D104 use with k2/100

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D104 use with k2/100

linda doyle
has anyone been sucessful with using the D104 xtal element with the k2/100,I'm wondering if the preamp will sucessfully make the transformation from high impedence to low impedence that the k2/100 needs would appreciate any input..Am Presently using the k2 proset but my audio reports are less than flattering..John K1GUN
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Re: D104 use with k2/100

Don Nesbitt
I use an xtal element D-104 with the built in pre-amp in the bottom of the
stand all the time with my K2 and get great audio reports.  Just be sure to
keep the gain on the mic amp low or you will overdrive the input to the K2.
If you don't have the stand with the amplifier in it you could easily build
a one transistor amp that would do the job - see the Elecraft web site.  If
you are going to go straight in to the K2 without the aid of an external
pre-amp, I'd recommend a "fix" from the "old days" of placing a 200 K or
larger (up to 2 meg) resistor in series with the hot lead of the mic.  The
D-104 was designed to look into the grid of a vacuum tube (remember those?)
and that is generally very high impedance.  The resistor in series with the
hot lead will allow the audio response to develop some low frequencies that
are greatly attenuated when you run the high impedance mic into a very low
impedance input.  If you go the resistor route, the audio drive to the K2
input will likely be marginal.  Some have used a small step-up transformer
instead with some success.  All in all, properly terminated, the D-104 is
still very hard to beat for great audio quality and punch!  YMMV Have fun,
73 es gud dx  --don n4hh K2/100 #2028 KAT100, KX1 #243, etc, etc.

----- Original Message -----
From: "linda doyle" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, August 04, 2004 7:33 AM
Subject: [Elecraft] D104 use with k2/100


has anyone been sucessful with using the D104 xtal element with the
k2/100,I'm wondering if the preamp will sucessfully make the transformation
from high impedence to low impedence that the k2/100 needs would appreciate
any input..Am Presently using the k2 proset but my audio reports are less
than flattering..John K1GUN
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Re: KSB2 Transmit Audio BFO Optimization

Eric Swartz - WA6HHQ
Administrator
In reply to this post by linda doyle
you wrote:
 > Am Presently using the k2 proset but my audio reports are less than
 > flattering ..John K1GUN

Hi John,

If are getting poor audio reports with the Proset-K2 this indicates that your
transmit BFO settings (BF1t) for both USB and LSB are not optimally adjusted.
The default BF1t settings in the KSB2 manual are just starting points and BF1t
  should be adjusted for best transmit audio for both USB and LSB. Shifting
BF1t will move your transmit passband up or down, allowing you to emphasize
your natural voice frequency characteristics. +/- 100 to 200 Hz in these
settings can make a huge difference in your transmit audio quality.

This procedure is detailed in the last part of the KSB2 manual and I've pasted
the text below:.
---
SSB Transmit BFO Optimization (Important)

When you transmit using SSB mode, the fixed filter on the SSB adapter is
always used (OP1). The way your voice sounds to other stations depends on the
BFO settings for this filter (i.e., BF1 in CAL FIL). Table 3 provides BF1
values for LSB and USB based on the measured crystal filter frequency (from
page 10). However, you may have to experiment with these settings, adjusting
them slightly to obtain best voice quality. You can use another ham-band
receiver, or ask a nearby station listen to your signal as you vary BF1. Use
CAL FIL, moving the BFO as much as +/- 200 Hz from the frequencies shown in
Table 3. Start with lower sideband, then upper. Moving the BFO too close to
the filter will worsen carrier rejection, so be sure to re-check carrier
amplitude whenever you change the BFO setting.

Note: The BFO settings for LSB and USB are swapped on 15, 12 and 10 meters due
to the K2's frequency mixing scheme. If you use 17 m or below for making BFO
changes, the following rules apply: LSB: moving the LSB BFO lower in frequency
will raise the voice pitch and improve carrier rejection. USB: moving the USB
BFO higher in frequency will raise the voice pitch and improve carrier rejection.
---

73, Eric   WA6HHQ
Elecraft

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