I like building and have built a BITX 40, uBITX, QCX, QCX mini and a Barb WB2CBA v1.02 uSDX. The first thing to know is that unlike the uBITX or QCX, there are several hardware variants with different capabilities and technology (SMD vs through hole). If you are interested, spend a little time thinking about what development track you want to build.
I posted a few articles on the uSDX here
and here
and the groups.io WIKI is useful.
BTW - if you are interested in SDR check this out:
note this talk "Ashhar Farhan VU2ESE - sBITX - An Open Source SDR that YOU can hack!"
--
? 73
??? Bob? KD8CGH
|
Re: uBitx V6 - schematics
Pierre,
It means that those windings are not connected.
HFSignals winds all transformers identically. In places where a bifilar (2 windings) is required
they leave the 3rd winding disconnected. It makes the manufacture parts list simpler.
Raj, vu2zap
toggle quoted message
Show quoted text
At 09/04/2021, you wrote: Could a member explain these odd things I find on the schematics wiring of four transformers :
- T5 : wires 1 and 6 end in a x ;
- T6 : the same ;
- T8 : the same ;
- T11: the same with wires 3 and 4.
73 - Pierre - FK8IH
|
Could a member explain these odd things I find on the schematics wiring of four transformers :
- T5 : wires 1 and 6 end in a x ;
- T6 : the same ;
- T8 : the same ;
- T11: the same with wires 3 and 4.
73 - Pierre - FK8IH?
|
uSDX enclosure :?
73 - Pierre - FK8IH
|
Robert - That's about what I was figuring, definitely no more than that and maybe less.? I already have a few Nanos since I couldn't use them on the Raduino with the header soldered on opposite and also have a couple of the clock boards so just need to put in an order to mouser or DIgiKey for the pieces-parts I don't have.? That will probably have to wait until fall as I am heading to the OK mountains next Saturday and won't be back to the home QTH until fall.? If the boards don't get here before I leave I'll have the XYL carry them up with her in May and I can mail them from the cabin.
73,
Justin B.
KI5GKD
|
My PICKit 3 programmer should be here Saturday so I'll let you know how it goes, if I don't brick it!
|
Re: Many uBitx's have reduced power on 40m CW
The phases I gave in the post included below for the various impedances?
when doing an AC Analysis in LTSpice of the Q90 uBitx stage are incorrect.
When LTSpice measures current through a device, it assigns a seemingly arbitrary direction to the current.
In the case of my AC voltage source, it assumed current was going into the top node, not out.
To show a correct phase in such a case, we must add a negative to the formula used in the plot.
For example, assume node n001 is the wire from the top of voltage source Vsrc to our network under analysis.
V(n001) is the voltage at that node, and I(Vsrc) is the current through the voltage source, so the impedance should be V(n001)/I(Vsrc)
But if that current is going the wrong direction, the formula should be modified to? -V(n001)/I(Vin)
The math used for evaluating that impedance is in the complex plane, using complex arithmetic.
? ??
Multiplying (or dividing) by a -1 is equivalent to a phase shift of 180 degrees.
For example, in a previous post I stated:
<? For the v3 configuration with C81=0.1uF and R83=2.2ohms, my simulation shows that
<? the Q90 stage has an input impedance of 51 ohms to 45 ohms, at 173 to 165 degrees
<? Voltage gain ranges from 4.5 to 3.65.
<? These values are for a range of 3.5mhz to 30mhz, in that order, Q90 stage has a load of 50 ohms.
Instead of a phase shift of 173 to 165, we have a phase shift of 180-173=7 degrees to 180-165=15 degrees.
Which is reassuring, since a phase shift of zero degrees would indicate a pure resistance, these values are slightly inductive.
The original phase shifts given don't make much sense for an impedance, it should always be somewhere between
+90 degrees for a pure inductance and -90 degrees for a pure capacitance.
Jerry, KE7ER
On Tue, Apr 6, 2021 at 11:07 AM, Jerry Gaffke wrote:
Given the variation in impedance as seen in the simulations of ideal components,
it's amazing to me that the output power manages to be as flat as it is.
Fun to figure out what all is going on here, more than it might seem at first.
