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Re: CQ PSK31 on Oscar 10



Regarding my PSK31 experiments on OSCAR 10:

At 07:12 AM 04/23/1999 -0500, "Harvey N. Vordenbaum" <k5hv@hilconet.com>
wrote:

>Since PSK31 is a continuous carrier mode it is not compatible with the usual
>transponder satellite system is it. . . ????????

PSK31 is not exactly "constant carrier."  When you modulate the signal
(idle), *measured* power drops to 50% of the raw carrier level.  PSK uses
cosine shaping of the keyed waveform to reduce the bandwidth, and this also
reduces the average power.  It's just not in the same power-hogging league
as FM.  It's FM that's not appropriate on analog satellites.

But Harvey, K5HV has brought up two questions that should be answered:

1.  Is PSK31 appropriate for use on OSCAR satellites?  I am going to defer
to AMSAT officials on this one.  My guess is that it is OK.  Correct me if
I'm wrong, but isn't even RTTY considered legitimate on the high-orbit
OSCARs?  I've personally had a PACTOR FEC contact on Oscar 10.  It worked
passably except during the deep fades.  PSK31 is much more power-efficient
than RTTY and capable of weak-signal work, and faster PSK keying is used on
the beacon of several digital sats.  

As far as transponder fairness goes, I would be much more concerned about
CW and SSB signals that are several S-units louder than the satellite
beacon.  These are quite common.

2.  What is the duty cycle of PSK31?  This should tell us, for in terms of
both RF safety and fair tranponder use, how much a PSK signal compares to
the more common CW and SSB signals we hear on the analog sats.

I am forwarding this email to an AMSAT official, and to Mr. "RF Safety" at
the ARRL for answers to questions #1 and 2, respectively.

73 from KD7MW,

--- Peter
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