Thanks for the comments Ron.
Ok ive just revisited my posting i didn't make it clear that I am
monitoring
my own recorded tx audio via recording with opt1 on rx/tx .
M1MGD G-QRP 11355
Elecraft K1 #1532
K2 #4785..72/73..
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Let's see if I understand. When you record your own transmitted audio, does
it sound muffled to you?
If so, how are you monitoring your audio? Is it on another receiver?
If you are playing a recorder into the K2 mic input, be careful not to
over-drive the audio input. The system will try to reduce the gain, but it
can be very easily overloaded. Also, a big impedance mis-match such as
between the low-impedance phones or speaker output of a recorder and the 1 k
mic input impedance of the K2 can cause change in the audio characteristics
of the signal.
I check my audio by listening to my own signal on a separate receiver as
generated by speaking into my microphone and recording it, then playing back
the recording. That ensures that what I'm transmitting is the same as what
I'd transmit in a QSO. The "trick" is to properly tune in your signal on the
auxiliary receiver. If you are able to zero beat a CW signal using SPOT on
your K2, you can use a similar technique to tune in your auxiliary receiver
precisely. Listen to the auxiliary receiver using headphones at a level
where you can hear your own voice comfortably when transmitting into a dummy
load with your K2. Now whistle or hum into the mic. As you adjust your
auxiliary receiver tuning, you'll hear a beat between your voice and the
received signal. Tune for zero beat. That ensures that your are precisely
tuned in on the auxiliary receiver. You want to be close to the right tuning
before doing that. Voices have very rich harmonic energy, and it's easy to
tune into a harmonic. If you hum at 500 Hz, it's easy to tune in 1 kHz off,
although it's pretty obvious when you listen to yourself talk! Get the
tuning as close as you can, then hum and listen for the beat.
Now record your signal as received. I use my computer. A tape recorder will
do FB as well.
My experience with the "standard" Elecraft OPT 1 filter is that the setting
of the BFO frequency is critical. The bandwidth of the filter is set near
the minimum for good voice intelligibility, because that give the signal the
greatest strength, or "punch". That's especially important for QRP
operators. But just a small change in the BFO frequency has a very large
effect on the intelligibility of the signal. A little one way and the signal
is 'tinny' and a bit the other and it's 'muffled'.
Try adjusting your BFO frequency to move the filter bandpass further from
the carrier. I have my filters set to roll off at about 400 Hz on the "low
end".
After I did that my audio was okay, but I eventually modified my K2 for the
wider bandwidth filter as described on the Elecraft web site. I was much
happier with the sound of my K2 after doing that on both transmit and
receive. I like to do a little A.M. Broadcast band "DX-ing" with my K2 from
time to time and, listening on headphones with my wider SSB filter, it's
hard to tell the difference between a broadcast station received on the K2
and one received on many broadcast band receivers.
Changing the bandwidth involves changing the capacitor values in the filter.
You use the same crystals. John, KI6WX, developed a couple of optional
bandwidths for the OPT 1 filter you can select by installing the correct
capacitors. The capacitor values are standard sizes. If you don't have
access to the right value caps where you are you can order SSBCAPKT from
Elecraft.
Ron AC7AC
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