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max PA PWR voltage ?

Adrien F4IJA
 

Hello,

What is the max PA PWR that can be supplied to the ubitx ? Also, what is the output power benefit to have more voltage on the finals of the PA PWR ?

Thank you,
--
73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

 

Hi Adrien,

See this post:  https://groups.io/g/BITX20/message/53765

73,


Mark.

ajparent1/KB1GMX
 

Running th efinal at high power with 100ma bias means that at 12V your heating
them at 1.2W no signal.  Bring that up to 24V and its 2.4W of heat.  

To run at higher voltages you need to insure the heatsinks and air circulation
are adequate.    Heat is a known killer.

However you will still be power limited as the drive level does not change with
increased voltage to the finals (separate power bus).  So the increase is notable
but not hugely greater.  HINT:  if you don't increase the power by a factor
of 4 the other guy will not have a clue (he will not hear it).

Allison

Adrien F4IJA
 

Thank you Allison for the answer. So if I put the PA voltage from 12v to maybe 16v it will not worth the pain regarding the final output power? 
--
73's
Adrien F4IJA
https://www.qrz.com/db/F4IJA

Don - KM4UDX
 

Adrien -- I did exactly this with a old 16v laptop brick power adapter. The 16v from the power adapter went direct (well, thru a fuse) to the brown wire, and direct to a  DC-DC down converter making 12v for the main board and everything else.

It was a fun project, and no pain.  What was gained? Mostly satisfaction. Extra watts? Yes, about 10% to 20% depending.  Would anyone on the receiving end know I had juiced my uBITX with extra carburetors? Not likely. But I did have to add bigger heat sinks for the extra heat generated and the digital mode. 

Try it. Nothing to lose, other than anything you might fry, burn up, or torch. hahaha. 

Tom, wb6b
 


Hi,

Here is a thread where the person powered the whole uBitx from 15 volts and raised the output power substantially. 

This was an earlier revision, so should re-evaluate if any components on the new uBitx revision would be bothered by 15 volts. One older version of the uBitx, for example, had issues with the audio amp IC rupturing and expelling smoke above 12 volts. But that was due to a batch of flakey ICs.

Raising the voltage to the whole uBitx seemed to have some advantage by improving the gain through the intermediate RF stages driving the finals. 

https://groups.io/g/BITX20/message/57370

Tom, wb6b

Murray Wills (ZL2IQ)
 

Hi. I am running mine on 13.8v with no problems.

Murray ZL2IQ.


From: BITX20@groups.io <BITX20@groups.io> on behalf of Tom, wb6b via Groups.Io <wb6b@...>
Sent: Friday, September 6, 2019 9:29:42 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] max PA PWR voltage ?
 

Hi,

Here is a thread where the person powered the whole uBitx from 15 volts and raised the output power substantially. 

This was an earlier revision, so should re-evaluate if any components on the new uBitx revision would be bothered by 15 volts. One older version of the uBitx, for example, had issues with the audio amp IC rupturing and expelling smoke above 12 volts. But that was due to a batch of flakey ICs.

Raising the voltage to the whole uBitx seemed to have some advantage by improving the gain through the intermediate RF stages driving the finals. 

https://groups.io/g/BITX20/message/57370

Tom, wb6b