Interesting argument.
Presuming that the case is all encompassing, then in the theoretical sense, the currents must flow on the outside of the case. ?Due to RF skin depth those currents won¡¯t be very deep. I¡¯m not sure exactly how deep. ? ? ( ? I suspect physical reality differs slightly due to imperfection)
However, the typical view of the conductive faraday cage is that there won¡¯t be currents on the inside surface and therefore there can be no potential differences between one point on the inside surface and another. ? ? ?
I had never really thought about that before. ? RF currents have a skin depth. ? I would encourage debaters to address how this electromagnetic theory applies to their position.
Gordon
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On Jul 11, 2021, at 14:41, gareth.paley@... wrote:
?I'd agree with it coming through the mike cable. Just added this electret fist mic from Amazon to mine (??) which doesn't appear to have a shielded cable. This LCD screen became corrupted on speech peaks and sometimes locked in TX which didn't happen with an electret element soldered directly to a mic plug. I'm running an end fed half wave on 20m but there's an RF choke on the coax just before it enters the shack which should block any RF, never-the-less RF was getting in through because as soon as I put a 22nF cap across the PTT and ground pins on the back of the mic socket it cured it. I seem to remember this being pretty standard practice even on CB's and the like. M0WWS
<Screenshot 2021-07-11 192944.jpg>
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I'd agree with it coming through the mike cable. Just added this electret fist mic from Amazon to mine (??) which doesn't appear to have a shielded cable. This LCD screen became corrupted on speech peaks and sometimes locked in TX which didn't happen with an electret element soldered directly to a mic plug. I'm running an end fed half wave on 20m but there's an RF choke on the coax just before it enters the shack which should block any RF, never-the-less RF was getting in through because as soon as I put a 22nF cap across the PTT and ground pins on the back of the mic socket it cured it. I seem to remember this being pretty standard practice even on CB's and the like.
M0WWS
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Thanks! Got to the menu at long last. Assigned the straight key and am in business. Thank you so very much!
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On Jul 10, 2021, at 6:48 PM, Evan Hand <elhandjr@...> wrote:
?Don,
To get to the v6 menu you press and hold in the encoder for 10 seconds or so until the settings menu comes up.? You then use the encoder to select the CW Keyer and then press the encoder to open the choices.? Turn the encoder again until the type of key is displayed that you want.? Press the encoder one more time and it will be set.? Rotate to Exit and then press the encoder again.
I would suggest taking Curt up on his offer to help with the antenna.
Hope this helps.
73
Evan
AC9TU
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I'd tend to mostly agree with Max.
With DC and low frequency AC, and sometimes at RF, grounding with individual
wires or traces from each circuit to a single point often works best, as KF6VB says.
Otherwise, if two circuits share a ground path, the E=I*R losses of ground currents
from one circuit can be injected into the local ground for an unrelated circuit.
In the case of RF, there is a conflicting requirement of preventing unwanted radio signals
from getting into those ground wires.? These unwanted signals might be from an external
source (such as an automotive ignition system), this is best addressed by grounding each
outside connector where it enters the metal box, the metal box forming?
a Faraday cage around all the electronics.
Sometimes we want to avoid having our rig generate unwanted radio signals that might?
float across the room and get into other gear.? Again, this is addressed with a Faraday cage
around the entire rig, connectors grounded where they enter the cage.
Sometimes we want to avoid having signals radiated from one circuit in the rig getting
received by some other part of the rig.? This is why ham gear is often built as a bunch?
of little metal boxes inside the big external chassis.
Think of this as a chassis full of little transmitters and receivers that must be kept
from talking to each other.
Between single point grounding vs Faraday cage,? it is not always obvious which is best.
Grounding can be a black art, where you just try stuff and see what works
under the constraints of cost and time.
In the large digital designs I have done, it was generally best to just use a multilayer board
with a solid ground plane across the entire design.? Only in special cases was it?
found necessary to cut small islands into that ground plane for especially sensitive analog parts.
With a solid sheet of copper, the E=I*R losses are very low, and unwanted ground return voltages
are quite small.
This is what has been done with the uBitx main board, it's cheap and generally works just fine.
In some cases a good Faraday cage (metal chassis) around the uBitx will help, but most
of us don't have strong RF sources in the vicinity that would require such construction.
