John:
I have a Proset (from Elecraft) with the included Kenwood adapter and it
works fine with the K3. I have tested it on the front panel with the
adapter and the rear panel without it. I've used both vox and an external
footswitch.
I think there has been some confusion about the bias pin. I believe that
the Proset IC element needs the bias applied to the microphone lead itself.
The K3 does that internally when you set the menu entry turn the bias on.
The additional bias pin on the front panel connector is for mics that have a
separate bias lead. I don't believe that pin is connected in the Proset
adapter, though I haven't rung it out. There is no need for it since the DC
bias is already present on the mic lead.
My understanding of bias on an electret mic is that DC must be applied
directly to the mic element for it to work, and the audio to the mic amp in
the rig is connected to it via a blocking capacitor. Some mics have the
blocking capacitor built in, so there are separate pins for the audio and
the bias on the connector. The Proset does not have the capacitor in it, so
the K3 provides it internally. That is why there is a mono connector on
the Proset mic lead - there is no separate pin for the bias. The bias pin
on the K3 mic connector is only needed for mics with the blocking capacitor
built it.
Some recent K3's (including mine) used a new batch of front panel boards
which were missing a ground connection to the capacitors filtering the bias
to this internal capacitor. The symptom that I experienced was that the mic
audio on the front panel (only) did not work, and if vox was enabled, the
transmitter would key and remain keyed unless the mic gain or the vox gain
was reduced to zero. The rear panel connections worked fine. A few hours
after reporting this to Elecraft support, I was sent a description of the
problem and a recommended fix (they had just discovered it themselves). It
involved adding a small wire to the front panel to provide the ground
connection for these caps. It was a very easy fix and worked perfectly. I
personally am aware of two other folks that had the same problem and have
successfully applied the fix. I don't know how many radios were affected,
but we all had serial numbers around 730 or so as I recall (mine is 728).
My understanding is the Elecraft is now applying this fix at the factory, so
it was probably just a small number of radios that were affected.
The bottom line is, if your Proset with its adapter is not working on the K3
front panel connection, then something is wrong (either the problem
described above or something else) and you should contact Elecraft support.
I've only ever dealt with them on this one issue and they are remarkably
responsive and helpful.
73 and have fun!
Rick
AI1V
K3 #728
John Reiser-3 wrote:
I have a question for those who have used the Elecraft/Heil Proset with
their K3.
The description on the Elecraft web site says: Includes plug adaptor
wired for Elecraft K2 pin out. I imagine that means it comes with an
extension cable that accepts the 1/4' and 1/8 audio plugs shown in the
picture and has an 8-pin Foster and 1/8 stereo audio plug at the other
end. Is that correct?
How do you like it with the K3? Are there any issues?
Many thanks and 73,
John, W2GW
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