I wanted simple, small and easy to build. Only needs to drive A-D input, so no buffering required and linearization can be done in software if desired. I'm only interested in 30 mHz and 10W QRP max, so hoping the reproducability of fixed components holds up. First article built looks good.
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Re: ubitx compared to Elecraft or Xiegu for spurs
#ubitx
Iz oos,
>>Do the users of these NASA rigs always check for their spectral purity or maybe they take for granted they are clean whatever the mods and equalization?<<
Some do some never even thought of it.? The Anan users tend to be very fastidious and?
a lot of them use the adaptive feedback (distortion error correction).? Very clean as an
example of what technology can do for transmitters.
Allison
?
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Re: ubitx compared to Elecraft or Xiegu for spurs
#ubitx
Put decent RF devices in uBitx and then we compare for sure...
Rahul VU3WJM
No, better devices made it more noticeable.? ?There are issues tied to board
layout and lacking filters.? Fix them and we have a competition.
Allison
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Re: ubitx compared to Elecraft or Xiegu for spurs
#ubitx
Hey, I'm just curious how all the other portable radio compare....
Are they :"clean"? Specs can be that "special" radio, just for testing.
Your mileage may vary,
Jim W0CHL
Read the specs.? If they don't have them don't buy it.
As a random comment Elecraft anything tends to be very good.
Some of the new imports are largely unknown.
However my CRkits KNQ7A is good.
Allison
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Larry,
>>You folks are all saying "carrier leakage". I thought that as well when playing with my rig. It turned out, in
my case but I expect yours as well, it is not the carrier but the unwanted sideband. <<
First as this is not the first time dealing with this, experience is from many prior
radios and the adjustment of many other commercial and kits.? ?There must?be
NO audio or other input to the modulator other than the BFO.? If that is true then
there cannot be another side band. and one can proceed to dial in the BFO.? Also any
measurement of carrier leakage requires that as a start.? Then one can add single or
two?tone audio and look at opposing sideband and carrier with modulation.
First the BFO must be set correctly and about 300hz down the edge of the filter.? More
and the audio suffers (RX and TX) from a lack of lows.
What? I measured is with audio shorted at the modulator and that cannot create another side band.?
Its the exact frequency of the BFO and its there if I remove the balanced? mod transformer and
diodes.? ? Its a board level leakage path of BFO pas the filter into the 12mhz?IF amp.? Also based
further work the balanced mod is well behaved and the carrier null should be at least 40db or better.
The first thing done was to ground the crystal cans, that improved filter leakage a few DB
especially at the edges.
The second was the filter in mine was 1670hz at the 6db points, terrible for voice work.
Change the caps to 82PF and got a 2150hz wide filter, on the tight side but much better.?
The filter shape factor is a rather soft 2.5:1 at -60db, (5300hz) that is typical for this
type of filter.
Then I set the BFO based on the filter sweep for mine that ended up being 11.99675
for about 10db/300hz down the slope.? ? Most the 11.9962 would result in the lower
700-1000hz part of the vice band being seriously attenuated both R and TX.? However
your filter could be offset lower over all, not uncommon.? FYI the upper edge is just
under 12.00000mhz as that is not the center frequency.
However the carrier due to the board issues carrier will still be there.? I've seen this on 5
units to date.? I have not seen it less than -33dbc, one CW op never noticed save for he had?
signals on the other side of zero beat, moving the bfo helped that.
An experimental fix was put a 12mhz crystal osc dialed to 11.99675mhz (for mine) and the balanced
mod in a mint tin connecting it to the filter input with a few inches of coax, same for audio.? Result
good modulator behavior and carrier at least 48db down and audio band pass starting at about
250hz to 2450hz (the filter 2150hz wide).
Allison
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Tom:
So, for the time it takes the hardware to figure out what
frequency you are at you maybe out of compliance until the filter
switches?
