[Elecraft] KX3 as a base station? Yes, because it's all relative

[Joe Subich, W4TV]

 > Does "home station" actually imply a fixed set of requirements?

No, but one would expect the minimum standard to include such things
as (separate) fixed level input and output for digital mode interfacing
particularly if the transceiver supports digital modes otherwise.

 > True, there's no separate line in/out. We will, however, be adding
 > separate gain controls for data modes.

While separate gain controls are nice, separate I/O should be a given
in a home station rig to avoid the need to plug/unplug cables - or the
need to build an outboard audio management device just to switch modes.
Even the low power IC-703 and FT-817 provide separate Line In/Line Out
connections and they've been around for what, 10 years?  Other than the
K2 and Flex radios, I haven't seen a transceiver without separate Line
in/Line Out connections since the FT-840 (20 years?) except in some
CW only trail radios.

> I also differ on some of your comments on the KX3's audio. There is
> no "lack" of a headphone amplifier. The KX3 has a headphone amp that
> is quite capable of driving any type of headphones to more volume
> than you need, at low distortion.

Perhaps I was given incorrect information by someone at Elecraft.  What
I received indicated that the headphones were being driven directly by
the DAC which had limited drive capability which might be a problem
particularly with inefficient, low impedance headphones.

I won't even repeat the issues with the speaker.

> The KX3's phase noise was recently tested a well-known third-party
> test organization. They measured -142 dBc/Hz at a 2.5 kHz spacing,
> and -145 dBc/Hz at a 20 kHz spacing. The noise was still going down
> monotonically all the way to 500 kHz (their last data point). This is
> better than almost all "home station" transceivers.

That's is good to know - congratulations.  How will that translate to
composite transmit noise spectrum?  I would absolutely hate to see a
low power radio with "home station features" be used with 100/1500W
amps and turn into a wideband noise generator like my neighbor's IC-746. 
  I realize the requirements for spectral purity are lower for
low power transceivers they should still be "good neighbors" when they
are used with amplifiers in a "home station" configuration - many of
the low power radio/inexpensive amplifier combinations are anything
but good neighbors.

73,

    ... Joe, W4TV


On 8/4/2012 3:56 PM, Wayne Burdick wrote:
> Joe Subich, W4TV wrote:
>
>> If Elecraft are marketing the KX3 as anything other than a trail radio
>> the design missed the mark by 5 km.  ... lack of headphone amplifier,
>> and lack of separate line in and line out
>> audio connections, the rig is severely lacking is the "home station"
>> department - particularly for digital (RTTY/PSK/JT65/etc.) operation.
>
> Joe,
>
> Does "home station" actually imply a fixed set of requirements? Prior to
> starting Elecraft with Eric, my entire home station was a Wilderness
> Radio Sierra transceiver (one of my earlier designs). I was quite happy
> to change bands with modules, log with a pencil, match antennas with a
> manual tuner, and key the rig with a homebrew keyer based on a Curtis
> keyer chip.
>
> Surely the KX3, with all-mode/all-band coverage, full I.F. DSP, dual
> watch, a generous user interface, attached keyer paddle, battery pack,
> ATU, roofing filters, and full remote-control command set, could be
> considered a home station -- at least for some operators.
>
> I also differ on some of your comments on the KX3's audio. There is no
> "lack" of a headphone amplifier. The KX3 has a headphone amp that is
> quite capable of driving any type of headphones to more volume than you
> need, at low distortion. This same jack can drive virtually any type of
> powered external speakers. Since the KX3 excels at stereo audio effects,
> including dual watch, I would think most operators would want to use
> dual external speakers anyway. Yes, the internal speaker is small, but
> it was never intended as the primary transducer.
>
> True, there's no separate line in/out. We will, however, be adding
> separate gain controls for data modes.
>
> Once we add the 100-W companion amp, the distinction between the KX3 and
> a much larger "home" transceiver will be further blurred.
>
>
>> ....with a SIS-570 based local oscillator and direct conversion
>> the jury is still out as to whether the phase noise/reciprocal mixing
>> performance is sufficient for use in strong signal (receive) and high
>> power (> 10W) transmit environments.  Unless SiS have improved their
>> products greatly or Wayne has some magic in his implementation, I am
>> very concerned (witness the phase noise in the XG3).
>
> Actually, the jury is in :)
>
> The XG3--a very small device--uses a CS-2100 to keep cost and current
> drain low. It has a noise floor of about -105 dBc/Hz at all offsets.
> This is appropriate for a simple RF generator.
>
> The KX3's phase noise was recently tested a well-known third-party test
> organization. They measured -142 dBc/Hz at a 2.5 kHz spacing, and -145
> dBc/Hz at a 20 kHz spacing. The noise was still going down monotonically
> all the way to 500 kHz (their last data point). This is better than
> almost all "home station" transceivers.
>
> So phase noise is not an issue.
>
> Of course a transceiver like the K3, with a superhet architecture and
> very narrow crystal filters, will outperform a zero-I.F. receiver in
> close-in dynamic range (0-2 kHz). But the KX3 is no slouch.
>
> 73,
> Wayne
> N6KR
>
>
>
>