Topics

Variable power control


 

On Tue, Jan 2, 2018 at 01:17 pm, N8DAH wrote:
Group has a lot got smart folks I'm sure we will figure out a nice mod.
I am not one of them if you can tell by typing skills hihi


M Garza <mgarza896@...>
 

Kind of crude, but you could power the entire radio with 24v.  Use a 12v regulator for the receiver and a LM350 for a variable regulator to the PA.  You could set it up to be variable for only a few volts change to vary the output.  You alternately could use a 12 v source and the LM350 to vary the voltage to the PA.  Again, you could design something that would vary by a few watts.
Running from 24v lets you get the higher output but allows you to turn things down, as needed.

Here are a couple of  LM317/350/358 calculator pages:


Hope this helps.

Marco - KG5PRT



On Tue, Jan 2, 2018 at 3:20 PM, N8DAH <Dherron@...> wrote:
On Tue, Jan 2, 2018 at 01:17 pm, N8DAH wrote:
Group has a lot got smart folks I'm sure we will figure out a nice mod.
I am not one of them if you can tell by typing skills hihi



Jack, W8TEE
 

Ok, I'll probably look silly asking this, but you all know I'm a software guy, not EE, so here goes. Why can I have a 24V supply and use this:

ebay # 152837387238

to drop the voltage to 5V? It seems that less power goes up in heat using one of these, so why won't these work?

Jack, W8TEE



From: M Garza <mgarza896@...>
To: BITX20@groups.io
Sent: Tuesday, January 2, 2018 4:32 PM
Subject: Re: [BITX20] Variable power control

Kind of crude, but you could power the entire radio with 24v.  Use a 12v regulator for the receiver and a LM350 for a variable regulator to the PA.  You could set it up to be variable for only a few volts change to vary the output.  You alternately could use a 12 v source and the LM350 to vary the voltage to the PA.  Again, you could design something that would vary by a few watts.
Running from 24v lets you get the higher output but allows you to turn things down, as needed.

Here are a couple of  LM317/350/358 calculator pages:


Hope this helps.

Marco - KG5PRT



On Tue, Jan 2, 2018 at 3:20 PM, N8DAH <Dherron@...> wrote:
On Tue, Jan 2, 2018 at 01:17 pm, N8DAH wrote:
Group has a lot got smart folks I'm sure we will figure out a nice mod.
I am not one of them if you can tell by typing skills hihi




Gordon Gibby <ggibby@...>
 

​Good plan -- that should work.  



From: BITX20@groups.io <BITX20@groups.io> on behalf of N8DAH <Dherron@...>
Sent: Tuesday, January 2, 2018 4:17 PM
To: BITX20@groups.io
Subject: Re: [BITX20] Variable power control
 

 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.


M Garza <mgarza896@...>
 

Jack,
Nothing wrong with that.  It should work fine, as long as it doesn't introduce any RF hash from the switching regulator.  
I would think that you could replace the variable that controls the voltage with a panel mounted one.

Marco - KG5PRT

On Tue, Jan 2, 2018 at 3:47 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
Ok, I'll probably look silly asking this, but you all know I'm a software guy, not EE, so here goes. Why can I have a 24V supply and use this:

ebay # 152837387238

to drop the voltage to 5V? It seems that less power goes up in heat using one of these, so why won't these work?

Jack, W8TEE



From: M Garza <mgarza896@...>
To: BITX20@groups.io
Sent: Tuesday, January 2, 2018 4:32 PM
Subject: Re: [BITX20] Variable power control

Kind of crude, but you could power the entire radio with 24v.  Use a 12v regulator for the receiver and a LM350 for a variable regulator to the PA.  You could set it up to be variable for only a few volts change to vary the output.  You alternately could use a 12 v source and the LM350 to vary the voltage to the PA.  Again, you could design something that would vary by a few watts.
Running from 24v lets you get the higher output but allows you to turn things down, as needed.

Here are a couple of  LM317/350/358 calculator pages:


Hope this helps.

Marco - KG5PRT



On Tue, Jan 2, 2018 at 3:20 PM, N8DAH <Dherron@...> wrote:
On Tue, Jan 2, 2018 at 01:17 pm, N8DAH wrote:
Group has a lot got smart folks I'm sure we will figure out a nice mod.
I am not one of them if you can tell by typing skills hihi





Jerry Gaffke
 

Yes, a switcher is much more efficient than a linear regulator,
but amps of current getting switched at one mhz or so can create hash you hear in the receiver if 
not properly filtered and shielded.   I can receive well using a desktop 12v brick meant for use with a monitor, 
it is also a switching power supply, so it may be possible to use that ebay buck converter.

Another possibility is to normally power from 12dc, and enable a boost converter to generate 24v
only when transitting. Many switcher chips have an enable pin, though I don't see an enable 
talked about on most of the board level products available on the web.

Much of the rig power during receive is going to the Nano and display and si5351.  
Could cut that significantly with a 12 to 3.3v buck switcher (using 3.3v display and processor)
if you could get it clean enough.

