Date   
Re: RF power chain mods and improvements..

Tim Gorman
 

I put the board on the top side by removing C80 and hooking the
input/output to the pads there.

As you predicted earlier, this is not optimum. While it increased my
output on 10m from 2w to 4w it also oscillates like crazy. The in/out
are just too close together for a 12db gain amp.

When I applied TX power in CW mode it would jump immediately to 4w out
but when I let up on the key it would still be putting out 2w until the
TX relay dropped and removed the TX power.

I didn't even check it on any other band.

Next time I have the board out I'll try putting the amp on the
underside where I can separate the in/out so they are further apart.
Pin 5 on T8 and the top side of RV1 are further apart and, like you
say, that allows RV1 to control the output better.

Thanks,

tim ab0wr

On Wed, 06 Jun 2018 21:14:50 -0700
"Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:

Tim,

The reason to add a stage of amplification like that is so we can
reduce the amplification of pretty much all the other stages.
With reduced gain, they have a much better chance of giving the same
gain at 30mhz as they do at 3.5mhz.

You could try patching this amp in when operating at 30mhz.
Turn RV1 down all the way, then slowly bring it up to get the power
you want. But you had best be ready to measure distortion in your
signal before getting on the air with it.

It could well be that Q90 will not work properly with the 10dB
increased input signal and will distort.  Having the amp after Q90
allows you to adjust RV1 down until any stage after the new amp does
not have too strong a signal, strong enough to distort.

I don't think you want this new amp in there at all when operating on
the lower frequencies with an otherwise stock rig.  Too much gain. 

I'm just kibitzing here, have not analyzed the Q90 stage.
You could take the LT-Spice model for the uBitx power amp from the
KE7ER directory in the files section, see what the simulation does
when Q90 is driven harder.

Jerry

On Wed, Jun 6, 2018 at 07:36 pm, Tim Gorman wrote:


Allison,
Jerry,

I have my little mmic board built. Would it be ok to add it before
Q90 by removing C80 and inserting the input and output on those
pads. Doing that would allow me to stick the board on top of the
relay that is right beside Q90. It would facilitate testing,
experimentation, and parts changeout if needed. It would also be
right beside my 7812 voltage regulator so I would have short power
leads.

Will another 10-12db of gain into Q90 be a problem?

tim ab0wr

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Do not copy anything I wrote as its not done.

If you ask questions via email Before then I'm trying to be active
in the ARRL VHF/UHF contest.

IF you have different parts to try there are two possible paths send me enough
and I will consider trying them or try them yourself and report.  

Due board layout using SOT part for leaded is messy and hard to get the lead layout right.
Also asking me on new oddball pats gets the now standard answer.

                   Try it and report your results..

Allison

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

Hint the ADA4895 will not drive the IRF510s to full power.  It cannot produce enough power.

The PHA22 at 1DB compression is 22dbm almost 160mW  add IRF510 (assume low 13db gain)
and you get to almost 3.2W (if high maybe 6W).  The PHA22 is really power hungry and
regulated voltage.  If the board layout and pad are not right they can take off or melt.  Most
mmics trade power in for bandwidth. 


Allison

External Amp

Howard Fidel
 

I have been working on a number of upgrades for the uBitx. One is an external amp. A number of people, including myself ordered an amp like this one: https://www.ebay.com/itm/70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3-Ham-Radio-DIY-Kits/401280684714?epid=579537921&hash=item5d6e3152aa:m:mTAXYtpMu9k-yfYI6Z1m1hQ

