Topics

Latest Build, Mods and results.

Mharpen@...
 

Hello, I enjoyed by first build so much I built another one. Avoiding all of the mistakes of the first one. Attached are the photos, below are the mods and results.
TX: 1. Choke in series with R86.
       2. All emitter resistors in buffer, predriver and driver bypassed.
       3. Feedback resistor in PA increased to 600 Ohms.
       4. Output Xformer replace with 2:4 on BN43-202.
       5. Adafruit audio compressor in mic line with chokes to eliminate RF feedback.
       6. PA powered by buck boost at 13.8V the rest of the board by 12V battery.
RESULTS: 30W on 80 and 40, 20W on 20. RV1 adjusted to reduce output to 15W.
RX: 1. ND6T AGC installed (underneath main board) at K3 powered by 5V regulator chip.
       2. Additional stage of audio gain installed between Q70 and U1 to make up for loss due to AGC.
RESULTS: Plenty of audio!! and good AGC action.
       3. VE1BWV audio pop mod (similar to the one standard on the new ubitx) installed underneath the main board.
       4. To further enhance the pop suppression PIN 1 at K3 is grounded.
RESULTS: Sounds fine to me.
Trivial Mods: a red/green LED TX/RX LED is installed on front. A TX/RX relay to key an external PA is installed on the back.
Ya'll have a nice day. Mike N6CMY. 

Skip Davis
 

Nice looking build Mike I like your enclosure. 

Skip Davis, NC9O

On Jun 11, 2018, at 18:28, Mharpen@... wrote:

Hello, I enjoyed by first build so much I built another one. Avoiding all of the mistakes of the first one. Attached are the photos, below are the mods and results.
TX: 1. Choke in series with R86.
       2. All emitter resistors in buffer, predriver and driver bypassed.
       3. Feedback resistor in PA increased to 600 Ohms.
       4. Output Xformer replace with 2:4 on BN43-202.
       5. Adafruit audio compressor in mic line with chokes to eliminate RF feedback.
       6. PA powered by buck boost at 13.8V the rest of the board by 12V battery.
RESULTS: 30W on 80 and 40, 20W on 20. RV1 adjusted to reduce output to 15W.
RX: 1. ND6T AGC installed (underneath main board) at K3 powered by 5V regulator chip.
       2. Additional stage of audio gain installed between Q70 and U1 to make up for loss due to AGC.
RESULTS: Plenty of audio!! and good AGC action.
       3. VE1BWV audio pop mod (similar to the one standard on the new ubitx) installed underneath the main board.
       4. To further enhance the pop suppression PIN 1 at K3 is grounded.
RESULTS: Sounds fine to me.
Trivial Mods: a red/green LED TX/RX LED is installed on front. A TX/RX relay to key an external PA is installed on the back.
Ya'll have a nice day. Mike N6CMY. 
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Ken Peck <kenbpeck@...>
 

Mike,
Thanks so much for sharing this.  I have been trying to assemble a list  of the mods that I want to do, and you just saved me the trouble!  Very nicely done!
73's.
Ken

Mharpen@...
 

FB Ken, I should have included in my list a 330 pF mica cap across the primary of the output former and a push button switch to produce a carrier for tuning an AT or external PA, e.g. my sb200.
Thanks for you interest.
Mike N6CMY

Nick VK4PP
 

On Tue, Jun 12, 2018 at 11:08 am, <Mharpen@...> wrote:
push button switch to produce a carrier
Mike, could you please share details on how you did this?

Thanks.

brad martin
 

Just taking a guess that it’s a push button wired to the CW Jack that when pushed its transmits CW as if your holding down a straight key. At least that’s how I’m planning on doing it this weekend.

Brad

On Tue, Jun 12, 2018 at 5:53 PM Nick VK4PLN <nickpullen@...> wrote:
On Tue, Jun 12, 2018 at 11:08 am, <Mharpen@...> wrote:
push button switch to produce a carrier
Mike, could you please share details on how you did this?

Thanks.

Mharpen@...
 

Brad, BINGO!

Mike N6CMY

Nick VK4PP
 

Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

brad martin
 

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad

On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

K9HZ <bill@...>
 

Check uBITx.net.  Already there. 

 

Dr. William J. Schmidt - K9HZ  


On Jun 13, 2018, at 12:07 AM, brad martin <emclinux@...> wrote:

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad
On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

 

 

Roy Appleton
 

What's already there????

