Background noise when PTT keyed.

M1AQO
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Background noise when PTT keyed.

Postby M1AQO » Tue Aug 06, 2019 11:04 pm

Hi,

I’m a new user of a 7000dle MKii.

I’m trying to set up the TX audio using the rear mic
input with a standard PC Condenser Mic.

I have set the Mic to tip, Bias to on and PTT to off utilising the space bar to key up.

With the monitor on mic unplugged and the PTT keyed without speaking there is -44db of noise showing on the mic display on the TX meter and there’s noise present through the headphones. If I plug the
mic in, the noise increases to around -36db.

When I speak in to the mic the audio sounds fine
but the background noise is present which sounds loud and is competing with the audio.

I don’t think the mic is faulty as there is noise present
with or without the mic plugged in.

I have also tried the mic through the front panel
and it’s no different.

I would appreciate any help with this.

Thanks

Glenn
M1 AQO
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Wed Aug 07, 2019 1:08 am

Is the plug on the end of the mic cable a stereo or mono plug?
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Wed Aug 07, 2019 4:40 am

It terminates to a trs plug.

Thanks

Glenn
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Wed Aug 07, 2019 7:16 am

I’ve done further testing and the noise isn’t
present on TX.

When I turn the mic gain down irrespective if
there is a mic plugged in or not, the noise disappears.

The noise is present through the monitor function and is shown on the panadapter when TX keyed and mic gain is turned up, with or without a mic being plugged in.

Any pointers would be appreciated.
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Wed Aug 07, 2019 1:46 pm

This smacks of a bad CODEC chip on the Orion MKII board. Because with nothing plugged into the microphone inputs there should be no significant audio, noise or otherwise, showing up on either the panadapter display or on the MON output. It would not be the first bad CODEC I've heard about.

Try this experiment: attach a USB headset to your PC and set things up to use VAC. See here for a tutorial. If the radio works fine then this is an even stronger indicator that the CODEC is bad and that it is not a setup issue that you can fix. That said, as a last ditch tactic, completely eliminating (not just resetting) the database.xml file is always worth trying, too.

If you have a suitable microphone preamplifier, you could also try using the line input as well.
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Wed Aug 07, 2019 4:42 pm

Hi,

Thanks for the advice.

I don’t have a USB headset but I do have a USB
microphone, so I assume I can use VAC2 to test because VAC1is being used for the receive audio.

My 7000 had the built in I7 processor so
I assume I will use the USB on the back of the radio?

Thanks

Glenn
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Wed Aug 07, 2019 6:18 pm

Glenn,

Unfortunately wrong on all assumptions.

Read the tutorial. Everything you need to know is in there already. No reason to type it all over again.

73,

Scott
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Wed Aug 07, 2019 6:38 pm

Thanks
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Wed Aug 07, 2019 10:06 pm

One correction (my bad, sorry): you will plug the headset into the USB port on the back.

BTW, you are the only person I know who bought the version with the built-in PC.
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Thu Aug 08, 2019 6:08 am

Hi Scott, Thanks.

I will pick up a USB head set and give it a go.

Once question,

Does the line in or USB connection not enter the CODEC via these routes ?

I thought the digital process started here after the microphone.

Thanks

Glenn
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Thu Aug 08, 2019 11:28 am

Glenn,

I think you'll find this post helpful:

https://apache-labs.com/community/viewtopic.php?f=12&t=2612&p=4075

The VAC facility of PowerSDR allows you to source/sink audio right at the PC, using the PC's sound interface, directly into/out of PowerSDR. It is actually a shorter, less complex path for the audio, rather than using the connections on the radio hardware.

I never really understood why the original openHPSDR design included what amounted to a custom sound card in the radio hardware. It's unnecessary complexity. But it does provide for a more "old school" feel to the hardware, perhaps.

73,

Scott
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Thu Aug 08, 2019 12:21 pm

Thanks Scott !
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Mon Aug 12, 2019 1:09 pm

Hi Scott,

I've looked at the information but can't figure out the audio path for the USB / Headset routes in relation to the codec.

I've taken your suggestion and set up a USB Headset and the noise isn't present when the microphone is keyed, so clearly there is
a problem with the front and rear mic audio path. It appears like there's to much gain present (with and without mic plugged in as previously stated)

Is there any other suggestions to cure this problem ?

I've also just updated to the latest Version 2.7 Orion Firmware to make sure it was nothing to do with that but there is no difference.

Regards

Glenn (M1AQO)
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Mon Aug 12, 2019 1:24 pm

The path for the front and rear mic and line inputs is here:

https://apache-labs.com/community/viewtopic.php?f=12&t=2612&p=4075

The path for a USB headset microphone would be as follows:

Mic --> PC sound interface (this is built into your USB microphone, but mentioned for completeness) --> PowerSDR via its VAC software interface --> Ethernet --> FPGA --> DAC --> RF amp --> Antenna.

As you can see, the VAC path does not use the CODEC at all, not for transmit or receive.

If VAC and your USB headset works fine, then it is either a configuration problem with the CODEC or a hardware fault. You say that the noise is present even when Mic gain is zero. This does imply a hardware fault with the CODEC.
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Mon Aug 12, 2019 1:43 pm

Hi Scott,

Thank you for the quick response.

If I reduce the Mic gain slider to -10db (minimum setting) the noise disappears on the panadapter with a mic gain reference on the meter of -80db. This is with no mic plugged in.

If I do the same procedure with mic plugged in the noise does reduce but is still present on the panadapter with a meter reference of -64db.

Regards

Glenn M1AQO
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Mon Aug 12, 2019 2:08 pm

I'm hoping somebody else chimes in here because I never use the Mic inputs on the hardware. I only use VAC. I'm curious what other people see for noise levels.
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Mon Aug 12, 2019 5:35 pm

To save rambling through the post, Anan 7000dle MKII
users using mic in (front or rear on radio).

If you TX and don’t speak do you hear noise through
the monitor and see it on the panadapter ?

I am experiencing this noise with and without the
mic plugged in with the mic level set.

Thanks

Glenn

P.S. Thanks Scott!
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Mon Aug 26, 2019 5:41 pm

Does anybody know how much voltage is applied for
the microphone when the Bias is selected?

Thanks

Glenn M1 AQO
M1AQO
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Re: Background noise when PTT keyed.

Postby M1AQO » Mon Aug 26, 2019 5:43 pm

Not forgetting this is the I7 version, if there is a difference.
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w-u-2-o
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Re: Background noise when PTT keyed.

Postby w-u-2-o » Mon Aug 26, 2019 9:05 pm

M1AQO wrote:Does anybody know how much voltage is applied for
the microphone when the Bias is selected?
Just go back and look at the posts I linked to above. The information is right there.

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