Howard
On 8/13/2018 1:17 AM, Tom, wb6b wrote:
toggle quoted message
Show quoted text
Hi,
I wan't to build a filter I can use with the uBITX. However, I
don't want to build a filter that is strictly tied to the uBITX.?
So I'm building a standalone Low Pass Filter box that will work as
an add on filter for the uBITX as well as become a general purpose
piece of Ham equipment I can use over and over for other needs.
It uses an Arduino to measure the frequency you're transmitting on
and select any individual or combination of filters you like. The
proposed design uses a set of filters and a relay switch board;
such as to ones by QRP Labs. But, the Sketch code should be easy
enough to modify for whatever you like.
The controller can show he selected filter with LEDs or with an
optional LCD display, and show the transmit frequency as well.
I'll need to order parts and build mine to finalize the design.
However, I built and tested a prototype with a signal generator.?
I'm releasing the preliminary design to everyone now because it is
complete enough for people to try out on their own filter designs.
It makes using outboard filters really easy, and I think people
will like it. I welcome feedback on improvements people make while
building their own "Auto Filters" with the controller.
The code for the controller is here:?
----
Tom, wb6b
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Tom:
I think there are a lot of readers here who will be interested in your work. To reduce a POF (point of failure) for those who use the sketch, I'd like to suggest you modify the #include directives to show the URL for those files:
#include <FreqCount.h>??????????? // Download: https://XXXX
#include <LiquidCrystal.h>??????? // Download: httpe://YYYY
I make this suggestion for two reasons: 1) the first one is a non-IDE header file that most people will not have installed on their system and they need to know where to find it, and 2) there are about a bazillion header files for LiquidCrystal libraries. One is distributed with the IDE, but many sketches use LiquidCrystal libraries that are not part of the distributed IDE and will not work with it. If it is distributed with the IDE, then I use:
#include <LiquidCrystal.h>??????? // Standard with IDE
That way, the user knows they are okay to use what came with the IDE. Indeed, these simple additions to any Arduino sketch would likely help users have greater success in compiling code.
Jack, W8TEE
On Monday, August 13, 2018, 1:17:25 AM EDT, Tom, wb6b <wb6b@...> wrote:
Hi, I wan't to build a filter I can use with the uBITX. However, I don't want to build a filter that is strictly tied to the uBITX.? So I'm building a standalone Low Pass Filter box that will work as an add on filter for the uBITX as well as become a general purpose piece of Ham equipment I can use over and over for other needs. It uses an Arduino to measure the frequency you're transmitting on and select any individual or combination of filters you like. The proposed design uses a set of filters and a relay switch board; such as to ones by QRP Labs. But, the Sketch code should be easy enough to modify for whatever you like. The controller can show he selected filter with LEDs or with an optional LCD display, and show the transmit frequency as well. I'll need to order parts and build mine to finalize the design. However, I built and tested a prototype with a signal generator.? I'm releasing the preliminary design to everyone now because it is complete enough for people to try out on their own filter designs. It makes using outboard filters really easy, and I think people will like it. I welcome feedback on improvements people make while building their own "Auto Filters" with the controller. The code for the controller is here:?  ----  Tom, wb6b
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Re: Needed - relay voltage versus frequency for each of the band-pass filter relay drivers
#ubitx-help
>>If your rig still has the M1 and M2 audio cutoff connections to relay K3, then what you are hearing in your audio is not a transmitter issue, but an RF overload condition from the TX output back into your audio preamp. In another post of mine I described how to eliminate this issue by cutting the paths in the audio from K3.<<
Switching audio in K3 was inviting pain.? I'd advise cutting traces to m1/m2 and and bridging them
pls add the pop fix.
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Joe,
I suspected its a Brune bridge.? Most of the other forms tend to be larger.
All the ones I've built C3 has to be variable or hand picked as its hard to
predict due to parasitic circuit elements.? One being the inconsistency
of FR4/G10 at high hf and? up.
