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[wxsig] Tx problem fixed

pedro.motilla at ono.com pedro.motilla at ono.com
Tue May 12 21:30:08 UTC 2009

Hi, today I isolated the problem, it was the capacitor 111, I do not know why, but it does not permit the signal to reach pin8 on P100.

The procedure was to follow the signal with the scope. Finally it was clear that this cap was causing the problem, so I jumped the cap, and, voilá¡¡¡¡¡ the signal was on the air.

Now I have one question, what is the function of this capacitor?, should I change the value of the cap? or can I leave it without the cap?

On my last comunication I made some mistakes with the measurements of the scope. Today it has been my second time on using a scope, I am not still used to work with the oscilloscope. The pin 7 on U100, has a sine wave signal with 500 Hz, not 50 Khz, as I said. I used a loudspeaker from an old toy. So, I could assure that from pin 7 were going out signal. Also on pins 1 and 2 voltage is not 30 mv and 20 mv, but 3 and 2 mv.

So I put the signal on the air, but a little bit worried because I do not know if the absence of the cap 111 could affect to the modem's performance or the transceiver.

Cable is good, the wiring works ok.

I do sorry if I confused some of you with my measurements.

Thanks to everyone, hope anybody can tell me something about the c111.

Best Regards.

EA5BFT, Pedrolo.

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