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Re: [Amps] Fwd: Fwd: *** PGXL Questions on CW Operation

To: "Amps group" <>
Subject: Re: [Amps] Fwd: Fwd: *** PGXL Questions on CW Operation
From: "Jim Garland" <>
Date: Thu, 1 Nov 2018 09:43:49 -0600
List-post: <>
        My comments about the new Flex amplifier's CW behavior has morphed
into a very interesting discussion about SDR vs. non-SDR transceivers and
their suitability for QSK keying. (BTW,  I should have said Ethernet in my
posting, not internet. Sorry!) I think Manfried analyzed the situation very
nicely. If I understand it, an SDR transceiver, like the Flex 6000 series,
can utilize time shifting to eliminate any potential incompatibility with an
external amplifier, no matter how long it takes the amplifier to bias itself
on-line and close its T/R relays. There is never a single dit truncated,
even at QRQ speeds.        
        On the other hand, SDR transceivers are not optimally suited for QSK
at high speeds because the time-shifting can potentially conflict with what
the other station is sending. For true high speed QSK, the transceiver needs
to get its RF to the amplifier with as little delay as possible, and the
amplifier has also to respond as quickly as possible. Ideally, the amp and
transceiver should be closely matched to each other and probably made by the
same manufacturer. If mismatched transceiver and amplifier are used, there's
a possibility for truncated dits and, at worst, amplifier damage.
        As a practical matter, it won't matter to most users whether an SDR
radio or  non-SDR radio is used. I'd think either could in principle handle
QSK below, say, 40 wpm or so, with the non-SDR winning the race at higher
speeds. Personally, I don't use QSK, so to me avoiding amplifier
incompatibility is the key consideration. But then I'm not contester!
Jim W8ZR 

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