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PCI MAX 3000+ v2 high pitch tone
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PCI MAX 3000+ v2 high pitch tone
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Cjaiceman
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Post PCI MAX 3000+ v2 high pitch tone Reply with quote
Hello all. I just got my PCI MAX 3000+ v2 and have it hooked up. When I play any audio in stereo I get a very high pitched tone coming through on any radio I listen too. When I play it in mono the tone goes away and I get full quiet. Things I have tried are 3 different power sources (2 external 12v/1.5amp, 1 PC power supply), the included antenna, a 5/8 wave 1.1:1 SWR tuned antenna 30' above the transmitter (and 2 stories above), audio via USB drivers from the PC, audio from the 3.5mm audio input on the board, mounted inside the PC with all sides closed, pulled out of the PC and moved away to another part of the house. It seems to happen at all power levels.

I'm out of ideas and I would like to ask if anyone else has had this issue and what was done about it?

Edit: After some tinkering around I have found some more info about the issue. First I have found is if I transmit in stereo, but I force mono on the receiver the tone goes away and I get nice mono sound. Second is it on happens when I run at or above 5% (the software shows 0.3W output). If I run 1%-4% (software shows 0.0W at 1%-4%) then I don't get the tone in stereo on the receiver and transmitter, but I get about 10' of range before it just turns to static, 5% being the lowest it will go with anything beyond 10'. I have also tried the pre-emphasis in the 50 and 75 (75 being what I should use here in the states), but no change on either of them.
Sat Jan 14, 2012 4:16 am View user's profile Send private message
pcs
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It is possible that the card is indeed broken.

I will post the results of testing for everyone in case they have a similar problem.

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Marko - PCS Electronics
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Tue Jan 17, 2012 1:46 am View user's profile Send private message Visit poster's website
berrall
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It could be the 19khz pilot tone he can hear, maybe the pilot level is too high on his card.

Nick
Thu Jan 26, 2012 1:16 pm View user's profile Send private message
pcs
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Nah, can't be that, It could be the difference between 19KHz and some other circuit (switcher).

I will post here what it was when I get the card for testing.

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Thu Jan 26, 2012 1:39 pm View user's profile Send private message Visit poster's website
berrall
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Marko, what is the absolute minimum and maximum supply voltage the PCI-MAX 3000 can take before strange things start happening?
Thu Jan 26, 2012 2:04 pm View user's profile Send private message
pcs
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Post Reply with quote
15V max, about 11V minumum

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Thu Jan 26, 2012 2:07 pm View user's profile Send private message Visit poster's website
berrall
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If the supply goes below 11v and the card loses lock, does the rf output get shut down?
Thu Jan 26, 2012 2:10 pm View user's profile Send private message
pcs
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It depends how much below 11V it goes. It will still work under 11 down to 10 or even less, but with less power and audio quality may suffer.

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Marko - PCS Electronics
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Thu Jan 26, 2012 4:12 pm View user's profile Send private message Visit poster's website
berrall
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I have made a homemade 12v UPS running a 12v ATX power supply (seems silly to me to have a 12v battery converting to 240v then back to 12v for the motherboard) for my system and have the PCI-MAX connected to this. When the system is on charge the voltage climbs to 14.5v and can go as low as 10v when running on batteries (accounting for voltage drop). I was concerned that if the voltage goes too low for the card that it would lose lock and the frequency start wandering.
Thu Jan 26, 2012 5:06 pm View user's profile Send private message
pcs
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Post Reply with quote
No, I don't think that will happen. You could see audio quality drop though at 10V.

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Marko - PCS Electronics
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Thu Jan 26, 2012 5:13 pm View user's profile Send private message Visit poster's website
berrall
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not too worried about the audio qaulity as the server does a shutdown at 11.2v, but the PCI-MAX is connected to the charger / UPS it will remain running.
Thu Jan 26, 2012 5:24 pm View user's profile Send private message
berrall
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At around 11.3v and below there is a funny low level motor boating noise on the modulation. I reckon that the 9v regulator on the PCI-MAX is dropping out of regulation at this point. Other than this the PCI-MAX is still running on frequency at this level.
Fri Jan 27, 2012 2:58 am View user's profile Send private message
pcs
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Post Reply with quote
Yes, the problem will be with audio only. PLL works off 5V.

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Marko - PCS Electronics
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Fri Jan 27, 2012 10:56 pm View user's profile Send private message Visit poster's website
berrall
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What is the 9v regulator by the HDD power connector for?
Sat Jan 28, 2012 1:06 am View user's profile Send private message
Cjaiceman
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Ok, so here is an update.

I have found that if I apply more transmitter power (75%+) the tone goes away, however 5% to 70% the tone is present and is audible on all frequencies. Some frequencies are more pronounced than others. I have tried several power supplies and have measured the voltage on the transmitter as 12.6volts while at 5%, and 12.4volts at 100%.

PCS was kind enough to send me a new unit, but I get the exact same issue with this new unit as I do with the old unit. I've noticed that 97.7MHz is very strong, however 93.9MHz is pretty weak (but you can still hear it if there is no other audio), 91.7MHz is also pretty strong. I had someone give another opinion


**"For what it is worth that tone is right about 8.8 kHz, but it is a moving target, I was able to get a couple of good readings of 8.8 and 8.9 however the noise floor is so high, my meter is choking up trying to grab a frequency lock.

