Kicad files #2
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Hi, good idea! Have added a parts layout here: https://github.com/dawsonjon/PicoRX/blob/master/PCB/pico_rx/component_layout.pdf Not quite sure which version of Kicad I used originally, but I'm using Kicad7 to work on them and haven't had any issues. |
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I thank you for the PDF!!! That will help a great deal...
I have Kicad 8.0 and couldn't get a layout. I then sent your files to my
boardhouse (in Iowa, that builds boards for my business (trying to retire))
and he couldn't read them either. Well, your PDF layout will be more than
adequate!
I had 5 main board pcb's made. If you have a friend in the USA that
needs one, let me know and I'll put it in an envelope.....
CHeers,
Jim W0CHL
…On Fri, Mar 15, 2024 at 2:04 PM dawsonjon ***@***.***> wrote:
Hi, good idea! Have added a parts layout here:
https://github.com/dawsonjon/PicoRX/blob/master/PCB/pico_rx/component_layout.pdf
Not quite sure which version of Kicad I used originally, but I'm using
Kicad7 to work on them and haven't had any issues.
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It's alive!! I just turned it on and it seems to work!
I found I had no Ferrite 0805, so I replaced them with 10uH 470 MOHM
inductors.
We have guests coming over soon, so I can't test more...
Thanks for a nice design!
Jim W0CHL
…On Fri, Mar 15, 2024 at 2:04 PM dawsonjon ***@***.***> wrote:
Hi, good idea! Have added a parts layout here:
https://github.com/dawsonjon/PicoRX/blob/master/PCB/pico_rx/component_layout.pdf
Not quite sure which version of Kicad I used originally, but I'm using
Kicad7 to work on them and haven't had any issues.
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Hi Jim, Many Thanks |
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Hi,
Playing more with you PICO RX, I found the LTC6226 preamp was not working
correctly: traced down to the two voltage divider resistors, one of which
seems to be the wrong value. I relapsed with 1% 10K's and that problem
went away.
It seems to work , although not overly sensitive. I measured each cap in
the low pass filter and used 2% inductors. I have an "ever present" TICK
when there is now signal present. I know it's from the SSD1306 charge
pump: if you remove the display, the tick goes away. Maybe you have a
display that doesn't have that issue? If so, let me know where you bought
it...
So I'm still happy, but work on my part, still has to be done.
Thanks again,
Jim W0CHL
…On Sun, Mar 17, 2024 at 4:11 AM dawsonjon ***@***.***> wrote:
Hi Jim,
Very pleased to hear that you have got it running! Best of luck with your
testing!
Many Thanks
Jon 2E0GXA
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Only one issue remains: receiving CW on the SSB portion of 20 meter band. (listening 14.237mHz, hearing 14.037) It seems to be a spur from the bottom of the 20 meter band. Otherwise the radio works well! |
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Hi, That sounds similar to this issue: dawsonjon/PicoRX#3. There are two possible causes. One possibility is images, caused by an imbalance in I and Q, in the linked example, the Q channel wasn't working at all. You could check for this by comparing the signal level on the I and Q input to the ADC, they should be about equal. If this is the problem, you would expect the signals to have the same signal strength at either frequency. If this does turn out to be an imbalance in the I/Q channel, I would be interested to know which IC you were using in the Tayloe detector, I suspect that the root cause was a signal integrity issue and I am considering revising the design to include some termination. The other possibility is aliasing which is a limitation in the current design. The ADC in the pi-pico doesn't have any anti-aliasing filters, and we are relying on the Tayloe detector to remove out of band signals. The Tayloe detector is effectively a second order low pass filter so only has a roll-off of about 12dB/octave. This means that a signal close to, but outside the 250kHz bandwidth would only be attenuated by a couple of S-points. Thanks very much for your feedback on your build, its been very useful to get another perspective :-) Kind regards |
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I'm using a SN74CBT3253D. In trying to probe for I & Q A/D input, (pin
31 & 32) I see a great deal of 140 kHz signal when I just hook up the
ground of the scope to the PICO RX. It's hard to tell what the actual
signal is. I then carefully resoldered and checked the components around
the LTC6227 op amp. With the antenna input grounded, I seem to have a
great deal of "birdies" present.
Can you explain the software? How does recall work? I guess you need to
tell me how to store frequencies for recall? It doesn't remember that last
frequency you were on?
One more thing: If I feed exactly 5 volts into the unit (drawing .022a),
the A/D reads 9.9 volts at -61C along with the SSD1306 charge pump noise
(ticking when no signal).. BUT if I feed only 4.75 volts in (at .038a) the
"tick sound" is not present! The voltage still reads 9.9 v and -59C.....
Ideas on that issue?
You privately email me if you want just read my bio on QRZ.com. My email
is at the end.
Thanks,
Jim W0CHL
…On Mon, Mar 18, 2024 at 1:35 PM dawsonjon ***@***.***> wrote:
Hi,
That sounds similar to this issue: dawsonjon/PicoRX#3
<dawsonjon/PicoRX#3>. There are two possible
causes.
One possibility is images, caused by an imbalance in I and Q, in the
linked example, the Q channel wasn't working at all. You could check for
this by comparing the signal level on the I and Q input to the ADC, they
should be about equal. If this is the problem, you would expect the signals
to have the same signal strength at either frequency.
If this does turn out to be an imbalance in the I/Q channel, I would be
interested to know which IC you were using in the Tayloe detector, I
suspect that the root cause was a signal integrity issue and I am
considering revising the design to include some termination.
The other possibility is aliasing which is a limitation in the current
design. The ADC in the pi-pico doesn't have any anti-aliasing filters, and
we are relying on the Tayloe detector to remove out of band signals. The
Tayloe detector is effectively a second order low pass filter so only has a
roll-off of about 12dB/octave. This means that a signal close to, but
outside the 250kHz bandwidth would only be attenuated by a couple of
S-points.
Thanks very much for your feedback on your build, its been very useful to
get another perspective :-)
Kind regards
Jon
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I have the latest Kicad files but can't seem to open your files. What version did you use? A PDF of parts lay out might be really nice!
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