Hello folks,

I got an NRG PLL PRO kit several months back and put it together without much fuss. I've had a few issues with it, but my main question right now is with regards to deviation and volume...

Specifically, what sort of voltage level does the MPX input expect, on average, for full deviation? I ask this because low impedance headphone outputs, such as you would find on mp3 players, don't appear to supply enough voltage unless you put their volume close to max. Of course, the input resistor on the NRG board is wide open.

I've also tried to use Stereo Tool to compress, pre-emphasize, and create the mpx output, but still volume seemed low. Obviously, I'm not expecting broadcast loudness or quality from my setup, but the NRG board just seems very picky with regards to the audio input. Is this the case, or could I have something funky going on in my path, crummy varicap, etc? I've tried tracing through the audio path before, but the signal from the oscillator makes it difficult to see exactly what's going on. Nevertheless, I didn't see anything out of the ordinary.

As a bit of an aside, I was really counting on the old site sticking around when I got this transmitter. There was a lot of information about these kits archived there. I'm a bit disappointed that no one has offered to put the archive online somewhere. It has taught me to not rely on web info sticking around. When forums are concerned, the waybackmachine (which I've relied upon several times) is not enough.

Oh, and yes I have been to the yellowbeard nrg workshop archive/site, but most of those files just give a general overview.

Cheers

Hello Modulator!
I dunno if this is much help? but the audio input level for the PLL PRO is 0.775v rms for +/- 75khz deviation!
I would also disable pre emphasis if you are using any external processing!
Also the tuning voltage present on the varicap diode can sometimes effect audio quality?
You could try finely tweaking the oscillator trimmer (purple one) and see if it makes any improvement?

the audio input level for the PLL PRO is 0.775v rms for +/- 75khz deviation!

Thanks. That is good to know. So about 1.1 Vpk? That's a pretty healthy level compared to some of my diy jobbies and some of the other designs I've seen but I guess it's better for SNR. Since my sansa mp3 player has a hard limit on output around 1 Vpk (at which it distorts), that would make some sense as to why I'm having issues. I will have to experiment some more with some sources that are closer to line level.

Hello modulator! If you have trimmer pot at input of some device (like this board) you do not have predefined input level. You need to set it. Also, 0dB or 0.775Vrms is 2.2Vpp (or 1.1V from 0V up and -1.1V from 0V down). Input level for deviation of 75kHz depends on more than this pot. It depends on varicaps used, coils... So, you need to set this trimmer that when you apply 0dB input signal, you have 75kHz deviation. It is very hard to get precise deviation level if you don't have some deviation meter, modulation monitor etc. Setting up to sound as loud as other stations is not a good option, because professional stations use broadcast processors which make sound "louder" (by emphasizing certain frequencies in audio signal) while keeping level of modulation signal at 0dB. You could try to use MpxTool software and base band (before stereo decoder) audio from some good old analog receiver, but you also need to set MpxTool properly before first use. I hope i explained. If you have any questions, ask!

modulator wrote:As a bit of an aside, I was really counting on the old site sticking around when I got this transmitter. There was a lot of information about these kits archived there. I'm a bit disappointed that no one has offered to put the archive online somewhere. It has taught me to not rely on web info sticking around. When forums are concerned, the waybackmachine (which I've relied upon several times) is not enough.

Too many "members" took the last site for granted. I bet those who moaned and groaned feel really sick now the site has vanished entirely, even though they won't admit it. Web sites disappear all the time, and if you want to rely on the information being available you should always make an offline mirror, or keep a scrapbook at the least.