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Finished my Nouveau 75, hum on transmit audio!

John P Lloyd
 

Greetings,

I finished my Nouveau 75 last night.
The receiver works fine, with nice audio. The sensitivity seems right in line with other comments that I have seen.

The transmitter puts out 2 watts; up to 6 watts with audio into a dummy load.
Although this is a bit low, none of the components are getting warm.


One issue that I have having is that there is a low level hum on the transmitted audio.
The hum is consistent regardless of the audio gain setting.
Other than that, the transmitted audio sounds FB.


Can anyone give me some advice on troubleshooting the audio hum issue?

Also, any comments about the low wattage? (I'm thinking right now if it ain't broke don't fix it!)

Thanks and 73, John W4JPL

P.S. I made some notes about building the rig, including mounting that pesky daughter board; if anyone is interested, I'll post them.

Dwayne R <masterdr@...>
 


Are you using a metal mic? where the hum can come from your
body and into the radio via your Mic?

On Wednesday, November 20, 2019, 2:15:34 PM CST, John P Lloyd via Groups.Io <w4jpl@...> wrote:


Greetings,

I finished my Nouveau 75 last night.
The receiver works fine, with nice audio. The sensitivity seems right in line with other comments that I have seen.

The transmitter puts out 2 watts; up to 6 watts with audio into a dummy load.
Although this is a bit low, none of the components are getting warm.


One issue that I have having is that there is a low level hum on the transmitted audio.
The hum is consistent regardless of the audio gain setting.
Other than that, the transmitted audio sounds FB.


Can anyone give me some advice on troubleshooting the audio hum issue?

Also, any comments about the low wattage? (I'm thinking right now if it ain't broke don't fix it!)

Thanks and 73, John W4JPL

P.S. I made some notes about building the rig, including mounting that pesky daughter board; if anyone is interested, I'll post them.

w9ran
 

On 11/20/2019 2:10 PM, John P Lloyd via Groups.Io wrote:

Can anyone give me some advice on troubleshooting the audio hum issue?
John, First off I'd check your power supply.    A scope would be the best tool but if you have a different supply that you could try, that should verify.   The next thing is a possible ground loop - if you can, try a battery or disconnect the antenna and put the N-75 on a dummy load that is not grounded.

Your output does sound low - mine has about 3 watts resting carrier and when I posed the question a  while ago no one replied to say they were getting 5 watts unmodulated carrier output.   The power supply voltage could easily make up the difference, mine is running at 13.5VDC.

73, Bob W9RAN

Charles W. Powell
 

Mine is somewhere around 3 watts dead key as well.

72,

Chas - NK8O

On Nov 20, 2019, at 5:50 PM, w9ran <w9ran@...> wrote:

On 11/20/2019 2:10 PM, John P Lloyd via Groups.Io wrote:

Can anyone give me some advice on troubleshooting the audio hum issue?
John, First off I'd check your power supply. A scope would be the best tool but if you have a different supply that you could try, that should verify. The next thing is a possible ground loop - if you can, try a battery or disconnect the antenna and put the N-75 on a dummy load that is not grounded.

Your output does sound low - mine has about 3 watts resting carrier and when I posed the question a while ago no one replied to say they were getting 5 watts unmodulated carrier output. The power supply voltage could easily make up the difference, mine is running at 13.5VDC.

73, Bob W9RAN



John P Lloyd
 

Hello Dwayne,
I'm using the handheld mic that comes with the kit.
What I have to figure out is how to key the rig without the mic, which I will do probably this weekend.
This way I can eliminate the mic as a possible problem.

John P Lloyd
 

Hello Bob,
I have tried it on 3 power supplies, in fact. One on my workbench (a switcher) and the other two are 50 amp astron's that I use everyday in the shack.
I always troubleshoot into a dummy load with a watt meter in line.
Putting it on an antenna has the same result with the hum.
The voltage from the PS's is 13.8.

I'm going to look into it a bit more this weekend, and let  you know if I come up with anything, especially about the power output.

Thanks for  replying!
John

Duane Brayton
 

How are you powering the radio & could you have a ground loop?  Is your mic cord shielded? Check these items first. 
Duane KE0IUV

On Nov 21, 2019, at 9:52 AM, "John P Lloyd via Groups.Io" <yahoo.com@groups.io target=_blank>w4jpl=yahoo.com@groups.io> wrote:
Hello Dwayne,
I'm using the handheld mic that comes with the kit.
What I have to figure out is how to key the rig without the mic, which I will do probably this weekend.
This way I can eliminate the mic as a possible problem.

