Date   
Re: UBITX V3 TX GAIN VARIATIONS

MadRadioModder
 

Current capabilities of capacitors in RF service.  The most forgotten issue.

 

 


Virus-free. www.avg.com

--

…_. _._

Which xmit transistor is blown?

Sean W7SKD
 

I have had periodic issues with the ubitx that led me to believe that my finals (IRF510) were blown, and the radio seemed to work as expected after replacement, so perhaps they were.

I have a question though...is there a good way to tell what has gone out in the xmit power chain?  I recently replaced Q90 with an mmbt2222a (smt version of the 2n2222a), and then the next two stages with 2n2222a's (in TO-18 form).  No other changes to the radio.

It worked fine for a few days, though the 2n2222a's would get hot to the touch in digital mode transmit (which I think is to be expected).  Today I started to experience 'bouncing' power readings during transmit (as shown in the meter on my tuner) before the radio simply stopped putting out much power at all.  Nothing feels hot...and nothing looks burned or heat stressed to the naked eye.

So...before I start replacing things, I wanted to ask how to diagnose the problem.  Is it most likely that I cooked some transistors, and how do I best till which ones?

73

Sean

Re: 4.2" Nextion Bezel? #3d_printing #ubitx-help

Terence Taylor
 

I talked to David and am going to laser cut one for him out of acrylic.


On Friday, August 31, 2018 12:21 PM, David Posthuma <davep@...> wrote:


Chris:
 
I would be looking for flat black. The inner dimensions are 4 1/8 inches by 2 11/16. I would be looking for a simple rectangle that is 1/8 inch in thickness and 1/4 inch wide all around. What would this (or a spool) cost???
 
David A Posthuma, WD8PUO
1 (616) 283-7703
 
From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Christopher Miller
Sent: Friday, August 31, 2018 11:49 AM
To: BITX20@groups.io
Subject: Re: [BITX20] 4.2" Nextion Bezel? #3d_printing #ubitx-help
 
I could probably help but I don't have any black pla to print with. Here in Tucson we have a maker space called xero craft. You may have one where you live. Xero for example has a couple of printers that can be used for a donation. Another option would be to use shapeway or some other site that will print and mail an object for a fee.
 
Feel free to contact me if you are willing to pay for a spool of filament and I will be happy to do it.
 
Chris
 
On Fri, Aug 31, 2018, 8:31 AM David Posthuma <davep@...> wrote:
I am using the 4.2" Nextion touch screen on my Ubitx. Does anyone know where I can get a small black bezel/frame for it? I only need about 1/4-inch on all sides. Unfortunately, I don't have access to a 3D printer. Thank you for any leads the group may provide.


Re: VK4PP uBitx LPF BANK add-on Board

Jerry Gaffke
 

Seems whatever I had in post 58293 is contagious.
Everyone should take precautions!

Wear a mask fitted with an appropriate low pass filter.   ;-)

Jerry, KE7ER



On Fri, Aug 31, 2018 at 12:12 PM, Gordon Gibby wrote:

....was  supposed to read  "a low pass filter above 20 METERS"  (not MHz)

cheers,  gotta go cut some grass before it pours again....

 

gordon

 

Re: UBITX V3 TX GAIN VARIATIONS

Jerry Gaffke
 

Parts do not come with solder on the pins.

When manufacturing, the usual process is to lay a stainless steel mask over the board with holes cut into it for each pad,
then squeegie on some solder-paste, which is solder with the consistency of play-dough.
Then auto-insert all those dinky R's and C's and transistors with a pick-and-place machine.
Send the board through a heat process of some sort.
Surface tension of the melted solder tends to pull any slightly wayward arts into the center of their pads.

Some hobbyists do this by applying solderpaste from a syringe, laying down a straight bead across consecutive pads
on something like a QFP with 100 pins on 20 mil centers. Then run it through a toaster oven.
When the solder melts it will adhere to the pad and separate nicely to one little blob per pin/pad.
    http://store.curiousinventor.com/guides/Surface_Mount_Soldering/Solder_Paste_and_Toaster_Oven

For rework on a uBitx of course, you can't use a toaster oven.
I'd melt some ChipQuik low temp solder alloy in around the part to be removed using a soldering pencil,
then use something like an embossing gun (a hot air heat gun, maybe 250 watts?) to get the part 
hot enough to pluck it off the board with tweezers.  For R's and C's, it's easiest to take two soldering
pencils, one on each end simultaneously.  For 3 pin parts such as all those mmbt2n3904's, perhaps heat
up that single pin on one side with the soldeirng pencil and lift it up off the board using a knife, then 
free up the other two pins using two soldering pencils as if it was an R or C.

