[Elecraft] KX1 keying and audio artifacts vs. K1

[Phil Wheeler]

Looks like we may get some "Builder's Resources" of the KX1 afterall  :-)

73, Phil

Wayne Burdick wrote:

>I've had a few questions on the topic of audio keying artifacts from prospective
>KX1 builders.
>
>The KX1 is nearly identical in its keying and audio characteristics to the K1.
>Both use audio-derived AGC and simple muting circuitry, and thus exhibit very
>slight keying artifacts. These are unavoidable without the addition of a lot
>more components in the audio stages. But as the rig's designer and first
>extensive user, I tried to minimize parts count (so it would fit in the box and
>be easy to build) while making it pleasant to use.
>
>There are certain conditions that can make things worse. The most obvious is
>your choice of headphones. If they have a lot of bass (low-pitch sentivity),
>you'll hear more artifacts. The effect can be lessened by using 12 to 18 k at
>R32 rather than 22 k. This resistor is on the bottom of the board and is
>relatively easy to change--you can even try paralleling other resistors to
>determine the ideal value.
>
>Other factors that contribute to keying artifacts are listed below, with
>possible ways to reduce them. All of this advice applies equally to the K1 and
>similar rigs.
>
>1. Band noise
>
>  If you have very strong QRN or QRM on frequency, reducing the RF GAIN can help.
>
>2. Filter bandwidth 
>
>  Tigtening the filter during CW use can also help. Experiment with different settings.
>
>3. Battery voltage 
>
>  If the battery voltage drops too low, the voltage regulators' output voltage
>can drop, inducing current or voltage spikes into low-level stages. Recharge or
>replace the batteries in this case.
>
>4. High SWR
>
>  This can cause RFI or ground loops that may cause clicks or thumps. In some
>cases RF can couple directly into the headphone cable; keep it away from the
>antenna. Improving your SWR, adding more ground radials, or using a balun may
>also help.
>
>5. Excessive transmit current
>
>  This can also cause ground loops, or impulses fed back from the DC supply into
>low-level stages. The usual reason for excessive current is working into a very
>low-Z load; check your SWR. High current can also lead to a drop in battery
>voltage (see above).
>
>73,
>Wayne
>N6KR
>
>
>  
>


--- StripMime Report -- processed MIME parts ---
multipart/alternative
  text/plain (text body -- kept)
  text/html
The reason this message is shown is because the post was in HTML
or had an attachment.  Attachments are not allowed.  To learn how
to post in Plain-Text go to: http://www.expita.com/nomime.html  ---