Date   

Re: UBITX V3 TX GAIN VARIATIONS

Gordon Gibby <ggibby@...>
 

Thanks Alyson!


On Aug 30, 2018, at 14:44, ajparent1/KB1GMX <kb1gmx@...> wrote:

Gordon,

For better than 10W on 80 and at least 7 on 20....

Replace q90 with something better, BFR106 was good.
MMBT2369 is ok.

Replace the standing 3904s with 2n2222A(to18) part.
Hint installing them from the bottom makes for better and easy.
take care to get them oriented the right way.  Also the cans for
adjacent devices can touch as they get connected together
at the board.

Test results.  On 5 of 5 that got the power up with minimum fuss.
10M will be better but not great maybe 2-3 more watts.

IF you don't want the power to soar on 80 try 470 to 1000PF at C81
(470, 510, 680, 820, 910, 1000pf are standard parts).
Pick the one that gets 80 tamed and 40 and 20 decent.  Getting
12W at 80 and 8 at 20 should be easy.  IF 30M is down its the
output low pass filter as 30M is near the cutoff frequency but 
not less than 5W and I usually saw 7w or more.

Allison


Re: Any Gerber Experts Round Here? #kicad #ubitx

Doug W
 

try messaging sellers direct instead of posting a job
--
www.bitxmap.com


Re: CW PTT attack time to slow #ubitx

ajparent1/KB1GMX <kb1gmx@...>
 

Another user installed the KD8CEC software and found it to be an improvement.

Changing the pull up will not help the issue.  The factory code is slow in
recognizing keying.

Allison


Re: uBitx Unfiltered

Jerry Gaffke
 

Allison had some good pointers on some first easy fixes to the uBitx in post
     https://groups.io/g/BITX20/message/57649
First and foremost, either fix the on-board transmit LPF routing somehow
or add an external LPF between the uBitx and antenna appropriate to the band you are using.

Beyond that, she suggested replacing Q90 with a BFR106, reduce C81 to 470-1000pf and
replace Q911,912,92,93,96,97 with 2n2222's to get a more even power across the bands.
These mods are not of much use if you are just using it on the lower bands to avoid spurs.

 
But if the current power amp is coupling into the IF amps and creating extra spurs
and we need significant mods to get the uBitx power amp to give reasonably clean and flat power
across all of HF, then perhaps best for the power amp to be a separate board.

So clean up the local oscillators and signal levels into the mixers on the uBitx.
Then saw off (or disable) the back end of the uBitx where we have the power amp and LPF's and LPF relays.
Replace that back end with a separate board for the power amp and LPF"s.
Perhaps use kits that Kees has up at 
    http://www.qsl.net/k5bcq/Kits/Kits.html
Perhaps use Han's upcoming QSX 10W amp, which he is planning to sell separately:
    https://groups.io/g/BITX20/message/57420
    https://radioaficion.com/news/qsx-sdr-transceiver/
If required, add per-band filters between the exciter and the new power amp board.

Would be nice to have a simple analog SSB exciter and receiver that works well from 3-30 mhz.
The uBitx can fill that role.  The QSX may turn out to be a fine rig, but the uBitx can remain
the rig of choice for analog experimentation.  Not all of us want to play with DSP firmware.
 
Jerry, KE7ER


On Thu, Aug 30, 2018 at 10:32 AM, ajparent1/KB1GMX wrote:
I still believe "there is a pony out there" .....small handful of parts and a good dual relay switched LPF board.
73 Kees K5BCQ 

Isn't the rest of that is "I can smell it...."

Yes ferrite and a few more caps in the right places plus some top pour of copper
with stitching to tie it all down so ground (there is no such thing) has less
transverse current paths and lower surface resistance.  

