Date   
Re: uBitx V3 low power continues

Ted
 



Michel,

I'm rather pleased that an obscure find such as this, helped someone else.  At least one or two transistors bravely gave their lives in the search for this fault, as weak output led to an assumption that Q90 was the issue.  Best wishes always.




Mark, 

"Denial" is a sneaky adversary in these pursuits; I mean, I'm not entirely sure what the purpose of that capacitor + resistor is, in parallel with the bias resistor on that leg of Q90. There's no denying that its important!

Having a strip of deer-tick sized 22-ohm resistors from the 2N2222 driver stages mod, I may just pair a few up and replace the R83 with a heavier "resistor" as a precaution. 



With appreciation,

Ted
K3RTA

Re: uBitx V3 low power continues

Michel Dupuy
 

Thanks Ted, a few days ago my output power had gone from 12W to 1W and reading your message this morning I checked and indeed the resistance R83 of 10 Ohms were cut off, I replaced it and I retrovated the nominal power. Indeed transistor Q90 instead of amplifying attenuated the signal. Thank you from F1GTX

Re: RF output when just keying the mike

Maurice Bersan
 

Thanks Raj, I tried 11.0555 but it was very much worse, however the setting I am using now is 11.055.995 and it sounds normal now.
Thanks again
Maurice

On 7 Nov 2019 1:47 p.m., Raj vu2zap <rajendrakumargg@...> wrote:

Set it to 11.0555 and see if it sounds fine and no carrier leak!

Raj

At 06/11/2019, you wrote:
>Thanks the help so far, yes it is a calibration/bfo settings issue. I still struggle to set them correctly. So I'm using factory default settings at the moment, works ok but sounds like it has to much trebble.
>Cheers
>Maurice
>Vk6hly





Re: RF output when just keying the mike

 

Set it to 11.0555 and see if it sounds fine and no carrier leak!

Raj

At 06/11/2019, you wrote:
Thanks the help so far, yes it is a calibration/bfo settings issue. I still struggle to set them correctly. So I'm using factory default settings at the moment, works ok but sounds like it has to much trebble.
Cheers
Maurice
Vk6hly

Re: uBitx RF Power Amplifier Standalone

JuanCarlos
 

Please send an email to Heriberto Tito Mendoza at
He design the new layout and tested it.
JuanCarlos

On Wed, 6 Nov 2019 at 12:55 PM <circular.simetry@...> wrote:
hello does anyone have the pcb layout for this amplifier ?

--


Qrv's, 73's

Mr.Juan Carlos Berberena Glez BSc.
WJ6C ex/CO6BG

www.frcuba.com (visíta mi website y déjame un mensaje usando "contacto")

“If you have a penny and I have a penny and we exchange pennies, you still have one cent and I still have one cent.  But if you have an idea and I have an idea and we exchange ideas, you now have two ideas and I now have two ideas.” 

Re: uBitx V3 low power continues

 

Glad you found it!

"Whether that swap "caused" R83 to open up is anyone's guess."

I'll take that bet hihi.  I always look at the last thing I did when I have an unexpected problem.  Sometimes this works with the XYL too.

Ted, for getting a better view at close-spaced waveforms you can use the x10 Mag control to cut the sweep time by 1/10th.

73,


Mark.

Re: bitx v3 zero pa output

David Nelson
 

Will try to work on this some more tomorrow. Thanks  Dave


On Wed, Nov 6, 2019 at 4:01 PM Evan Hand <elhandjr@...> wrote:

I had similar problem that I traced to rf feedback getting into the Nano controls.  That does not mean that it is your issue, just one other thing to test.  That fact that you changed the IRF510 is a potential pointer to the RF feedbackissue, as it is very lead and postion orientation.

Have you tried into a dummy load so that htere is minimal RF in the shack?  If you do not have the issue on the dummy load, then I would guess feedback is the issue.  If the problem still persists, then I would recheck the wiring and the solder joints on the devices that you replaced.

I would also use the DMM to measure the current to the PA (brown wire) and do the bias adjustments.