Jerry, KE7ER


On Fri, Aug 31, 2018 at 12:20 PM, Bo Barry wrote:
Question. Do the tiny parts have solder on them? I read about some that do and they can be mounted by using hair dryer. I assume you have to hold them down good.

Re: UBITX V3 TX GAIN VARIATIONS

Christopher Miller
 

Smd parts don't come with solder on them. You can use a hot air gun to rework a pcb. A decent iron with a fine tip is what I use with leaded solder. I also use tweezers designed for smd work to hold parts in place. It would be advisable to get a couple of practice boards before working on something important. 

Re: 4.2" Nextion Bezel? #3d_printing #ubitx-help

 

Chris:

 

I would be looking for flat black. The inner dimensions are 4 1/8 inches by 2 11/16. I would be looking for a simple rectangle that is 1/8 inch in thickness and 1/4 inch wide all around. What would this (or a spool) cost???

 

David A Posthuma, WD8PUO

1 (616) 283-7703

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Christopher Miller
Sent: Friday, August 31, 2018 11:49 AM
To: BITX20@groups.io
Subject: Re: [BITX20] 4.2" Nextion Bezel? #3d_printing #ubitx-help

 

I could probably help but I don't have any black pla to print with. Here in Tucson we have a maker space called xero craft. You may have one where you live. Xero for example has a couple of printers that can be used for a donation. Another option would be to use shapeway or some other site that will print and mail an object for a fee.

 

Feel free to contact me if you are willing to pay for a spool of filament and I will be happy to do it.

 

Chris

 

On Fri, Aug 31, 2018, 8:31 AM David Posthuma <davep@...> wrote:

I am using the 4.2" Nextion touch screen on my Ubitx. Does anyone know where I can get a small black bezel/frame for it? I only need about 1/4-inch on all sides. Unfortunately, I don't have access to a 3D printer. Thank you for any leads the group may provide.

Re: UBITX V3 TX GAIN VARIATIONS

Bo Barry <bobarr@...>
 

Enjoying all the mod ideas, just can't keep up with them.
I keep doing screen captures on my iPhone for later reference. I follow about 90% of the technical ideas, but working on these tiny parts dulles my excitement. 

I'm starting the easy way for now. Socket pins for the 6 3904s.  Just got a bunch of supposedly Motorola 2222A's to try. And some 3866A's.  Use WT15 code at www.  witonics.  Com and get 15% off for next 2 weeks. 😁

Question. Do the tiny parts have solder on them? I read about some that do and they can be mounted by using hair dryer. I assume you have to hold them down good. 🤔.  
Bo W4GHV 

Re: VK4PP uBitx LPF BANK add-on Board

Gordon Gibby <ggibby@...>
 

....was  supposed to read  "a low pass filter above 20 METERS"  (not MHz)

cheers,  gotta go cut some grass before it pours again....


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Gordon Gibby <ggibby@...>
Sent: Friday, August 31, 2018 2:41 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 

Warren, you are right on, but you might not have seen all the posts where I did exactly what you are saying.   Both BEFORE the daughterboard and AFTER the daughterboard so i had proof of its effectiveness.   I also did some calibrations of the S-meter using BNC attenuators (which is all I have).   I then did the suggested measurements of today, measuring bleed-through (unmeasureable, whereas I was clearly able to measure the harmonics and able to measure their reduction by moving the input side of the relay chain OFF the board.)


Here, I'll see if I can find the posts (I'm not too used to that):


(1)Very first "before" measurements:   https://groups.io/g/BITX20/message/57840

(2)Complete baseline data:   https://groups.io/g/BITX20/message/57974

(3) Calibration of the S-meter and proof that the measurement setup itself didn't have bleed thru:  https://groups.io/g/BITX20/message/58070

  [This distinctly showed that 1 S unit in the range of 7-9 is 12 db onthat receiver on that frequency)

(4)Photos of the measurement setup:  https://groups.io/g/BITX20/message/58070

(5) DAta AFTER daughterboard:   https://groups.io/g/BITX20/message/58070



What I CANNOT prove is that the receiver maintains identifical response at all frequencies (hence, is "flat")  however it is reasonable that the differnces aren't mroe than a few dB based on specifications for rigs of this price range etc.   


