RE: [amsat-bb] RTTY on AO-40

[<BobDonnell@xxxxxxxxxxxx>]

Hi Emily and all

On a properly operating SSB transmitter, there's no difference in the on-air emmision characteristics for AFSK vs. FSK.  Either is narrowband digital FM. 

However with AFSK, there's more chance that the sending station will have hum, RF feedback, or even a live microphone, in the transmitted audio, causing a wider bandwidth signal than is necessary.

Using AMTOR FEC would be less error-prone than using conventional Baudot coding, due to each character being sent twice in the process of transmitting the data.  Hence lower power could be used with a low error rate than with Baudot.  The bandwidth would be slightly higher, due to the higher baud rate.

73, Bob, KD7NM, former AEA customer service tech

>-----Original Message-----
>From: Emily Clarke [mailto:w0eec@AMSAT.Org]
>Sent: Wednesday, October 08, 2003 4:53 PM
>To: AMSAT
>Subject: [amsat-bb] RTTY on AO-40
>
>
>
>Just a note about RTTY.  I was reminded by one of our 
>colleagues that RTTY 
>has two possible modes of operation - a full key down mode 
>similar to CW, 
>and AFSK mode. When speaking of RTTY with respect to AO-40 
>please use the 
>AFSK mode (which is what the soundcard RTTY programs produce.
>
>I was also asked to remind people that as with all modes on 
>AO-40 please 
>reduce power to the minimum amount needed to make your 
>contact.  It appears 
>to me to take about 1/2 the amount of power or less to make an 
>error free 
>RTTY contact than to make a voice contact.
>
>73,
>
>Emily
>
>
>
>
>W0EEC - CM87tm
>ARRL - AMSAT - MSARC - ARCA - Project OSCAR
>http://www.projectoscar.net
>http://www.emilyshouse.com/W0EEC
>http://www.experthams.net/ao7
>
>
>----
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