Date   
Re: uBITX drive level.. #ubitx

John Backo
 

RV1 is, in effect, the bridge between the power amplifier
and the rest of the radio. It sets the drive level to the output
amplifier.

If it is too low, then there is not enough "oomph" in your power
output. If it is set too high, then there is a lot of distortion from
"overdrive".

The signal input to RV1 should be about 1-2 mv. Measure with an RF
probe or detector. The drive level should be about 1 mv, though that
may vary a great deal depending on impedances and output power level.

You will know when the level is right by the reports you get in a QSO
about audio quality. Upping the power output will mean upping the drive
level to some degree...but this is not always the case; sometimes there
is enough drive to accomodate any reasonable power level. But this is
the exception rather than the rule...

Occasionally, there is not enough drive to handle a greater power level.
In that case, the RF level into RV1 (or whatever adjuster is used) has to
be increased. I should think that a simple RF amp (with a 2N5109 or
equivalent) would be enough to provide the extra gain. On the uBITX,
that would mean moving RV1 to the RF amp output and maybe an attenuator
at the input to match things.

The biggest contributor to increased power output is increasing the IRF510
drain voltage from 12v to 24 or 36v. Usually, simply increasing the drive by increasing
RV1 a little bit is enough to fix the created problem.

Ordinarily you can get by with a simple adjustment of RV1 for most power levels
on the BITX. Pay attention to the heat generated and mind the thermal sinks.
And watch for oscillation and high levels of SWR. That should do it.

As to saturating the T30-6, build a new LPF with T50-6 cores; they should easily
handle anything up to 100W or so. Watch out for RF leakage and feedback at
higher power levels. Shielding may be required.

john
AD5YE

Re: uBITX drive level.. #ubitx

Jerry Gaffke
 

Twiddling RV1 is for uBitx owners, it's the pot that determines how hard to drive the power amp on transmit.
On the Bitx40, RV1 sets the bias voltage to the IRF510 gate, definitely not something to mindlessly twiddle
or you will smoke the IRF510,  It's R136 on the Bitx40 that sets the drive level  

On the uBitx, it is RV2 and RV3 that set the bias voltage to the IRF510 gates.
Should be adjusted for around 100ma per IRF510.
A wee bit too far and suddenly you have several amps through the IRF510, not good.

All these pots are backwards, fully clockwise is minimum.


On Tue, Jan 30, 2018 at 05:59 pm, Jerry Gaffke wrote:
Increase RV1 until received audio starts getting distorted, then back it off a little.
Alternately, if you don't have a big enough heat sink, increase RV1 until the IRF510's blow, then back it off a little.

Re: uBITX Firmware (CEC) 0.30 released (Test version). #ubitx

Ian Lee
 

I released v0.33 to reflect the feedback of testing v0.31 and v0.32.

I thought there would be no more functionality without hardware modifications. It's completely wrong.

So many good comments have been received by mail.

With the addition of too many features, the arduino nano has not had much flash rom left, but luckily it reflected most of the comments.

I have not been able to do a complete test for a few hours, but I will continue to fix the bugs that are found.

If no more features are added, this version(0.3x) will be renamed to V1.0 over the test period.

If want using my code, please use it after v1.1. Perhaps v1.1 is intended to reduce code size. i will optimize the menu configuration and duplicate code, message display function, warning messages, etc.

i will continue to fix bugs in this firmware.  also add if you require additional functionality. I just put in all the features I want to put in.

The added functions are as follows. (v0.31 -> v.033)

  - Change CW Key select type : choice by knob
  - Change confirmation key PTT -> function key (not critical menu)
  - Added feature IF Shift
       (change Set IF Sfhift type (v0.32 -> v0.33))

  - Added mode CWL, CWU  (Of course, you can still transmit in CW Key even in LSB, USB mode, Use BFO separately from SSB.). 