If all that fails to point you to the problem, then may need to build an RF probe to go with your DMM and trace the RF from TP2 through each TP until you get to the antenna output. (TP2 to TP7).  You should see a signal growing in strength from roughly 200mv PP to over 50v PP at the antenna.  Here is a link to scope traces of a version 5 (has the same power circuits) https://groups.io/g/BITX20/message/72786

73
Evan
AC9TU

Re: uBitx V3 low power continues

Ted
 

Problem located.

The scope pictures posted above showed no gain out of Q90 and I missed that obvious failure.  It seems that R83 measured out at some 1.8K when it's supposed to be 10 ohms.  I did wonder why the emitter of Q90 had close to the same scope reading as the base.  Now, with a proper R83 in place the waveform on the emitter is present, but low; meanwhile, the output of Q90 is now quantum levels above where it was.  RF out of the radio on 80m, 40m, 30m, and 20m are (about) 13, 12, 10, and 8 watts right where they ought to be.

Incidentally, I shoved a can-type 2N2222 into the Q90 spot some time ago to see if it would add the same benefit that changing out the 6 driver transistors gave. If anyone has a better suggestion for the application, please do tell.  Whether that swap "caused" R83 to open up is anyone's guess.

Thanks again to each and all. 


73,

Ted
K3RTA

Re: Kit-Projects Restock Digital interfaces

 

Errata: I have found on Diode D4's Anode side to GND did not make it to GND. I have covered this in the new build pdf, but wanted to post it here as well. Simple fix is to scrap some solder mask and bridge some solder to ground.

Sorry for the mix up.


--
David

 N8DAH
Kit-Projects.com

Shop is open!

Re: uBitx V3 low power continues

Ted
 

Here's TP 2 (C80 at Q90) @ 10ųv/div:


Power supply hum acknowledged. Battery power was used for TP 3-7 measurements.

And here's the collector of Q90 at T8, with lots of jitter (which disappears by the time the signal goes through RV1):

Re: RF output when just keying the mike

Maurice Bersan
 

G'day Terry, yes receives fine however does not transmit on 6793 which is a commercial frequency I occasionally use. I haven't looked into that one yet but no problems on any of the ham bands.
I find if I zero beat during calibration to a local am radio station that's when the problem with Ptt occures, so I must be doing something wrong there.
Cheers
Maurice

Re: uBitx V3 low power continues

Ted
 

OK.  Now that you fellows have reminded dad me of what I've forgotten over time, let's revisit some of those points.  Scope is set to .5ųs/div. The probe is 1x, as I'm getting nothing while using the 10x option:




Here is TP 3 (RV1 wiper) @ 20ųv/div:





TP 4 (C90) @ 20ųv/div:




TP 5 (R95) @ .2V/div:




TP 6 (R92) (ibid):




TP 7 (T11-5) @ 2V/div:



Please note that I have a pot on the CW level and have that down by about half. Here's TP 7 at full output (same settings):





Aaannnd, here's an approximate 600-Hz whistle into the mic (same settings):




This will hopefully give a better impression of where things are.


With much appreciation,

Ted
K3RTA

Re: RF output when just keying the mike

vk6qa
 

Hi Maurice

Is your radio receiving ok and have good sensitivity?

Have you tried it on several frequencies i.e. 3 .5 mhz, 7.10mhz and 14.1 mhz? for both RX and TX?

 

Keith Perry

 

 

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Maurice Bersan via Groups.Io
Sent: Wednesday, November 6, 2019 3:27 PM
To: BITX20@groups.io
Subject: [BITX20] RF output when just keying the mike

 

Hi everyone looks like I have problem.
I have RF output of about 5w when I key the mike with no modulation input. When I do speak into the mike the modulation is very distorted as heard on a local SDR.
CW seems fine with a nice clean signal.
The problem happened suddenly while trying to tune up with a manual antenna tuner.
I replaced the two irf510 fets but no change. Anyone have any ideas where I can start looking?
Thanks for any help
Maurice
Vk6hly

Re: bitx v3 zero pa output

Evan Hand
 

I had similar problem that I traced to rf feedback getting into the Nano controls.  That does not mean that it is your issue, just one other thing to test.  That fact that you changed the IRF510 is a potential pointer to the RF feedbackissue, as it is very lead and postion orientation.