For the price it is a good deal, but it doesn't include the heat sinks or the needed low pass filters for each band. I currently have the unit running with my uBitx only on 20 meters. I temporarily but an appropriate filter on the board while I work on my uBitx daughter board that will be a collection of several improvements. I have attached my  version of the original schematic and also my revised schematic. I made one major change and a few minor ones. The major change is that I use two IRF520s in parallel instead of the original IRF530s. This came about accidentally, but it is a could change. When I put the amp together and started testing it, the FETs quickly self destructed, before I could shut it off. I looked through my parts been and found that I have a number of IRF520s but no IRF530. I checked the data sheet, and found that when you put 2 in parallel, the total capacitance increases by about 20%. But the thermal impedance for 2 in parallel is lower for the two, and the temperature rise in each is lower because the current is 1/2 for each, and the on resistance is not much higher in the IRF520. The bottom line, is you get much better thermal performance and can use a smaller heatsink. To the amp itself, I found that I get better performance by changing the 150 ohm feedback resistors to 235 ohm (to 470 in parallel) and I made the output transformer secondary 4 turns instead of 3. I got slightly better output power, and I believe a better antenna match, since my antenna is closer to 70 ohms then 50. Lastly, I changed R2 to 4.7K from 10 K and put a 6.8 volt zener in series with it so that the PTT can be put in parallel with the uBitx PTT switch. If you want to use the amp for both SSB and CW, then you will need to or the two lines together with a couple of diodes. I'm not running CW now, except for testing, so I didn't bother with it.

When I finish my daughter board design, I will post it. Probably in day or so. The amp is tested, the daughter board will be just the design at this point, with some parts breadboarded. 

Howard

Re: RF power chain mods and improvements..

ajparent1/KB1GMX <kb1gmx@...>
 

On Sat, Jun 9, 2018 at 01:48 pm, Tim Gorman wrote:
As you predicted earlier, this is not optimum. While it increased my
output on 10m from 2w to 4w it also oscillates like crazy. The in/out
are just too close together for a 12db gain amp.
There is the are problem but the power increase didn't track either
as an additional 12DB should have driven the finals to well over 20W....
From 2-4W is only 3db increase.

Why didn't it?  First the pre-driver and driver have issues. and then 
the mmic took off oscillating as the input and output are way too close.

The amplifier from Q90 though the irf510s have to be taken as a system.
Every part of the chain has to meet some reasonable specs or the whole
mess fails.  This is why there is no simple fix.

Allison

Re: External Amp

Howard Fidel
 

OOPs, I forgot to attach the schematics.

On 6/9/2018 5:19 PM, Howard Fidel wrote:
I have been working on a number of upgrades for the uBitx. One is an external amp. A number of people, including myself ordered an amp like this one: https://www.ebay.com/itm/70W-SSB-linear-HF-Power-Amplifier-For-YAESU-FT-817-KX3-Ham-Radio-DIY-Kits/401280684714?epid=579537921&hash=item5d6e3152aa:m:mTAXYtpMu9k-yfYI6Z1m1hQ

For the price it is a good deal, but it doesn't include the heat sinks or the needed low pass filters for each band. I currently have the unit running with my uBitx only on 20 meters. I temporarily but an appropriate filter on the board while I work on my uBitx daughter board that will be a collection of several improvements. I have attached my  version of the original schematic and also my revised schematic. I made one major change and a few minor ones. The major change is that I use two IRF520s in parallel instead of the original IRF530s. This came about accidentally, but it is a could change. When I put the amp together and started testing it, the FETs quickly self destructed, before I could shut it off. I looked through my parts been and found that I have a number of IRF520s but no IRF530. I checked the data sheet, and found that when you put 2 in parallel, the total capacitance increases by about 20%. But the thermal impedance for 2 in parallel is lower for the two, and the temperature rise in each is lower because the current is 1/2 for each, and the on resistance is not much higher in the IRF520. The bottom line, is you get much better thermal performance and can use a smaller heatsink. To the amp itself, I found that I get better performance by changing the 150 ohm feedback resistors to 235 ohm (to 470 in parallel) and I made the output transformer secondary 4 turns instead of 3. I got slightly better output power, and I believe a better antenna match, since my antenna is closer to 70 ohms then 50. Lastly, I changed R2 to 4.7K from 10 K and put a 6.8 volt zener in series with it so that the PTT can be put in parallel with the uBitx PTT switch. If you want to use the amp for both SSB and CW, then you will need to or the two lines together with a couple of diodes. I'm not running CW now, except for testing, so I didn't bother with it.

When I finish my daughter board design, I will post it. Probably in day or so. The amp is tested, the daughter board will be just the design at this point, with some parts breadboarded. 

Howard


Re: RF power chain mods and improvements..

