Topics

Variable power control


_Dave_ AD0B
 

I have been powering my bitx40 with a 3s Lipo battery Nominal voltage 12.  last night I thought maybe I could put in a LM317 and set the bias for 12 v and power the radio with a higher voltage lipo. Leaving the power for the power amp at battery voltage. it would be easy enough to change batteries for different power levels.

Things didn't go quite as planned. I think some RF may have gotten into the regulator (a guess) The regulator became quite hot even though i had put on a power transistor to carry most of the load. The sensitivity of the radio was noticeably less. I stopped the experiment for now. The Bitx is my only radio and I didn't want to burn something out. . 


John Backo
 

Good thought, Marco.

But most. if not all variable VR's have a fixed or lesser
VA output. IF you lower the voltage, usually the available
amperage goes down as well...

I use two in my bench supply, one with a 7815 and one
with a LM338. They work well to provide a variable voltae
but the available current is not 5A (say) for the LM338
unless the voltage is quite high. At very low voltages,
the available current is 0.5A or less.

But it is a good thought. Possibly it could be rigged
as a linear supply with 2 LM338's and a LM324 regulator...

It would be cheaper than buying separate fixed supplies.
Also cheap are variable shunt and digital supplies, but
they usually have a big RF noise problem and require
some hefty filtering..

john
AD5YE


Tim Gorman
 

Walter,

What voltage are you feeding this with? I assume it is more than
24v in order for you to have a 24v position.

If you are running in the 10 volt position, for instance, that would be
drop of at least 24v - 10v = 14v. Fourteen volts at .5amp is 7W being
dropped into that transistor. That's a pretty fair amount of heat.

tim ab0wr

On Fri, 09 Mar 2018 06:17:16 -0800
"Walter" <@whuyckjr> wrote:

On Wed, Feb 21, 2018 at 06:23 pm, LKNDAVE wrote:


i did the hokie pokie and this jpg came out

Based on this design I built this attached circuit.

It controls voltage nicely.  Really helps limit output power while
working digital.

However the TIP 142 really generates some heat.  I have a heat sink
on it but it will need to be much larger.  it is only drawing
about .5 amp (1/2 amp) while transmitting.

Does that seem normal?  it the heat something I should be concerned
about?  Or just provide a better heat sink and run it?

Thanks for the circuit idea and plan.
 
--
73, W9KJO
Walter


Walter
 

On Wed, Feb 21, 2018 at 06:23 pm, LKNDAVE wrote:
i did the hokie pokie and this jpg came out

Based on this design I built this attached circuit.

It controls voltage nicely.  Really helps limit output power while working digital.

However the TIP 142 really generates some heat.  I have a heat sink on it but it will need to be much larger.  it is only drawing about .5 amp (1/2 amp) while transmitting.

Does that seem normal?  it the heat something I should be concerned about?  Or just provide a better heat sink and run it?

Thanks for the circuit idea and plan.
 
--
73, W9KJO
Walter


LKNDAVE
 

i was thinking 2nd nano and i2c lcd maybe a 20x4, leaving system rad do its thing unencumbered.
dc voltage current, swr, rf power, s meter, real time clock etc on health display. still dreaming but i want an isolated monitor.


Walter
 

Very nice and helpful.  I will save this.

So, you seem to be saying that anything under 4.6volts is too low?

Will you system health display show on your current LCD display?  How will it input into the processor?

Thank you again.
--
73, W9KJO
Walter


LKNDAVE
 

Here is a pot controled version of my original zener power control. since i am an anti-rail go i added high limit and lo limit resistors. 
when i was young i persued a second class commercial operators license. in the log everyday the on air guy had to write down plate voltage and current. those 2 multiplie provided the FCC required station wattage. that was at the transmitter  so swr, connector, and line loss were not factored. P=I x E. this was not the RF OUT or the effective radiated power.  
i will be adding a simple accuate circuit add on to this to report voltage and current supplied to the output stage using 2 analog inputs to my system health display.
dave N4LKN


Jerry Gaffke
 

Here's an old thread well worth reading that touches on pin diode attenuators, mostly in regard to agc for the receiver.
    https://groups.io/g/BITX20/topic/5945215
Here's another old thread:
    https://groups.io/g/BITX20/topic/5913954

Jerry, KE7ER


On Thu, Feb 22, 2018 at 06:34 am, Karl Heinz Kremer, K5KHK wrote:
There is an HP application note about PIN diode attenuators: http://www.hp.woodshot.com/hprfhelp/4_downld/lit/diodelit/an1048.pdf

I was just about to recommend a PIN diode attenuator as well. The device used in this particular configuration reached it's end of life, and may be hard to get soon. There are alternatives: 

https://www.nxp.com/docs/en/data-sheet/BAP70Q.pdf

The data sheet has a chart that shows insertion loss based on frequency and control voltage. 
--


Gordon Gibby <ggibby@...>
 

​Thanks -- great info.  3db insertionloss.  



