Topics

Variable power control

ad4xx@...
 

I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?

M Garza <mgarza896@...>
 

Just an idea, how about a variable voltage regulator on the PA power input?  I have not tried this, it's just an idea.  Variable voltage from 24v down to say about 10v?

Marco - KG5PRT 

On Jan 1, 2018 10:19 AM, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?


Scott McDonald
 

I'd second variable power, and perhaps a 50 ohm 50 milliwatt pickoff point and/ or mode for driving transverters.

HNY Scott ka9p - first uBITX QSO yesterday - very nice :)

In a message dated 1/1/2018 10:27:50 AM Central Standard Time, mgarza896@... writes:

Just an idea, how about a variable voltage regulator on the PA power input?  I have not tried this, it's just an idea.  Variable voltage from 24v down to say about 10v?

Marco - KG5PRT

On Jan 1, 2018 10:19 AM, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?

 

 


Arv Evans
 

On Mon, Jan 1, 2018 at 9:19 AM, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?


John Seager <jseager2009@...>
 

Arv, a) Happy New Year. b) Aside from using an attenuator, drive is controlled by
the preset RV1. This could be replaced by a variable pot., perhaps on the back panel. 
However I think it was Farhan who pointed out a long time ago that the only problem
with this is the temptation to keep turning it up!  73,  John  G0UCP



On Monday, 1 January 2018, 17:05, Arv Evans <arvid.evans@...> wrote:



On Mon, Jan 1, 2018 at 9:19 AM, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?




Virus-free. www.avast.com

Jerry Gaffke
 

Farhan did, using RV1.
Alternately, build a new mike preamp with audio gain control, though that solution will not affect CW power level.


On Mon, Jan 1, 2018 at 08:19 am, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?

Clark Martin
 

That’s easy enough to fix.  You put a power control pot (2 terminals only) between the +5V and the bias pot(s).  You set the power control to maximum and adjust each bias pot(s) for for the proper current draw.  Now you can turn down the bias / power, as you please.  But you can’t turn it up past “full”.

Clark Martin
KK6ISP

On Jan 1, 2018, at 11:54 AM, John Seager <jseager2009@...> wrote:

Arv, a) Happy New Year. b) Aside from using an attenuator, drive is controlled by
the preset RV1. This could be replaced by a variable pot., perhaps on the back panel. 
However I think it was Farhan who pointed out a long time ago that the only problem
with this is the temptation to keep turning it up!  73,  John  G0UCP



Daniel Isaza
 

Just a tought...

what happens if we reduce the voltage to the electret mic with a simple pot? distortion? variable power?

Dan

On Mon, Jan 1, 2018 at 4:09 PM, Clark Martin <kk6isp@...> wrote:
That’s easy enough to fix.  You put a power control pot (2 terminals only) between the +5V and the bias pot(s).  You set the power control to maximum and adjust each bias pot(s) for for the proper current draw.  Now you can turn down the bias / power, as you please.  But you can’t turn it up past “full”.

Clark Martin
KK6ISP

On Jan 1, 2018, at 11:54 AM, John Seager <jseager2009@...> wrote:

Arv, a) Happy New Year. b) Aside from using an attenuator, drive is controlled by
the preset RV1. This could be replaced by a variable pot., perhaps on the back panel. 
However I think it was Farhan who pointed out a long time ago that the only problem
with this is the temptation to keep turning it up!  73,  John  G0UCP




Arv Evans
 

John  G0UCP

Agreed.  Some just can't have enough knobs and some percentage of those "must have
them turned to the right-most position". 

There is also the problem of change in operating parameters when power levels are changed
without a good idea of what the effect might be. 

Attenuators for QRP power levels are inexpensive and easy to build.  Add a switch or relay
and they allow the exciter to run at design specifications and still have controllable output. 

Using an attenuator on the input of a power booster helps insure that the impedances are
matched (maybe!) between exciter and linear amp.

HAPPY NEW YEAR! 