None the less if, we put together the frequency measured of 8.8 kHz, and even though it is not 9.5 kHz, which would be an expected subharmonic of the 38 kHz sub carrier used to deliver the L-R needed for stereo or a subharmonic of the 19 kHz pilot tone used to indicate the presence of stereo, and the fact it disappears when mono is enabled, I strongly believe it is related to something in that transmitter is not linear, and when operating under reduced power is distorting either the 19 kHz pilot signal and or the 38 kHz sub carrier producing an audible subharmonic.

And just to add a twist, the 38 kHz sub carrier it transmitted as a suppressed carrier double sideband AM signal which may not be playing well with the others under reduced power.

Now there a few areas which can cause the non-linearity, the modulator and stereo injection, the power amplifier (PA), and the antenna / feed line, going out on a limb we can probably rule out the antenna and feed line, as the problem worsens with a power reduction, that leaves the modulator and stereo injection and or the PA, all of which are problems you have no real way of solving."**


I was wondering if I could get the community to try something for me if they have a PCI MAX 3000+ V2. Could I have some of you try 97.7 (or there abouts) and 91.7 (or there abouts), and set your power level to 5% - 20%, with no audio, set mode to stereo and see if you get any tone simular to the one I am getting? Please report back if you are or are not getting any tone with those settings.

Thank you.

***EDIT*** Sorry, I forgot to include a link so that everyone can hear the tone for themselves.
http://dl.dropbox.com/u/7859299/tone.zip (11.5MB)
Thu Feb 02, 2012 6:38 am View user's profile Send private message
berrall
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Wow that's a bad annoying noise. I can confirm on my PCI-MAX V1 that when it is set to any power level or freq, that with no modulation it gives a total dead carrier. Have you tried running your PCI-MAX off a 12v battery to eliminate any PSU noise? Also try running it totally outside the computer case as it may be picking up interference from nearby PC components.
Thu Feb 02, 2012 7:44 am View user's profile Send private message
pcs
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Post Reply with quote
1. Did you send the first unit back to us to the provided address?

2. I think something in your PC is creating a signal that's 19KHz+8.8KHz, probably a switcher in your PC's power supply or a switcher feeding your CPU on your mainboard. When you turn the stereo on a beat tone is generated that's the exact difference between the two signals.

3. The cards on their own do not generate any such signals, carrier in clean environment is completely dead silence. After some thousands sold over the course of some years (model 3000) I can say with confidence that this has to come from the card's environment. Now that you've tried two cards this is definitely confirmed.


The best solution in these apparently extremely rare cases would be to use PCIMAX 3000 in external box:
http://www.pcs-electronics.com/cyber-micro-digital-p-1681.html
These basically contain pcimax with LCD control unit. They are shielded and outside of the PC, powered by external power supply, everything else is the same.

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Marko - PCS Electronics
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Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Thu Feb 02, 2012 11:16 am View user's profile Send private message Visit poster's website
Cjaiceman
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So I tried taking the unit (outside of a PC) about 20 miles away from the house, and ran it directly off of a car battery (not the one in the vehicle) and used a 3rd laptop, using the included antenna outside the vehicle I get the same tone on the vehicle's stereo. The only conclusion I can make of this is that its nothing inside my home or around my home causing the tone.

Side Note- I never got a return address to send the card back to. If you provide me one I will send back the original card so you can test it in your lab and see if you get the same result.
Thu Feb 02, 2012 7:44 pm View user's profile Send private message
pcs
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Post Reply with quote
Guess what, I just went through 30 boards and I did find this weak tone in a few of them.

This is only noticeable when you set power very low, 20-30% of the max. If its set to full there is no tone.

The culprit is that some digital noise of the CPU is getting into the signal, but only when power is set low.

It is quite easy to reduce this tone sufficiently without soldering, all it takes is a ELKO capacitor 100-470uF rated at at least 5V, such as this one here:
http://search.digikey.com/us/en/products/ECA-0JM471/P5114-ND/244973
I believe many of you have something similar at home. 470uF worked great here in the lab.

You don't even have to solder it to the board, just cut the legs short (half an inch or so), than plug it into socket provided for RDS daughter board.
Align the negative pin to the socket marked GND and positive pin to the socket marked +5V.

We will be installing these capacitors on all boards starting today, just in case.

Thanks for catching a bug, it is appreciated!

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Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Fri Feb 03, 2012 3:16 am View user's profile Send private message Visit poster's website
Cjaiceman
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Post Reply with quote
Ha, just my luck, to get the one that starts a chain reaction forcing a new problem to be solved. Good to hear that there is an easy fix though. I might venture out tomorrow (but I doubt it due to a major snow storm in the area) to pick one of those up from Radio Shack.

This does raise one question though, what happens if I wanted to put a RDS board on the unit? Would the RDS board solve the issue, make it worse, or am I just not able to use an RDS board with a card that has the "tone effect"?
Fri Feb 03, 2012 8:08 am View user's profile Send private message
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