  - Added BFO for CWL, CWU only, you can set cw bfo in menu
    (SSB and CW use BFO separately)

  - Use the upper line that was left empty.
    (shown other VFO Frequency, Encoder Step, CW Key Type)

   -I included an example for using the meter. (using S.meter Power, SWL etc), f you need to remove the remark from the code, you can see a simple meter.

  - Add frequency scrolling function, The upper line VFO frequency display is displayed in kHz. if set scroll option in uBITX Manager, show all the other VFO frequency by scroll

  - split TX/RX  (very simple, I switched to another VFO when pressed the PTT or CW key)


Hex codes, source code, etc. can be found in the release section of github.


Thank you for your test and comments.





2018-01-30 17:02 GMT+09:00 Chris Herd <zl2tch@...>:

Nic

I like your thinking, if you add the swr function, generate a low level tone and thus low level rf out. Arrange for the nano to sweep a range of frequencies, ta dah cheap and cheeful antenna analyser.

looking forward to your mods

chris



--
Best 73
KD8CEC / Ph.D ian lee
kd8cec@...
www.hamskey.com (my blog)

Re: uBITX drive level.. #ubitx

John Backo
 

Jerry makes an excellent point which should be kept in mind.

RV1 on the BITX40 is for adjusting the voltage level on the gates
of the IRF510. This should never go beyond about 3v or so.
Rv2 and RV3 are used on the uBITX for the same thing.

It is a bit unfortunate in the nomenclature as it is easily confused.

The corresponding device on the BITX40 to the RV1 on the uBITX
is R136. These only should be fiddled with. Once the gate voltage
on the IRF510 is set, forget about adjusting it.

john
AD5YE

Re: Audio gone on new ubitx

 

Erik,

I suspect a relay. k3 mostly..

Check the continuity between M1 and M2. It should be short on RX and open on TX.

Check if you have 12V on the TDA2822 pin 2

Raj

At 31/01/2018, you wrote:
LCD is working...completely disconnected the ptt..still nothing...it worked for a short time when did 1st power up...
_._,_._,_

Re: Audio gone on new ubitx

Jerry Gaffke
 

Erik,

On the hfsignals wireup page   http://www.hfsignals.com/index.php/ubitx-wire-up/    it says:  
  DANGER : If you power up the µBITX without the pull-up resistor the µBITX can randomly go into CW transmit

Do you have the 4.7k pullup to 5v on the CW key pin?
If not, it could be going into transmit mode.


On Tue, Jan 30, 2018 at 11:25 am, César EA3IAV wrote:
Do you still have the lcd working? If so, does the radio work but without sound? 
Maybe the ptt is activated....

Re: Software support Request for Full QSK BITX40

Gary O'Neil
 

On Mon, Jan 29, 2018 at 07:09 pm, Jerry Gaffke wrote:


 

Re: Software support Request for Full QSK BITX40

Gary O'Neil
 

 

Hi again Jerry;

 

It looks like you caught me, or I failed to catch myself on this, but I wasn't clear on my comment: “At 20W output, the switch could theoretically see 180V P/P when presented with a perfect open circuit infinite VSWR”. In my defense however; I did follow that with “I'm not entirely certain that I'm simulating the operating environment realistically,...”

 

So here's my line of thinking on this... In order to experience 180V P/P at the source of a 20W transmitter, the fundamental and reflected waves must add algebraically, be simultaneously present at the transmitter's output port, both at the exact same amplitude, and be precisely aligned in phase. Assuming a zero impedance source driving a 50 ohm transmission line as it's load, and by applying Ohm's law (at time zero... when the load “looks” like it truly is 50 ohms), 20 Watts output at the source yields a source voltage of 90 Vpp. This forward voltage wave must now travel precisely 360 degrees in time before presenting itself at the source in order to achieve the feat of actually performing the said “in phase” algebraic addition. It must also do this in a lossless manner in order that the magnitude of 180 Vpp can be realized.

