With FD upon us, I have been receiving requests for a low-RFI supply
like the 14 V Kx33, but in a 19 V version for laptops. For those of you
who have such laptops, what is the current demand, and what is the most
common plug which such a supply would need to have?
Cheers, 73 & good luck all on FD! I'll once again be part of the 9A 5 W
CW crew at W4EZ.
> Hi all,
> With FD upon us, I have been receiving requests for a low-RFI supply like
> the 14 V Kx33, but in a 19 V version for laptops. For those of you who
> have such laptops, what is the current demand, and what is the most common
> plug which such a supply would need to have?
> Cheers, 73 & good luck all on FD! I'll once again be part of the 9A 5 W
> CW crew at W4EZ.
> Howie - WA4PSC
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My old HP supply is marked 18.5V 3.5A. My wife's newer HP is 19.5V 2.31 A. The two DC plugs are very different (not sure how to specify them). that could be an interesting product. Mind you, experiments have shown that my laptop creates a bit of RFI from every port (USBs, audio etc.) and the screen, not just the power supply. But every bit that is quieter ought to help.
On 6/19/2018 7:50 PM, Howard Hoyt wrote:
> With FD upon us, I have been receiving requests for a low-RFI supply
> like the 14 V Kx33, but in a 19 V version for laptops. For those of
> you who have such laptops, what is the current demand, and what is the
> most common plug which such a supply would need to have?
Several observations. First, that 14V supply is NOT quiet when providing
enough current for transmit. Second, some laptop power supplies are
quieter than others. For more than ten years, I've used nothing but
Thinkpads, and I've always choked their cables. As a result, I don't
hear noise. Third, the charge regulators for batteries inside laptops
are at least somewhat dependent on the power supply feeding them.
Failing to take this dependence into account could eventually result in
premature end to the life of the battery.
As to universality -- my older vintage Thinkpads came with a 16VDC
supply with a rating in range of 3-4.5A, depending on model. Newer ones
use a 20VDC supply in the same current range. There is little
standardization of power plugs -- Lenovo's latest is rectangular in shape!
Someone in this thread said he uses a DC-DC converter. The circuitry
that does this has the same likelihood to create noise as any other
switch mode power supply.
I've standardized on Power Poles for all the DC in my home and shack.
For most of the equipment, including laptops, I break the DC cables and
add mating Power Poles to both the end coming from the PSU and the end
going to the device. I've even done this for several laptop power
supplies. This allows me to get around the non-standard connector issue,
and also to use power supplies for older laptops that no longer work for
other things. I never throw stuff like this away. I'm using vintage
linear wall warts to replace noisy SMPS wall warts provided with new
equipment. I'm using two old laptop power supplies to float-charge the
batteries that run my shack, using a suitable charge regulator. Genasun
makes several MPPT charge regulators for small solar systems, each
designed for different battery chemistries and different panel voltage
and current ratings. These Genasun regulators are pretty RF-quiet. If
used VERY close to antennas a choke will kill what little noise you