From a practical standpoint, Curt's bigger C81 strikes me as the best fix,
for those that care about the slightly reduced power when operating 40m CW.
But with C81 too big, the difference in output power between 3.5mhz and 30mhz
may become too extreme.
For the v3 configuration with C81=0.1uF and R83=2.2ohms, my simulation shows that
the Q90 stage has an input impedance of 51 ohms to 45 ohms, at 173 to 165 degrees
Voltage gain ranges from 4.5 to 3.65.
These values are for a range of 3.5mhz to 30mhz, in that order, Q90 stage has a load of 50 ohms.
On v4, R83 was moved to 2.2 ohms for more gain.? ?
Input impedance dropped to a range of 18 to 19 ohms, 170 to 183 degrees.
Voltage gain ranges from 5.5 to 6.7.?
On v5,v6 the cap at C81 was moved to 470pF so high frequencies have more gain than low frequencies,
this compensates for losses at high frequencies in the various power amp stages.
Input impedance now ranges from 200 ohms to 45 ohms at 150 to 100 degrees.
Voltage gain for the Q90 stage runs from 1.0 at 3.5mhz to 5.5 at 30mhz.
The v3 configuration is likely the best as far as giving the filter and mixer a proper 50 ohm load.
But we needed more gain at higher frequencies to get sufficient power out,
without too much drive on 3.5mhz.
I haven't analyzed the effect of the Q90 impedance phase angle
on how the filter or mixer might behave.
Jerry, KE7ER
|
Hi Justin,
That article looks interesting. I wouldn¡¯t mind buying one of the PCB¡¯s off of you. How does $5.00 sound, is that fair? I usually look at this group each day so let me know what you think.
73,
Robert, AG6LK?
|
Re: Many uBitx's have reduced power on 40m CW
Jerry,
I agree with your assessment.? I really need to do the IMD and power tests for SSB.
Doing some more simulation, I do believe that increasing R83 to allow for a better filter impedance match is probably a good thing.? The 10 ohms with 1nF C81 seems to be the best but does reduce the total output.?
Thank you again for the input.
73
Evan
AC9TU
|
Re: Many uBitx's have reduced power on 40m CW
Actually 80,40,20 are all fairly even.
So adjust RV1 or R83 as appropriate for SSB use.
toggle quoted message
Show quoted text
On Thu, Apr 8, 2021 at 10:24 AM, Jerry Gaffke wrote:
Evan,
I have no idea if you will have trouble with IMD on 80m.
Increasing R83 would cure IMD and also further improves the impedance seen by the filter,
but reduces power on all bands.
Could just rotate RV1 for suitable 80m power levels.
Could use TXC (turns on the 80m LFP) to turn on a FET which attenuates the signal at RV1
Could add something at Q911,912 that reduces gain at low frequencies similar to C81,R83
Having Q90 as a buffer should give the filter and mixer a proper load impedance.
Jerry, KE7ER
|
Re: Many uBitx's have reduced power on 40m CW
Evan,
I have no idea if you will have trouble with IMD on 80m.
Increasing R83 would cure IMD and also further improves the impedance seen by the filter,
but reduces power on all bands.
Could just rotate RV1 for suitable 80m power levels.
Could use TXC (turns on the 80m LFP) to turn on a FET which attenuates the signal at RV1
Could add something at Q911,912 that reduces gain at low frequencies similar to C81,R83
Having Q90 as a buffer should give the filter and mixer a proper load impedance.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Thu, Apr 8, 2021 at 09:41 AM, Evan Hand wrote:
Jerry,
I did not think of the LPF causing the dip on 30meters.? That makes sense.
I will check the SSB signal on 80meters with my RSP1A and the SA software.? The choice would then be to change R83 to a higher value like in the v3 10ohms.? Maybe 6.8ohms?
Guess I am not finished yet.
73
Evan
AC9TU
|
Re: Many uBitx's have reduced power on 40m CW
Jerry,
I did not think of the LPF causing the dip on 30meters.? That makes sense.
I will check the SSB signal on 80meters with my RSP1A and the SA software.? The choice would then be to change R83 to a higher value like in the v3 10ohms.? Maybe 6.8ohms?