Roy
WA0YMH

On Wed, Jun 13, 2018, 9:15 AM K9HZ <bill@...> wrote:
Check uBITx.net.  Already there. 

 

Dr. William J. Schmidt - K9HZ  


On Jun 13, 2018, at 12:07 AM, brad martin <emclinux@...> wrote:

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad
On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

 

 

Jerry Gaffke
 

Pot RV1 on the uBitx varies output power.

VK2ETA came up with a way of using the shoulder of the 45mhz crystal filter to vary the output power. 
 https://groups.io/g/BITX20/message/46235
and wrote software to implement it:  https://groups.io/g/BITX20/message/50215
I believe this has also been incorporated into the KD8CEC firmware.
Requires no hardware mods.  This only works for SSB transmissions and not for CW,
though could be extended to CW if signal CW-KEY were injected into the second mixer instead of the first mixer.
No easily discernible change to the audio, though will be some variation in the audio response:
    https://groups.io/g/BITX20/message/50265
    https://groups.io/g/BITX20/message/50279

The uBitx.net site is getting rather large.  To say there's some sort of solution there
is becoming akin to saying there's a solution in one of the 52000 posts in this forum.
My best guess is that Dr Bill is suggesting an implementation involving a new PC board
controlled by extra pins from the Raduino to run some relays that select various 
preset attenuators.

There are plenty of other ways to do this, most involve hacking in some sort of attenuator.

Jerry, KE7ER


On Wed, Jun 13, 2018 at 07:14 am, K9HZ wrote:
Check uBITx.net.  Already there. 

 

Dr. William J. Schmidt - K9HZ  

 
On Jun 13, 2018, at 12:07 AM, brad martin <emclinux@...> wrote:

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad
On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

 

 

brad martin
 

Just an idea, Ignore CW tone all together and focus of SSB.  Now if I understand right SSB output power is based on the audio in volume.  You yell into the mic you put out more power, you whisper you get less.  At least thats how its showing on my SWR meter and my power supply amp meter.  The CEC firmware can already do WSPR on its own with a push of the PTT button.  What if we implemented a tune feature that just produced a 700khz tone on SSB and you can vary the output power by simply (I assume) changing the output voltage/duty cycle of the tone.  Thinking it would go something like this, Change mode to tune, Push PTT to send a tone,  In the software it will change the duty cycle to generate 1W out on the band you are on.  On 40m that may be a 10% duty cycle where on 20m it may be 60%.

For me I am OK at best with hardware mods and a better coder.  Now off to clone CEC firmware repo to see if it can be done.

73,
Brad
KG5SPR

On Wed, Jun 13, 2018 at 11:25 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Pot RV1 on the uBitx varies output power.

VK2ETA came up with a way of using the shoulder of the 45mhz crystal filter to vary the output power. 
 https://groups.io/g/BITX20/message/46235
and wrote software to implement it:  https://groups.io/g/BITX20/message/50215
I believe this has also been incorporated into the KD8CEC firmware.
Requires no hardware mods.  This only works for SSB transmissions and not for CW,
though could be extended to CW if signal CW-KEY were injected into the second mixer instead of the first mixer.
No easily discernible change to the audio, though will be some variation in the audio response:
    https://groups.io/g/BITX20/message/50265
    https://groups.io/g/BITX20/message/50279

The uBitx.net site is getting rather large.  To say there's some sort of solution there
is becoming akin to saying there's a solution in one of the 52000 posts in this forum.
My best guess is that Dr Bill is suggesting an implementation involving a new PC board
controlled by extra pins from the Raduino to run some relays that select various 
preset attenuators.

There are plenty of other ways to do this, most involve hacking in some sort of attenuator.

Jerry, KE7ER


On Wed, Jun 13, 2018 at 07:14 am, K9HZ wrote:
Check uBITx.net.  Already there. 

 

Dr. William J. Schmidt - K9HZ  

 
On Jun 13, 2018, at 12:07 AM, brad martin <emclinux@...> wrote:

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad
On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

 

 




--

Jerry Gaffke
 

That should work fine.

Take the filtered sidetone from the junction of R252, R253,  add a 10k pot from there to ground to attenuate that audio signal,
the attenuated signal goes through a switch and a series 1uF cap to the base of Q6.  Flip the switch on to enable this feature.
Only software change needed is to turn the sidetone on when tuning.  Adjust the pot for the desired power level during tune.
No additional Nano pins required.