 

One way to induce this condition is to terminate the transmission line in a short circuit at 90 degrees, forcing the forward voltage to zero, which in turn reflects the wave back to the source, and arriving there as a reflected voltage maxima. Assuming a lossless transmission line and zero ohm short, this would be 90 Vpp, and also in phase with the source.

 

Any lossless 90 degree phase shift network terminated in a short is an alternate means of inducing an infinite VSWR condition. Alternating shorts and opens at 90 degree intervals perform this task as well... assuming this can be done in a lossless manner... but I think you get the idea.

 

What I struggle with however; is how to define a realistic mismatch model at the transmitter output. I've not yet been made aware of an infinite (open circuit) mismatch condition that would induce the theoretical doubling of the source voltage at the source. However; in the case where a transformer is employed, and an inductively coupled winding is not terminated, the flyback voltage induced in the unterminated winding can be many times higher than the induced voltage due to Q multiplication. At the same time, I believe this too is limited by the loading impedance of the primary, and any reflected energy in this case is sensed at the source as a reflected current rather than a voltage. Perhaps the decoupling inductor in the collector/drain does this, but I've not attempted it... Something fun to try when I feel like letting the smoke out of an otherwise good transistor. LOL!

 

I routinely shunt the collector/drain load of my amps with 470 ohms to reduce the Q and minimize any tendency to build up to a dangerous flyback potential. 1K as you suggest I'm sure is probably just as effective.

 

Acknowledging the fact that I'm repeating myself, I'm doing so intentionally... it being an important caveat to convey:

 

“I'm not entirely certain that I'm simulating the operating environment realistically,...”

 

Caveat aside, some of what I'm observing in my attempts at simulating this without the ability to sanity check any of it on my bench, could be gotcha's on what I'm doing here. I may not be simulating precisely what I actually have working on the bench and tested, I may be making incorrect assumptions, or any of a number of other inconsistencies between what I'm playing with here in simulation, and what I have working and measured is suspect at the moment, and may not get sorted out until I return home. I sometimes get bogus results between LTSpice runs also that I haven't yet been able to resolve as well. There's also the risk that my simulations are valid, and they're simply telling me something I don't wish to hear. <sigh!>

 

 

At the moment; my confidence is high based on linear simulation results and bench measurements that show good agreement; but my inability to mirror those results in transient simulations is a bit disturbing. As I give this some thought however; some of what I'm observing may be due to limitations in the linear device models, and the fact that I'm driving the switch at a peak to peak voltage many times greater than the 13.8V switch bias supply. I was on the cusp of testing this latter point just before leaving for vacation; although a preliminary quick first look didn't reveal anything that caught my attention at that time. e.g. My simulations suggest the series connected 2N7000 dissipates 7W for a 20W output transmitter. I would have detected that much power with my calibrated finger thermometer. :-) I also got sidetracked when I discovered Allard's code wasn't yet supporting Full QSK and ran out of time to do more robust testing at the BITX output power level.

 

 

I obtained excellent agreement between measured and simulated linear performance before leaving for vacation. As I discovered in the audio stages, a transient analysis can reveal other artifacts that can become issues if not properly addressed, such as circuit stability, noise, and even ground loops if properly and adequately modeled. Something similar may be at play here with my RF switch as well. For example; the enhancement of switch isolation through output matching isn't predicted in simulation. This could be a good thing or a bad thing, and its an important detail to understand before assuming switch survival is the end goal of the design. Since the switch is also a direct feedback path to the input of the transmitter chain, it's isolation may not be sufficient to prevent the transmitter chain from breaking into self oscillation. This is my biggest concern, and the first item I hope to put to rest when I have Full QSK code to work with. If I identify this as an issue, it could well send me back to the drawing board with respect to the RF switching part of this feature. This may well be the case, and perhaps my transient analysis results are telling me what I don't want to know and I am just stubbornly keeping myself in denial. :-(

 

LTSpice allows one to make differential measurements, and thus verify whether or not device limits are being such as Vgs, and Vds, are being exceeded. It also has the utility to assess the Pd of components that you feel may be at risk of excess thermal stress. It's an incredibly powerful tool, and the only cost is the effort expended to learn how to use it. I think I've simulated everything but the TX chain in the BITX, and I may end up having to do that as well if what I'm seeing in my RF switch analysis proves to be valid. It's as much a troubleshooting tool as it is as a design tool.

