Re: [amsat-bb] 1200/9600 Baud REAL test

[Jon Ogden <jono@xxxxxxxxxxxx>]

on 7/19/00 10:13 PM, Bob Bruninga at bruninga@nadn.navy.mil wrote:

> Yes, but you are comparing apples and oranges since one is AFSK and the
> other is FSK.  One is analog and the other is digital.  But this test
> finally gives me some confidence that they are both in the same ballpark.

This isn't exactly true.  There is less difference between AFSK and FSK than
one would think.  First off, BOTH signals are analog signals.  All RF is
transmitted by an analog waveform.  Marketing hype makes people thing their
digital cell phones transmit digital signals which they do not.

What you are doing is modulating the RF signal with digital data.

In both FSK and AFSK, the data modulating the signal is digital data.  Both
modes are digital modes.  It's just that in the AFSK situation you are
applying the modulated data at the audio stage in the transmitter while at
the FSK end of things you modulate the RF signal at one of the RF stages.
Either way as the signal gets mixed up to the final RF output frequency, the
RF signal is Frequency Modulated according to the signal applied earlier.

So FSK and AFSK aren't all that far apart.

I think your tests show very clearly that the link budget with a 9600 baud
data link is far less than with a 1200 baud link.  The fact that with a
crude measurement setup you got very close to the theoretical value tells me
you did a good job.

73,

Jon
NA9D

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Member:  ARRL, AMSAT, DXCC, NRA

http://www.qsl.net/ke9na

"A life lived in fear is a life half lived."

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