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[wxsig] Radio Interference Question

William Beals will at beals5.com
Sun May 20 02:28:17 UTC 2007

Leon (and all):

For starters, thanks to Mark, John, and w0nx for helping out.  I was on a week-long business trip and while I could read emails, could not post to wxsig through my home email account.

Leon, tough call, I'd go for neat and tidy, but that is me.  A spring loaded solder-sucker is a great way to clean out holes if you have practiced with it enough.


-----Original Message-----
From: wxsig-bounces at lists.tapr.org [mailto:wxsig-bounces at lists.tapr.org] On Behalf Of Leon Bruner
Sent: Saturday, May 19, 2007 2:46 PM
To: TAPR Weather Station SIG Mailing List
Subject: Re: [wxsig] Radio Interference Question

OK, I think I have it sorted.  I tacked a 0.1 uF capacitor onto the 
existing C111 as Mark sugested below.  I now have an audio signal that 
is being picked up by the network.  Check out NT8B-3 on findu.com.  
Thanks to everyone for the help- much appreciated!

Now, unfortunately I have a rather tacky looking capacitor sticking out 
from underneath the modem board.  What I'd like to do is cut the 
original 100 pF cap off from the top of the board, heat the joints and 
pull the wires out from the bottom.  I also have a vacuum style solder 
remover I could use to suck away the old solder in order to open the 
holes so I can put the new 0.1 uF cap in its place.  Does this sound 
reasonable or should I operate by the addage, if it ain't broke don't 
fix it? 



>>wn0x at earthlink.net wrote:
>>>Since these are plated throug holes, you might consider "tacking" the 4.7K resistor over the existing R101 and trying that first. Removing components with plated through holes can be treacherous without the correct equipment.
>>>Since capacitance in parrallel is additive, you can also tack a capacitor across the existing C111 to increase capacitance.  I wouldn't replace the components at this time, just try adusting the values.  Both should increase the level of audio.
>>>-----Original Message----
>>>>From: leon at ljjf.net
>>>>Sent: May 18, 2007 9:39 AM
>>>>To: wxsig at lists.tapr.org
>>>>Subject: Re: [wxsig] Radio Interference Question
>>>>Thanks for the suggestion.  I borrowed a scope from work, hooked the
>>>>ground lead of the probe to pin 4 of U101 and looked for a signal on pin 7
>>>>of U100.  When the TX LED lights there the scope shows a trace.  So,
>>>>assuming my hookup is correct, it looks like tones are being generated. 
>>>>I've also tried adjusting pot R114 but still don't hear audio during
>>>>I've looked in the archives and found a chain of messages about low audio.
>>>>The suggested correction seems to be to change  R101 to 4.7K and C111  to
>>>>.1uf.  Does the group agree this is my next step?  To be honest I simply
>>>>don't have enough knowlege to be able to answer this question...  My radio
>>>>is an ICOM 27 H if that helps.
>>>>Thanks again to all for the suggestions.  Because of your help I think I'm
>>>>making progress.

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