[Elecraft] Default K3 transmit delay may be too short for slow QRO amplifiers

[Dimitry Borzenko]

Hello.
Why in the 20 century we need to use foot switch?
Why not to do longer TX delay?
Why I can not set 200mS TX DLY ?
For QSK operation or for use with new fast switched TX/RX relays or PIN 
diodes user can to set minimum TX DLY.
Today is possible to change only firmware and do not need to do any 
hardware changes.
TRX mast be more flexible.
You can say , What about CW??.
Nothing , in winkeyer possible to set long TX DLY why in K3S is 
impossible?
All possible, need only wish to do.

Best Wishes.


------ Original Message ------
From: "Wayne Burdick" <n6kr at elecraft.com>
To: "Elecraft Reflector" <elecraft at mailman.qth.net>
Sent: 08.06.2018 2:43:13
Subject: [Elecraft] Default K3 transmit delay may be too short for slow 
QRO amplifiers

>It has come to our attention (thanks to N7YK and N6TV) that the default 
>value of CONFIG:TX DLY, 8 ms, may actually be closer to 5 ms.
>
>The associated T/R control firmware hasn’t changed in a long time, so 
>hopefully there aren’t many users affected (or we would have heard 
>about it). The shorter delay may be related to the improved KSYN3A 
>synth, which switches faster than the original. We’re looking into 
>this, and will update the displayed value to reflect the actual value.
>
>Details:
>
>When using a QRO amp with the K3, the KEY OUT line from the radio is 
>used to key the amplifier, setting it up to receive RF. Since the K3 
>has very fast QSK, the amp’s T/R control circuitry has to be similarly 
>fast.
>
>Those of you who are using KPA500s and KPA1500s need not be concerned 
>about the K3’s fast QSK speed, since our amps use PIN diode T/R 
>switching. They can easily keep up with the K3 at any code speed and 
>with the default setting of the CONFIG:TX DLY menu entry.
>
>However, some other amps, especially older ones, use slow T/R relays. 
>If the transceiver generates RF before the amp is ready, this might 
>result in key clicks.
>
>(In practice there’s a bit of a grace period because the RF keying 
>envelope rises very slowly. It’s a "raised-cosine sigmoid," resulting 
>in the transceiver itself having incredibly clean keying sidebands. See 
>K9YC white paper on this topic.)
>
>If you suspect your amp has a slow T/R relay, you should do a listening 
>test, or better yet have someone else listen from a good distance. If 
>you (or they) hear any evidence of clicks, increase the value of 
>CONFIG:TX DLY.
>
>Use the lowest setting that eliminates the clicks. CW keying at higher 
>code speeds may be affected if the value is too high. Other modes not 
>using fast QSK will generally be unaffected (voice and data).
>
>An alternative to increasing TX DLY is to use a foot switch, as do many 
>users of old amps regardless of transceiver type.
>
>73,
>Wayne
>N6KR
>
>
>
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