Date   
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.

Re: uBitx V3 low power continues

Evan Hand
 

I used 10x probes, direct on the TP.

Re: RF output when just keying the mike

Maurice Bersan
 

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 V3 low power continues

Ted
 

Well, I went and tested the points specified, and could not get the resolution seen in the photos.  

Here are TP 3 -




and TP4 -




Considering some of the Chinese hand-held scopes on the market, newer technology be helpful.  What sort of buffering are you using between the test point and the end of the test leads?

-Ted
 K3RTA


On Tue, Nov 5, 2019 at 18:56, Evan Hand
<elhandjr@...> wrote:
Here are the oscilloscope pictures of test points 3 to 7.  First two are at different time scale than the last one.  The last picture is the power reading using my NISSEI SWR/Power meter.

Hope this helps.
Evan
AC9TU

 

Re: NXP Homebrew RF Design Contest

Razvan (M0HZH)
 

Dennis, if you could sign up for email notifications here, I'll let you know when the first batch will be available:

https://qrpblog.com/a600-hf-6m-600w-ldmos-amplifier/

Allison, at the moment it will be just the PA unit as seen in the article / video, with some improvements. I am working on developing all the other necessary components (monitoring & protection, switching, filtering etc) but as you probably know these things take time. In the mean time, I will make available all the necessary documentation.

Cheers,
Razvan (M0HZH)
 

Re: uBitx V3 low power continues

Ted
 

Cool!  My scope is a bit more primitive than that one :)   I'll give it a workout and compare.

Thanks very much.



-ted
 K3RTA


On Tue, Nov 5, 2019 at 19:01, Evan Hand
<elhandjr@...> wrote:
Mode was CW.

Re: RF output when just keying the mike

iz oos
 

I in my opinion the carrier is within the passband, you should move the BFO to have a crystal clear modulation.


Il 06/nov/2019 08:27, "Maurice Bersan via Groups.Io" <Vk6hly=yahoo.com@groups.io> ha scritto:
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: RF output when just keying the mike

 

Check you BFO. If that is fine then it my be a mixer diodes D5.

Raj

At 06/11/2019, you wrote:
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: RF output when just keying the mike

Maurice Bersan
 

Sorry forgot to mention it's ubitx v5

RF output when just keying the mike

Maurice Bersan
 

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: uBitx V3 low power continues

Evan Hand
 

Mode was CW.

Re: uBitx V3 low power continues

Evan Hand
 

I should have included that the frequency was 7.077 mhz into a 50 ohm dummy load.

Also, I have two pictures of TP 5.

Re: uBitx V3 low power continues

Evan Hand
 

Here are the oscilloscope pictures of test points 3 to 7.  First two are at different time scale than the last one.  The last picture is the power reading using my NISSEI SWR/Power meter.

Hope this helps.
Evan
AC9TU

 

Re: uBitx V3 low power continues

Ted
 

On Fri, Nov 1, 2019 at 10:18 PM, ajparent1/KB1GMX wrote:
There is nothing that dies prior to Q90 that is in the Power amp.

However there are two IF amps that can be all sorts of wrong
and the alignment of the oscillators as well.

However CW is generated differently than SSB and for CW TX
none  of the IF stages are used.

Allison,

Thank you for those insights. Now might I test the IF sections for fitness ?  

Just as an aside, the radio was working for a good while up until it didn't.  I was doing one thing or another on the bench the specifics of which I don't recall, when this power diminishment occured.   The amp section seems fine, but can't amplify what it has not been given from earlier stages;  I'll try anything at this point.


Tnx Agn ,

Ted
K3RTA

Re: Ubitx V5.1 frequencies below 3MHz down to 500KHz

David Forrest
 

I learned a lot from looking at the source.  The odd decimal points are controlled by this bit of code: https://github.com/afarhan/ubitx_v5/blob/master/ubitx_ui.ino#L140 -- it puts out the first 1 or 2 characters of the ultoa() conversion of the frequency, then intersperses the decimal points between the remaining characters.

It looks like KD8CEC uses a more robust scheme: https://github.com/phdlee/ubitx/blob/v1.20/ubitx_20/ubitx_lcd_1602.ino#L470

The way the 45MHz IF and the 11.053MHZ IF/BFO/Carrier work with the tuning and the USB/LSB is also much clearer from reading the source code.

Re: uBitx V3 low power continues

Ted
 

Mark [et al],

Using a basic oscilloscope for measurements and a tone generator app for audio, each stage of the amp section seems to raise the RF level an appropriate amount. The exception to this is Q90, whose Collector output is lower than the Emitter input.  Maybe that's how that stage is meant to operate; the voltage measrements are about what the V4 troubleshooting guide says they should be.  Actually, all transistor voltage levels in the driver and PA stages are where they belong.

Regarding mike compression, that part works great as verified by an audio tracer and on the 'scope.  Even with tons of gain cranked up for the sake of following patterns through the circuit board, the peak-to-peak level only comes to about 2/3 of CW levels.  This dispairity is evident as early on as L1-L4.  My checks at Q20-Q22 are hard to read (by me at least).

That's where my hour of patience got me today.  I can try tomorrow to repeat some stuff, maybe/possibly get some pics if it's of any help.

73,

Ted
K3RTA

Re: NXP Homebrew RF Design Contest

ajparent1/KB1GMX
 

Being retired means I don't fund loosing projects.
https://www.w6pql.com/a_1.5kw_lpf_for_160-6m.htm

He makes them and they are stout enough to take 600W.

Allison