It took me a week, but I finally found the time to fire up Chris Cuff’s creation on the test bench. My unit came set for operation on 1500 kHz (at my request). You can change the crystal to operate on other frequencies. Lacking a power supply with the correct connector, I fired it up on batteries (an internal battery holder is included). Eight AA’s will apparently power the unit for 8-10 hours continuously.
I connected a short wire antenna to the Fahnestock clip on the back and grounded it to the wall outlet. Next, I hooked up a stereo audio source to the RCA input connectors and fired it up! Immediately, I heard the program material in stereo on my tuner. I have only one AM stereo radio left; it is a modified Radio Shack tuner. The sound quality was not perfect, but it was in stereo!
I reduced the level a bit until the audio sounded cleaner. I seem to recall that you have to limit the modulation to 100% with AM stereo. In any event, I am not certain that the transmitter is capable of more than 100% peak positive modulation.
Although the transmitter comes with a few explanatory notes on how to set it up, there is no schematic. The output circuit is interesting; the coil appears to be wound on a glass test tube (with great care, apparently), along with a nice vernier tuned air variable capacitor. You adjust the capacitor for the strongest signal, as observed on a field strength meter or nearby radio. I jumped in the car and drove down the street. My preliminary observation is that the range is comparable to my SSTRAN when operated under similar conditions. The output appears to be taken directly from the “hot” side of the parallel tuned tank circuit.
This is an interesting unit, and probably destined to become a collector’s item. Chris told me that he has built 350 of them by hand and that he does not have parts to build any more. Classical music sounds great in AM stereo, as those of you who live in the Kansas City area can probably attest, due to the presence of KXTR.
Update: I have discovered that the carrier frequency is off by quite a bit; probably in excess of several hundred Hz. I’m not sure if I’ll bother fixing it as I intend to purchase the programmable oscillator from Digi-Key (if I can remember the part number)! But for anyone who wants to use it crystal controlled, it should be an easy matter to add a trimmer on the board. The microprocessor crystal Chris sent with the unit is probably not very accurate.
Chris included a copy of the
Chris included a copy of the schematic for the Alfredo-Lite when he sent me one of his transmitters. I have it as a pdf file. If you want, give me your email address and I’ll gladly send it.
What I need is someone who can help me increase the output power to a full 100mw. Chris built my TX for only about 50mw output. I’d ask him to do it but he seems to be unavailable.
C5
Schematic
Hello CS,
You can e-mail it to WEAK-AM at part 15 dot U.S. Although, if it’s a pdf of that tiny jpg file I found posted elsewhere on this site, I don’t think I’ll be able to read it any better. If I CAN read it, I’ll see if I can come up with any ideas on how to set the power accurately to 100 mW. Please note; FCC rules allow 100 mW DC INPUT power to the final amplifier, NOT OUTPUT power. If you are actually getting 50 mW RF OUTPUT power, that would be a plausible number for 100 mW INPUT considering Class C amplification. However, I don’t know how you would measure that, because the basic transmitter has a completely unfiltered output, so that all of the harmonics would be included in the measurement. My particular unit has a special outboard tank circuit that is designed to drive a wire antenna, which it is high impedance. Therefore, it would be almost impossible to actually measure the output power.
WEAK-AM
Classical Music and More!
I tried to send a clearer
I tried to send a clearer copy of schematic to your email address but my software wouldn’t acknowledge that address. I’ll keep working on it.
How long is the wire antenna your using and how are you tuning it?
C5
Wire Antenna
Hello CS,
I think there is some latitude about the length it will tune, but I am testing it with a 9′ length of thermoplastic insulated hookup wire draped over the top of the TV in the living room, and the ground is connected to the electrical outlet ground screw. Nothing very fancy.
This is good enough to cover down to the end of my block, which is probably 300 or 400 feet. When I turn the corner, it dies almost instantly, but resurfaces in a few places 5 or 6 blocks away (go figure)! This I assume is primarily being propagated through radiation into the power lines.
The e-mail address is on this domain (the one for the board). If you joined the board and have a login, you can get a free e-mail address. They are supplied through Google Gmail. Once you’re logged in, just go to Member Email (see along the left hand side of the page) and you can create your own account too. Remember that top level domains are not capitalized, so the suffix for the e-mail addresses will be “@part15.us”.
WEAK-AM
Classical Music and More!
Hi C5
I’d Really Appreciate Any Info, On These 2 CCuff Xmitters.
My Name Is Dennis, And Email is
DFMoore at optonline dot net
Thanks A Million !
CCuff “Stereo Transmitter”
Hi, lot’s of interesting stuff here!
I bought 2 of Chris’ transmitters, and neither of them worked. Both were damaged, (not his fault), in shipping when I moved. I asked for his help many times, but he never replied. I just wanted a web cam snapshot of the one corner, with the tiny light bulb & the jumpers, because he wouldn’t give me a schematic, but for some reason he wouldn’t. I was able to repair the few things I could.
I eventually dumped both ($150.00) in my parts box and bought an Sstran. I have two different versions. Both have different output transistors, the xtal socket is a 4 pin socket on both. One came with a 2 pin xtal, one with a 4 pin (something). Of course, in the rough shipping, again, not his fault, I had no idea which way to put the xtals in. Remember, I never claimed to be a rocket scientist.
I’m in my mid-50’s, have built hundreds of kits, starting with, Lafayette electronics, and Heathkit…please no laughing! Without a schematic, I’m lost! Too bad there wasn’t a way of converting these to “am-mono” units. I guess Chris had his reasons, for refusing to send me a schematic, or at least tell me where I could purchase xtals, but after talking with him on a few occasions, before I bought the units, it makes me wonder what happened.
I never would have brought this up, but I noticed the postings here about his am stereo units. If anyone could give me a hand, I’d appreciate it. Ok. I’m really enjoying all this great info about the Sstran unit I’m putting together. Has anyone thought about making magnetic a van top mount “short whip” and an added coil on the bottom to be used at outdoor company picnics, or ham flea markets?
To all the dads out there, “Happy Fathers Day”
Ron
I will try to help
I have not had time to do much more investigating with mine, but I will try to answer your questions. I got a better version of the schematic from one of the members of this board that I can share with you. Just tell me where to send it. The schematic does not show the output tuning network in my unit, however.
I also got details of the crystal unit, in case you want to purchase one for a different frequency. They are available from Digi-Key.
I had a couple of e-mail exchanges with Chris. He is not a conversationalist, but he did respond. I would say that if you want to use this thing on the air for more than a demonstration, you’ve got some work ahead of you. There is no documentation on how to measure the power input, and the output tuning network is far from optimal. You could bypass it, but then there would be NO output filtering!
There is no audio processing of any sort built into the unit that I can find, such as the SSTRAN has.
WEAK-AM
Classical Music and More!