Guess I am not finished yet.
73
Evan
AC9TU
|
Re: Many uBitx's have reduced power on 40m CW
Evan,
The dip on 30m is because it is using the 40m LPF, which must attenuate a 20m second harmonic.
But hey, it's primarily an SSB rig.
My only concern would be that the big C81 causes too much power out on 80m.
Shouldn't be a problem for CW where the PA can be non-linear,
but for 80m SSB there may be some IMD popping up unless you back off some on RV1.
Or increase R83.
Jerry, KE7ER
On Thu, Apr 8, 2021 at 02:48 AM, Evan Hand wrote:
The only abnormality with that mod is the dip for 30meters.? I am not going to pursue that issue as I consider it a good tradeoff for the 40meter increase.
|
Re: ArduinoShrink - reduced size Arduino AVR Core
If it's at least a 16 bit machine and either has lots of registers or an easy way to
access words in RAM as an offset from the stack pointer,?C is the way to go.?
This applies to pretty much all modern processors.
The instruction set for the MSP430 is designed for C and is very simple,
worth looking over (the peripherals are a tough read though).?
I'd be hard pressed to write assembly language for it that was faster than compiled C.
The old Sun Sparc was pretty good too, especially if access to stack space
in main memory was slow.
The ATMega328P, not so much.? ?
A very small 8 bit machine, and the Harvard architecture limits access to data stored in flash.
https://www.reddit.com/r/linux/comments/73in9/computer_holy_wars_png/
Jerry, KE7ER
toggle quoted message
Show quoted text
On Wed, Apr 7, 2021 at 10:31 PM, Tom, wb6b wrote:
On Wed, Apr 7, 2021 at 09:33 AM, <quad@...> wrote:
ArduinoShrink?replaces Arduino AVR Core functions with smaller and faster versions.
The Arduino Blink example sketch built for the Uno takes 924 bytes of flash, but only needs
196 bytes with ArduinoShrink.
Looks really cool.?
Upon reading his explanation of his code, I need to revisit my assumption that writing assembly is almost never worth the effort now days.?
Although it looks like he put an additional restriction on specifying pin numbers (probably not a bad thing) to do some shrinking in the wiring library.
Tom, wb6b
|
TSW Teensy 4.1 Raduino for the (V6 uBITX) News
#ubitxv6
Even though the sources for the Silicon Labs Si5351a chips have pretty much dried up and the remaining stock at some suppliers is being sold at highly inflated prices, we found, thanks to a post by one of the BITX20 groups members,? that there is a Chinese equivalent (MS5351M) readily available, with reasonably fast (DHL) shipping from at least one supplier out of China (www.chipmall.com) who has very reasonable prices (High DHL shipping cost can be offset by larger volume orders).
TSW placed a volume order and we have enough on hand now that there will not be a shortage of the Teensy 4.1 Raduino Kits. They have been tested and are virtually identical to the Si5351, at least in pinout, appearance? and I2C address (0x60). In the Raduino, they? produce clean output at least as good as the Si Labs chips. Once our small supply of Si5351a's is depleted,? the MS5351M's will be used in our kits.
The currently listed kit prices will not change and they are available for order.
W0EB found a "test socket" that will take the SMD 5351's footprint and is currently designing a test fixture that will be used to test each Si or MS 5351 prior to installing it on the Raduino board to insure (especially with the MS5351M's that the I2C address is in fact 0x60 and the output levels are at least as good as the Si5351 from Silicon Labs.? That way if any substandard ones have made their way into the batch on hand, they can be rejected before causing any problems for the user(s).
Current kit description and pricing information is available on the TSW website at www.w0eb.com .
Jim, W0EB
TSW Project Coordinator
|
Re: ArduinoShrink - reduced size Arduino AVR Core
As someone who started in I.T.? on a Mainframe with 16 k Magnetic core memory no disc drives and only ran a single program at a time there was always a bottleneck. Whenever a routine had to run with minimal memory and as fast as possible it was a good candidate for optimising, rewriting or if that didn't achieve it it was rewritten in machine code. It's funny in some ways not much has changed. There are still bottlenecks.
