[Elecraft] Elecraft QSK

[Guy Olinger K2AV]

I've lost four vacuum relays in three different amps. All the failures
occurred in a contest.

#$%**&^@!))(#

Why was that?  Easy to see after cooling down and some minor reflection:

99% of my QSK is in contests because without CW traffic nets, that is the
only place I need it. Which further means that 99.95% of the relay closures
occurred in contests while I was still running amps running QSK. So what
does that do to the odds of failure of the relay in a contest?

Having an intelligent speed sensitive word spaced PTT rail, from the WinKey
chip that knows when the string is actually starting and ending, means the
amp clicks on at the beginning of the logger-generated character stream
passed on by WinKey and clicks off at the end and there is never any
hot-switching.

I get to decide why I don't want to replace those relays based on my own
reasons:

Losing an amp in the middle of a great run in a contest p***es me off. Why
in the middle of a great run? Where *else* would you expect to see the
longest most intense QSK use of a T/R switching relay? The least amount of
cooling off time matched with maximum heat stress?

I can't throw around 80 pound things any more. I have to get one of the
local grandsons or great nephews in for an evening to horse it out of the
operating position for me, lug it to the workbench and then return it. Just
too much work for my back. If I drop it I could really badly hurt myself. I
have seen elder fellows in silly accidents like that turn an active life
into a years-shortened bed-ridden one.

And take risks to prove what? Win an argument about the QSK contest
life-span of a Jennings vacuum relay?

I hear very different stories than you put forward about the Alpha pin
diodes. Congrats on on your pin diode success. Couple of fellas I know/knew
had the same set of 8874's in their Alpha 76A's for the entire couple
decades they owned them. But I have no basis to call their experience
typical either.

As to the switching diodes, as I hear rumors, the availability of less
expensive and more reliable diodes for switching is but one of the reasons
for the KPA500 power break at 500 watts instead of 1500. Those kinds of
diodes were in my failed Ameritron QSK-5 box that I used with my Ameritron
AL-1200. After the third diode blowout failure in the QSK-5, I gave up on
it.

It became clear that I was going to have to adjust everything to favor not
blowing the QSK-5 diodes.

So way back, W2CS and I decided to have an amp mod party and built a
then-new AG6K QSK board into four of our amps. Interesting, the RJ1A style
vacuum relay that wound up in W2CS' SB220 has lasted a decade still in
service while a specific few RJ1A style relays in contest use on the same
Dick Measures board did not made it for a year. As best as I could tell,
the relay closure time goes long as the relay gets heated up and the
resultant hot switching does the rest. It was clearly not the AG6K boards.

I have a KPA500 and it is always used with my KAT500 which is preset for
the band. It is my never-worry-about-incoming-SWR run up and down the band
QSK S&P amp/tuner for 160 and 80. I have not forgotten the lessons from the
QSK-5. On 160 the KAT can take the L/FCP up to 1925 and probably higher.

Running the K3 QSK, hearing in between the dits on an RX antenna, and the
8410 T/R on the WinKey intelligent word space bridging PTT, there's just no
good reason anymore to flagellate the 8410's T/R relay. Best of the fast
and best of the slow at the same time.

73, Guy K2AV

On Tue, Feb 28, 2017 at 6:16 PM <wb6rse1 at mac.com> wrote:

> The Elecraft KPA500 silent QSK is achieved without expensive PIN diodes
> but rather with relatively inexpensive switching diodes. I’ll guess that
> the 1500 watt Elecraft prototype amp of some years ago used a similar
> inexpensive, silent design.
>
> Avoiding QSK should be because of operator preference not because of fear
> of relay failure. In the case of operating non-QSK, it’s vital for the
> operator to keep calls short and not be caught in a cycle of doubling with
> the DX that’s heard all too often.
>
> My Alpha 87A of 17 years or so has never had a PIN diode failure. When the
> 87A was first introduced there were indeed PIN diode failures. This was
> attributed to a bad batch (or batches?) of PIN diodes. Subsequent runs of
> 87A's ceased to exhibit PIN diode failures. Yet the urban legend persists
> that 87A’s should be avoided because of the PIN diodes - which are
> expensive to replace.
>
> The real question is why amplifier manufacturers continue to use vacuum
> relays when inexpensive switching diodes can do the job. Thank you Elecraft.
>
> 73 - Steve WB6RSE
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