Milli Vanilli Watts

[Mongo82]

Bought one of those car transmitters for fun, 5v choose frequency, led stuck on a board with 5 buttons etc. Quite impressed by something so small how effective. Checked the tiny sa, noise seemed pretty similar to most just a little lower. Anyway I decided to add a wire antenna soldered to board. Checked my tiny sa again and deviated either side considerably, and it wiped the scanning function on my fm/dab radio and some stations. My thought was its a cheap DAB £20 jobby I was right up close to Chinese sprogger. Then thought occurred if like most antennas, could it be because its not to freq. Would it solve that issue? I made a flowerpot antenna again night before, and managed to get it bang on. Not digressing, but could you make a flower pot but thin version using 2bits of 1mm ground wire to make an ultra thin version but with similiar dimensions? Because the wire is so thin I wonder if you might get some gain and ofcourse better results? Probably a dopey question but I'm not too proud to ask...

[radionortheast]

I don’t think its possible to get the bandwidth of an antenna narrow enough for it work as a filter.
I have one without a display, the numbers on the chip are scrubbed off I suspect it is an 8027, the sound quality is very good on it, you’ve got stereo the right pre emp, nothing to mess about with, its a shame the rf signal is very noisy on it, knocks out other fm stations compleatly, there are two duplicates less strong that the main 12mhz either side of the main.

I played about with one of the small lcd ones only yesterday afternoon, someone said reducing the voltage down would get rid of the noise, at 2v there was a nice clean carrier, but it wouldn’t lock onto a frequency, I guess the advice here and else were about dropping the voltage down ending up with some useable dosen’t make sense. I didn't think these 8027 things were useable, I found this from Albert, maybe they'd found some way to config it with their own board, these things are so tiny theres noway you'd be able to solder the chip, sounds like they are set up to produce perfect stereo from the get go with no messing.

I was really surprised by the output spectrum from the QN8027. I expected it to be like the Rohm chips - noisy! They're surprisingly monotonic, with the 19 kHz pilot at exactly 9% of maximum deviation. There's little or no carrier noise when run at 3.3V, but the noise floor rises as the voltage goes up towards the upper limit of 4.2V. We found that there was more noise from the Atmel chip we were using to programme it! We had serious problems getting the digital crud from the logic out of the 8027 carrier. The solution turned out to be a combination if physical separation (we put the SM ICs on opposite sides of the board) and two ground planes - an RF one and a logic one.

I guess the only way to get the stereo would be to pick it up from a radio send it into a mono transmitter, seems like a lot to do, I guess the radio will be filtering out the stereo pilot, as I don't think there is an mpx output on the 8027.

[Mongo82]

radionortheast wrote

I played about with one of the small lcd ones only yesterday afternoon, someone said reducing the voltage down would get rid of the noise, at 2v there was a nice clean carrier, but it wouldn’t lock onto a frequency, I guess the advice here and else were about dropping the voltage down ending up with some useable dosen’t make sense. I didn't think these 8027 things were useable, I found this from Albert, maybe they'd found some way to config it with their own board, these things are so tiny theres noway you'd be able to solder the chip, sounds like they are set up to produce perfect stereo from the get go with no messing.
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I know people moan about Dazaro on youtube on his oscilator manipulation stuff and its not crystal controlled but he does have value eductionally. Anyway he added an rf amp to one of those lcd transmitters but did insist in adding a low pass filter. So would perhaps bring voltage down on transmitter, then into an rf amp which i think gave him 3 watts at 15vs but instead keep the voltage around 9v with the low pass filter? Would that work and be a lot cleaner?

[Albert H]

NO!

Really don't bother. If you want to conect your portable MP3 player or CD player to your car radio wirelessly, it's fine for the purpose. If you want a bigger signal to transmit further, it's NOT the way to go.

No matter what you do to these ICs, they are inherently dirty. One or two of them are (slightly) better than others, but it really is a waste of time trying to get a clean signal from one of these.

Just for amusement, I played with the '8027, which seemed to be a bit better than some of the others, but I still wouldn't use it for more than its intended purpose - wireless connection to your car radio!

[radionortheast]

I know people moan about Dazaro on youtube on his oscilator manipulation stuff and its not crystal controlled but he does have value eductionally. Anyway he added an rf amp to one of those lcd transmitters but did insist in adding a low pass filter. So would perhaps bring voltage down on transmitter, then into an rf amp which i think gave him 3 watts at 15vs but instead keep the voltage around 9v with the low pass filter? Would that work and be a lot cleaner?