Could do away with the pot, use two fixed resistors there to set maximum tuning power, and adjust the duty cycle
of the sidetone to reduce power under program control as you suggest.   The simple tone() function call currently used
is fixed at 50%, need to find some other way to create that tone.  Harmonic content of the tone would predominate
as duty cycle is reduced, but the RC filter at R250,251,252 should mostly take care of that.

Alternately, could use a spare Nano pin to drive a second RC filter that only injects its tone into Q6,
leaving the current sidetone  generator alone.  Then you can do without the extra switch.

Or create a tone using a smartphone app.
Or whistle softly into the mike.  

Lots of ways!

Jerry


On Wed, Jun 13, 2018 at 08:46 am, brad martin wrote:
Just an idea, Ignore CW tone all together and focus of SSB.  Now if I understand right SSB output power is based on the audio in volume.  You yell into the mic you put out more power, you whisper you get less.  At least thats how its showing on my SWR meter and my power supply amp meter.  The CEC firmware can already do WSPR on its own with a push of the PTT button.  What if we implemented a tune feature that just produced a 700khz tone on SSB and you can vary the output power by simply (I assume) changing the output voltage/duty cycle of the tone.  Thinking it would go something like this, Change mode to tune, Push PTT to send a tone,  In the software it will change the duty cycle to generate 1W out on the band you are on.  On 40m that may be a 10% duty cycle where on 20m it may be 60%.
 
For me I am OK at best with hardware mods and a better coder.  Now off to clone CEC firmware repo to see if it can be done.
 

K9HZ <bill@...>
 

Digital power adjustment.  Several ways. 

 

Dr. William J. Schmidt - K9HZ


On Jun 13, 2018, at 9:55 AM, Roy Appleton <twelveoclockhigh@...> wrote:

What's already there????
 
Roy
WA0YMH

On Wed, Jun 13, 2018, 9:15 AM K9HZ <bill@...> wrote:
Check uBITx.net.  Already there. 

 

Dr. William J. Schmidt - K9HZ  


On Jun 13, 2018, at 12:07 AM, brad martin <emclinux@...> wrote:

Isn’t there a pot that controls the output power? If so you could make a low power switch that is just adding a resistor in parallel or series depending on the circuit. I’m just walking and thinking here so don’t have the schematic easy to get.

Brad
On Tue, Jun 12, 2018 at 6:47 PM Nick VK4PLN <nickpullen@...> wrote:
Ah, too easy, I was hoping it was done via software and able to TX a much lower power carrier for tuning, not the full 15W...
Any ideas and thoughts?

 

 

 

 

Mike
 

Hi @Mharpen do you have a shematic of the audio amp circuit you used to compensate for the gain loss of the AGC circuit?

Mharpen@...
 

Hello Mike. The amp is a verbatim copy of the Q70 amp including the blocking caps and C52 and R52. It is installed between VOL-H and R70 with a 10k trim pot on the input to adjust the drive. Thanks for your interest. Mike N6CMY

Paul k9mv
 

Mike-
Please specify what chokes you used to block feedback with the Adafruit mike.  I have a serious feedback problem using their P/N P1063 adjustable gain module.
Thanks.
-Paul  K9MV

Mharpen@...
 

UPDATE. In addition to my earlier  mods I have incorporated Allison's mods (substituting 2n2222's and a BFR106 for the 3904's). In terms of output power the results are impressive. But in terms of leveling the output... well I measured 12W on 10M and over 35W (that scared me!) on 40M. I finally bit the bullet and used K9HZ's multi relay/pot method for leveling the response. A picture is attached. I was reluctant to use such a brute-force solution for a subtle problem but now I measure 15W on 80, 40, 20 M and 12 on 10M. VICTORY!! Now I can start thinking about other mods. Mike N6CMY.

M Garza <mgarza896@...>
 

Hi Mike,
Is that at 12v PA voltage or higher?

Thanks

Marco - KG5PRT 

On Wed, Jun 27, 2018, 6:06 PM <Mharpen@...> wrote:
UPDATE. In addition to my earlier  mods I have incorporated Allison's mods (substituting 2n2222's and a BFR106 for the 3904's). In terms of output power the results are impressive. But in terms of leveling the output... well I measured 12W on 10M and over 35W (that scared me!) on 40M. I finally bit the bullet and used K9HZ's multi relay/pot method for leveling the response. A picture is attached. I was reluctant to use such a brute-force solution for a subtle problem but now I measure 15W on 80, 40, 20 M and 12 on 10M. VICTORY!! Now I can start thinking about other mods. Mike N6CMY.