Have you tried into a dummy load so that htere is minimal RF in the shack?  If you do not have the issue on the dummy load, then I would guess feedback is the issue.  If the problem still persists, then I would recheck the wiring and the solder joints on the devices that you replaced.

I would also use the DMM to measure the current to the PA (brown wire) and do the bias adjustments.

If all that fails to point you to the problem, then may need to build an RF probe to go with your DMM and trace the RF from TP2 through each TP until you get to the antenna output. (TP2 to TP7).  You should see a signal growing in strength from roughly 200mv PP to over 50v PP at the antenna.  Here is a link to scope traces of a version 5 (has the same power circuits) https://groups.io/g/BITX20/message/72786

73
Evan
AC9TU

bitx v3 zero pa output

David Nelson
 

I have an bitx v3 with stock firmware. It was working fine with good output on all bands. Very good receive. I did not use it 
for a couple of weeks then when I started to use it again receive was fine but zero output. Thought it was my meter but I
tried some other meters with same results. Tried meter on another radio. Meter works fine. Tried listening on another
receiver and could hear myself very faintly. M y only test gear is a pretty good dmm. Replaced tr relay no change. Replaced
both irf510. Now when I key the mike instead of showing tx on display the display goes blank and I get a squeel. I do not know
if I have counterfiet 510 or I need to redo the bias adjustments. I found a test fixture on the net and built it. Both the old
510 and the new test good. I am retired heavy equipment mechanic at 82 yo and all I know about electronics is self taught.
Greatfull for any advice  anyone has for me.  Dave kc2ipx

Kit-Projects Restock Digital interfaces

 

Hello all,

25 more kits for the Digital Interface have been made available. This is a new revision to the board same layout and function with universal labeling and BOM. All boards labeled GLG v2.3 should follow the new build instructions "DigiBuildNew.pdf"

73
--
David

 N8DAH
Kit-Projects.com

Shop is open!

Re: uBitx RF Power Amplifier Standalone

circular.simetry@...
 

hello does anyone have the pcb layout for this amplifier ?

Re: uBitx V3 low power continues

 

Hi Ted,

Scope triggering should be set to "Auto".  Since your signal is in the MHz range your sweeptime needs to be a lot shorter.  If you had a 1MHz signal, the time of one full sinewave would be the inverse of that -- in other words 1uS.  So if you set your sweep time to 1uS, then a 1MHz cycle would show one full cycle per division of the scope screen, and with a 7MHz signal you would have 7 full cycles per division.  This would be a bit hard to see, so you want an even shorter sweeptime.  The 0.5uS as suggested.  For measurements, make sure the red "SWP Var" and "Var Volts/Div" knobs are all the way clockwise.

Where did you measure the Q90 signals?  The input signal would be on the base (not emitter) and I would take the output signal from RV1's wiper side.

Hand-help scopes are crappy compared with what you have now unless you spend megabucks on one (and then you might as buy a better used analog scope).

73,


Mark

Re: uBitx V3 low power continues

Evan Hand
 

The scope traces are dim, so not sure if I am reading correctly.  To me it looks like the TP3 signal is stronger than the TP4 signal.  As David suggested, increase the scan rate of the scope (reduce the horizontal trace time / div) to get a better picture of those two points.  I would also check the bias voltages on Q911 and Q912.  That could be your issue.

73
Evan
AC9TU

Re: uBitx V3 low power continues

David Forrest
 

Is that 1ms/div? It looks like your dial will go down to 0.5us/div, which could show a couple cycles of a 7.2MHz wave in a division.

But voltage-wise with 1mV/div and 10x you’re at about 20mVpp and  50mVpp  versus the reference traces at 672mVpp and 1.96Vpp.  

I’d look upstream.

Dave


On Nov 6, 2019, at 9:55 AM, Evan Hand <elhandjr@...> wrote:

I used 10x probes, direct on the TP.