Bill raises a good point that I should've mentioned and which catches me up
occasionally.
You have to take the DSP out of the picture by telling the K3 that the
bandwidth of your 2.7Khz filter is wider. Unless you do that, you'll be
looking at the dsp filter and not the xtal filter, and you'll n
Barry N1EU wrote:
>
> Bill, I think the 2.9Khz bandwidth measurements for that filter were taken
> at r.f. - for whatever reason, that bandwidth is not translating into a.f.
> - I've seen a.f. measurements done on about 5 samples of the 2.7Khz filter
> and they all run several hundred hertz nar
I figured out the bandwidth issue at a.f. - it's due to low pass filtering
inherent in the current dsp code. If you shift the center freq up from
default 1.6Khz to 1.75Khz, you will indeed see 2.9Khz a.f. bandwidth at the
-6dB points. You'll lose a bit of the low end response however.
73,
Barry
I've received several inquiries about the software used - as I indicated,
it's called "SpectraPlus". Unfortunately it's not freebie software.
73,
Barry N1EU
Barry N1EU wrote:
>
> My SpectraPlus plots are viewable at
> http://www.n1eu.com/images/K3_2700usb_lsb.gif
>
--
View this message i
Bill, I think the 2.9Khz bandwidth measurements for that filter were taken at
r.f. - for whatever reason, that bandwidth is not translating into a.f. -
I've seen a.f. measurements done on about 5 samples of the 2.7Khz filter and
they all run several hundred hertz narrower than the 2.9Khz figure.
Wow, that is dramatically different then what I am getting. Here is the
response I am getting using a bandwidth setting of 0 to 6000:
http://mysite.verizon.net/respk8uz/k3/id1.html
I am open to any suggestions, I have tried changing FL FRQ and
re-calibrating the synthesizer.
73,
John, KD8K
My SpectraPlus plots are viewable at
http://www.n1eu.com/images/K3_2700usb_lsb.gif
LSB is the acqua trace and USB yellow
As you can see, they're very close and both fairly flat in the passband. RX
EQ was zeroed for the measurements and config menu FL FRQ setting was
adjusted for best match be
Stewart G3RXQ wrote:
>
>
> On USB the trace was substantially flat with the -3dB points at
> 430Hz and 2.77KHz. Not too bad and could probably be improved by
> moving the carrier offset frequency.
>
>
One more point. The -3 dB bandwidth you are reporting is only 2.34 kHz on a
filter that i
Stewart G3RXQ wrote:
>
> Having run a quick test switching between USB and LSB on a quiet
> band 10m, I noticed an appreciable difference in the tone of the
> noise spectrum.
>
> I dug out my noise generator and examined the audio response using
> Spectrum Lab. I set the DSP B/W to the maximum
>On USB the trace was substantially flat with the -3dB points at 430Hz
and 2.77KHz. Not too bad >and could probably be improved by moving the
carrier offset frequency.
>On LSB, however the trace was far from flat having a slope from audio
LF to HF of about 6dB. >Not very good at all...
>I wonde
That is very useful information Stuart. As a VHF operator I do not care about
the LSB response, but I do care very much about USB.
I think for most SSB use the 5 pole filter will be fine. SSB operating is
not like CW, filter shape factor is less important as you can't operate
within a filter band
Stewart G3RXQ wrote:
>
> On USB the trace was substantially flat with the -3dB points at
> 430Hz and 2.77KHz. Not too bad and could probably be improved by
> moving the carrier offset frequency.
>
> On LSB, however the trace was far from flat having a slope from
> audio LF to HF of about 6dB.
Hi Stewart,
Although I have not ran all the tests you did, I also noticed that there
is a significant difference in tone response between LSB and USB. I also
tried adjusting FL FRQ with about the same results as you got. My 5
pole 2.7 filter does not seem to have a very flat response. I have
Having run a quick test switching between USB and LSB on a quiet
band 10m, I noticed an appreciable difference in the tone of the
noise spectrum.
I dug out my noise generator and examined the audio response using
Spectrum Lab. I set the DSP B/W to the maximum as what I wanted to
see was the 2.7KHz
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