Allison
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Is this bitx-40 or bitx20 or uBitx? as they are not the same?
Since it happens with the loop I'd suspect its the radio.? I say that?
as people will run off and blame the endfed half wave.
Generally of the SWR is good its something else.
Things in the radio such as long wires, possible radiation from the board
to antenna connector, grounding issues within the box.
Generally plastic cases being RF transparent are likely to make this worse.
Allison
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FYI, I posted the LTSpice schematic, so you can analyze if you wish.If there's interest, I can post the whole LTSpice package if anyone requests it.
Joe
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That’s probably radio frequency interference. ? With a slightly Squirrley antenna, you may have RF pick up in microphone cables etc., leading to all kinds of weird behavior. ? it will look like the radio took off on its own. ?Try ferrites, better SWR, better
grounding of things together, ?that sort of thing
toggle quoted message
Show quoted text
Hello!
Finally I made a few first contacts with my uBitx. Mostly I used the antennas at my local ham radio club, which has dipoles for 80m and 40m and a beam antenna for all the upper bands. At these antennas the uBitx works perfectly and I was also able to make a
few DX contacts.
But while trying my Antennas at home, I figured out, that the PA breaks into terrible oscillations on any band while working with an endfed halfwave antenna or a magnetic loop antenna. Sometimes the oscillations occur also on my portable trap dipole.
So does anyone of you have such problems with your Bitx too? And does anyone have an idea, what's going wront with my Bitx?
73,
Ludwig, DM2LCT
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Hello!
Finally I made a few first contacts with my uBitx. Mostly I used the antennas at my local ham radio club, which has dipoles for 80m and 40m and a beam antenna for all the upper bands. At these antennas the uBitx works perfectly and I was also able to make a few DX contacts.
But while trying my Antennas at home, I figured out, that the PA breaks into terrible oscillations on any band while working with an endfed halfwave antenna or a magnetic loop antenna. Sometimes the oscillations occur also on my portable trap dipole.
So does anyone of you have such problems with your Bitx too? And does anyone have an idea, what's going wront with my Bitx?
73,
Ludwig, DM2LCT
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Re: Needed - relay voltage versus frequency for each of the band-pass filter relay drivers
#ubitx-help
If your rig still has the M1 and M2 audio cutoff connections to relay K3, then what you are hearing in your audio is not a transmitter issue, but an RF overload condition from the TX output back into your audio preamp. In another post of mine I described how to eliminate this issue by cutting the paths in the audio from K3. The RF is so strong due to coupling between the contact pairs inside the relay that after you make the mod to not use the relay to interrupt the audio, you can use the righthand connection to the old R70 as a convenient RF pickoff to look at with a 'scope or a spectrum analyzer!
Larry N2AJX
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You folks are all saying "carrier leakage". I thought that as well when playing with my rig. It turned out, in my case but I expect yours as well, it is not the carrier but the unwanted sideband. This rig's scheme always uses the upper sideband generated by the balanced modulator in both USB and LSB transmission. You need to look in real close with a spectrum analyzer using 100 Hz resolution bandwidth to see the difference. I have found the sweet spot for the BFO to be 11.9962 MHz, just as many of you have already found. If you can measure the output of the balanced modulator, you should see the carrier being down at least 40 dB from the sideband output. You shouldn't see the carrier in the transmitted signal, especially after the modulator output passes through the crystal filter.
Larry N2AJX
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Hey, very cool Glenn!!!
Also, now I understand what you mean about mounting the relays on the backside.
Great work!
On Aug 13, 2018, at 06:15, Glenn < glennp@...> wrote:
toggle quoted message
Show quoted text
Here's another take on the PCB for the extra LPF switching relays. As per my previous suggestion, fitting the PCB to the edge of the uBITX main board by seam soldering them together.
This preserves a very good ground return.
The PCB uses HK4100F-12v relays which are cheap on ebay. 'Should' be ok for qrp levels.? They are a SPDT type relay and mounted on the back of PCB shown. They are similar in height to existing LPF relays.
