Anyone ever used one of these? It's an AM Transmitter made for selling real estate and since the Market has crashed, they can be found on Ebay for fairly cheap. There is a thread on the Low Power AM site that tells much about these. Of course their aim is to broadcast legally, I'm sure these can be amped.
OK, I actually bought one of these things, now I need to find the best way to boost it up to 5-10 watts. I don't actually have it yet, it's being shipped, so I have a few days to play around with small AM amp circuits. These things supposedly put out about 80-100 MW so I just need one or two stages. Any ideas?
Well if you know how to build stuff with electronics you can make a linear amplifier. It does have to be linear for the audio information to be right in the carrier signal. Luckly down at medium wave frequencies most any transistors will work up to a few megahertz so you can use bipolar or mosfets. Mosfet would be the ideal way to go as they are very efficient. A simple IRF530 should be able to be driven with 100 milliwatts. You will have to balance the signal so that you get a perfect linear output. You almost have to have an oscilloscope to build it right but I guess if the audio sounds normal and if you don't have a scope then it should be fine.
Thanks Darklife, do you know of any schematics you might recommend? I looked at the Ramsey LP-1 but I don't think it will work at 180 meters, as I believe it is primarily used to boost FM, and it is only a watt. I find Ramsey to be overpriced anyway. I thought that maybe a 160 meter QRP amp would be fine at the AM 180 meter area, even if it is made to boost CW it should be possible, right?
Thanks Darklife, do you know of any schematics you might recommend? I looked at the Ramsey LP-1 but I don't think it will work at 180 meters, as I believe it is primarily used to boost FM, and it is only a watt. I find Ramsey to be overpriced anyway. I thought that maybe a 160 meter QRP amp would be fine at the AM 180 meter area, even if it is made to boost CW it should be possible, right?
Hmm well a 160 meter amp may work, you may have to modify the coils a little or tune it up to get full gain as long as you are using the end of the AM MW band. As far as schematics go I don't know of any good sorces to point you at but it shouldn't be too hard to design a circuit yourself. Just use a breadboard and build it from scratch, that way you can play around and test stuff before you actually build it fully. That's what I do anyways.
Cool 12VMan thats interesting to know. I believe that the SStran does about the same output as the Talking House. If the audio sounds clear then I would be very interested in knowing how much it amps your signal. My understanding was that the Ramsey LP 1 wouldn't work at that low frequency, but who knows? Did it seem to increase your range?
I never check the range. I just seen the difference on the field strength meter. It tripled (at least) the reading from just the straight SSTran reading without moving the antenna/Xmtr.. ~Don
If the LP 1 works, then I wonder if the 40 meter 20 watt amp they make would work as well? That would mean that you could buy or build a small AM transmitter (less than 100 MW,) add an LP-1 to get 1Watt and then add the 40 meter thingy for a 20 watt AM transmitter for less than $150.00. 20 Watts on AM goes much further than the same power on FM, though you do have to sacrifice some audio quality and the antenna is trickier. Another plus I see for AM is that there is probably less chance for being turned in because there are over-powered latin stations (mostly Cuban I assume) that already bleed all over the place on AM and because all the Huge market money stations seem to be on FM. I am still going to look for a 160 meter amp solution, I'll let you know what I find.
If the LP 1 works, then I wonder if the 40 meter 20 watt amp they make would work as well? That would mean that you could buy or build a small AM transmitter (less than 100 MW,) add an LP-1 to get 1Watt and then add the 40 meter thingy for a 20 watt AM transmitter for less than $150.00. 20 Watts on AM goes much further than the same power on FM, though you do have to sacrifice some audio quality and the antenna is trickier. Another plus I see for AM is that there is probably less chance for being turned in because there are over-powered latin stations (mostly Cuban I assume) that already bleed all over the place on AM and because all the Huge market money stations seem to be on FM. I am still going to look for a 160 meter amp solution, I'll let you know what I find.
I don't think you are going to get the 40 meter amp to work at all down at such low frequencies since the 40 meter band is right around 7MHz.
I bet that Ramsey uses the same board and design for the 20 and 40 meter amps. They probably just switch out a tuning coil or inductor or something. If that is the case, then it's just a matter of finding the right part to replace for 180 meters. Maybe, maybe not.
Ok , I got this thing in the mail last week and finally got around to messing with it and it puts out about 80- 100 milliwatts, depending on audio. The design is pretty slick, as it has a built in tuner that you can watch re-tune automatically when you change freq. I have been searching for amp schematics but they are rare. I can find very large amps for 160 meters, but nothing yet for anything small. If the Ramsey LP will get it up to a watt then maybe an old CB linear might work with some tweaking.
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