[Elecraft] K3: R/T and T/R timing

[Tom Hammond]

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
>--
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