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QDX Transceiver DC Power Center Pin

Al Sines
 

If you must use a wallwart check out this wallwart tamer. 


Alan, W3AL 


On Nov 22, 2022, at 14:27, Mark WO7T <wo7t@...> wrote:



Wall warts are notorious for rather loose regulation.  Often I find they control the voltage at  different voltage levels
depending on whether there is a load or not.  Also, I find very OLD (Japan/US) wall transformers seem to have better regulation
than some of the new stuff out of China, which is often some sort of switcher affair that can also lead to noise.

YMMV,

Mark 
Laurence KL7 L
 

Watch out for some of the Jamco unreg or reg wallwarts they sell - they can be noisy at lower freqs as no caps across rectifying diodes - there are space for them but nothing installed - messy dremmel job to correct


From: QRPLabs@groups.io <QRPLabs@groups.io> on behalf of Dave Edwards <kd2e@...>
Sent: Tuesday, November 22, 2022 11:27:34 AM
To: QRPLabs@groups.io <QRPLabs@groups.io>
Subject: Re: [QRPLabs] QDX Transceiver DC Power Center Pin
 

The very old (large) wal warts typically have no regulation.

If you use a variac, and swing the input around, the output will follow. I used this 'flaw' just recently to build a 120 volt monitor system at work that uses a 0-5 volt sensor. So, I used an old 5 volt wal wart. Put a slight load resistor on it, and now as the AC input varies, the output varies in a linear fashion.

When I first looked at the cheap switchers, they would not work. They STAY at 5 volts even when the input drops down below 50, and over 130....so, no good for my project!!

....Dave

On 11/22/22 2:27 PM, Mark WO7T wrote:

Wall warts are notorious for rather loose regulation.  Often I find they control the voltage at  different voltage levels
depending on whether there is a load or not.  Also, I find very OLD (Japan/US) wall transformers seem to have better regulation
than some of the new stuff out of China, which is often some sort of switcher affair that can also lead to noise.

YMMV,

Mark 
Dave Edwards
 

The very old (large) wal warts typically have no regulation.

If you use a variac, and swing the input around, the output will follow. I used this 'flaw' just recently to build a 120 volt monitor system at work that uses a 0-5 volt sensor. So, I used an old 5 volt wal wart. Put a slight load resistor on it, and now as the AC input varies, the output varies in a linear fashion.

When I first looked at the cheap switchers, they would not work. They STAY at 5 volts even when the input drops down below 50, and over 130....so, no good for my project!!

....Dave

On 11/22/22 2:27 PM, Mark WO7T wrote:

Wall warts are notorious for rather loose regulation.  Often I find they control the voltage at  different voltage levels
depending on whether there is a load or not.  Also, I find very OLD (Japan/US) wall transformers seem to have better regulation
than some of the new stuff out of China, which is often some sort of switcher affair that can also lead to noise.

YMMV,

Mark 
Dave Edwards
 

Colin....What does it measure with no load?

....Dave

On 11/22/22 2:31 PM, Colin Kaminski wrote:
Dave VE3GSO
 

I have used the QDX at 13.8V and then thought better of it.  Stick to 12V and don’t use a cheap wallwart with your marvellous QDX unless you want to build another!

Dave

On Nov 22, 2022, at 14:00, kg4lac via groups.io <kg4lac@...> wrote:

OK. Thanks!

Now to locate a wall wart that actually outputs 12 VDC as everyone I locate that's marked 12 VDC are actually higher, often much higher, than 12 VDC.

What is the highest VDC for the 12 volt DC QDX without causing problems?

Colin Kaminski
 

Interesting, Thank you Evan. I will monitor it and see how it behaves in real life. Since I am always drawing at least 146ma at 12V I hope that is enough to keep it stable. I will have to make up a cord to insert a amm meter.
--
Colin - K6JTH 
http://tangokeys.com
Evan Hand
 

Colin,

If you read the spec sheet on that supply, you will find that the no-load voltage is 15volts.  That is much higher than the QDX is designed to accept.  Under load it may be dropping down to the design 12volts of the QDX, but still can be an issue.

II have not used this one from Amazon:
https://smile.amazon.com/Adapter-100-220V-Switching-Security-Accessories/dp/B0711Q5B49/

It is a switching-regulated supply.  A linear would be better, but with Amazon, you can try and return if it is too noisy.  Be sure to get one that is regulated and rated for 2amps or more.

73
Evan
AC9TU

73
Evan
AC9TU
Colin Kaminski
 

Cliff
 

Wallwarts are usually unregulated to will show high without a load. Put a small load on it to see what it really is and realize that as you draw more power durning Tx it will drop some.

13.5VDC will not hurt the QDX, especially in Receive. Generally you do not want that much voltage for transmit.

73,
Cliff, AE5ZA

On Nov 22, 2022, at 13:00, kg4lac via groups.io <kg4lac@...> wrote:

OK. Thanks!

Now to locate a wall wart that actually outputs 12 VDC as everyone I locate that's marked 12 VDC are actually higher, often much higher, than 12 VDC.

What is the highest VDC for the 12 volt DC QDX without causing problems?

Mark WO7T
 

Wall warts are notorious for rather loose regulation.  Often I find they control the voltage at  different voltage levels
depending on whether there is a load or not.  Also, I find very OLD (Japan/US) wall transformers seem to have better regulation
than some of the new stuff out of China, which is often some sort of switcher affair that can also lead to noise.

YMMV,

Mark 
kg4lac
 

OK. Thanks!

Now to locate a wall wart that actually outputs 12 VDC as everyone I locate that's marked 12 VDC are actually higher, often much higher, than 12 VDC.

What is the highest VDC for the 12 volt DC QDX without causing problems?
n4qa at_hotmail.com
 

Center pin is positive.
Bill, N4QA
kg4lac
 

Is the QDX transceiver DC power center pin positive or negative?

Thanks.

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