I guess we must of seen the same video, when I saw it with the lcd one he hooked up to a little amplifier, I went out and got one, he didn’t seem to mention the noise they put out over fm at all, it turned out to be something that couldn’t use, I got afew from different places they all did the same thing unforuanately. It was a nice idea, they could sit on a shelf in a small box not taking up much room, could be very neat, at 1w would not even need a fan, he did say they were not to be used is fair enough I suppose but not much fun or help with what we're trying to do.
I dropped the voltage down to 3.3, I couldn’t see much difference in the noise comparing when it was run on 5v, I don’t think its really useable. I don’t think you’d beable to get the aerial far enough from the neighbours with 3w to not cause them a problem, don’t know how strong the two duplicates would become, the band pass filter on darklife would be a pain to construct, goes against the point of having something simple, if you want to change frequencies your going to have to mess around with those big capacitors, just goes against what you’d want, best left to hams.

He's has actually done videos lately using s14713 using an ardunio, he tested compared it to the output on one of those lcd ones that use the 8027, it looked much cleaner on his tiny sa, at 10mw level. I think I had one of those s14713, it didn’t seem to come on without been connected to a computer, I will have a go at making one, I think you have to connect it to a computer to change the freqeuncy, I hope he might come out with one with buttons on the unit itself.
It does look like these things are easy to make you have stereo, I think he said the sound quailty was good through the s14713. Theres another there were he uses a little single board computer, esp32 it is a different transmitter module with it, it does have a touch screen display to alter the things, I guess I will get the parts together for both sometime and have a go. There is not much soldering involved, just the computer part he has the code for, they only cost £20 to make. I do think its funny he makes these things in the kitchen or users the cooker, I suppose were else would you make them.

[Mongo82]

NO!

Really don't bother. If you want to conect your portable MP3 player or CD player to your car radio wirelessly, it's fine for the purpose. If you want a bigger signal to transmit further, it's NOT the way to go.

No matter what you do to these ICs, they are inherently dirty. One or two of them are (slightly) better than others, but it really is a waste of time trying to get a clean signal from one of these.

Just for amusement, I played with the '8027, which seemed to be a bit better than some of the others, but I still wouldn't use it for more than its intended purpose - wireless connection to your car radio!

It's so annoying, you'd think the chinese might understand this. I know things are at a price so cheap, but surely for a few more quid they could rectify this, put something decent out and still make a profit? But what you seem to get financially, no between, instead you get a huge jump in price, like the warner range.

Would the chinese boards need a major upheaval in re design or is it just a couple of chips, that could easily be replaced for something better?

[Mongo82]

I know people moan about Dazaro on youtube on his oscilator manipulation stuff and its not crystal controlled but he does have value eductionally. Anyway he added an rf amp to one of those lcd transmitters but did insist in adding a low pass filter. So would perhaps bring voltage down on transmitter, then into an rf amp which i think gave him 3 watts at 15vs but instead keep the voltage around 9v with the low pass filter? Would that work and be a lot cleaner?

I guess we must of seen the same video, when I saw it with the lcd one he hooked up to a little amplifier, I went out and got one, he didn’t seem to mention the noise they put out over fm at all, it turned out to be something that couldn’t use, I got afew from different places they all did the same thing unforuanately. It was a nice idea, they could sit on a shelf in a small box not taking up much room, could be very neat, at 1w would not even need a fan, he did say they were not to be used is fair enough I suppose but not much fun or help with what we're trying to do.
I dropped the voltage down to 3.3, I couldn’t see much difference in the noise comparing when it was run on 5v, I don’t think its really useable. I don’t think you’d beable to get the aerial far enough from the neighbours with 3w to not cause them a problem, don’t know how strong the two duplicates would become, the band pass filter on darklife would be a pain to construct, goes against the point of having something simple, if you want to change frequencies your going to have to mess around with those big capacitors, just goes against what you’d want, best left to hams.

He's has actually done videos lately using s14713 using an ardunio, he tested compared it to the output on one of those lcd ones that use the 8027, it looked much cleaner on his tiny sa, at 10mw level. I think I had one of those s14713, it didn’t seem to come on without been connected to a computer, I will have a go at making one, I think you have to connect it to a computer to change the freqeuncy, I hope he might come out with one with buttons on the unit itself.
It does look like these things are easy to make you have stereo, I think he said the sound quailty was good through the s14713. Theres another there were he uses a little single board computer, esp32 it is a different transmitter module with it, it does have a touch screen display to alter the things, I guess I will get the parts together for both sometime and have a go. There is not much soldering involved, just the computer part he has the code for, they only cost £20 to make. I do think its funny he makes these things in the kitchen or users the cooker, I suppose were else would you make them.

Explaining to the missus why you have used her best chopping board to solder on, or why there is solder splatter on the carpet. Something tells me he perhaps lives alone. Not that I would do something like that