[aprssig] 9600? Faster?

[Stephen H. Smith]

archer at eskimo.com wrote:

>On Thu, 7 Jul 2005, Phillip B. Pacier wrote:
>
>  
>
>>Robert Bruninga wrote:
>>
>>    
>>
>>>Same here.  We did extensive tests with 4 different
>>>radios over 200 feet separation using lab attenuators
>>>and a very long run of RG58 to eliminate any chance
>>>of leakage.  The diffrence was 7 dB.  So it takes
>>>50W at 9600 to equal 10W at 1200 baud.  Or
>>>about half the range.
>>>
>>>
>>>      
>>>
>>I have heard you say this before, and we have just not found this to be
>>the biblical case here in southern California.  Mobile works fine.
>>Distance from station to station is the killer.  Maybe it's the
>>soil....maybe it's the earthquakes... it just works here. :)
>>    
>>
>
>Might part of this be the different pre-emphasis used on some of the
>9600 baud rigs/TNC's?  I recall that being a problem.  Or was that
>just the 1200 baud pre-emphasis on the Kenwoods that was different?
>
>  
>
.
There IS NO pre-emphasis on the Kenwoods tx at all!  The tones are fed 
directly into the modulator "flat", even at 1200.   These two links are 
audio recordings captured directly off the discriminator "demod out" 
jack of an IFR-1500 communications monitor with all RX equalization 
switched off,  as seen in the CoolEdit (a.k.a. Adobe Audition) audio editor:

     http://webs.lanset.com/wa8lmf/1-Mic-E-Burst.gif
     http://webs.lanset.com/wa8lmf/Mic-E-Burst-Extreme-Closeup.gif

Note that there is even a slight high-frequency rolloff - the high tone 
is actually slightly LOWER in level. The grass at the extreme left and 
right of the first one is the no-signal unquieted open-squelch 
background noise level.




Stephen H. Smith             wa8lmf (at) aol.com
                                                    
Home Page:                   http://wa8lmf.com

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