Posted by
Don Wilhelm-4 on
Oct 06, 2007; 12:46am
URL: http://elecraft.85.s1.nabble.com/New-Product-request-tp454236p454239.html
Paul,
I believe you may be making the situation overly complex. Certainly
specialized test equipment can be used to do the task you request, but
the tools are already available if you are willing to use your computer
to assist with the task - you apparently are already familiar with
Spectrogram.
The transmit passband response will be the same as the receive passband
response set for the SSB FL1 position, so the transmitted audio passband
can be properly set in receive using Spectrogram.
The SSB FL1 BFO settings are the ones used for transmit as well as
receive (when the K2 is set to receive on the FL1 filter), and when
these BFOs (FL1 LSB and USB) are properly set on receive, the same audio
passband will be transmitted - there is no transmit frequency offset
involved on SSB.
Unless your voice is unusually low or high pitched, set Spectrogram
markers at 300 and 2600 (for the 2.4 kHz OP1 filter width) and center
the receive passband between those two markers. Do that on both LSB and
USB for the FL1 filter position and the BFOs should be properly set to
transmit an audio spectrum containing energy in the 300 to 2600 Hz
range. If your voice requires content in the audio range higher or
lower than that, skew the passband (but not more than 100 Hz on the low
frequency end) so it covers the audio range that you require.
If you wish to actually look at the transmit passband using Spectrogram,
I would suggest that you use another relatively wideband receiver to
listen to the transmitted signal - connect that receiver to the computer
running Spectrogram, transmit with the K2 into a dummy load and couple
the other receiver (with a short antenna) so you receive about an S-9
signal.
For white noise, or pink noise input (or most any other kind of audio
waveform) to the K2, download the NCH Tone Generator from
http://www.nch.com.au/tonegen/index.html and use that to provide the
output from your soundcard. If you do not have 2 computers available,
download Audacity to record the output of NCH Tone Generator in WAV
format and burn that to a CD which you can play on a non-computer CD player.
There are many ways to 'skin the cat' without resorting to specialized
equipment - computer based tools abound, particularly in the audio
realm. If you have a 32 bit soundcard, you can achieve close to a 90 dB
dynamic range.
Elecraft does produce the 2T-GEN which can be used to produce a 2 tone
test signal for adjusting your SSB audio for minimum IMD. The same
setup using Spectrogram on a separate receiver will give you a good
picture of the transmitted audio spectrum.
73,
Don W3FPR
Paul Pollock wrote:
> Since I have now constructed a K1 and a K2, I can say that setting the
> K2 up for SSB is more involved than it might be for CW. To that end,
> there needs to be another Elecraft test device, to assist people to
> set up the K2. Most of what is needed is already present in individual
> tools Elecraft makes as kits. We need an item that does three(3) things:
>
> 1). A dummy load to handle at least 20-watts
> 2). A pad buffer (at the output of the dummy load) to be used to
> filter out/reduce the transmitter RF, and detect/output the audio.
> This is used as the input to a computer soundcard (for use with
> Spectrogram or other spectrum analyzer)) for transmitter bandwidth/BFO
> analysis.
> 3). A audio white-noise generator which is fed to a cable terminated
> with a 8-pin mic-plug. This would be used to source the signal which
> would be used by the entire transmission chain, finally outputting
> signal which can be bandwidth and quality analyzed for proper
> transmitter alignment.
>
> Alignment of the receiver IF/BFO is much more straight-forward and
> requires little more than a N-Gen (K2 audio output fed to computer
> soundcard). But getting the transmitter aligned to the same point as
> the receiver, and calibrating the voice response thru the SSB filter
> is nothing less than hunt-&-peck for most of us (hope the best and
> pray the fellow on the other end is forgiving <grin>).
>
> This message should be taken as a formal request for Wayne and Gary,
> and not as a huge new source of discussion. We all know this request
> is reasonable and has utility.
>
> -Paul Pollock-K2 #6148
> KD7BWB
>
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