Howard Fidel
 

Allison
You are absolutely correct. I simulated it is LT Spice. I did not look close enough at the results. The drive current needed into the IRF510 is 220 ma peak at 30 MHz. The opamp is only good for 80. I need to add a current buffer to each opamp output.

Howard

On 6/9/2018 5:18 PM, ajparent1/KB1GMX wrote:
Hint the ADA4895 will not drive the IRF510s to full power.  It cannot produce enough power.

The PHA22 at 1DB compression is 22dbm almost 160mW  add IRF510 (assume low 13db gain)
and you get to almost 3.2W (if high maybe 6W).  The PHA22 is really power hungry and
regulated voltage.  If the board layout and pad are not right they can take off or melt.  Most
mmics trade power in for bandwidth. 


Allison


Re: uBitx first power on - issues

tituskz1g@...
 

Instructions I received with a kit about 10 days ago show the resistor and a warning on page 8.  That said, it would help to have page numbers in documents as well as a version number and a date.  The MBITX "WIRE UP" instructions need revising and editing.  Better diagrams and photos would also improve the documentation.  I volunteer to help with such efforts.  Who's in change of docs?
--
Jon Titus, KZ1G
Herriman, UT USA

Re: PA transistor Heatsinking of a uBITX #ubitx

Ralph Mowery
 

I made several modifications as designed by others.  I am not an engineer,but can do the 'mechanical work'.

I installed 330 pf capacitors across r87/r88, feedback reisitors r261/r261 to 820 ohms, the output transformer was changed ot a BN43-202 core with 2 turns primary and 3 turns secondary.  I think I should have used a 33 pf across the primary of the new transformer,but used a 150 pf.
That was with the change of the output transistors.

Here is my power out with the drive pot cut back some.

Freq   output watts

3.7 MHz  11.9
5.33         10.5
7.2           11
10.1         10
14.2          8
18.1         10.1
21              6.8
24.89         8.3
28.2           8.7

Not totally flat, but except for the dip at 21 mhz it is not too bad.
That was made with an IFR 1200s service monitor and a 13.8 volt 50 amp  Astron supply.

On Sat, Jun 9, 2018 at 1:34 PM, <rcbuck@...> wrote:
Ralph,

Did the RF16HHF1 change make the output more consistent across the frequency range of the transmitter?

Ray
AB7HE
_._,_._,_


Re: PA transistor Heatsinking of a uBITX #ubitx

Jerry Gaffke
 

That looks pretty good!
Was it otherwise a stock rig, so these are the only changes?

Jerry


On Sat, Jun 9, 2018 at 03:21 pm, Ralph Mowery wrote:
I made several modifications as designed by others.  I am not an engineer,but can do the 'mechanical work'.
 
I installed 330 pf capacitors across r87/r88, feedback reisitors r261/r261 to 820 ohms, the output transformer was changed ot a BN43-202 core with 2 turns primary and 3 turns secondary.  I think I should have used a 33 pf across the primary of the new transformer,but used a 150 pf.
That was with the change of the output transistors.
 
Here is my power out with the drive pot cut back some.
 
Freq   output watts
 
3.7 MHz  11.9
5.33         10.5
7.2           11
10.1         10
14.2          8
18.1         10.1
21              6.8
24.89         8.3
28.2           8.7
 
Not totally flat, but except for the dip at 21 mhz it is not too bad.
That was made with an IFR 1200s service monitor and a 13.8 volt 50 amp  Astron supply.

Re: KD8CEC Firmware S-Meter usage

Ralph Mowery
 

If you use the ND6T AVC board you can just hook the s-meter wire to it at the Jumper # 2 point.


de ku4pt


On Sat, Jun 9, 2018 at 2:50 PM, Mark M <junquemaile@...> wrote:
I'm planning to use the circuit on Ian's site that uses an LM386, just waiting to get the parts. Is there a simpler circuit?

Mark...     AA7TA
_._,_._,_



Re: Different Encoder

tituskz1g@...
 

I tried an encoder similar to the one provided with the kit.  Mine has detents, but it did not work well.  Went back to the original no-detents encoder.  Mounted a separate pushbutton on the front panel.  The encoder often slipped when I used its internal switch.

