Re: NRG Pro 6 help
Posted: Sun May 07, 2023 11:24 am
Looks like the same pll but with 10w pa instead of 6w and screen to set frequency instead of dip switches
OK, I altered the MPX input adjustment on the rear of the Pro 6 this evening, but the highest deviation I can get is 4Khz, 5%.
Thanks for the reply, Albert.
Hello,nrgkits.nz wrote: ↑Mon May 08, 2023 8:37 am Hi MiXiN
You've got an earlier revision of the board which requires a higher rms on the MPX input, as it was designed to be fed from a computer sound card running StereoTool which generally output a higher rms voltage. The stereo encoder you're using is likely a lot lower. To fix this, you can change R2 from 10K to 4K7 and will increase the sensitivity the MPX input. Then with only the stereocoder going in with pilot tone (no audio), adjust the pot through the back of case so you get around 6.7KHz deviation.
Also there is another change we made in the new revision of this board, R39 was changed from 330R to 470R to reduce the drive slightly to the output device. We had a couple instances where under certain conditions and customers reducing the power right down below 1W, the RD15HVF1 output device would fail after a few months of running. Output power is controlled by varying the bias voltage on the gate of the output device, and when wound right down so the output is less than 1W, this in turn results in a slightly higher peak to peak voltage measured at the gate. The gate to source maximum for the RD15HVF1 is -5v to +10v. So replacing R39 brings it back down to below 5v peak to peak. If you don't intend to run it at a very low power, then there won't be any issues.
The resistors are all 0603, I usually use a fine pair of tweezers and hot air. An easier way to do this, just use a 10K through hole resistor, bend one lead around 180deg so its parallel to the other, trim both down to same size and then solder across the existing 0603 10K resistor, you'll get 5K then which is close enough to 4K7. Alternatively, running the pilot tone at 4KHz isn't going to cause any major problems, if anything it will improve reception slightly in fringe areas as receivers will drop to mono sooner due to less pilot tone.MiXiN wrote: ↑Mon May 08, 2023 9:39 amHello,nrgkits.nz wrote: ↑Mon May 08, 2023 8:37 am Hi MiXiN
You've got an earlier revision of the board which requires a higher rms on the MPX input, as it was designed to be fed from a computer sound card running StereoTool which generally output a higher rms voltage. The stereo encoder you're using is likely a lot lower. To fix this, you can change R2 from 10K to 4K7 and will increase the sensitivity the MPX input. Then with only the stereocoder going in with pilot tone (no audio), adjust the pot through the back of case so you get around 6.7KHz deviation.
Also there is another change we made in the new revision of this board, R39 was changed from 330R to 470R to reduce the drive slightly to the output device. We had a couple instances where under certain conditions and customers reducing the power right down below 1W, the RD15HVF1 output device would fail after a few months of running. Output power is controlled by varying the bias voltage on the gate of the output device, and when wound right down so the output is less than 1W, this in turn results in a slightly higher peak to peak voltage measured at the gate. The gate to source maximum for the RD15HVF1 is -5v to +10v. So replacing R39 brings it back down to below 5v peak to peak. If you don't intend to run it at a very low power, then there won't be any issues.
Many thanks for the informative reply & fast response to my message.
I'll go inside & have a look at R2. If it's a 0805 size or larger, I'll be OK swapping it out, but if it's a 0603 it might be a bit of a challenge unless there's good space around it - so I'll leave it. Those 0603 parts are tiny.![]()
Is running it at its current maximum of 4Khz going to be of any detriment, or is it "essential" to achieve around 6.7Khz?
If anybody knows of any coders that output an higher RMS level, or know how to increase this from the Pro 3 that would be great as it would save me having to swap out R2?
I'll leave this set to full output power and don't intend reducing to 1W, so there's no problem with the final.
Thanks very much for your help.
Thanks again for the reply.nrgkits.nz wrote: ↑Mon May 08, 2023 10:51 amThe resistors are all 0603, I usually use a fine pair of tweezers and hot air. An easier way to do this, just use a 10K through hole resistor, bend one lead around 180deg so its parallel to the other, trim both down to same size and then solder across the existing 0603 10K resistor, you'll get 5K then which is close enough to 4K7. Alternatively, running the pilot tone at 4KHz isn't going to cause any major problems, if anything it will improve reception slightly in fringe areas as receivers will drop to mono sooner due to less pilot tone.MiXiN wrote: ↑Mon May 08, 2023 9:39 amHello,nrgkits.nz wrote: ↑Mon May 08, 2023 8:37 am Hi MiXiN
You've got an earlier revision of the board which requires a higher rms on the MPX input, as it was designed to be fed from a computer sound card running StereoTool which generally output a higher rms voltage. The stereo encoder you're using is likely a lot lower. To fix this, you can change R2 from 10K to 4K7 and will increase the sensitivity the MPX input. Then with only the stereocoder going in with pilot tone (no audio), adjust the pot through the back of case so you get around 6.7KHz deviation.
Also there is another change we made in the new revision of this board, R39 was changed from 330R to 470R to reduce the drive slightly to the output device. We had a couple instances where under certain conditions and customers reducing the power right down below 1W, the RD15HVF1 output device would fail after a few months of running. Output power is controlled by varying the bias voltage on the gate of the output device, and when wound right down so the output is less than 1W, this in turn results in a slightly higher peak to peak voltage measured at the gate. The gate to source maximum for the RD15HVF1 is -5v to +10v. So replacing R39 brings it back down to below 5v peak to peak. If you don't intend to run it at a very low power, then there won't be any issues.
Many thanks for the informative reply & fast response to my message.
I'll go inside & have a look at R2. If it's a 0805 size or larger, I'll be OK swapping it out, but if it's a 0603 it might be a bit of a challenge unless there's good space around it - so I'll leave it. Those 0603 parts are tiny.![]()
Is running it at its current maximum of 4Khz going to be of any detriment, or is it "essential" to achieve around 6.7Khz?
If anybody knows of any coders that output an higher RMS level, or know how to increase this from the Pro 3 that would be great as it would save me having to swap out R2?
I'll leave this set to full output power and don't intend reducing to 1W, so there's no problem with the final.
Thanks very much for your help.