[Elecraft] slow amp relays

Tue Oct 28 22:36:00 2003

The range of slowdown that can be anticipated is probably measurable
by the "bucket brigade" delay that Yaesu puts in the MP's for CW
operation.

The delay between relay key and the presence of the delayed RF is
variable between 0 and 30 milliseconds. Having listened to clipping or
not in various Ameritron amps with the slow relays, 25 ms always takes
care of it. Interestingly enough, the high speed reed relays need 4 or
5 ms to guarantee closure before RF. Zero as a delay setting is always
spiking the relays. Timing shows that there is a 3-4 ms delay between
hitting the paddle and the MP's initial state change. If the paddle
closure drives amp state changes directly (instead of via the MP
circuitry and the jack on back of the MP) a reed relay changeover is
on the hairy edge but mostly works clean.

At NY4A when we have an MP driving an AL1200 without the reed relays,
we set the delay to 25 ms. For the amps with reed relays, we set them
to 5 ms. Before we caught on to this one or the other of us had at
various times and places destroyed the contacts on three different amp
relays, AND a pin diode QSK box. Even the pin diodes need 2 or 3 ms
for the circuit to "settle" before slapping 1.5 kW on them.

If the input contacts close before the output on an amp you can be
transmitting into an open relay which is MURDER on amplifier
components and bandswitches.

Many so-called "lemon" relays are really the unfortunate victims of
timing abuse and are really the fault of the operator.

Having a very clean and fast QSK switchover less than 5 ms is hard to
accomplish and requires very careful attention to timing throughout
the entire equipment string.

Several of the contest logging programs have this function in the
logger software. At the point of sending, transmit/receive is
immediately applied, after a delay set in configuration then the keyed
content, and another small delay before transmit/receive is lifted.

It's not only keeping the K2 from spiking, but controlling the timing,
so the K2 never gets spiked in the first place.

73, Guy.

----- Original Message ----- 
From: "Wayne Burdick" <[email protected]>
To: "Vic Rosenthal" <[email protected]>
Cc: "Floyd Sense" <[email protected]>; "Elecraft"
<[email protected]>
Sent: Tuesday, October 28, 2003 12:34 PM
Subject: [Elecraft] slow amp relays

> Vic Rosenthal wrote:
>
> > The AL800H uses an open-frame t/r relay whose pull-in time is just
too
> > slow.  You can replace the relay with a reed relay for input and a
> > vaccuum relay for output (see <http://www.somis.org/QSK922.html>)
and
> > the amp will be fast enough for full QSK if you wish.  Ameritron
also
> > makes an (expensive) PIN-diode QSK unit, but the vaccuum relay
system is
> > effective and cheap.  The 8r hold function will keep the relay
closed
> > during characters and prevent hot-switching when it opens, but
obviously
> > can't anticipate your sending!
>
> Vic,
>
> Just how slow is it? I'd like to attempt to add a bit of
preventative logic to
> the KPA100's firmware so that the KPA100 can handle this situation
without
> instantly shutting down.
>
> tnx
> Wayne
> N6KR
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