Why say that...  Adding parallel caps is useless if the ground it goes to has
RF resistance (or inductance).  The DC lines start right next to the power amp
so ferrite and caps liberally spread about limits the distribution.  At one point the 
R18, R28, R38, and R48 were tried at 330 ohms with 9.6V Zener at each
corresponding cap to ground was added.  That stuffed the spurs (not the
primary ones) down by 6DB.   So yes there undesired RF on the switched
DC.

Allison


Re: Amplifier #ubitx #ubitx-help #parts

ajparent1/KB1GMX <kb1gmx@...>
 

Due to filtering issues and spurious outputs doing that is not recommended.

If you do, familiarize yourself with telecommunications rules that apply to your
country.  You may not be in compliance.


Allison


Re: Any Gerber Experts Round Here? #kicad #ubitx

Ben Holmes
 

You might find this amusing, but I already did this... and Fiverr responded with the following:

Unfortunately, your Gig request "Gerber Files... Convert RS-274D to..." did not pass our review.

It was misleading or unclear. Please explain, in a clear way, what service you need.

Repeating these violations can result in your account being restricted.



Re: UBITX V3 TX GAIN VARIATIONS

ajparent1/KB1GMX <kb1gmx@...>
 

Gordon,

For better than 10W on 80 and at least 7 on 20....

Replace q90 with something better, BFR106 was good.
MMBT2369 is ok.

Replace the standing 3904s with 2n2222A(to18) part.
Hint installing them from the bottom makes for better and easy.
take care to get them oriented the right way.  Also the cans for
adjacent devices can touch as they get connected together
at the board.

Test results.  On 5 of 5 that got the power up with minimum fuss.
10M will be better but not great maybe 2-3 more watts.

IF you don't want the power to soar on 80 try 470 to 1000PF at C81
(470, 510, 680, 820, 910, 1000pf are standard parts).
Pick the one that gets 80 tamed and 40 and 20 decent.  Getting
12W at 80 and 8 at 20 should be easy.  IF 30M is down its the
output low pass filter as 30M is near the cutoff frequency but 
not less than 5W and I usually saw 7w or more.

Allison


Re: Any Gerber Experts Round Here? #kicad #ubitx

Doug W
 

I've had some luck with hiring on fiverr.com for totally unrelated small tasks.  Might be worth seeing what you can find searching "convert gerber".  Contact anyone that has a listing close to what you need and see what they say.
--
www.bitxmap.com


Re: CW PTT attack time to slow #ubitx

Ben Holmes
 

This might be a possible fix: https://qrpguys.com/ubitx-cw-conditioning-adapter


CW PTT attack time to slow #ubitx

Joop Stakenborg <joop.stakenborg@...>
 

Hi there,

just finished a ubitx build and I am trying to use it with my K3NG arduino keyer. I have set the CW configuration to straight key. The keyer output is open collector.

I get a nice sidetone and there is enough power output, about 11 Watts on 20 meters. But if I use the paddle the PTT response is to slow, either the first ‘dit' is lost or the first ‘dah' is turned into a ‘dit’.

Does it help changing the pull-up resistor at the keyer input? Anyone have a suggestion?

Regads,
Joop PG4I


Re: uBitx Unfiltered

ajparent1/KB1GMX <kb1gmx@...>
 

On Thu, Aug 30, 2018 at 09:14 AM, Kees T wrote:
Since there is not much shielding between sections on a uBITX, wouldn't it help going to RD16HHF1 (or RD15) part, so at least the MOSFET Source lead can be solidly grounded vs tying it to a "heatsink antenna". I would also make those MOSFET leads ALL "REALLY short".
I've side stepped that.  That has been done on every IRF510 amp in Bitx and a big handful more
radios out there.  In every case my reaction to that is, it is insane.   Everyone I see I tell them
heat sink paste, insulator kit, and ground that heat sink.  The difference is better heat remove
is the sink is outside the case and less RF all over.   So far I know of two kits that do not do
that and both are the most stable I've seen maybe they have learned something.