Poor man's spectrum analyzer.   What is problematic is the 24MHz harmonic range --- here I achieved only 6 dB reduction so there is something else going on there...maybe a series resonance in a filter or somethign I haven't thought of.   Every other range was dramatically reduced by the daughterboard system.   So for my purposes --- a low pass filter above 20 MHz and I have every digital band I need for what I need out of the radio and I don't need to use the bands where the "spurs" are a thorn.   



Hope that makes more sense.   

Cheers,


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Warren Allgyer <allgyer@...>
Sent: Friday, August 31, 2018 2:24 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 
Gordon

Your reasoning makes perfect sense. But I think you can measure at the actual harmonic frequencies which is where the issue would be . Your IC-718 can tune the third, fifth and 7th harmonics of 80 meters. So you can know exactly (within the limits of the S meter calibration and linearity) what the residual level is at the harmonic frequencies themselves. You have checked your S-meter and you know what represents 45-50 dB below S9+30 (normally one S unit = 6 dB but in real life S meters rarely replicate that). So just tune the harmonics directly and measure them. Or am I missing something?

WA8TOD

Re: VK4PP uBitx LPF BANK add-on Board

Gordon Gibby <ggibby@...>
 

Warren, you are right on, but you might not have seen all the posts where I did exactly what you are saying.   Both BEFORE the daughterboard and AFTER the daughterboard so i had proof of its effectiveness.   I also did some calibrations of the S-meter using BNC attenuators (which is all I have).   I then did the suggested measurements of today, measuring bleed-through (unmeasureable, whereas I was clearly able to measure the harmonics and able to measure their reduction by moving the input side of the relay chain OFF the board.)


Here, I'll see if I can find the posts (I'm not too used to that):


(1)Very first "before" measurements:   https://groups.io/g/BITX20/message/57840

(2)Complete baseline data:   https://groups.io/g/BITX20/message/57974

(3) Calibration of the S-meter and proof that the measurement setup itself didn't have bleed thru:  https://groups.io/g/BITX20/message/58070

  [This distinctly showed that 1 S unit in the range of 7-9 is 12 db onthat receiver on that frequency)

(4)Photos of the measurement setup:  https://groups.io/g/BITX20/message/58070

(5) DAta AFTER daughterboard:   https://groups.io/g/BITX20/message/58070



What I CANNOT prove is that the receiver maintains identifical response at all frequencies (hence, is "flat")  however it is reasonable that the differnces aren't mroe than a few dB based on specifications for rigs of this price range etc.   


Poor man's spectrum analyzer.   What is problematic is the 24MHz harmonic range --- here I achieved only 6 dB reduction so there is something else going on there...maybe a series resonance in a filter or somethign I haven't thought of.   Every other range was dramatically reduced by the daughterboard system.   So for my purposes --- a low pass filter above 20 MHz and I have every digital band I need for what I need out of the radio and I don't need to use the bands where the "spurs" are a thorn.   



Hope that makes more sense.   

Cheers,


gordon




From: BITX20@groups.io <BITX20@groups.io> on behalf of Warren Allgyer <allgyer@...>
Sent: Friday, August 31, 2018 2:24 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 
Gordon

Your reasoning makes perfect sense. But I think you can measure at the actual harmonic frequencies which is where the issue would be . Your IC-718 can tune the third, fifth and 7th harmonics of 80 meters. So you can know exactly (within the limits of the S meter calibration and linearity) what the residual level is at the harmonic frequencies themselves. You have checked your S-meter and you know what represents 45-50 dB below S9+30 (normally one S unit = 6 dB but in real life S meters rarely replicate that). So just tune the harmonics directly and measure them. Or am I missing something?

WA8TOD

Re: BITX40 Saving Settings Issue

Allard PE1NWL
 

Hi Gary,

it could also be a timing issue.

At line 2327, there is a short 100ms delay:

delay(100);               // allow the voltages on the Arduino inputs to
settle for some milliseconds after power on

Perhaps the 100ms is just not enough for your radio.
You could try 200ms and see if it helps.
Simply change
delay(100);
to
delay(200);
Then recompile and upload to the Raduino. Please let me know if this helps. 73 Allard PE1NWL

KARMA and BITX

Lawrence Macionski <am_fm_radio@...>
 

Is  this Karma?