The uBitx does have some trouble with signals from one part getting into the other (perhaps the
reason for some residual transmitted carrier, and the power amp might inject some crap into
the IF chain),?but it seems to work well enough.
We might see less noise in the receiver if the ground return from the Raduino
was routed back to the main power connector coming into the uBitx chassis.? However, now the three
clocks out of the Raduino might have power supply noise on their nearby ground returns, so it's a tradeoff.
I'm guessing that for the Raduino, it's best to just make sure all those grounds (mostly the power ground and
clock signal grounds, the digital control signals into the uBitx main board might also be of concern)
are well connected to the main uBitx ground plane.? This is how it is currently implemented.
Jerry, KE7ER
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On Thu, Jul 8, 2021 at 11:54 AM, jerry@... wrote:
On 2021-07-08 11:47, Max via groups.io wrote:
Sounds like rf maybe coming in through the mike cable. The bigger
problem is the fact that none of the jacks (mic, keyer, antenna, etc.)
are grounded to the case BEFORE entering the radio. AS is, I'm not
sure if the case does much shielding at all. Sorry to say it, but this
part is a bad design!
** I disagree. Vehemently. Connectors should NOT be individually grounded
to the case. The case should be grounded to the ground plane in one spot,
and one spot only.
If you ground the case in multiple places, you risk causing RF currents
to flow through it. This can cause the case to act as an antenna, rather than
as a shield. For low level audio, it can cause "ground loops". Same deal.
- Jerry KF6VB
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switch off the keyer?!?
Am 10.07.2021 um 20:08 schrieb Don Carter:
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When I plug in a straight key, my uBITX transmits a series of dots as long as the key is plugged in. How do I get the reg to properly see a straight key?
KD7QW Seattle
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Re: Interfere local Broadcasting radio station
Maybe sometimes there is a nuance between agc and avc from the tube aka valve days. Its rarely as easy as it sounds. In a modern receiver like the ubitx, gain is minimized until after the xtal filter. Then there is a opportunity to provide gain control using a complex circuit, or merely forgo it completely and let the operator use the volume control. It works decently. The bidirectional amplifier makes implementing IF agc a bit more complex, but it could be done. Most ubitx solutions major on implementing agc from the audio stage, whether the actual attenuation occurs at audio or near the front of the receiver. I find that a partial agc helps when tuning across a band. Respecting we have many languages on the planet, the debate among us English speakers whether to call this audio agc or avc seems one of style or dialect. Maybe like elevator or lift. Enjoy tickling ions with your silicon or thermions.
Curt wb8yyy?
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Hi Ashar,
I succeeded in building the sbitx software from your repository
on a RasPi-Zero on a recent/fresh copy of Raspberry Pi OS.??
The building went rather smoothly and had no errors but took like
forever ... (especially for the fftw library).
I also modified a little RasPi Hat that I made for a previous
project (see picture, the RasPi-Zero itself is somehow hidden
under the Hat). Nothing fancy, just a WM8731 connected to the
40pin connector with its I2S and I2C, the latter also being
connected to a Chinese Si5351 module.? This little Hat has been
hacked several times over the past years, this time a 12.288MHz
crystal and a Si5351 module were added.? It is quite close to your
digital board concept, I think, save for the small series
resistors in the digital lines.?
When booting the WM8731 seems to be initialized somehow (the
analog in/outputs come to 1.6V), when subsequently starting the
sbitx application the I2S comes alive at 96ks/s.? However no sound
at the output save for a faint hum that seems to follow the volume
setting, see picture of the gui.
Obviously something is very wrong, even if there is no signal at
the input sbitx sees a rather strong white noise signal (according
to the spectrum).? When injecting a 25kHz sine at the ADC, a small
peak (and harmonics) is to be seen on the spectrum, however
nothing at the audio output (I expected a 1kHz tone).
A subsequent test with the alsa applications such as
"speaker-test" were unsuccessful (no I2S activity), though "aplay
-l" correctly identified "audioinjector-wm8731" as the "0" card
(i.e. the default card) and "loopback" as the "1" card.