Three things shall be done, ground the heatsink, if it is inside a box provide openings to allow
convection cooling to happen, and keep the leads on RF power devices short and that includes
traces on the board.

For those that want to try that:  Get the heatsink and insulator kit.  Bend the leads at the case UP
90 degrees and then install with the case of the mosfet flush to the bottom of the board.  The
heat sink is not in an awkward place (under the amp).  Solution is thick aluminum L (.25" minimum)
to the rear wall (aluminum) of the box with a finned heatsink outside.  Use insulator kits and
(non conductive) thermal transfer paste.  Everything gets bolted up solid for best heat transfer.

Allison


Re: uBitx Unfiltered

ajparent1/KB1GMX <kb1gmx@...>
 

I still believe "there is a pony out there" .....small handful of parts and a good dual relay switched LPF board.
73 Kees K5BCQ 

Isn't the rest of that is "I can smell it...."

Yes ferrite and a few more caps in the right places plus some top pour of copper
with stitching to tie it all down so ground (there is no such thing) has less
transverse current paths and lower surface resistance.  

Why say that...  Adding parallel caps is useless if the ground it goes to has
RF resistance (or inductance).  The DC lines start right next to the power amp
so ferrite and caps liberally spread about limits the distribution.  At one point the 
R18, R28, R38, and R48 were tried at 330 ohms with 9.6V Zener at each
corresponding cap to ground was added.  That stuffed the spurs (not the
primary ones) down by 6DB.   So yes there undesired RF on the switched
DC.

Allison


حمد المزين <hamad.kalid@...>
 

Hello everyone I want to amplify the power by amplifier so i want the amplifier for it with simple so i want some suggestions


Re: Any Gerber Experts Round Here? #kicad #ubitx

Ben Holmes
 

Yes... but look at how much fun I'll have!

Provided someone here can help me figure this out!


Re: UBITX V3 TX GAIN VARIATIONS

Gordon Gibby <ggibby@...>
 

Thanks so much Allison --- now that I have a handle on the harmonics, working on Q90 will be one of my next projects.   That looked like the easiest gain target....   I have read your posts earlier and purchased parts...just need to get that project done sometime.   I have two people inour group planning to build uBitx's.   If I can get 10W on 80 and 5 watts on 30 I'll be pretty happy for my digital goals.


I have a transistor amp (and switched LPF system) waiting on me somewhere to connect up.   Had to tame the harmonics a bit before that was a possibility.   


Cheers,


gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of ajparent1/KB1GMX <kb1gmx@...>
Sent: Thursday, August 30, 2018 1:17 PM
To: BITX20@groups.io
Subject: Re: [BITX20] UBITX V3 TX GAIN VARIATIONS
 
VEry annoying I attached three things and none followed the post!

So 2n2222A datasheet
2n3904 data sheet
and picture of said amp built on Kitsandparts board.


BITX40 Saving Settings Issue

Gary K4VIG
 

Just finished putting the BITx40 in an enclosure and most things are working.  I set it up first in the default configuration and tested per directions.  I then installed sketch v.1.28 per instructions and all seemed well. Next I did all the modifications for raduino-v1.28 except the capacitance touch sensor.  
 
One issue is that when I make changes in the Settings and set up the rig for cw operation, when I shut down the rig, I lose all the previous settings for cw and only lsb or usb is available.  When I turn on again the VFO may show the mode as CWU/L but no keyer or ptt and when I go to Settings no CW options.  I am not able to send cw and cw is not shown as one of the modes available when go to Select Mode.  If I do a default reset and then set up cw it works until I shut it down.  Then I lose the settings. Must be missing something.  I downloaded v1.28 again and reinstalled it. No luck.
 
Another issue I have is that the CW Spot does not work.  I have installed a momentary push switch, but it appears to not be grounding the pin.
I am impressed with the rig and it works perfectly when set up either for ssb or cw with the above exceptions.  Only when I shut down, I lose the settings.
 
