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[wxsig] Radio Interference Question

Leon Bruner leon at ljjf.net
Sat May 19 01:35:15 UTC 2007


Thanks- I appreciate your making this comment.  To be honest, I've been 
a little worried about how I was going to manage changing the 
components.  I certainly have no special equipment and I don't want to 
wreck the board after getting this far!

I'm gathering that nobody has any experience with the ICOM 27H- Is it 
common that older radios have a lower microphone input impedence than 
more recent radios?  I guess another question to ask is what radios work 
well with the standard unit?  While I'd like to get the old 27H to work, 
maybe I should consider an alternative...

Thanks again for all the comments.  It's great to have the help.

Leon

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
>>
>>Mark,
>>
>>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
>>transmission.
>>
>>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.
>>
>>Regards,
>>
>>Leon
>>
>>
>>
>>
>>
>>
>>    
>>
>>>>        
>>>>




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