See also the console messages of sbitx when starting, on some
occasion there was a permanent request for a loopback device.? I
must confess I have no clue yet about how and where to put the
"plughw:CARD=Loopback,DEV=1" statement (in my opinion somewhere in
a asound.conf file, but I could not find any on the root folders).
I know you are a very busy person, still I would greatly
appreciate any comment, advise, hint, pointer, etc. many thanks on
beforehand.
I somehow reworked the "install.txt" file, I hope you don't mind.?
73 ON4JRT / Jean
Op 5/07/2021 om 11:57 schreef Jean
Taeymans:
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Thanks Ashhar,?
Your right, one should face his fears ?, I'll give it a try
(once I am back home).? I'll do it on both a RasPi-400 and a
RasPI-Zero, I'll keep you posted when I succeed in building it
from your sBITX repository.
According to my simplistic "guestimations" the SDR / DSP part
of the sBITX software would need some 2 MFLOPS plus some for the
sound driver.? According to what I can find here and there on
the internet, the RasPi-Zero is capable of 350 MFLOPS, which
should be adequate (the RasPi-4 does 13500 MFLOPS !).?
Beside the clock speed it is really the floating point
coprocessor that does it, the humble RasPi-pico does barely 50
kFLOPS. ?
73 ON4JRT / Jean.
Op 5/07/2021 om 05:49 schreef Ashhar
Farhan:
Jean,
If you can do Arduino, you can do RPI. I have
extensively used arduino api (lile digitalRead(), etc. It is
simple C. Check the repository.
Many thanks Ashhar for the brilliant work so far, it is
by far the most exciting hackable SDR (or at least
partially SRD) project so far.
Take all the time you need, no pressure, I'll be patient
?. ?
If I can be of some assistance, let me know:? I have
experience in hardware design (mostly with micro
controllers), including PCB design (as it happens with
the Si5351 and the WM8731) and in software design,
mostly Arduino (AVR, ESP, some RP2040, I wish I was more
fluent in Raspberry Pi).?
73 ON4JRT / Jean.
Op 4/07/2021 om 15:51 schreef Ashhar Farhan:
I have been hacking away at the small
stuff for sbitx. There were ground loops between the
digital board and the rf board. Then, there were
oscillations in the PA. Finally, there was change to
40 Mhz filter, changing IF from 27 MHz to 40 MHz.?
I am working on the T/R switching with
a reed relay, hopefully getting to full QSK. I hope
to work one contest before posting it all.?
I am holding back because these are
interrelatef issues and resolving each needs rework
elsewhere. I want to be able to wrap it up asap. I
am experiencing design fatigue. This should finish
with a creative 'yay!' rather than an exhausted
'whew!'
Hi Jean,
In answer to one of your questions Ashar went
over a couple of things in his video, one was
the concept of a SDR contronolled uBitx which
was basically bolting the Pi onto the front end
of a uBitx and feeding CAT commands to the
existing Raduino?over serial, he then moved on
to to talk about the what was actually the sbitx
which is substantially different from the
existing uBitx and where the Raduino is scrapped
and the transceiver is controlled directly by
the RPi. All the diagrams and info are included
in the docs/presentation that was shared above
along with the video. The docs don't show the
schematic for the sBitx hardware but you can
screenshot them from the video. It's a shame
this thread has went a bit quiet because this is
quite exciting, tons for potential for
experimenting with this.?
Greetings to all,
More or less the same question here, plus
also a few remarks and questions for Asshar
I suppose.
I sincerely hope that all is well in
Hyderabad and that Asshar is able the pursue
his work on the sBITX after his brilliant
presentation last spring.
Many thanks to him for sharing this with us
all.
Over the past years I experimented myself a
bit with the quadrature direct conversion
architecture, using various micro
controllers: STM32F446, ESP32 and recently
RP2040 in a set up with a WM8731 (running at
8ks/s), a FST3253 and a Si570.? Though all
of this more or less worked, I never
succeeded in having an adequate side band
suppression (typically not more than 30dB).?
This is of course related to the rather
challenging hardware task of having a very
precise 90¡ã relation between the I and Q
signals (of both the VFO and the audio) and
having precisely the same gain on both I and
Q amplifiers.
Asshar's double conversion architecture
with one sharp IF filter at 27/40MHz in
hardware and a second at 24kHz implemented
in software is i.m.h.o. absolutely
brilliant, as it circumvents all the above
problems.? Also is the idea of performing
filtering, demodulation, etc. in the
frequency domain.