On Thu, 8 Apr 2021, 3:02 pm Tom, wb6b, < wb6b@...> wrote: On Wed, Apr 7, 2021 at 09:33 AM, <quad@...> wrote:
ArduinoShrink?replaces Arduino AVR Core functions with smaller and faster versions.
The Arduino Blink example sketch built for the Uno takes 924 bytes of flash, but only needs
196 bytes with ArduinoShrink.
Looks really cool.?
Upon reading his explanation of his code, I need to revisit my assumption that writing assembly is almost never worth the effort now days.?
Although it looks like he put an additional restriction on specifying pin numbers (probably not a bad thing) to do some shrinking in the wiring library.
Tom, wb6b
|
Re: Many uBitx's have reduced power on 40m CW
I put my v4 back together with the stock L1-4 toroids.? The only change I made was to C81.? I put a 2.2nF in parallel with the 470pF that was there.? Here are the CW results with 12 volts to the rig:
80meters? ? ?3.510MHz? ? ? 13.4watts
40meters? ? ?7.010MHz? ? ? 14.5watts
30meters? ? ?10.110MHz? ? ? ?7.8watts
20meters? ? ?14.010MHz? ? ?12.6watts
17meters? ? ?18.078MHz? ? ? ?9.9watts
15meters? ? ?21.010MHz? ? ? ?7.0watts
10meters? ? ?20.010MHz? ? ? ?3.6watts
The only abnormality with that mod is the dip for 30meters.? I am not going to pursue that issue as I consider it a good tradeoff for the 40meter increase.
So here is what I think that I have learned:
1 - The production filter is not optimal, but does work
2 - The modification that Curt used works, though through playing with LTspice the optimum value that I found is 2500pF for C81.? The closest I could come was 26700pF which worked.
3 - Probably the biggest impact with changing the C81 value is the impedance impact on the LPF, not really the gain.? The mismatch on the impedance was causing signal distortion that reduced the CW output to 40meters.
4 - Going too high a value for C81 will produce a larger difference in the 80meter vs 10meter output.? Increasing the capacitance does impact the gain of Q90 as well as the impedance.
I still need to do the purity tests for both CW and SSB.? I will do this by modifying my v6 with the above change to C81, test to see that I get the same results, and then do the spectral analysis.? I did change the relays on the v4 and tests with my TinySA confirmed that the harmonic issue was resolved, however, I have not done the spur fix yet.? The v6 should be clean before the mod, so that will be the test to indicate if there is an impact on the signal purity.
This is Fun!? Thank you, Jerry, Curt, and Farhan for the feedback!? Jerry especially thank you for the LTspice link and information.
73
Evan
|
Justin, FYI, There is a Groups.io for that work.? It is here: /g/ucxThe original project was called ?CX, which the group felt was too close to the QCX/QSX names that are used by QRP-Labs.? The official name is now ?SDX or uSDX though the Groups.io page (like this page) has a different net ID. Have fun! 73 Evan AC9TU
|
Re: ArduinoShrink - reduced size Arduino AVR Core
On Wed, Apr 7, 2021 at 09:33 AM, <quad@...> wrote:
ArduinoShrink?replaces Arduino AVR Core functions with smaller and faster versions.
The Arduino Blink example sketch built for the Uno takes 924 bytes of flash, but only needs
196 bytes with ArduinoShrink.
Looks really cool.? Upon reading his explanation of his code, I need to revisit my assumption that writing assembly is almost never worth the effort now days.? Although it looks like he put an additional restriction on specifying pin numbers (probably not a bad thing) to do some shrinking in the wiring library. Tom, wb6b
|
After getting my feet wet with the UBITX I ran across this interesting sounding project:
I sent off the Gerber files and I'm waiting for the boards to arrive by slow-boat as I am in no hurry.? If anybody else might want to play around with this I will have extra boards.? Minimum order was 10 PCB and with shipping was a whole $24!
Hope I'm not breaking any rules.
73,
Justin B.
KI5GKD
|
Bob Benedict, KD8CGH
Raj vu2zap
Jim Sheldon