Similar track cutting mods as Gordan has stated, except a variation in the 400nH LPF section so all inputs are on the egde of the uBITX board.? The PA output feeds the board at the end nearest the heatsinks. ie a very short coax cable is required.? Four short
(5mm) wire links from the edns of the LPF sections to this board. You can see the 4 holes down the left side which is actually rotated left 90deg when fitted.
The transistor relay driver stages have been duplicated, but can also be not fitted, as pads are provided for this also. All relay coils are bypassed both sides and along the tracks too.? I might add some ferrite beads also.
The PCB is approx 36 x 50mm in size.
<LPF_EXTRA_RELAYS_DRAFT pcb_v3.jpg>
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the kdcec manual says that it can be set to any ham band
does that include the 60 mtr (5 Mc/s) band
terry gm4dso
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Here's another take on the PCB for the extra LPF switching relays. As per my previous suggestion, fitting the PCB to the edge of the uBITX main board by seam soldering them together. This preserves a very good ground return. The PCB uses HK4100F-12v relays which are cheap on ebay. 'Should' be ok for qrp levels.? They are a SPDT type relay and mounted on the back of PCB shown. They are similar in height to existing LPF relays. Similar track cutting mods as Gordan has stated, except a variation in the 400nH LPF section so all inputs are on the egde of the uBITX board.? The PA output feeds the board at the end nearest the heatsinks. ie a very short coax cable is required.? Four short (5mm) wire links from the edns of the LPF sections to this board. You can see the 4 holes down the left side which is actually rotated left 90deg when fitted. The transistor relay driver stages have been duplicated, but can also be not fitted, as pads are provided for this also. All relay coils are bypassed both sides and along the tracks too.? I might add some ferrite beads also. The PCB is approx 36 x 50mm in size. 
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Hi Allison,
Thanks for the compliment on the picture.
It's a pretty straight-forward Breune bridge, but I'll put up the schematic when I get a chance to edit it with actual values...maybe today. The novelty, if any, is mountIng it right on the connector and using the center pin as the transformer primary.
When I do these things from my tablet, I tend to take shortcuts and fill in details later. Mea Culpa.
W3JDR
Joe
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Re: high frequency noise from speaker
Thanks again for ur reply.
OK, 3 Nanos are on the way now and I will order another 3 Nanos so I can try 6 of them this time.
Yes, I know that I need Nanos without pins soldered.
Maybe I’ll solder “both sides long pins” then I can use in anyway later.
So far, my uBitX is working good, I could listen some HAMs on 7MHz and could transmit 5W on CW and 10W PEP on SSB if I shout to the mic.
Next to do is to build a transmittable antenna.
Again, thank you so much. I’m enjoying my uBitX now.
BR,
// hiro, JJ1FXF
Hiro,
I would think with 3 or 4 Nano's you would have one without the objectionable tone.
The processor clock frequency is determined by a 16mhz ceramic resonator
which can be off by perhaps plus or minus 100khz.
Since it is probably the 3'rd harmonic of the 16mhz resonator creating the tone,
if it is off by 10khz, then the tone would be 3*10khz = 30khz.
Buy Nano's that do not have the pins soldered in such as this:
? ??
To plug the Nano into the Raduino's socket on the v4 uBitx, the pins must be soldered?
into the top side of the Nano, not the bottom side where the pins usually are.
Jerry
On Sun, Aug 12, 2018 at 10:24 PM, JJ1FXF wrote:
?
It seems that my issues is the same one discussed at the thread you pointed out.
?
I happeningly ordered some extra Arduino Nano for my another projects, so let me try to switch Nano at first.
?
What do you think How many of Nano I can buy to get the right one?
?
I’m just asking you the possibility. No commitment, of course.
?
// hiro, JJ1FXF
?
?
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HIRO, JJ1FXF