This comes at a price however, running the
codec at 96ks/s and performing a 1024 bins
floating point FFT every 10ms excludes the
low end micro controllers, even the RP2040
(no FP coprocessor).? Hence the use of the
Raspberry Pi as a computational platform.??
A few questions if I may.?
- Would the sBITX software run in a headless
configuration (only CAT, no GUI) on a
Raspberry Pi Zero ? (and obviously without
the WSJT-X application).? I am particularly
interested in using the sBITX in a remote
battery operated (= low power) TRX set up.?
- The hardware setup diagram shows a Raduino
board connected to the Raspberry Pi by USB.?
Can the Si5351 not be controlled directly
through the I2C bus of the Raspberry Pi ??
It is otherwise used for the WM8731.?
- The repository on
is a bit confusing:? two libraries for bit
banging the I2C bus, tough WiringPi includes
the I2C functionality.? A library for the
Si570 seems a bit lost in this context.?
- The WM8731 codec seems to be setup (sample
rate, gain settings, etc.) by its driver
build in Raspbian driver, which is fine I
guess.? Can it be controlled (e.g. gain,
microphone input, etc.) by alsa config ?
- A more elaborate guide to the installation
of the various libraries and the building of
the software would be greatly appreciated.?
Is e.g. any flavor of Raspbian ok ??
73 ON4JRT / Jean.
Op 3/07/2021 om 00:15 schreef Peter
McCracken:
Hi Niels,
Did you ever make any progress with this or
get a board up and running ?
Also did you source some 27Mhz crystals, if
so which ones did you go for ?
Thanks!
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Re: Signal bars on display?
Answering my own question -?
Looking at ? - I'm guessing ST stands for "straight" as in straight key for CW
Everyday's a school day.
M0WWS
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Re: Interfere local Broadcasting radio station
Re-read question. High-pass filter is the BCI cure. AGC or AVC is kinder on the ear.
73!
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Re: Interfere local Broadcasting radio station
Question: AGC or AVC?
AGC is automatic GAIN control - that cuts the gain of the incoming signal to knock back overly STRONG signals.
AVC is automatic VOLUME control - that cuts the gain (usually of the audio stage/s) to knock back overly LOUD signals.
From reading, it would seem to ARRL circuitry is RF-sensing AGC - that will cut back gain (below 160m?) by detecting overly strong RF (there), where kit-parts is AF-detecting AVC of overly loud audio, though cutting RF gain based on that. That allows overly strong RF right through wide-open receiver until Audio is detected, allowing overload of the previous stages. Both will have effect, but ARRL's is kinder to the RF stages and could be more generally applicable, allowing weak signal with strong audio (RFI and static) full sensitivity / gain. I don't have access to either hardware, software or design/s to test: someone with such access (or able to afford it :) ) might verify or debunk as appropriate.
73 all de ZL2DEX, OTC (50yr), NZCE.
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Re: Signal bars on display?
Thanks for the link. It's a bit of an unknown this box. I got if off ebay and there was lots wrong with it - the speaker had come detached in shipping and rolled all over the PCB smashing a couple of toroids that I had to replace and rewind. Q90 had been replaced by a TO-92 package but it had been soldered in the wrong way round resulting in zero output power. After I fixed that I set the bias and got 10 watts out - just worked W3LL on 20m SSB -?3481 miles !!?
There's a purple wire connected to A7 but it's just flapping in the breeze. I'm guessing it's either picking up noise and/or the s-meter is set wrong in?uBITX Manager - I'll download a copy and have a look once the USB mini-B cable arrives from Amazon. Think I'd rather get the S-meter that came with the case working ( a la ?) so I might just switch this feature off.
Occasionally it displays "ST" in place of the signal bars - any idea what that means?
Thanks for the link.
M0WWS
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Re: Signal bars on display?
Hello Peter,
I¡¯ve been trying to reach you via direct email about the boards I shipped and haven¡¯t heard back. ?Perhaps my messages are getting caught up in spam folder?
Best,
Jim
KM4TXR
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On Jul 10, 2021, at 10:26 PM, Peter McCracken <peter.mccracken@...> wrote:
?
