Diodes checked.
Question re:J5 - +12/-12 these are the first 2 screw downs, or 1 and 3?
Holy cow this thing is resilient - I have probably misconfigured this in the worst possible way (other than flipping polarized components the wrong way round), power to the wrong place, wrong input of audio, not enough audio, over driving audio, ugh.
And this little tx just kept on keeping on.. excellent work on this design, for sure.
I'm pretty sure the power terminals are side by side (1 and 2), I'll check the manual when I get home.
andre: They are - Phil confirmed that for me. Thanks!
General question: If I decided to put my tx/antenna at ground level; will a wooden fence interfere? Would it be better up on my roof or on the ground?
Hi mir...
Only a guess, but I think ground is always the best for AM.
Just back away from the fence as far as possible. Most of the signal will go over it or around it or under it.
I agree with Carl about the ground mounting.
That's the way I did it with an AMT-3000.
This is great! I think your set-up will work
really well.
Bruce, The DOGRADIO Group
I think I posted this years ago, but since you are having trouble, this is how I used to feed my old SSTRAN.
The box was from an old 1200 baud modem. You can see the 18 VDC laptop power supply I used, attached to the binding posts. You could just as well use the AC adapter that you have. I used an old motherboard power connector (the white plug) inside, but this was overkill. I also fused the power going to the Cat5. The LED is just to let me know that the power is on.
On the left is the audio input jack, some resistors to combine the stereo signal to mono, and an isolation transformer from Radio Shack.
Everything is wired to the terminal strip near the back. The Cat 5 goes from the terminal strip to the transmitter. I labeled the terminal strip with the colors for each pair, so I would remember how to hook up the Cat5.
You can ignore that small circuit board that is attached to the top cover of the box. It is a temperature logger. I had the sensor inside the transmitter housing, so I could log the temperature (just because). I had to remove this, because the RF (even a puny 100 mW) was interfering with the sensor.
This entire interface was made mostly from junkbox parts and was easily assembled. The wiring diagram is below (again, ignore the wiring for the temperature sensor).
You will note that I used two pair for the power, to minimize the voltage drop over a long run of cable. To keep the self-shielding properties of the twisted pair, make sure to use a pair of wires that is twisted together for the audio. Don't use what are called "split pairs", where you have one wire from one pair and another wire from a different pair.
Just in case you need to know, the impedance of unshielded twisted pair (like Cat5) is 100 Ohms.
Joe
Man.. thank you guys for the help; I think I mostly have it worked out. Now I am just trying to figure out the shed situation - need to build one 🙂
mojoe: any chance you would have the circuit diagram/schematic and parts list for that stereo->mono bit?
regarding the fence: I am in a typical california bay area postage stamp lot - so maybe 15-20 feet between house and fence. Is that still the route to take?
15 to 20 feet is fine.
As little as 6 feet from the fence would probably be the minimum, but take all you can get.
awesomeness.
So i was thinking either chicken wire, or tapping into the house grounding...
IF given the choice I would avoid the house power system ground or a water pipe ground. I'll explain some of the reasons.
Your transmitter/antenna is being planned for out in the yard, but the house power grounding is back at the house. If you ran a long ground wire it would have two negative effects: 1) it would violate the "long ground lead" restriction; 2) it would raise the impedance between transmitter ground and earth ground, resulting in less radiation efficiency.
FOR most efficient results, the ground should be centered below the transmitter/antenna, most desireably an 8-foot ground rod into the earth for electrical safety, and surrounded in a symetrical pattern by the chicken wire, which would provide the ground plane for antenna efficiency.
I don't remember exactly what I used, but it was probably something like this:
http://www.epanorama.net/circuits/linesum.html
Joe
The two SSTran transmitters each have stereo to mono mixers built in, of the type shown on the datasheet linked above.
Yes, the resistor circuit is in the SSTRAN. The reason I combined things down below was so I didn't have to run stereo audio all the way to the roof. Since I wanted to use a pair for temperature logging, I didn't have another spare pair. Because we are broadcasting in mono anyway, I didn't see the sense in sending stereo all that way down a cable.
Joe