I have experience with various Alphas including my current 8410. Their
relays *are* loud. Noise cancelling headsets can take that way down.
As to going to diodes to get rid of relay clang, that is another matter.
Though some say they never have had those diodes go bad in their Alpha,
others seem to blow them every two, three, four years. I had a QSK box
using those diodes from Ameritron that worked very well until a strike in
the neighbor's back yard trees took it out along with my fancy house
thermostats for the heat pumps and a couple of control boards in one of the
compressor units. I am still mystified by whatever path the zap got to the
QSK board (I've heard all the did-you-do-this or that rejoinders back when
it happened, tons of it).
I replaced diodes and three months later they got zapped again. It's still
on the shelf
Other than that, the QSK unit worked wonderfully. As do Alpha's diode
switched amps, until they get zapped.
The word I have (subject to verification on this subject) is that diodes
that can actually stand up to zappies, military grade stuff, are
prohibitively expensive for the cheep-skate ham market. Think of it, if
they hadn't been, Alpha would have gone to them years ago.
As to the clang, there's an easy answer to that. Sonic conduction paths for
the relay noise. In my 8410 they have the relay in a rubber mount. BUT they
have the relay leads soldered to the supporting board with stiff wire. And
the design flexible weave wire on the switched end behaves like stiff wire.
This would work if the solder didn't wick into the weave and turn it into
equivalent of stiff #10 for the purposes of sound conduction. And also this
little board is hard bolted to the chassis, which transmits the sound to
the chassis and case, which behave just like the sounding board in a
guitar, violin or grand piano.
It is easy enough to run flexible wires to the winding terminals of one of
these relays and key it. It barely makes any noise at all. The same relay
mounted to a glob of RTV on a perfboard with flexi wire to all the
connections in my 3-1000Z cannot be heard at all outside the amp with any
room noise. Perfectly quiet in the room you can hear quiet clicks when it
is keyed. Same exact relay as 8410.
But when I listen to my Sony MDR-7506 studio headphones, and keep the
volume up a little bit, which I would do anyway, the clang, and the noisy
through-the-wall air conditioner are significantly muted to the level of
the band noise, and who cares.
These days I am more concerned with wearing out the relay in the 8410, and
even in contests use the WinKey chip in my microHam u2R to keep a precise
CW speed related letter pause hang in CW operation.
HLO[fast drop]JOE[fast drop]HW[fast drop]R[fast drop]TNGS?[fast drop ...
That's 5 relay closings opposed to 44. So that should have relay last nine
times longer than pure QSK. If I start sending CQ and someone starts
replying to my prior CQ at that point, I hear him between the "CQ" and the
"TEST".
When I really want actual QSK I use the K3/KPA500 whose integration and QSK
is flawless, particularly post K3 synthesizer upgrades.
The KPA does have diodes, but I don't know why the KPA diodes seem to make
it and others don't. Maybe not stressed as bad switching into an open load,
which might be the real culprit that folks don't want to admit to.
Anyway, back to the original post, I will recommend the Sony MDR-7506. They
double as an amazing "ear piece" for my iPhone music. Used with the K3 dual
RX in diversity, the headphone clarity allows for some pretty good
between-the-ears discrimination of weak signals in the muck.
73, Guy K2AV
On Sat, Jun 18, 2016 at 4:19 PM, <wb6rse1@mac.com> wrote:
> Chuck -
>
> I’ve been very pleased with Heil ProSets for both CW and SSB.
>
> If you can, borrow the recommended models to see how you like them.
>
> What’s “best” is always going to be subjective just because there are so
> many variables.
>
> Communications frequency response vs full range.
> Over the ear or on the ear cushions.
> Built in microphone boom; dynamic or electret element.
> Mic frequency response.
> Cord as a Y vs on one side or wireless.
> Overall comfort and aural fatigue.
> Price.
> Etc.
>
>
> The question begs a second question: Amplifier QSK relay noise.
>
> My reference standard for a legal limit amp is the Alpha 87A with PIN
> diodes. The diodes are expensive vs vacuum relays that are popular with
> manufacturers. The Alpha 9500 relays could wake up the dead wearing
> earphones. A deal breaker for some.
>
> Expert Linears has a mod to quiet the stock SPE 2K-FA relays which is
> supposed to be very effective although I don’t have any first hand
> knowledge. The SPE 1.3-FA review in July 2016 says that you might want to
> use headphones when operating QSK. No mention is made of any kind of
> quieting mod having been done.
>
> The Elecraft KPA-500 amp uses inexpensive switching diodes for T/R
> switching and is as seamlessly quiet as the Alpha 87A. No doubt their legal
> limit amp that never came to market used the same design.
>
> I’d like to see manufacturers use solid state diodes vs relays as T/R
> switches. Elecraft has shown this to be a commercially viable design.
>
> 73 - Steve WB6RSE
>
>
>
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