The supplied encoder has a 6-mm shaft.  So a knob for 1/4-inch shafts makes the knob motion eccentric.  To overcome this, I took a large 1/4-in-shaft knob and filled the back, including the shaft well, with MinWax epoxy wood filler.  (Oil the set screw so it the epoxy won't stick to it or infiltrate the threads.) After the epoxy cured and sat for a couple of hours I machined off the excess epoxy in a mini lathe and drilled a new shaft well with a letter "B" drill.  The set screw easily breaks through the thin epoxy in the shaft well.   (See attached photo.)
--
Jon Titus, KZ1G
Herriman, UT USA

2.8" enhanced demo with expansion board #ubitx

Bo Barry <bobarr@...>
 

What fun! Learning the Editor and Nextion fast! (Well it takes a whole day at my age).

I've put In the files the original 3.2" example by Vectorspace converted to the 2.8" display.

Lessons learned:
The clock can be displayed better/easier using the variable function, instead of converting the clock digits to text like in my previous demo. Lots easier and to understand.

The demo has a screen brightness example, a time display with the ability to adjust the seconds, and a control page that:
1) 6 buttons (inputs) on the expansion board light up their image on the display.
2) makes the beeper beep when you touch the beeper on the display(output),
3) Lights the tiny LED on the board when you touch it on the display(output)
Touching the buttons on the display only blink them
The original example was 3.2" not 2.3 like stated.

The 240x400 images can be resized to 240x320 using the InkScape program. I haven't conquered it yet so I used a handy program (pgv.com) that I had.

As you replace the images you have to move the 'icons' to fit your smaller display. When you try to delete the original images no longer used, the program will tell you when one of your icons is off screen, so you simply move it until they all fit.
Hope that helps someone - I know I was about to throw mine in the trash until I youTube'd and Google'd it to death.
Bo W4GHV

New file uploaded to BITX20@groups.io

BITX20@groups.io Notification <BITX20+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the BITX20@groups.io group.

File: expansion.hmi

Uploaded By: Bo Barry

Description:
2.8" enhanced with expansion board demo. Bo W4GHV since '54

You can access this file at the URL:
https://groups.io/g/BITX20/files/expansion.hmi

Cheers,
The Groups.io Team

Re: 2.8" enhanced demo with expansion board #ubitx

Doug W
 

sounds pretty interesting.  how about a picture of your masterpiece?
--
www.bitxmap.com

New file uploaded to BITX20@groups.io

BITX20@groups.io Notification <BITX20+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the BITX20@groups.io group.

File: ubitxassessories.pdf

Uploaded By: Howard Fidel

Description:
A collection of accessories and improvements for the uBitx. See post for description

You can access this file at the URL:
https://groups.io/g/BITX20/files/ubitxassessories.pdf

Cheers,
The Groups.io Team

Re: 2.8" enhanced demo with expansion board #ubitx

Bo Barry <wn4ghv@...>
 

Need a video of it. Not my original, just resized and learned lots.

Re: RF power chain mods and improvements..

Tim Gorman
 

When it started oscillating who knows what the actual output consisted
of. I didn't try to measure it on the SA.

It may even be like Jerry surmised that I was overloading Q90 and
causing problems.

I'll try to do a better job of shielding sometime in the future and see
what happens.

tim ab0wr

On Sat, 09 Jun 2018 14:25:32 -0700
"ajparent1/KB1GMX" <kb1gmx@...> wrote:



There is the are problem but the power increase didn't track either
as an additional 12DB should have driven the finals to well over
20W....
From 2-4W is only 3db increase.

Re: pcb for modifications ver3 to ver4

Rusdi Lee
 

Thanks for your work and information.It's help me a lot.

Screen brightness examples (5" basic & 2.8" enhanced) added to Files #ubitx

Bo Barry <bobarr@...>
 

Something to learn from. See a funny command, check the instruction set. This one should be easy to figure out. If you are 78 years old or YOUNGER. :)
Haven't learned how to create HMIs that load or run  on other the device they were created on.
But you can enter them in the editor and shrink/expand them and save them for your model.
Bo W4GHV