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Nauveau 75 no modulation

Tim
 

Nice 5 watt carrier but I get no modulation with MIc.
PTT on mic is very stiff but I do not think that is a problem.
Anyone else have that issue before I drag out Oscope!
Tim W4YN

KG0DQ
 

Tim,

Check your microphone, it’s not a high dollar microphone. Mine was wired wrong. The speaker was wired to the tip and the electret was on the ring ground was the sleeve. 

Timothy East
 

Tim,
This is Tim, K0EMP.

I also had a similar experience.  Turned out I had a short in the mic cable just below the mic head.  I suggest you check the mic writing first and if that is not it that you next try keying the PPT and manipulating the mic cable to see if things start working.

Mine did start up and I got a replacement mic that corrected the problem completely.

Best of luck.  Its a great kit.

Tim
K0EMP

On Apr 14, 2020, at 9:22 AM, KG0DQ <KG0DQ.listen@...> wrote:

Tim,

Check your microphone, it’s not a high dollar microphone. Mine was wired wrong. The speaker was wired to the tip and the electret was on the ring ground was the sleeve. 

Tim
 

took back off mic and there is something wrong with wiring!
is there a clearer schematic for rig? when I view the one on 4sqrp site it is blurry
Tim

Timothy East
 

I don’t have a better copy. Perhaps contacting the kitter or a member of 4sqrp leadership to obtain a clearer schematic. 
Tim
K0EMP 

On Apr 14, 2020, at 11:29, Tim <w4yn@...> wrote:

took back off mic and there is something wrong with wiring!
is there a clearer schematic for rig? when I view the one on 4sqrp site it is blurry
Tim

N7JS
 

With the stock microphone, I'm having to crank up the mic gain all the way to get the LED to flicker.  Also noticing a lot of hum on the audio (even though using a regulated power supply).

73 Jim, N7JS

On 4/14/2020 8:22 AM, KG0DQ wrote:
Tim,

Check your microphone, it’s not a high dollar microphone. Mine was wired wrong. The speaker was wired to the tip and the electret was on the ring ground was the sleeve. 

K0WDO Will Osborn
 

Hi Tim! Finished my N75a yesterday. I had the same issue and thought I had a bad mic until I maxed out the mic gain and talked very loud in the mic. Even at 90% mic gain there is zero audio but turn it clockwise till it stops and I now get about 10 watts PEP and a 4 watt carrier. I can hear myself on a nearby receiver. 

Keep us posted! I’m still testing mine. 

73, Will 
K0WDO 


On Apr 14, 2020, at 8:45 AM, Tim <w4yn@...> wrote:

Nice 5 watt carrier but I get no modulation with MIc.
PTT on mic is very stiff but I do not think that is a problem.
Anyone else have that issue before I drag out Oscope!
Tim W4YN

K0WDO Will Osborn
 

This is how mine is wired. Are you thinking we’re using the speaker as a dynamic mic of sorts instead of the electret and that’s why we have to crank the gain all the way up and shout?

73, Will 
K0WDO 


On Apr 14, 2020, at 11:01 AM, KG0DQ <KG0DQ.listen@...> wrote:

Tim,

Check your microphone, it’s not a high dollar microphone. Mine was wired wrong. The speaker was wired to the tip and the electret was on the ring ground was the sleeve. 

w9ran
 

On 4/14/2020 12:06 PM, K0WDO Will Osborn via groups.io wrote:
Are you thinking we’re using the speaker as a dynamic mic of sorts instead of the electret and that’s why we have to crank the gain all the way up and shout?
To be clear, the speaker connection from the speaker-mic is not hooked up inside the radio, only the mic terminal is used.   It's on the ring closest to the sleeve and seems to be a non-standard wiring scheme.   The PTT switch is connected in series inside the mic and PTT is sensed by Q14 and U2 while the mic audio from the electret element is capacitively coupled to another section of U2 where it is amplified and gain-adjusted.    If the radio is switching to transmit mode (speaker audio is muted) but there is no TX audio, I'd look in that area.

I guess it was done this way because of the desire to supply a mic as part of the kit,  but in my view it would have been preferable to go with a conventional mic preamp and PTT line that would be grounded to transmit so users would be able to easily use any mic of their choice, or an external audio source.   The supplied mic sounds OK but lacks the mids and highs that greatly improve speech intelligibility.   I use a TRRS extension cable on it since the right-angle plug was always rubbing against the knob and adjusting the mic gain setting for me ;-)

73, Bob W9RAN

Tim
 

No using condenser mic
I see 2200 ohm resistor across mic output lifted it ant no PTT so there needs to some resistance there
I an going to see what  max resistance will trip PTT maybe that will cut the attenuation 
Second up is change mic element I have a few spares
Even wired correctly and mic gain to max I an getting no modulation!
Tim W4YN

K0WDO Will Osborn
 

Okay now I understand! Thanks for the terrific explanation Bob!

73, Will
K0WDO

On Apr 14, 2020, at 12:37 PM, w9ran <w9ran@...> wrote:

On 4/14/2020 12:06 PM, K0WDO Will Osborn via groups.io wrote:
Are you thinking we’re using the speaker as a dynamic mic of sorts instead of the electret and that’s why we have to crank the gain all the way up and shout?
To be clear, the speaker connection from the speaker-mic is not hooked up inside the radio, only the mic terminal is used. It's on the ring closest to the sleeve and seems to be a non-standard wiring scheme. The PTT switch is connected in series inside the mic and PTT is sensed by Q14 and U2 while the mic audio from the electret element is capacitively coupled to another section of U2 where it is amplified and gain-adjusted. If the radio is switching to transmit mode (speaker audio is muted) but there is no TX audio, I'd look in that area.

I guess it was done this way because of the desire to supply a mic as part of the kit, but in my view it would have been preferable to go with a conventional mic preamp and PTT line that would be grounded to transmit so users would be able to easily use any mic of their choice, or an external audio source. The supplied mic sounds OK but lacks the mids and highs that greatly improve speech intelligibility. I use a TRRS extension cable on it since the right-angle plug was always rubbing against the knob and adjusting the mic gain setting for me ;-)

73, Bob W9RAN




AndyH
 

Hi Tim,

   There's a good copy of the schematic in the build instructions on pages 14-16:  http://www.4sqrp.com/kits/n75/N75NewManual.pdf
  
    73, Andy, KG5RKP


On Tue, Apr 14, 2020 at 11:29 AM, Tim wrote:
took back off mic and there is something wrong with wiring!
is there a clearer schematic for rig? when I view the one on 4sqrp site it is blurry
Tim

Tim
 

Well about out of hair! 
Tried everything still no modulation.
Changed mic element, verified mic cable was ok and pins connected properly. 
Out of ideas.
On RX I did notice on very strong signal there was motorboating in audio and no tuning cycled power back to normal.
Not sure that is even related!
Tim 

Tim
 

More testing
Connected mic on bench to DC pwer thru 1K resistor, shorted PTT and measure 40mV P-P on oscope while talking in normal voice, seems abt right
Tapped into the mic jack on rig, activated PTT and there was a strong signal applied to mic input from rig, I would say 200-300mV P-P and nulled any audio from mic.
So I think there is an issue with my rig :(.
Tim 

Tim
 

Measured the signal on mic input and it was RF! Right on TX frequency.
Audio is getting thru but swamped by RF signal.
Tim