Arv  K7HKL
_._


On Mon, Jan 1, 2018 at 12:54 PM, John Seager <jseager2009@...> wrote:
Arv, a) Happy New Year. b) Aside from using an attenuator, drive is controlled by
the preset RV1. This could be replaced by a variable pot., perhaps on the back panel. 
However I think it was Farhan who pointed out a long time ago that the only problem
with this is the temptation to keep turning it up!  73,  John  G0UCP



On Monday, 1 January 2018, 17:05, Arv Evans <arvid.evans@...> wrote:



On Mon, Jan 1, 2018 at 9:19 AM, <ad4xx@...> wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?




Virus-free. www.avast.com


Art Howard
 

I agree, attenuator would be the best/simplest option

On 1 Jan 2018 3:51 pm, "Daniel Isaza" <hk4dei@...> wrote:
Just a tought...

what happens if we reduce the voltage to the electret mic with a simple pot? distortion? variable power?

Dan

On Mon, Jan 1, 2018 at 4:09 PM, Clark Martin <kk6isp@...> wrote:
That’s easy enough to fix.  You put a power control pot (2 terminals only) between the +5V and the bias pot(s).  You set the power control to maximum and adjust each bias pot(s) for for the proper current draw.  Now you can turn down the bias / power, as you please.  But you can’t turn it up past “full”.

Clark Martin
KK6ISP

On Jan 1, 2018, at 11:54 AM, John Seager <jseager2009@...> wrote:

Arv, a) Happy New Year. b) Aside from using an attenuator, drive is controlled by
the preset RV1. This could be replaced by a variable pot., perhaps on the back panel. 
However I think it was Farhan who pointed out a long time ago that the only problem
with this is the temptation to keep turning it up!  73,  John  G0UCP




Ghericoan
 

Take a look at this, http://www.toptechboy.com/arduino/lesson-8-writing-analog-voltages-in-arduino/

I am trying to figure out a way to use this inline with the PA power supply to be able to control the output power from software. Just brainstorming, but if you had a spare pwm pin and buffered its output with some capacitors into a transistor controlling the power rail, it might be doable. But I am really new to all this and am just looking at projects to try when my kit comes in.

Someone feel free to poke a hole in this and save me from wasting an afternoon if this isn't on the right track for a software controlled solution...
--
----------
N5WLF, Greggory (or my nickname, Ghericoan)
General Class, Digital Radio Hobbyist

Clark Martin
 

The Nano and other AVR Mega based MCUs do not have DAC outputs.  The AnalogWrite function sets a PWM.  So that pin is switching between 0 and 5V with an average value proportional to the programmed value.  It can be filtered to produce a DC signal.  But it might require a lot of filtering, and the size of the caps might get big depending on what frequency is being used.

I’ve been thinking about using a Micro Chip MCP4725.  It’s a 12 bit DAC interfaced with I2C.  This would give you a nice DC signal with very low parts count.

Clark Martin
KK6ISP

On Jan 1, 2018, at 7:27 PM, Ghericoan <boakawizkid@...> wrote:

Take a look at this, http://www.toptechboy.com/arduino/lesson-8-writing-analog-voltages-in-arduino/

I am trying to figure out a way to use this inline with the PA power supply to be able to control the output power from software. Just brainstorming, but if you had a spare pwm pin and buffered its output with some capacitors into a transistor controlling the power rail, it might be doable. But I am really new to all this and am just looking at projects to try when my kit comes in.

Someone feel free to poke a hole in this and save me from wasting an afternoon if this isn't on the right track for a software controlled solution...


Diver Martin <diver.martin@...>
 

If I need a true DAC output, I'll sometimes throw on a $2 MCP4921.  Depends on if you need i2c or SPI though.  There's a bajillion single chip / single output DAC's out there in the wild.

On Mon, Jan 1, 2018 at 8:50 PM, Clark Martin <kk6isp@...> wrote:
The Nano and other AVR Mega based MCUs do not have DAC outputs.  The AnalogWrite function sets a PWM.  So that pin is switching between 0 and 5V with an average value proportional to the programmed value.  It can be filtered to produce a DC signal.  But it might require a lot of filtering, and the size of the caps might get big depending on what frequency is being used.

I’ve been thinking about using a Micro Chip MCP4725.  It’s a 12 bit DAC interfaced with I2C.  This would give you a nice DC signal with very low parts count.