Jerry, KE7ER


On Tue, Jan 2, 2018 at 01:47 pm, Jack Purdum wrote:
Why can I have a 24V supply and use this:    ebay # 152837387238
to drop the voltage to 5V? It seems that less power goes up in heat using one of these, so why won't these work?


Jack, W8TEE
 

Much of the rig power during receive is going to the Nano and display and si5351.  
Could cut that significantly with a 12 to 3.3v buck switcher (using 3.3v display and processor)
if you could get it clean enough.
Thanks, Jerry. This is one reason why I'm interested, as I'm moving to a Teensy 3.5, Si5351, and a true touch screen display.

Jack, W8TEE


From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: BITX20@groups.io
Sent: Tuesday, January 2, 2018 5:03 PM
Subject: Re: [BITX20] Variable power control

Yes, a switcher is much more efficient than a linear regulator,
but amps of current getting switched at one mhz or so can create hash you hear in the receiver if 
not properly filtered and shielded.   I can receive well using a desktop 12v brick meant for use with a monitor, 
it is also a switching power supply, so it may be possible to use that ebay buck converter.

Another possibility is to normally power from 12dc, and enable a boost converter to generate 24v
only when transitting. Many switcher chips have an enable pin, though I don't see an enable 
talked about on most of the board level products available on the web.

Much of the rig power during receive is going to the Nano and display and si5351.  
Could cut that significantly with a 12 to 3.3v buck switcher (using 3.3v display and processor)
if you could get it clean enough.

Jerry, KE7ER

On Tue, Jan 2, 2018 at 01:47 pm, Jack Purdum wrote:
Why can I have a 24V supply and use this:    ebay # 152837387238
to drop the voltage to 5V? It seems that less power goes up in heat using one of these, so why won't these work?



Jack, W8TEE
 

Maybe Jerry's idea of only boosting on TX would be the way to go in removing any hash.

Jack, W8TEE



From: M Garza <mgarza896@...>
To: BITX20@groups.io
Sent: Tuesday, January 2, 2018 4:56 PM
Subject: Re: [BITX20] Variable power control

Jack,
Nothing wrong with that.  It should work fine, as long as it doesn't introduce any RF hash from the switching regulator.  
I would think that you could replace the variable that controls the voltage with a panel mounted one.

Marco - KG5PRT

On Tue, Jan 2, 2018 at 3:47 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
Ok, I'll probably look silly asking this, but you all know I'm a software guy, not EE, so here goes. Why can I have a 24V supply and use this:

ebay # 152837387238

to drop the voltage to 5V? It seems that less power goes up in heat using one of these, so why won't these work?

Jack, W8TEE



From: M Garza <mgarza896@...>
To: BITX20@groups.io
Sent: Tuesday, January 2, 2018 4:32 PM
Subject: Re: [BITX20] Variable power control

Kind of crude, but you could power the entire radio with 24v.  Use a 12v regulator for the receiver and a LM350 for a variable regulator to the PA.  You could set it up to be variable for only a few volts change to vary the output.  You alternately could use a 12 v source and the LM350 to vary the voltage to the PA.  Again, you could design something that would vary by a few watts.
Running from 24v lets you get the higher output but allows you to turn things down, as needed.

Here are a couple of  LM317/350/358 calculator pages:


Hope this helps.

Marco - KG5PRT



On Tue, Jan 2, 2018 at 3:20 PM, N8DAH <Dherron@...> wrote:
On Tue, Jan 2, 2018 at 01:17 pm, N8DAH wrote:
Group has a lot got smart folks I'm sure we will figure out a nice mod.
I am not one of them if you can tell by typing skills hihi







John Backo
 

"I understand now that it's not a simple add of a potentiometer. Anyone done this yet?"

Jim, this is relatively simple for the BITX if one builds a linear power supply, and regulates
it with a LM338 or other regulator capable of 5A output. make the regulator variable by adjusting the
voltage input to the ground reference. Use about 24v for the top value and about 9v for the bottom.
Just be aware that the lower one goes in regulated voltage, the less current is available. But 12v and above
with 4-5A is easily possible. You can double these regulators with the proper configuration and so
double the output. Or you can easily add a bypass transistor and increase the power available that
way. See the datasheets for the details.


I use a similar home-brew power supply for all my bench work. It works well.

john
AD5YE


Clark Martin
 

Might be a problem with CW as caps in the boost converter will take time to charge up.

Clark Martin
KK6ISP

On Jan 2, 2018, at 7:42 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:

Maybe Jerry's idea of only boosting on TX would be the way to go in removing any hash.



Walter
 

I am very new to UBITX.  Just putting mine together.

I want to use this for digital modes as well and need to lower the output power to 5w for use with my amp.

Has anyone actually put any of these suggestions to work? 

Do I need to adjust the power to the whole transceiver or just the PA Power?  I notice that the power connector has a PA supply on it.  Can I regulate the PA power and control the power output of the rig?