Howard E. Michel, WB2ITX, is New ARRL Chief Executive Officer

The ARRL Board of Directors has elected Howard E. Michel, WB2ITX, of Dartmouth, Massachusetts, to be ARRL's new Chief Executive Officer. He will start on October 15. Michel (rhymes with "nickel") is currently Chief Technology Officer at UBTECH Education, and Senior Vice President of UBTECH Robotics, a $5 billion Shenzhen, China, artificial intelligence and robotics company. As the Chief Technology Officer at UBTECH Education, Michel helped build this company from a startup in China to $100 million in valuation.
Full Story......
http://www.arrl.org/arrlletter?issue=2018-08-31

NNNN
Larry W8LM
ARRL Life Member

Re: VK4PP uBitx LPF BANK add-on Board

Warren Allgyer <allgyer@...>
 

Gordon

Your reasoning makes perfect sense. But I think you can measure at the actual harmonic frequencies which is where the issue would be . Your IC-718 can tune the third, fifth and 7th harmonics of 80 meters. So you can know exactly (within the limits of the S meter calibration and linearity) what the residual level is at the harmonic frequencies themselves. You have checked your S-meter and you know what represents 45-50 dB below S9+30 (normally one S unit = 6 dB but in real life S meters rarely replicate that). So just tune the harmonics directly and measure them. Or am I missing something?

WA8TOD

Re: VK4PP uBitx LPF BANK add-on Board

Gordon Gibby <ggibby@...>
 

Hi, I get that.   I but Icannot measure it at all frequencies.  I don't have a spectrum analyzer, I have a RECEIVER and I've calibrated portions of its response in order to use it as a poor-mans spectrum analyzer.    Presumably the blow-by is capacitive for the most part, but not at all parts.   Lacking a spectrum analyzer, I measure the effective blow by at ONE frequency and then draw assumptions at others based on a model that it is primarily capacitve in nature (which has been the major point of discussion for weeks now......)


So if you know that capacitive reactance goes down by 10X when you increase the frequency by 10X, and in both cases you are feeding into a 50 ohm load.......the voltage you're going to get will go up on the order of 10X.    


​Thus you can make a prediction (based on the model) of what the bleed through might be at higher frequencies.   Or you can risk your rig by making other measurements if you don't have any other way to do it (which is me).   Does that make more sense?


Cheers,


gordo



From: BITX20@groups.io <BITX20@groups.io> on behalf of Warren Allgyer <allgyer@...>
Sent: Friday, August 31, 2018 1:50 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 

Gordon

"Bleed through" or "blow by" at the operating frequency is not the issue. It is bleed through at the 5th and 7th harmonic that allows those harmonics to reach levels that are non-compliant.

WA8TOD

Re: 4.2" Nextion Bezel? #3d_printing #ubitx-help

Bill Cromwell
 

Hi,

I made the bezel for my stock display from a nice piece of scrap wood. You could do the same for your bigger display.

73,

Bill KU8H

On 08/31/2018 11:31 AM, David Posthuma wrote:
I am using the 4.2" Nextion touch screen on my Ubitx. Does anyone know
where I can get a small black bezel/frame for it? I only need about
1/4-inch on all sides. Unfortunately, I don't have access to a 3D
printer. Thank you for any leads the group may provide.
--
bark less - wag more

Re: VK4PP uBitx LPF BANK add-on Board

Warren Allgyer <allgyer@...>
 

Gordon

"Bleed through" or "blow by" at the operating frequency is not the issue. It is bleed through at the 5th and 7th harmonic that allows those harmonics to reach levels that are non-compliant.

WA8TOD

Re: UBITX V3 TX GAIN VARIATIONS

Kees T
 

On Thu, Aug 30, 2018 at 09:42 PM, ajparent1/KB1GMX wrote:
The cap does not need to be a 500V part even at 28V as the mosfets will self destruct
at 100V, so a 100V cap is fine so long as it can handle high RF current.
I've found that the 500V caps are more "robust" from a current handling and stability standpoint...and those are 500V DCWV. At RF (AC) they are all derated. I use a "rule of thumb" (which is easy for me to remember) ....50%.  That also means you have to consider the RF voltage rating of the blocking capacitors in the feedback loops. If they fail the associated MOSFET is toast.