Clark Martin
KK6ISP

On Jan 1, 2018, at 7:27 PM, Ghericoan <boakawizkid@...> wrote:

Take a look at this, http://www.toptechboy.com/arduino/lesson-8-writing-analog-voltages-in-arduino/

I am trying to figure out a way to use this inline with the PA power supply to be able to control the output power from software. Just brainstorming, but if you had a spare pwm pin and buffered its output with some capacitors into a transistor controlling the power rail, it might be doable. But I am really new to all this and am just looking at projects to try when my kit comes in.

Someone feel free to poke a hole in this and save me from wasting an afternoon if this isn't on the right track for a software controlled solution...





--
Martin Held - AE7EU
http://ae7eu.com/
-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

John McFadden
 

How variable does it need to be? Could the Raduino drive a relay to switch between the board's power level and a higher voltage source by a software menu satisfy your need? Or are you looking for more than two levels?

John


On 1/1/2018 11:19 AM, ad4xx@... wrote:
I'd love it if I could add a variable control to adjust output power on the uBitx.  After looking for solutions, I understand now that it's not a simple add of a potentiometer.  Anyone done this yet?

ad4xx@...
 

I was hoping for a higher degree of variability...say, 3W up to max, with 5 watts being my target (for CW). Not sure how I will proceed yet but I am hearing a few pretty good suggestions.

Thanks!

Jim
---- John McFadden <johnamcf@...> wrote:

How variable does it need to be? Could the Raduino drive a relay to
switch between the board's power level and a higher voltage source by a
software menu satisfy your need? Or are you looking for more than two
levels?

John


On 1/1/2018 11:19 AM, ad4xx@... wrote:
I'd love it if I could add a variable control to adjust output power
on the uBitx.  After looking for solutions, I understand now that it's
not a simple add of a potentiometer.  Anyone done this yet?

 

Will trimming down RV1 work? I just want it set to a nice 5W cw key down. 

Gordon Gibby <ggibby@...>
 

​yes that will work.....but it won't be 5 watts on the NEXT band you check....




From: BITX20@groups.io <BITX20@groups.io> on behalf of N8DAH <Dherron@...>
Sent: Tuesday, January 2, 2018 2:32 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 
Will trimming down RV1 work? I just want it set to a nice 5W cw key down. 

ad4xx@...
 

That's why I was hoping for an adjustable pot on the front panel.



Jim - AD4XX

-------- Original message --------
From: Gordon Gibby <ggibby@...>
Date: 1/2/18 3:28 PM (GMT-05:00)
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control

​yes that will work.....but it won't be 5 watts on the NEXT band you check....




From: BITX20@groups.io <BITX20@groups.io> on behalf of N8DAH <Dherron@...>
Sent: Tuesday, January 2, 2018 2:32 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 
Will trimming down RV1 work? I just want it set to a nice 5W cw key down. 

Gordon Gibby <ggibby@...>
 

​lots easier to adjust the AUDIO INPUT on the front of a signalink, eh?




From: BITX20@groups.io <BITX20@groups.io> on behalf of Jim - AD4XX <ad4xx@...>
Sent: Tuesday, January 2, 2018 3:49 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 
That's why I was hoping for an adjustable pot on the front panel.



Jim - AD4XX

-------- Original message --------
From: Gordon Gibby <ggibby@...>
Date: 1/2/18 3:28 PM (GMT-05:00)
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control

​yes that will work.....but it won't be 5 watts on the NEXT band you check....




From: BITX20@groups.io <BITX20@groups.io> on behalf of N8DAH <Dherron@...>
Sent: Tuesday, January 2, 2018 2:32 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 
Will trimming down RV1 work? I just want it set to a nice 5W cw key down. 

 

 I will set for the band that has the highest output and live with what I get.

 I just need 2-5W on all bands and I will be happy with that.

 I have plans for digital work as well as use with an amp so not stressing the irf510's is mostly my priority. I realize its not the solution people are looking for, I have been lowering my audio drive level to adjust but for CW and ssb its a no go.

I too would like some adjustment but can live with what I get.

Group has a lot got smart folks I'm sure we will figure out a nice mod.