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[aprssig] 9600? Faster?

Robert Bruninga bruninga at usna.edu
Thu Jul 7 17:00:14 UTC 2005


>>> ad6nh at arrl.net 07/07/05 11:51 AM >>>
>> We did extensive tests...  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.  

Ah, but again, it all depends on the definition of "works"..

>Distance from station to station is the killer. 

Yep, a 7 dB difference in performance equates to 
about half the range...  It is very easy to test.
And anyone with a D700 and a D7 can do this
test:

1) Go to a simplex freuqency.
2) Set your D700 to 9600 baud and drive.
3) Record data from a second station,
    Let the map fill with track histories of 
    your mobile.

THen staying on the same frequency, change to 
1200 baud and change the Mobile call and drive again.

You will find the 1200 baud reaches much further...
Notice you must not try to compare 9600 on a
frequency #2 with performance at 1200 on
144.39 since the latter is interference limited
not performance limited...

Since anyone with a D7 and a D700 can do this test,
it might be usefull for people to do this test over a
few days and report their results.  And since the mobile
to another mobile or to an HT range is so small in
the first place, it doesnt take much driving to
get a good data set...

Bob






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