 

72/73

 

Gary, N3GO

 

Re: New case found

MVS Sarma
 

I suppose that vu3pop cabinet that is specifically engineered for ubitx is much easier and even cheaper, compared to the ebay item, One has to struggle drilling and milling all things.

POPs enclosure comes with certain p-refixed pcb attachments and speaker etc.
Regarding color choice, Perhaps iof preordered we may request him. Lert me declare that I am not related to POP in any way while suggesting this, nor do I have a finanacial deals .

regards
 

Regards
MVS Sarma
 

On Wed, Jan 31, 2018 at 5:35 AM, Paul Smith <paulsmi55@...> wrote:
They're nice cases. It was a tight fit but I used this one for my BITX20 V3B
https://www.aliexpress.com/item/90-200-165mm-Metal-metal-chassis-instrumentation-shell-with-panel-screws-enclosures/32833797285.html?spm=a2g0s.9042311.0.0.H9P2R3

Be aware that the panels are steel so they're harder to work with. I had an alu one cut to replace the front one.

Paul ZS2OE


Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

I'll have to think about this worst case 180v pk-pk of yours, I may learn something here.
Mostly caught up on sleep during the class that covered transmisssion lines oh so many years ago,
my interest by then was in things digital.

Here's the LTSpice simulation I did of the Bitx40 final one year ago: 
     https://groups.io/g/BITX20/files/KE7ER/bitx40pa.pdf

I cooked up a simulation that covered the rest of the board in LTSpice, not posted there.
The mixers seemed to work as expected, but I couldn't get anything to go through the crystal filter.
Best guess is that there are some LTSpice settings that need to be adjusted to get crystals to behave,
didn't follow through on that to figure it out.

Jerry


On Tue, Jan 30, 2018 at 09:16 pm, Gary O'Neil wrote:

I think I've simulated everything but the TX chain in the BITX, and I may end up having to do that as well if what I'm seeing in my RF switch analysis proves to be valid. It's as much a troubleshooting tool as it is as a design tool.

 

Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

The LTSpice schematic file to simulate the Bitx40 final is also up there, not just the pdf: 
     https://groups.io/g/BITX20/files/KE7ER/bitx40pa.asc


On Tue, Jan 30, 2018 at 09:49 pm, Jerry Gaffke wrote:
Here's the LTSpice simulation I did of the Bitx40 final one year ago: 
     https://groups.io/g/BITX20/files/KE7ER/bitx40pa.pdf

Re: uBITX AM BCI Filter #ubitx

John <passionfruit88@...>
 

Hello Nick,

I also need a broadcast station filter. I was also thinking along your line of inserting it in the Rx chain rather than in the antenna circuit so that I can use small toroids and not worry about saturation.

Have you tried the filter as described?

All the best,

73, John (VK2ETA)

Re: Final schematics for Bitx 40 and uBix?

VU3ECN
 

Thanks Jerry for the detailed explanation for BitX20 ! 

But a similar one remains for uBitx . May be Farhan would be the right person to comment. 

73's 

Ujjwal 

Re: Final schematics for Bitx 40 and uBix?

MVS Sarma
 

you can rerad it on hfsignals.com/ubitx


Regards
MVS Sarma
 

On Wed, Jan 31, 2018 at 11:51 AM, <ujjwalis@...> wrote:

Thanks Jerry for the detailed explanation for BitX20 ! 

But a similar one remains for uBitx . May be Farhan would be the right person to comment. 

73's 

Ujjwal 


Re: Final schematics for Bitx 40 and uBix?

