ground using a few turns of insulated wire around the antenna and ground.

I would like to avoid changing the circuit of my radios, and it would be nice to be able to move the transmitter next to the radio I want to use. I also don't like the idea of having anything more than a low power ... or no power... transmitter going continuously in the room I am in, so range is no issue. That is why I would like to couple it to the radio some way.

It may not even need a ground, though would likely have better range... With approx 10ft of antenna and similar amount of ground, you should have useable reception anywhere in your house...

Tom

Thanks Tom, that is good news. Do you know what pieces of equipment these days use those oscillator units in that frequency range? Most computers are much higher in frequency.

Would this work?http://www.ebay.com/itm/1KHz-to-33MHz-Adjustable-Oscillator-Module-LTC1799-/400282572127?pt=LH_DefaultDomain_0&hash=item5d32b3555f

I built and have been very pleased with Charles Wenzel's version. http://www.techlib.com/electronics/amxmit.htm

I kept it below 100mW and got about a mile out of it.



I admit I modified the version in the schematic above to use my frequency synthesizer (http://www.beecavewoods.com/radios/freq ... synth.html) rather than the crystal. Transmitting up near 1700 mHz really made a difference in the range I achieved. I used a simple field strength meter to tune it up. Using my wide band AM receiver, audio sounded about as good as FM. Antenna was similar to the SStran antenna mounted on a roof.