Ignacy and All,
Everything Jim says is true, but still, the K2 can be a very good
contest transceiver.
The K2 is indeed a viable contest station, either portable or home
station - especially for CW, but a bit less so for SSB for the reasons
that Jim stated. VOX is not going to work well, so use PTT.
The normal SSB filter (OP1) - normally used as receive FL1, and always
used for SSB transmit is a good flat filter that provides a fine
response if the filters are properly aligned to place the bandpass
correctly.
The SSB FL2, FL3, FL4 filters formed using the RF Board crystal filter
are a bit 'ragged', but if properly aligned can be used successfully if
one is willing to sacrifice 'critical ears' and maintain communications
when narrowing the receive filter becomes a necessity. I would not run
a contest with those filters switched in, but would use them to narrow
the filter to eliminate QRM in the midst of a contact. That does
require the filters be optimized. The manual gives workable filter, but
are not optimum. To adjust for optimum filter, one must adjust the
filter width and the passband position using a wideband noise generator
and observing the passband position with an audio spectrum analyzer such
as Spectrogram or SpectrumLab.
For contest operating, I suggest setting the K2 SSBC parameter to 4:1,
and for normal operating set it to 3:1.
As for mic gain, there are only 3 settings. With an electret type
microphone such as the Elecraft MH2/MH4 or the ProSet-K2 (or Proset-iC),
an SSBA setting of 1 is normally adequate.
For dynamic microphones, a setting of SSBA 2 is normally adequate except
for the more recent Heil elements such as the HC-6 which may want an
SSBA of 3 to produce adequate output.
Jim's mod for reduced low frequency response of the KSB2 involves
replacing 2 capacitors. C34 should be replaced with a 0.47uF capacitor
and C32 replaced with a capacitor in the range of .0033uF to .005uF. I
normally use .0047 with success.
The KX2/KX3/K3/K3S has both transmit equalizers, plus better compression
and mic gain handling, but a K2 with properly aligned filters is
entirely usable for contesting and is better than a lot of other amateur
rigs out there being used in a contest - except for the hard-core
contesters who insist on having only the 'best' transceivers.
73,
Don W3FPR
On 2/27/2019 3:19 PM, Jim Brown wrote:
On 2/27/2019 5:33 AM, Ignacy wrote:
K3 has an excellent speech processor with equalization. K2 has compressor
and sounds OK but not dramatic with good microphone. IMHO KX3
processor is
not too efficient and even below K2. But KX3 has an equalizer allowing
any
mic to sound good.
Yes. The K2 is compromised in several ways on SSB. First, the audio
stage is low on gain, so a mic doesn't hit the peak limiter hard enough
to do much. Second, the audio chain has a flat response, so low
frequency components of the voice waste transmitter power. I did a mod
for mine, which W3FPR knows about, that provides some low end rolloff
and increases mic gain by about 6dB. That helped, but it's nowhere near
what the K3 and KX3 are capable of.
Second, the narrow settings of the receive filter are produced by
stagger-tuning of the multi-stage CW filter, and their combined response
looks like a side view of the Rocky Mountains, so the accompanying phase
shift distorts the RX audio enough that using the narrow settings often
degrades speech intelligibility (that is, it makes voices HARDER to
understand).
73, Jim K9YC
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