Date   
AE7EU Top mod update

Diver Martin <diver.martin@...>
 

Update for this week... All the parts came in, finally got everything built up, just need to let the smoke out tomorrow.

1) Mechanical clearances are okay.  Front panel mic/headphones need to move up by about 0.15" to be flush to the encoder/display level

2) .1" headers are misaligned, just needs adjusting in the gerber files, shouldn't be too bad.  Big 'PITA' will be wiring directly to the uBitx on the first run for power, and since I only care about single power supply, this mod will only be roughly tested.

3) Messed up on a few pin headers on the front panel; mostly in that the pins from the AF gain resistor interfere with the main PCB, requiring that they be sanded down.  A 0.062" move is all that's needed.

4) BoM was heavily not optimized.  Optimized out a bunch of components to make everything 50-ohm, 1k, 2.2k, 5k, 10k, and 100k resistors, 0.01uF caps (minus one required 1000pF cap), and removed a bunch of 0.01uF caps that can be replaced with capacitor arrays, but some testing with the new values will need to be done.  Board is populated with optimized values.

5) Footprint for HC595 is incorrect, but usable.  Too narrow footprint, component wider.  Failure due to rushing out the door with the design before checking the footprints on a printout (didn't have the component in hand).

6) Display module is actually the limiting factor for overall height.  A smaller display module, and the whole thing could fit in 1.25 (right now, designed for 1.5")

7) PA Gain cutout is slightly off; still useable with a phillips head screwdriver though.

8) Incorrectly specified Aluminum electrolytics; changing to TH in next design, all 10uF

9) Found the RTC battery was almost fully discharged... will have to check out current consumption when not plugged in, it's probably trying to run the CPU full tilt.

10) Need to change $1.5 PV36W 20-turn pots to 3/4 turn TX33 pots ($.10 each or whatever)

11) Optimize mods comes next after powerup and verification.

12) Need to verify winding orientation of the SWR bridge

Pictures: Front panel:  Headphone, Microphone, Encoder (from uBitx kit), 4 pushbuttons, AF gain, uBitx standard display.

Rear Panel:  +8V input, +12V (or 'PA') input (switchable), RF output, Teensy micro USB (CAT), PTT, Key, DSP Audio (from Teensy3.2), Linear control.  


--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

Re: uBITX AM BCI Filter #ubitx

John <passionfruit88@...>
 

Hello Nick,

I tried the filter in the antenna path and it works very well. So I will order some small toroids and try it in the Rx path when I receive them.

Cheers,

John (VK2ETA)

Re: #ubitx-help Strong Audio Tones in and outside audio receive passband #ubitx-help

John <passionfruit88@...>
 

Problem solved.

Just to re-state the issue: strong tones within the passband, mostly fixed in ferquency. Some slight variation in frequency when scanning through the menu items. Also strong tones outside the passband (near 6400Hz and 14900Hz). These were fixed in frequency and would change with BFO frequency adjustments.

I also had noises when turning the tuning encoder each time the frequency was changed. I thought these were normal as they were mentioned in the Bitx40 rig.

I bought a cheap Arduino on eBay and after some struggle I changed the Nano, re-programmed it and all came good. The tones within the passband are gone and the ones outside the passband can be eliminated with a careful choice of BFO frequency.

Also the tuning noises have disappeared. 

So it must have been a bad Arduino in all logic.

As an interesting aside, when chasing this issue I changed the first two mixers VFOs thereby changing the alignment between the 45Mhz filter and the 12Mhz one. I noticed that the default values produced a signal around 8dBs lower than when "re-aligning" the two passbands.

If anyone is interested I can share the code for this test (I simply re-assigned the RIT menu item and had an extra variable which was added to the first two VFOs so that the net received frequency stayed the same, but the first IF was shifted correspondingly).

Please note that I found the removal of the Arduino a challenge and resorted to cutting the edges out of the Arduino board with a
Dremel and cut the plastic spacer between each pin to be able to de-solder each one individually. I have not mastered James technique obviously!

Since I have mounted the display remotely and have space towards the front of the Raduino, I opted to put some female headers so that I can plug/unplug the Arduino, just in case.

Hope this helps,

73, John (VK2ETA)

Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

> At 7mhz, the IRF510 never shuts off, even if I drive the gate directly from a square wave LTSpice voltage source.

Only true when the antenna port is at high impedance.
With a 50 ohm load the IRF510 shuts off fine because the drain voltage is not rising far or fast.

