K3: R/T and T/R timing

[David Windisch]

CONTENTS DELETED

The author has deleted this message.

[Tom Hammond-2]

Hi Dave:

About 25 or so years ago, I added full QSK to my Alpha 76PA (using
the QSK circuitry from the Alpha 78 (which had QSK from the factory).

Since that time, I've used the QSK-ed Alpha with every radio I've
had, full QSK, with NO HOT SWITCHING... EVER!  And I'm NOT(!) using
the built-in (Alpha) pre/post keying circuitry, which never gave
satisfactory timing. Just letting the rigs key the T-R line.

The K3 is fully-timed such that you'll close the T-R line before RF
appears, and you'll drop RF before the T-R line drops... unless
you're using some sort of slow open-frame relay.  Vacuum relays, reed
relays, and PIN diodes will all switch long before RF appears and
well after it disappears.

For what it's worth, the DELAY control does NOT control key-down to
RF-available timing... it controls key-up to return-to-RX timing.

73,

Tom Hammond   N0SS

p.s.

If ANYONE with an Alpha 78 might happen to be interested, I have a
completely designed, and working PC board to add both full QSK AND
grid overdrive protection to your Alpha 78-series
amplifier.  ETO/Alpha Power no longer offers the Alpha 78 QSK PC
board, but I DO...!  Cost for the conversion is about $120
complete.  Info sent on request.


At 09:38 03/26/2010, David Windisch wrote:

>Hi, all concerned:
>
>The time from key-down to rf-available, is well-defined, and controllable
>with the DELAY knob from 8ms to 2s.
>
>Is the time from key-up to no r-f output as well-defined, and controllable?
>
>My concern is hot-switching an amplifier, in my case either a Ten-Tec 425 or
>an Alpha 89, operating QSK c-w.
>
>After key-up, on quiet bands or a dummy load, I hear a short "tail" (sounds
>like an echo) at the end of each code element.
>
>Is the situation different on SSB?
>
>Any ideas out there, please?
>
>Tia & brgds,
>Dave, N3HE
>--
>View this message in context:
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>Sent from the Elecraft mailing list archive at Nabble.com.
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[N5GE]

On Fri, 26 Mar 2010 06:38:26 -0800 (PST), David Windisch
<[hidden email]> wrote:

See comment below:

[snip]
>After key-up, on quiet bands or a dummy load, I hear a short "tail" (sounds
>like an echo) at the end of each code element.

After 20 years of using good QSK rigs, I have occasionally noticed the
echo you are hearing when in the sunspot peaks and with good
conditions, but it's not the rigs, it's the signal making the round
trip.  In your case, if you can hear it on the dummy load it's
probably a switching or RF problem.

TOM, N5GE BT

73 ES GUD LUK
AR DE N5GE SK

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