73 Kees K5BCQ 

Re: ATU for mBITX

Lawrence Galea
 

Google picatune ATU

On Fri, Aug 31, 2018 at 5:46 PM n5ib_2 <n5ib@...> wrote:
The bias tee isn't used to power the T1, since it has internal battery power, and, with latching relays, only draws power when tuning.
The bias tee, using a lithium coin cell for DC power, fires an optical isolator at the antenna end that triggers the remote control line on the T1.

So the only connection between the Tx and the T1 is the coax.

N5IB







Re: VK4PP uBitx LPF BANK add-on Board

Gordon Gibby <ggibby@...>
 

The measurements that I made  for the daughterboard  bleed-through indicate that for the ENTIRE SYSTEM,  including the printed circuit board, connecting leads, relays, coils, coil wiring and all the RF wiring,  the bleed  through is almost NEGLIGIBLE. (lifted the bottom green wire in the accompanying photo and measured bleed through that had to go through ALL SIX RELAYS).    Far, far below the pass through the filter....  down to unmeasureable on the ICOM718..whereas properly filtered harmonics  were depressed into the S5 or S6 range from 30dB overS9  fundamental (as predicted by others' measurements indicating the FILTERS had acceptable performance)     Measurement performed at 3.5  MHz.  Presumably capacitive coupling would increase related to frequency, perhaps 10 times the amount would be expected at 30 MHz --- but that would only be 10dB more signal, perhaps reaching to S2   I don't want to risk my finals by doing  the experiment over and over.   The bleed through with a daughterboard --- even with unshielded wires --- is far far far below  the requirements to meet FCC specs.    (-43 dB being  somewhere around S7.5 in my tests).    Get the relays separated, get the things apart physically that need to NOT bleed into each other....and it isn't that difficult to fix the harmonics.  (The spurs are a different issue).   





From: BITX20@groups.io <BITX20@groups.io> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Friday, August 31, 2018 12:17 PM
To: BITX20@groups.io
Subject: Re: [BITX20] VK4PP uBitx LPF BANK add-on Board
 
I interpret this measurement from Glenn:
    "-32dB from one set of contacts to the other. (common terminal)"
as being from KT1 pin 14 to pin 16 as seen in the uBitx schematic.

Also, interpret his -39 and -41 dB numbers to be from one relay section to the other,
which I averaged as -40dB.    For example, KT1 pin 12 to pin 5.

I now suspect those assumptions are incorrect, but the analysis could easily be adjusted to for any change to those two numbers.

Jerry


On Fri, Aug 31, 2018 at 03:40 AM, Glenn wrote:
All good points Warren.   I did some checks of isolation using a typical DIP relay, type HK19F. DPDT

I made a small jig to hold the relays and measure isolation across contacts etc.
Typically it was -34dB across open contacts,
-32dB from one set of contacts to the other. (common terminal)
-41dB from open terminals on each side
-39dB from common of one pole to open on the other pole.
-48db from common to coil.
 At 30MHz.  Better as freq drops of course.
That's without effects of a PCB and various other traces.

glenn

Re: VK4PP uBitx LPF BANK add-on Board

Jerry Gaffke
 

I interpret this measurement from Glenn:
    "-32dB from one set of contacts to the other. (common terminal)"
as being from KT1 pin 14 to pin 16 as seen in the uBitx schematic.

Also, interpret his -39 and -41 dB numbers to be from one relay section to the other,
which I averaged as -40dB.    For example, KT1 pin 12 to pin 5.

I now suspect those assumptions are incorrect, but the analysis could easily be adjusted to for any change to those two numbers.

Jerry


On Fri, Aug 31, 2018 at 03:40 AM, Glenn wrote:
All good points Warren.   I did some checks of isolation using a typical DIP relay, type HK19F. DPDT

I made a small jig to hold the relays and measure isolation across contacts etc.
Typically it was -34dB across open contacts,
-32dB from one set of contacts to the other. (common terminal)
-41dB from open terminals on each side
-39dB from common of one pole to open on the other pole.
-48db from common to coil.
 At 30MHz.  Better as freq drops of course.
That's without effects of a PCB and various other traces.

glenn