I am thinking about a three position switch on the front panel with targets of 3w/5w/full power. 

Is there a good solution for this problem.  BTW I am not an EE guy either.  I am a ham radio hobbyist so please make the answer simple.  LOL

73


Jerry Gaffke
 

You can adjust power out using RV1.
Fully clockwise is minimum power (it's backwards).

You can also adjust power out by adjusting the voltage into the PA supply connector pin
Most rigs just have that connected to 12v.
You could go up to 24v (and get nearly 4x the power out) if you improve the IRF510 heatsinks.



On Tue, Feb 20, 2018 at 05:51 am, Walter wrote:
Do I need to adjust the power to the whole transceiver or just the PA Power?  I notice that the power connector has a PA supply on it.  Can I regulate the PA power and control the power output of the rig?


Walter
 

Would a 5amp adjustable boost supply be enough current?

And Thank you for your help.  It is greatly appreciated.

73


LKNDAVE
 

simple series pass regulator on PA supply line.
i would probably go with 4 zeners on a 4 pole rotary. ie: 5.6, 9.1, 12.0 and 15 volts so then the output is "adjustable," with fixed known intervals. 100uh rf choke on output should choke the rf backfeed from the supply. a hidden benefit is this is also a capacitor multiplier that will use the transistors gain to multiply its effective capacitance. ie, a 100 ufd cap on the base of the pass transistor will be like a 1000 ufd cap based on hfe gain of 10. using a npn darlington with a gain of 1000 makes the effect crazy like 100 ufd x hfe 1000 = effective capacitance like 10,000 ufd. smooth baby smooth output.
i miight draw this up if interested 
if using a 12v supply maybe 2 or 3 position switch might do it for you. the darling will lose .7 volts so if you have a 12.00 volt supply you will get ~ 11.3 out

dave, n4lkn


Walter
 

If you could draw this up that would be great.  I am no EE just a layman enjoying the hobby. 

From what I can tell Zeners are in the mAmp range and I thought I was told in an earlier post that I needed in the 3 to 5 amp range.  Perhaps you can tell me how this works out?  I'm sure there is a way.

I have a boost power supply I can put on my 13.8 VDC supply to boost this voltage up to 24 VDC or perhaps a little less to give me the maximum allowable voltage for the PA line (Again an earlier post by another with great advice).  I have ordered a 6 position rotary switch to mount on my front panel.  it is actually 2 pole rather than one so I thought I would use the other set of poles for LED's to show what power setting I am on, not necessary but LED's are always a fun add :)

You help will be greatly appreciated and a drawing would help me greatly.

Thanks and 73 W9KJO


Walter
 

A second thought and question about the zener voltages.

Is there a way to estimate what the output power in watts will be at various voltage levels? 

I need to get my Low setting below 3 watts so I can tune with my amp on, as tuning with the amp off for some reason the SWR changes when I turn this amp on.  However a mere 5 watts into this amp will give me a little over 100 watts out and that is over the tuning range of my LDG Auto Tuner. 

So, I need perhaps 2 or 3 watts out on low power.

Thanks.


K9HZ <bill@...>
 

Zeners probably wont work for this application by themselves because the loading requirements are too great.  They may work as drivers for higher current transistors though. 


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton - J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com


email:  bill@...

 


On Feb 21, 2018, at 9:53 AM, Walter <W9KJO@...> wrote:

If you could draw this up that would be great.  I am no EE just a layman enjoying the hobby. 

From what I can tell Zeners are in the mAmp range and I thought I was told in an earlier post that I needed in the 3 to 5 amp range.  Perhaps you can tell me how this works out?  I'm sure there is a way.

I have a boost power supply I can put on my 13.8 VDC supply to boost this voltage up to 24 VDC or perhaps a little less to give me the maximum allowable voltage for the PA line (Again an earlier post by another with great advice).  I have ordered a 6 position rotary switch to mount on my front panel.  it is actually 2 pole rather than one so I thought I would use the other set of poles for LED's to show what power setting I am on, not necessary but LED's are always a fun add :)

You help will be greatly appreciated and a drawing would help me greatly.

Thanks and 73 W9KJO


LKNDAVE
 

THE ZENERS SET THE PASS VOLTAGE OF THE 100 VOLT 10 AMP DARLINGTON. sorry caps lock. they are 1 amp devices but the transistor slaves them to 10 amp handling. i have used this ciruit fo over 40 years. tayda has most of the parts, total like 5 bucks plus cheap shipping. read notes on schem. this is a 2 voltage control. my crappy software didnt have 4 position rotaries but most will get the idea. the transistor also has reverse emf diode built in.
dave


LKNDAVE
 

2 more things, a 10k from + of c1 to ground will stop voltage screaming to the rail while changing it with power on. if you go to a rotary make sure it is make before break and the spike wont happen.i am going to fix the size of the wschem but i needed folks to see what have done 
dave


Walter
 

So do I need both the 10k ohm resistor from c1 to ground and the make before break rotary or just one or the other?