With just the IRF510 and the transformer and an ac coupled 50 ohm load, the gate driven hard by a 30mhz square wave,
we get a reasonably nice square wave across the load.


On Thu, Feb 1, 2018 at 08:09 pm, Jerry Gaffke wrote:
At 7mhz, the IRF510 never shuts off, even if I drive the gate directly from a square wave LTSpice voltage source.

Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

I was getting a bit overenthusiastic about posting when new revelations hit.
The final email of that series is the executive summary:
    https://groups.io/g/BITX20/message/40918

So I concluded that the Bitx40's T7 *is* a flyback transformer, and your 2n7000 could see kilovolts
if the antenna port is left open circuit.  (In this case an autotransformer, part of it is both primary and secondary)
But only if the RF is of fairly low frequency, and on the Bitx40 it never will be low enough in freq to care.

At 7mhz, the IRF510 never shuts off, even if I drive the gate directly from a square wave LTSpice voltage source.
Probably because as drain current decreases, the drain voltage shoots up due to T7 wanting to keep the current going,
and the miller capacitance causes the gate (internal, not necessarily the TO220 pin)  to rise as well,
tending to keep the IRF510 turned on.  Negative feedback at work.

As the Wikipedia entry shows, a flyback converter has a diode on the secondary.

I've worked around buck and boost switching converters, and had to figure out what those inductors and diodes are doing.
Moving to a flyback transformer is not much of a transition, it just adds another winding that can tap into
the same energy that the first one sees.   Which is to say that in addition to your 2n7000, the IRF510 could also blow
if the antenna port is left open at low frequencies.  Which explains the zener from drain to ground
you often see in this kind of amp.

The uBitx probably won't have this issue, I believe T11 truly does behaves as a forward transformer.

Jerry, KE7ER


On Thu, Feb 1, 2018 at 06:11 pm, Gary O'Neil wrote:
I think I agree with your assessment of T7 being wired as a forward transformer. I haven't studied it closely, but I don't think an open load would be sufficient to create a flyback condition. It certainly isn't a flyback converter though, as i think may be the correct terminology when used with a diode in the primary... The diode which creates a lo w impedance pulsed current input for half the input cycle, and a high impedance load on the other half of the cycle which allows the secondary... typically as an autotransformer voltage to grow. I think CRT HV supplies used this technique. 

Re: Software support Request for Full QSK BITX40

Jerry Gaffke
 

I pulled some example crystal parameters from measurements somebody else made, I think from W7ZOI's EMRFD.
Tried modeling a single crystal.

The AC Analysis looked good, showing the parallel and serial resonances just like all the references.
The transient analysis didn't find the resonance at all, I think the resonance is too sharp and sudden and
the tools are optimized to make long jumps after evaluating current trends.  Could most likely be cured 
by some sort of spice directive telling it to do more thorough processing.  Perhaps this
"sweep frequency resolution choice" you mentioned.  Though I did fiddle with what I thought was the
obvious stuff before giving up.

Jerry


On Thu, Feb 1, 2018 at 05:44 pm, Gary O'Neil wrote:

Where did you get the x-tal parameters for the filter you modeled in LTSpice? As I'm certain you already know, X-tal selection and matching is a critical component of their design, and doing this in a cavalier manner can yield disappointing results. I suspect the same attention to matching criteria in the selection of X-tal models is likely necessary to achieve successfull and realistice simulation results as well. I'm guessing you weren't missing anything in LTSpice. The x-tals are modeled as L's and C's, and the analysis is linear and no different than a standard LCR filter.  Perhaps you're using the exact parameters for each x-tal and thinking "I can't match them any closer than that!" :-) I suspect that it might result in unrealisticly high Q, and easily missed in the sweep frequency resolution choice.   

MBITX

n4dxx@...
 

Just joined the group after ordering my MBITX Kit ..Does this mean they are on back order?Shipping will start ex-stock in by Februry end, until then the orders are being booked in advance
Thanks N4DXX

Re: Diy oscilloscope #parts

Jerry Gaffke
 

Yes, it's useless for RF as is, and likely kind of ideosyncratic and of sub 200khz bandwidth.
But for $23, it's very interesting.  Gets good reviews on Amazon:
      https://www.amazon.com/JYE-DSO-13801K-Open-Source/dp/B00WAQGGZ

Could add an SA612 mixer, bring your transmitted signal down to 100khz
and then monitor it using the DSO138.

