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[wxsig] Radio Interference Question

Mark Patton k0yg at msn.com
Thu May 17 01:23:26 UTC 2007


The problem I had was just the opposite - the audio level was to low.  I 
needed to make some changes to resistors and caps in the audio path in 
order to get the audio level up.  I think this was due to a low 
impedance input to the radio.  Check the email archive.  Several others 
have had this same low audio problem.

If you have a scope, check the output of the modem chip to see if you 
are getting tones generated.  That will give you a big clue as to where 
the problem is.

73's
Mark, K0YG

John Bennett wrote:
> Be sure you are not over-deviating. If severe enough, it will cause the
> problem you described.
>
> GL es 73,
>
> John, N4XI
>
> On Wed, 2007-05-16 at 20:47 -0400, Leon Bruner wrote:
>   
>> John,,
>>
>> Tonight I sat down with a glass of my favorite and a handleld radio and 
>> kept an eye on the unit for a reasonable period of time.  I have 
>> verified that the red PTT LED goes on approx every 5 minutes and it keys 
>> the transmitter.  The signal from the keyed transmitter is received on 
>> the handheld.  However, there does not appear to be any audio output 
>> associated with the transmission.  Said another way, the radio is keyed, 
>> a signal is transmitted but there appears to be no information going 
>> out.  The transmission is very short- only a second or so...  So it 
>> appears that I have an audio problem...  I'll have a look through the 
>> manuals tonight to see if I can identify a solution.  In the meantime, I 
>> thank you for the help and hope you're having a great time in Dayton.
>>
>> Leon
>>
>>
>> John Koster wrote:
>>
>>     
>>> I don't see any choices for TX frequency.  So I guess we're stuck with 5 
>>> minutes.  Need a clever way to 'capture' the event.  
>>>
>>> At this time we really don't know whether its' a PTT problem or an audio 
>>> problem.  If you have a receiver and audio recorder perhaps you could 
>>> record the audio on the frequency over a period of time and see what you 
>>> might hear.  I assume you've checked the radio with  microphone to be sure 
>>> it's not developed a problem over the years.  You'd want the monitoring 
>>> receiver to have a poor or no antenna so you don't pick up other signals.
>>>
>>> I am a little puzzled by the low voltage reading.  If I didn't read the 
>>> schematic wrong the reading is from collector to ground of the PTT 
>>> transistor.  It should be 5 unless you have a real low impedance 
>>> voltmeter.  Of course that also depends on you having a solid +5 VDC rail.
>>>
>>> I'm leaving in the morning for Hamvention, so I'll probably not be reading 
>>> my email very frequently.
>>>
>>> On Tue, 15 May 2007, Leon Bruner wrote:
>>>
>>>  
>>>
>>>       
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