> I have to comment on Carl's thread. I have not been able to get
> through to them lately, either. My bone with them is that their Quality
> Control is awful, almost non-existent. Since I have started messing with
> QSK, I have bought two QSK-5, stand alone units, from them.
I recently purchased a used QSK-5 to use with an SPE solid-state amp. The
electrical concept of the QSK-5 is quite good although mechanically, it can
use some improvements.
The low-level SO-239 panel connectors use the aluminum cabinet exclusively
for the RF return. I detest construction practices where only the case and
hardware are used to complete return paths. Same issue with their RCA
keying connectors. The panel is used for the DC returns. If the KEY 2 jack
becomes slightly loose -- and looses contact against the cabinet, the QSK-5
will hot-switch - guaranteed.
To deal with these issues, I installed toothed solder lugs on the SO-239 and
RCA jacks. On the RF connectors, I then brought individual leads from each
jack directly back to circuit ground. On the RCA connectors, I grouped the
returns together with #20 buss bar back to circuit ground. At least now,
the QSK-5connections are solid.
Finally, I replaced the line cord with a detachable IEC type with
combination RFI/EMI filter. I really hate having to find the end of an AC
cable when it's time to perform some maintenance on a piece of equipment.
The IEC cord makes it easy to pull the unit from the desktop.
I did find it odd that the QSK-5 makes a "ticking" sound when keying - with
or without RF applied. Although a frame signal relay is used as part of the
unit's bypass system, the relays are not the root cause. The tick is caused
by the moderately-high switching voltage being applied to the T/R diodes. I
haven't taken a good look at that part of the schematic, but I'm curious as
to why such high voltage (400V) is needed for switching? Fifteen years ago,
I designed a PIN diode T/R switch using Microsemi UM2110 types and the
diodes are fully biased with low voltage and moderate levels of forward
current. The UM2110 is optimized for HF switching and easily handles 1.5KW
with a reverse voltage rating of 1KV.
Paul, W9AC
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