Just fixing a secondhand uBITX from ebay. it's a v4 and it's running uBITX v0.20 +v1.200 firmware according to the start up display
I'm puzzled by the bars in the 14th and 15th characters on the top line of the 2 line LCD display (see attached photos).
Are they supposed to be a signal meter? They seem to appear sometimes when a signal is detected but they stay there when the signal drops until you tune away. Or are they for some other purpose?
It's got an s-meter in the chassis but it isn't connected to anything. I'm planning to drive that off the vol high pot eventually.
M0WWS
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Re: Signal bars on display?
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Just fixing a secondhand uBITX from ebay. it's a v4 and it's running uBITX v0.20 +v1.200 firmware according to the start up display
I'm puzzled by the bars in the 14th and 15th characters on the top line of the 2 line LCD display (see attached photos).
Are they supposed to be a signal meter? They seem to appear sometimes when a signal is detected but they stay there when the signal drops until you tune away. Or are they for some other purpose?
It's got an s-meter in the chassis but it isn't connected to anything. I'm planning to drive that off the vol high pot eventually.
M0WWS
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Don,
To get to the v6 menu you press and hold in the encoder for 10 seconds or so until the settings menu comes up.? You then use the encoder to select the CW Keyer and then press the encoder to open the choices.? Turn the encoder again until the type of key is displayed that you want.? Press the encoder one more time and it will be set.? Rotate to Exit and then press the encoder again.
I would suggest taking Curt up on his offer to help with the antenna.
Hope this helps.
73
Evan
AC9TU
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Don
Email me direct and we could brainstorm on antenna. My call at yahoo.?
Its summer, but bands aren't that dreadful overall. Ubitx not my favorite cw rig, still I have made hundreds of cw contacts and a few on ssb.?
If you are still stumped by menu let's text or talk. Remember this was a rig designed for anyone on the planet. Mine arrived with bfo out of calibration. At least the v6 has the mods pre-installed, don't ask how much time many of us spent to refine our v3 and v4.?
Curt wb8yyy?
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¡°Using¡± V6.1. Between the menu issue and the limited space for an antenna, and dead bands, I have not been having a good time.
Thanks.
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On Jul 10, 2021, at 4:53 PM, Evan Hand <elhandjr@...> wrote:
?Hi Don,
Which version of uBiTx do you have. and are there any modifications from stock?
Most versions with stock displays are as Curt has stated.? You change settings through the encoder (tuning knob) and pressing the knob in to select.
The v6 and those upgraded to KD8CEC software with touch screens do have menus through the touch screen.??
Either way, there is a menu setting used to set straight key or iambic a or b.
73
Evan
AC9TU
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Hi Don,
Which version of uBiTx do you have. and are there any modifications from stock?
Most versions with stock displays are as Curt has stated.? You change settings through the encoder (tuning knob) and pressing the knob in to select.
The v6 and those upgraded to KD8CEC software with touch screens do have menus through the touch screen.??
Either way, there is a menu setting used to set straight key or iambic a or b.
73
Evan
AC9TU
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Just fixing a secondhand uBITX from ebay. it's a v4 and it's running uBITX v0.20 +v1.200 firmware according to the start up display
I'm puzzled by the bars in the 14th and 15th characters on the top line of the 2 line LCD display (see attached photos).
Are they supposed to be a signal meter? They seem to appear sometimes when a signal is detected but they stay there when the signal drops until you tune away. Or are they for some other purpose?
It's got an s-meter in the chassis but it isn't connected to anything. I'm planning to drive that off the vol high pot eventually.
M0WWS
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Press the tuning knob and then as you turn it you should see various menus. To select a topic press again, then you can scroll through the settings. If all else fails then find a YouTube video. My ubitx is a v4 using stock firmware but each should be similar. You can only communicate with the microcontroller by this main button and knob.?
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Thanks. But Where is the menu?
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On Jul 10, 2021, at 11:50 AM, Curt via groups.io <wb8yyy@...> wrote:
?There is a menu setting for choosing keyed or straight key. Step through menus, press the main tuning know to get there, and you will see things to adjust.?
I mostly use my ubitx on straight key, maybe we can cross paths on skcc.?
Curt wb8yyy?
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