Duane Brayton
 

Sorry, I got the other msg first.  In that case mic cord shielding & rf feedback are possibilities. Keying the transmitter without mic attached should resolve that question quickly. You should be able to easily determine the keying line at the mic cord Jack and apply a temporary ground while checking the rf waveform. Let us know how that goes.
Duane KE0IUV

On Nov 21, 2019, at 10:00 AM, "John P Lloyd via Groups.Io" <yahoo.com@groups.io target=_blank>w4jpl=yahoo.com@groups.io> wrote:
Hello Bob,
I have tried it on 3 power supplies, in fact. One on my workbench (a switcher) and the other two are 50 amp astron's that I use everyday in the shack.
I always troubleshoot into a dummy load with a watt meter in line.
Putting it on an antenna has the same result with the hum.
The voltage from the PS's is 13.8.

I'm going to look into it a bit more this weekend, and let  you know if I come up with anything, especially about the power output.

Thanks for  replying!
John

w9ran
 

On 11/21/2019 9:00 AM, John P Lloyd via Groups.Io wrote:
Putting it on an antenna has the same result with the hum.
John -

So are you saying the hum is still present on the dummy load?  Or only when used on an antenna?

73, Bob W9RAN

PS:   There is not a separate PTT line as in most radios, the N-75 detects the change in voltage that occurs when the mic PTT switch is closed.  To key the radio w/o the mic you'll need a 4-circuit TRRS plug - short the sleeve and first ring together.

John P Lloyd
 

Hi Bob,

The hum is there regardless.

Thank you for the information on keying the rig!
73, John W4JPL

On Thursday, November 21, 2019, 12:04:43 PM EST, w9ran <w9ran@...> wrote:


On 11/21/2019 9:00 AM, John P Lloyd via Groups.Io wrote:
> Putting it on an antenna has the same result with the hum.

John -

So are you saying the hum is still present on the dummy load?  Or only
when used on an antenna?

73, Bob W9RAN

PS:   There is not a separate PTT line as in most radios, the N-75
detects the change in voltage that occurs when the mic PTT switch is
closed.  To key the radio w/o the mic you'll need a 4-circuit TRRS plug
- short the sleeve and first ring together.




John Lonigro
 

John:
Do you by any chance have a 12 volt gel-cell or a cigarette lighter plug for your car that you can temporarily power the radio with?  If you run the radio off D.C., and the hum is still there, you can eliminate any power supply issues.

72 and good luck,
John, AA0VE

On 11/21/19 12:54 PM, John P Lloyd via Groups.Io wrote:
Hi Bob,

The hum is there regardless.

Thank you for the information on keying the rig!
73, John W4JPL

On Thursday, November 21, 2019, 12:04:43 PM EST, w9ran <w9ran@...> wrote:


On 11/21/2019 9:00 AM, John P Lloyd via Groups.Io wrote:
> Putting it on an antenna has the same result with the hum.

John -

So are you saying the hum is still present on the dummy load?  Or only
when used on an antenna?

73, Bob W9RAN

PS:   There is not a separate PTT line as in most radios, the N-75
detects the change in voltage that occurs when the mic PTT switch is
closed.  To key the radio w/o the mic you'll need a 4-circuit TRRS plug
- short the sleeve and first ring together.





John P Lloyd
 

Yes sir!
That was on my list of things to try.
Thanks!
John

On Thursday, November 21, 2019, 2:23:01 PM EST, John Lonigro <jonigro@...> wrote:


John:
Do you by any chance have a 12 volt gel-cell or a cigarette lighter plug for your car that you can temporarily power the radio with?  If you run the radio off D.C., and the hum is still there, you can eliminate any power supply issues.

72 and good luck,
John, AA0VE

On 11/21/19 12:54 PM, John P Lloyd via Groups.Io wrote:
Hi Bob,

The hum is there regardless.

Thank you for the information on keying the rig!
73, John W4JPL

On Thursday, November 21, 2019, 12:04:43 PM EST, w9ran <w9ran@...> wrote:


On 11/21/2019 9:00 AM, John P Lloyd via Groups.Io wrote:
> Putting it on an antenna has the same result with the hum.

John -

So are you saying the hum is still present on the dummy load?  Or only
when used on an antenna?

73, Bob W9RAN

PS:   There is not a separate PTT line as in most radios, the N-75
detects the change in voltage that occurs when the mic PTT switch is
closed.  To key the radio w/o the mic you'll need a 4-circuit TRRS plug
- short the sleeve and first ring together.