From: BITX20@groups.io <BITX20@groups.io> on behalf of Karl Heinz Kremer, K5KHK <khk@...>
Sent: Thursday, February 22, 2018 9:34 AM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 
There is an HP application note about PIN diode attenuators: http://www.hp.woodshot.com/hprfhelp/4_downld/lit/diodelit/an1048.pdf

I was just about to recommend a PIN diode attenuator as well. The device used in this particular configuration reached it's end of life, and may be hard to get soon. There are alternatives: 

https://www.nxp.com/docs/en/data-sheet/BAP70Q.pdf

The data sheet has a chart that shows insertion loss based on frequency and control voltage. 
--
Karl Heinz - K5KHK


Karl Heinz Kremer, K5KHK
 

There is an HP application note about PIN diode attenuators: http://www.hp.woodshot.com/hprfhelp/4_downld/lit/diodelit/an1048.pdf

I was just about to recommend a PIN diode attenuator as well. The device used in this particular configuration reached it's end of life, and may be hard to get soon. There are alternatives: 

https://www.nxp.com/docs/en/data-sheet/BAP70Q.pdf

The data sheet has a chart that shows insertion loss based on frequency and control voltage. 
--
Karl Heinz - K5KHK


Gordon Gibby <ggibby@...>
 

Thank you very much! I learned something from that.  Do you have any idea what is the minimum insertion loss?


On Feb 22, 2018, at 06:50, Roberto Vannucci <robertovannucci128@...> wrote:


I want to suggest a circuit that I have tested to regulate the power in my previous self-built HF transmitter. It is based on an HSMP3816 QUAD PIN DIODE.
I enclose the circuit file 73 IK6BLO

2018-02-22 9:33 GMT+01:00 Walter <W9KJO@...>:
Thank you very much

That is a very nice schematic drawing and readable

Thank you,  I cant wait to get the parts and build it.

73, W9KJO, Walter


<ss.bmp>


Roberto Vannucci
 


I want to suggest a circuit that I have tested to regulate the power in my previous self-built HF transmitter. It is based on an HSMP3816 QUAD PIN DIODE.
I enclose the circuit file 73 IK6BLO

2018-02-22 9:33 GMT+01:00 Walter <W9KJO@...>:

Thank you very much

That is a very nice schematic drawing and readable

Thank you,  I cant wait to get the parts and build it.

73, W9KJO, Walter



Walter
 

Thank you very much

That is a very nice schematic drawing and readable

Thank you,  I cant wait to get the parts and build it.

73, W9KJO, Walter


Thomas Sharka
 

What if you replaced the diodes with an LM317? Would that be as reliable?
 


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On Wednesday, February 21, 2018 9:23 PM, LKNDAVE via Groups.Io <novatronix@...> wrote:


i did the hokie pokie and this jpg came out




LKNDAVE
 

i did the hokie pokie and this jpg came out


LKNDAVE
 

my software, expresssch only puts out .bmp i will look at doing something about the quality asap.
sorry for the poor quality.
dave
no changes the i can think of to rv1


Walter
 

Thank you very much.

I have ordered the parts and will build this to add to my ubitx.

I think this will supply power to the PA power wire on the power connector.  Is this correct?

Do I need to do anything with RV1?

I will have my Watt/SWR meter on the ubitx so I will know what my actual power output is.

Would you be able to post an PDF or Jpeg of your print?  The print on this blog is not very clear.

I very much appreciate your help.

73, W9KJO, Walter


Nick VK4PP
 

What about replacing RV1 with an AD5246, and an SWR bridge to monitor output power and then a PID loop to adjust drive level to attain desired output...


LKNDAVE
 

SUBTRACT A FEW PARTS AND A POT AND IT IS CONSTANTLY VARIABLE ADD ASC712 TO MONITOR CURRENT AND A VOLTAGE DIVIDER TO SEE WHATs GOING WITH REALTIME DETAIL.
DAVE
Ihate caps lock


LKNDAVE