Thanks for any help.
Gary K4VIG
 


Re: UBITX V3 TX GAIN VARIATIONS

ajparent1/KB1GMX <kb1gmx@...>
 

VEry annoying I attached three things and none followed the post!

So 2n2222A datasheet
2n3904 data sheet
and picture of said amp built on Kitsandparts board.


Re: UBITX V3 TX GAIN VARIATIONS

ajparent1/KB1GMX <kb1gmx@...>
 

On Thu, Aug 30, 2018 at 08:46 AM, Kees T wrote:
I was wondering about the reasoning behind using several parallel 2N3904 transistors in the uBITX circuit.....they are inexpensive, but why not just use a single 2N2222 ?
For the driver you need about 400mw and one 2n2222A would not do it maybe
as push pull as I've run them as linear that way for 500mw.

The big thing is the 3904 is high power and trying spread the load. To me it
creates more issues.  Same for the pre-driver.

As stated before the 3904 peak HFE is at 10MA and for the 2n2222A its 150MA.
For a power amp diminishing HFR with increasing currents means you get non linear
operation.

However farhan has the bias so high the driver and predriver runs at AB levels. 

>>>the BFR106 has the dissipation, but the 3.5 to 5GHz Ft invites instability

No it doesn't as the amp is a resistive feedback amp and gain max is 18DB
if the device can do that.  A 3904 can but the gain corner is 8mhz and drops
from there to about 10db at 30mhz.  For that amp to hit 18DB at 28mhz the
device must have an FT of 1100mhz or higher.  Bipolars have FT as a limit
for common emitter amps.  For Q90 its works well.

For the predriver and driver part none of those listed are better than 2n2222A
Though the DXT2222 (ignoring footprint) is also good as it behaves like the
TO18 part at high currents.  Other parts are 2n2219A (same die as 2n22222A
in TO5/TO39 and can handle more power) but FT limited.   The classic 2n3866
is better but FT is 500mhz and the 2n5109 is better still.  This is from better to best.

I built an amp using a KITSANDPARTS board (5W CW AMP) with mods using a
2n5109 driving a pair of IRF510s.  The result is flat (within 2DB) power from
3 to 30mhz and at about 26db overall gain.  With 14DBM drive I get 10W and
at 20dbm its up to near 17W at 13.8V.  At 20V 20W is easy with additional drive.
The only changes were replace his 2219 with 5109, and lift the driver transformer
center tap to inject bias there.  Transistors are mounted on top as are the IRF510s
and the output transformer and bias transformer  also the bias network are on the
underside to allow for heatsinks (board was designed to take BD139s).  Bias
anything in the range of 100 to 350ma was tried but about 180ma per mosfet
was about right for linear operation.

You need a driver that can product the desired gain across a decade and
the transformers have to be better.  The layout must be like its a VHF amp!

There are other IRF510 amps that do that or better!  MOSFETs have no FT
however impedance matching is a challenge regardless the part.

Allison


Re: ATU for mBITX

Dennis Zabawa
 

I have one of the Chinese tuners, with the plastic, variable capacitors, that I built from a kit.  I found the adjustments to be very touchy and not repeatable.  I have since replaced it with an MFJ-9201, QRP Antenna Tuner.  It is well made and is a lot easier to use than the Chinese, kit tuner.


Re: Any Gerber Experts Round Here? #kicad #ubitx

Gordon Gibby <ggibby@...>
 

​Wow, that's a pretty complicated printed circuit board....and we already have a ton ofproblems with one laid out by a fellow who has years of experience at it.....wish you good luck!!!   


cheers,


gordon



From: BITX20@groups.io <BITX20@groups.io> on behalf of Ben Holmes <judosandan@...>
Sent: Thursday, August 30, 2018 12:40 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Any Gerber Experts Round Here? #ubitx #kicad
 
P.S. How 'bout a free PCB for the help?  I'm looking to build this: https://groups.io/g/BITX20/message/54034