I've successfully used QSK with the LK550ZC. It's not quite correct that the
amp has to be keyed before the exciter. What's true is that the amp relay
must close before the rig emits RF.
How you configure the amp depends on whether the exciter has a QSK keying
loop. I'm not familiar with the IC-7000, but Yaesu and Ten-Tec rigs have
this option. In this configuration, the rig's amp relay output is connected
to the amp's key input. The rig's TX INH or TX ENA input is connected to the
amp's key output. The LK550ZC's QSK switch is in the ON position for this
configuration. The exciter is keyed first, via the usual means -- a paddle
using the internal keyer or via a line from an external keyer. On key-down,
the rig immediately keys the amp. This causes the amp to switch the vacuum
relay. When the switching is complete, the amp grounds its key out line,
which enables RF transmission from the rig. Until this line is grounded, the
rig can't transmit. Once the amp's relay has safely switched, the line is
grounded and the rig can transmit.
The Yaesu keying loop uses a solid state output so it can switch fast enough
for QSK. The Ten-Tec Orion uses a fast reed relay for the keying output. The
amp key relays in some rigs aren't fast enough for QSK. That's generally
true of the Yaesu line -- the amp key relay is designed to be able to handle
the high switching voltage of older amps, and isn't fast enough for QSK.
That's why you have to use the solid-state key output for QSK (as far as I
know, all QSK amps use low voltage keying.)
You don't necessarily have to use the rig and amp keying loops. Most modern
rigs have a delay between key-down and the start of the RF envelope,
anywhere from 5ms-15ms. Sometimes the delay is fixed, sometimes it's
adjustable. If the rig has a long enough delay, the amp will have sufficient
time to switch the vacuum relay before RF begins. In that case, you just
have to connect the rig's amp key output to the amp's key input and turn off
the amp's QSK switch. Vaccum relays can switch pretty fast -- in some cases
in as little as 1-2 ms. Probably any delay greater than 5ms will work with
the LK550ZC, but I'd be more comfortable with at least 8-10ms.
Another approach involving the key loop is to connect an external keyer to
the amp's key in line, and use the key out line to key the rig. The amp's
QSK switch is ON in this configuration. Of course, you can't use the rig's
internal keyer. I'm not sure CW timing will be correct in this
configuration, but it would be the only way to deal with a rig that doesn't
have a keying loop and doesn't have a long enough delay between key-down and
the RF envelope.
Hope this helps.
73, Dick WC1M
> -----Original Message-----
> From: Hugh Phillips - K7XM [mailto:hphillips@mho.com]
> Sent: Saturday, December 22, 2007 8:41 PM
> To: amps@contesting.com
> Subject: [Amps] Keying the LK550ZC
>
> I have a LK550ZC, using a IC-7000 as the exciter. Is there a
> work-a-round to key the LK550ZC with the IC-7000 using QSK so as to
> utilize the keyer in the 7000?
> According to the amp manual, for QSK to work, the amp has to be keyed
> first, then to the exciter. However there's only a two conductor RCA
> input and then the same for the out to the exciter for the keying
> line.
>
> Has anyone modified this amp so as to utilize QSK keying through the
> amp?
>
> TIA
> Hugh,
> K7XM
>
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