Page 75 of the datasheet for the STM32F103C8 used on that scope
    https://www.mouser.com/ds/2/389/stm32f103c8-956229.pdf
says the sample time of the ADC when operating at 1msps is 0.107us
Could see Dexter's modulation envelope on sub 1mhz RF as a cloud of dots,
accumulating that cloud over many trigger events. 

If you had a fast sample and hold, and some way to measure time from trigger to sample, 
you could create a sampling scope.  That would be useful for RF, and could be very cheap.
One possible way to cheaply measure time from trigger to first ADC sample strobe would be counters in a 250mhz PAL,
read a count from the STM32 through an SPI interface into the PAL.  So a $3 PAL plus an STM32 and the sample and hold
gives a sampling head that effectively samples at 100mhz.   Samples after the first can be well timed, so could grab
many samples for each trigger.

Here's another possible way:  About $25 worth of parts as shown here but paired with a $2 STM32 dev board
instead of Houtman's 10mhz analog scope, gives us a 1 GHz bandwidth sampling scope.
    http://www.redrok.com/sampscope.htm
 
Thinking about cheap way to do test gear is almost as much fun as
thinking about cheap ways to do ham gear.

Jerry, KE7ER


On Thu, Feb 1, 2018 at 03:29 pm, Master Ice wrote:
Be warned these scopes are of absolutely NO use for RF work.
The bandwidth is 200KHz AT BEST!
No use whatsoever for RF work.
 

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

bill richardson
 

Loaded this tonight on my newly build uBitx.. Wow what a great firmware. It’s fantastic!

Thank you


On Feb 1, 2018, at 12:33 PM, David S via Groups.Io <dcsuk10@...> wrote:

Ian

 I'm a late comer to your party, amazing code functionality, takes the radio to another lever with the CAT, especially for digital.   No issues with uploading to the radio, I figured out how to use Xloader, a really simple way of getting the right code into the radio. 

I've also more or less got to grips with the uBitx manager and have a few comments, I entered my callsign and set it to display (permanently) on the previous manager software, the latest version has the alternate VFO frequency displayed in the callsign position and wipes it out.  I can't see any way of stopping either the 2nd VFO frequency or the Step from displaying, it could do with a settings flag. 

There's also an anomaly in the code step function, probably I didn't read about the it correctly.  It works as expected, a little fiddly getting the correct function press time, however  when I entered 500Hz, it's accepted by the manager, it saves and recovers from disc correctly but is implemented as 244Hz by the radio.

A quick question about the band frequencies, the maximum frequency I can enter is 99999 (Hz), sometimes a read from the radio gives a sensible frequency 554970912 (Hz) & mode 1.  Sorry I just can't figure this at all.

The other oddie is that I would expect to be ably to read a configuration file from disc both with or without the radio being connected.  I find that I have to read from the radio to allow a backup to be read from the disc.

I can see that you've got the bit well and truly between your teeth, are there any plans to add functionality for a 4 line or any other display.

Best regards & many thanks for the sharing the huge increase in functionality. 

David  G8DJM

Permission?

Jack, W8TEE
 

Naw, just kidding you. I think it's great that you took the plunge. However, you just might find it addicting!

Jack, W8TEE



From: Charles D. Smith <laborlawyer@...>
To: BITX20@groups.io
Sent: Thursday, February 1, 2018 9:58 PM
Subject: Re: [BITX20] First Arduino sketch loaded

One book at a time ... your “projects” book is all I can handle right now ... I’m hoping if I put it under my pillow, I’ll learn some code ;-)


On Feb 1, 2018, at 9:21 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:

I know of a great book that can help you... :>)

Jack, W8TEE



From: Charles D. Smith <laborlawyer@...>
To: BITX20@groups.io
Sent: Thursday, February 1, 2018 8:42 PM
Subject: [BITX20] First Arduino sketch loaded

nobody laugh ... (ok, go ahead)  ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff!  But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot. 




Re: First Arduino sketch loaded

Charles D. Smith
 

One book at a time ... your “projects” book is all I can handle right now ... I’m hoping if I put it under my pillow, I’ll learn some code ;-)


On Feb 1, 2018, at 9:21 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:

I know of a great book that can help you... :>)

Jack, W8TEE



From: Charles D. Smith <laborlawyer@...>
To: BITX20@groups.io
Sent: Thursday, February 1, 2018 8:42 PM
Subject: [BITX20] First Arduino sketch loaded

nobody laugh ... (ok, go ahead)  ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff!  But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot. 


