[Elecraft] K2: Various Receive Problems

[Guy Olinger K2AV]

Just one of many differences between analog and digital radios.

Since radios' frequency generation schemes have become more accurate,
most casual SSB operators will settle on half or integer kHz
frequencies.  I have the coarse adjustment on my K3 set for 1/2 kHz
steps, which makes it possible to scan a band with the tuning know
very quickly.  Except during contests, almost all signals will be
perfectly tuned as I scan across.  It is an observed fact that those
who tune to these settings want their rigs to be exactly on those
frequencies.

Many of us have decades of analog radio use before we laid hands on a
radio with digital features.  With a little research in the reflector
archives there is a steady stream of posts asking whether some
artifact of digital processing is normal.  Half-century old artifacts
of analog processing are considered "normal".

The K2 is a half-way-ish merge between a pure analog radio and the K3.
 My K2 became more digital when I added the DSP option.

We already have radios that go digital immediately after RF
amplification, almost at the very front end and whose functions are
accomplished in a program running on a PC.  The Flex transceivers are
an example of that.

There has been a lot of energy spent making a digital radio behave
analog, because for the most part "intuitive" is also analog.

If you analyze the K3 in detail, you will find many more digital
"isms" that have been specifically designed/disguised to mimmick
analog behavior, some of which are debatably not needed, but whose
analog-reflective presence would simply be a stumbling block to most
operators' now unconscious and instinctive expectations of how a radio
functions.

One item of such technical interest in the K3 is the RF gain, which
really only provides an advice number to the main K3 CPU, which is
combined with other considerations to control the gain of an 8 MHz IF
amplifier just ahead of the 2nd mixer driving the digital to analog
converter.  The only real control of RF gain in the RX is the PRE and
ATT controls, which don't directly control a circuit either.  Not
having an RF gain control likely would have been a human factors
nightmare, however valid that tactic may have been technically.

Enjoy the digital journey and 73,

Guy.

On Sun, Jul 11, 2010 at 9:13 AM, Jon Perelstein <jperelst at yahoo.com> wrote:
> This is an update to a post I made in Nov 2008.  I've received a fair number
> of off-board emails over the past 1-1/2 yrs asking me about the problem and
> solution, so I figure I'll post the solution and save others from some
> embarrassment.
>
> My original problem was described as follows:
>
>
>>>2. On receive, stations are either there or not there.
>
>>>In this case, if I hear a signal, I hear it at the same volume as I tune
> across the signal's bandwidth.  The perceived signal strength simply does
> not change.
>
>>>Along with this, there is no interference from adjacent signals.  I'm
> always hearing the strongest station and only the strongest station at
> whatever spot that my VFO is tuned to.
>
>>>3.  As I tune across a CW station's signal, there is no change in audio
> frequency.