[Elecraft] OT: definition of semi-breakin

[Joe Subich, W4TV]

Ed,

> I am evaluating a pcboard relay for switching RF (Tx/Rx) and need to
> know what speed that the relay needs to qualify for semi-break in.
> Also, a precise definition of semi-breakin would be nice.

I don't know that there is a precise definition of the speed needed for
semi-break in.  However, you can approach it be considering that most
transceivers have between 5 and 10 msec (the K3 is 8 msec) from key
closure to the onset of RF.  *Any* proposed T/R system for an amplifier
needs to transfer from receive to transmit *and settle* in that time.

The transmit to receive time - following the cessation of RF - may be
a bit slower but that is usually set by the semi-break in delay (VOX
delay) in the transceiver - not necessarily the relay transfer speed.

If I were writing specifications "out of the air" - I would probably
shoot for a receive to transmit time between 3 and 7 msec and transmit
to receive time of less than 10 msec but those numbers are essentially
SWAG based on the overall system considerations.  Yes, with those
transfer speeds, the same relay(s) could probably qualify as "QSK"
if the transceiver PTT keying line had no delay.

73,

    ... Joe, W4TV


On 12/4/2012 7:28 PM, Edward R Cole wrote:
> I suppose this forum is a good place to ask as so many are CW ops.
>
> I am evaluating a pcboard relay for switching RF (Tx/Rx) and need to
> know what speed that the relay needs to qualify for semi-breakin.  Also,
> a precise definition of semi-breakin would be nice.
>
> I get that QSK results in transfer from Tx to Rx after every CW
> character.  I'm guessing semi-breakin switches when there is a pause in
> transmitting.  I can evaluate the switching speed of my candidate relays
> using a storage scope but need a precise number on how fast they need to
> be.
>
> 73, Ed - KL7UW
> PS: these relays will be switching 300w RF.
>
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