Re: First Arduino sketch loaded

John P
 

That's where every "C" programmer in the world started! Congrats! 
--
John - WA2FZW

Re: First Arduino sketch loaded

Ken
 

Pitch Jack, pitch it...hi hi

73

Ken VA3ABN

On Thu, Feb 1, 2018 at 9:20 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
I know of a great book that can help you... :>)

Jack, W8TEE



From: Charles D. Smith <laborlawyer@...>
To: BITX20@groups.io
Sent: Thursday, February 1, 2018 8:42 PM
Subject: [BITX20] First Arduino sketch loaded

nobody laugh ... (ok, go ahead)  ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff!  But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot. 



Re: First Arduino sketch loaded

Jack, W8TEE
 

I know of a great book that can help you... :>)

Jack, W8TEE



From: Charles D. Smith <laborlawyer@...>
To: BITX20@groups.io
Sent: Thursday, February 1, 2018 8:42 PM
Subject: [BITX20] First Arduino sketch loaded

nobody laugh ... (ok, go ahead)  ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff!  But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot. 


Re: Software support Request for Full QSK BITX40

Gary O'Neil
 

Hi again Jerry;

I think I agree with your assessment of T7 being wired as a forward transformer. I haven't studied it closely, but I don't think an open load would be sufficient to create a flyback condition. It certainly isn't a flyback converter though, as i think may be the correct terminology when used with a diode in the primary... The diode which creates a lo w impedance pulsed current input for half the input cycle, and a high impedance load on the other half of the cycle which allows the secondary... typically as an autotransformer voltage to grow. I think CRT HV supplies used this technique. 

I need to review the references you provided and refresh my own understanding of this and how to correctly differentiate the differences between transformer configurations and their implications. I don't think it has relevance to this forum, but its an area where my understanding is weaker than I would like. It will serve me well to revew this in some detail and gain a deeper understanding. 

73

Gary, N3GO

Re: [uBITX] Key line resistor: OK to mount on Raduino board?

K5DH
 

Thanks, guys!

HF Pelican case clone

Vince Vielhaber
 

The online Harbor Freight coupon code (can also be used in store) for the Pelical 1150 clone for $9.99 is 68377487. This code is only valid till 2/28.

Vince.
--
Michigan VHF Corp. http://www.nobucks.net/ http://www.CDupe.com/
http://www.metalworkingfun.com

Re: Software support Request for Full QSK BITX40

Gary O'Neil
 

Jerry;

The 180V P-P I was referring to was the source voltage required to achieve the P-P voltage at the switch input for my speculated assessment of an infinite VSWR reflection for a 20W transmit output power. I'm all but certain that this "first pass" guess was/is unrealistic, and my previous post (the LTSpice model I posted) which shows 112V P-P is sufficiently worst case for the BITX operated from a 28V PA supply. That model does indicate an exposure to exceeding the spec boundaries of the 2N7000, but for power dissipation rather than voltage. I think that model is close, but I still need to verify it through measurements.  

Where did you get the x-tal parameters for the filter you modeled in LTSpice? As I'm certain you already know, X-tal selection and matching is a critical component of their design, and doing this in a cavalier manner can yield disappointing results. I suspect the same attention to matching criteria in the selection of X-tal models is likely necessary to achieve successfull and realistice simulation results as well. I'm guessing you weren't missing anything in LTSpice. The x-tals are modeled as L's and C's, and the analysis is linear and no different than a standard LCR filter.  Perhaps you're using the exact parameters for each x-tal and thinking "I can't match them any closer than that!" :-) I suspect that it might result in unrealisticly high Q, and easily missed in the sweep frequency resolution choice.   

73

Gary, N3GO

First Arduino sketch loaded

Charles D. Smith
 

nobody laugh ... (ok, go ahead)  ... I just loaded and modified my first sketch ... so changing out “world” and putting in my town isn’t much of a change, it’s something. Plus, I varied the count too ... woohoo!
before I plug the computer into the raduino, I’m going to get a much better handle on this stuff!  But it’s very exciting to a pencil and paper guy!
72/73 de Chas ai4ot. 

Re: Care and Feeding of SMD Parts

Jerry Gaffke
 


On Thu, Feb 1, 2018 at 03:44 pm, Vince Vielhaber wrote:
Replying to myself...

This is the one I like. Don't have one, I got some smd sample kits in binders, but I plan on getting one in the not too distant future.

https://www.ebay.com/itm/BOXALL-SMD-SMT-resistor-capacitor-storage-box-Organizer-1206-0805-0603-0402-020/170644661655?hash=item27bb36e597:g:gzUAAOSwoydWrdnM