MVS Sarma
 


Regards
MVS Sarma
 

On Wed, Jan 31, 2018 at 12:15 PM, Mvs Sarma <mvssarma@...> wrote:
you can rerad it on hfsignals.com/ubitx


Regards
MVS Sarma
 

On Wed, Jan 31, 2018 at 11:51 AM, <ujjwalis@...> wrote:

Thanks Jerry for the detailed explanation for BitX20 ! 

But a similar one remains for uBitx . May be Farhan would be the right person to comment. 

73's 

Ujjwal 



Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

While I'm dim on transmission lines, your description of the reflection is easy enough to follow and makes good sense.
Magnetics I'm even dimmer on.
I had been assuming that T7 was primarily a forward transformer, not a flyback transformer.
Hadn't really thought about it.
But you are probably right that the source of energy when the IRF510 turns off
would be coming from the magnetics of T7, and thus it is a flyback transformer.

I once ran a simulation of the Bitx40 final with a 50 ohm load, and without any load.
The output voltage with no load increased by maybe 20%, perhaps because of lower IR losses in the IRF510.
Would be interesting to see what the output voltage does when the duty cycle at the IRF510 gate changes.
No idea what happens to your reflected wave, will have to think about that one.

These are really interesting questions, and fundamental to how this all works.
I may have to get out the scope, and maybe cut a quarter wave of coax.

Jerry, KE7ER
   


On Tue, Jan 30, 2018 at 09:16 pm, Gary O'Neil wrote:
What I struggle with however; is how to define a realistic mismatch model at the transmitter output. I've not yet been made aware of an infinite (open circuit) mismatch condition that would induce the theoretical doubling of the source voltage at the source. However; in the case where a transformer is employed, and an inductively coupled winding is not terminated, the flyback voltage induced in the unterminated winding can be many times higher than the induced voltage due to Q multiplication. At the same time, I believe this too is limited by the loading impedance of the primary, and any reflected energy in this case is sensed at the source as a reflected current rather than a voltage. Perhaps the decoupling inductor in the collector/drain does this, but I've not attempted it... Something fun to try when I feel like letting the smoke out of an otherwise good transistor. LOL!

Re: SMD Group Build

VU3ECN
 

Hi Ashhar! 

We have come long way from Leg-Strips used on Valve radio age. Its really humbling to hear that amazing designer like you still stick to basics for putting a quick PCB before all the ideas vanish, like those happening to people like me

As a Class 8th kid, I learned "Silk Screen Printing"  at local Card Printing shop, in scarce resourced small town of 90's India, to make my DIY Electronics and HAM PCB. Today you get ready to use Sensitized Copper Clad Board on ebay/Ali, which  you can expose with PCB artwork film (Laser Printout) and etch with FeCl3.  You can even put "Solder Mask" using ready to iron "film" and later wash away.

https://www.aliexpress.com/item/5-pcs-PP-Kinsten-Positive-Acting-Presensitized-PCB-Board-Single-Side-Plate-Pcb-75x100MM/32797510908.html?priceBeautifyAB=4

https://www.aliexpress.com/item/Free-shipping-5pcs-5-color-UV-Curable-Solder-Mask-10CC-for-PCB-Circuit-board-protect-Soldering/32778631471.html

 

Just took my HAM exam yesterday, again after 20 years. So wish me luck

73's 

Ujjwal 

UPLOAD FIRMWARE IN RADUINO

Michel Dupuy
 

Hello ,
I want to know if to load the firmware in the Raduino it is necessary to feed the raduino card or only the USB port via the PC. Thank you . Michel

Re: uBITX AM BCI Filter #ubitx

Nick VK4PP
 

Hi John,
Not as yet, I have cut some PCB and got some NPO SMD caps and t30-6s ready to go, just have to solder it all up and then remove my uBitx from the casing and install, hopefully in the new few days..
73, Nick, VK4PLN.

Re: uBITX Firmware (CEC) 0.30 released (Test version). #ubitx

Kari Syrjänen
 

Is there compiled version available somewhere?

Kari OH6YW