Don't put all switching power supplies in the same bucket. There are
very good ones that ARE QUIET, and then there are those that generate
noise. Just because it has the side or back posted with all types of
certifications basically says "they met specs at one time".
I have 3 Astron switching supplies that are quiet. I have personally
performed conducted and radiated emissions testing on those supplies.
However, I've repaired several linear supplies an one switcher where the
3 pin AC ground wire was insulated from the chassis by their beautiful
paint job. Those did create issues until the cause was discovered and
corrected.
73
Bob, K4TAX
On 11/19/2017 7:39 PM, Barry wrote:
Rich,
You just discovered the problem with switching power supplies. I'm
unaware of any computer power supply that isn't a switcher, but for
most 12 volt needs an analog supply should fix the problem. The only
downside that I can see is weight; analog supplies can be a bunch
heavier, but they are RF quiet.
There some quiet switchers out there. You just need to do some
research to discover those. One that is quiet is the Tentec. It is
actually an Astron that Tentec did some work on. I think the one
Elecraft sells is quiet. Bit, you really need to investigate before
buying a switcher.
73,
Barry
K3NDM
------ Original Message ------
From: "rich hurd WC3T" <[email protected]>
To: "stan levandowski" <[email protected]>
Cc: [email protected]
Sent: 11/19/2017 7:31:48 PM
Subject: Re: [Elecraft] (OT) - Unplanned Discovery
Wow.
Going to try that. Thanks for this great post.
On Sun, Nov 19, 2017 at 19:23 stan levandowski <[email protected]>
wrote:
Most people on this Reflector are well educated and intelligent.
Apparently, I'm the exception because this one got by me. I'm only
owning up to this in the hope that it might help someone else on the
Reflector.
For the last couple of years I've been bothered by a high background
noise level. It happened on my K1, K2, K3, KX2 and KX3. I
attributed
this to the fact that my antenna has been in my attic for the last
fifteen years and propagation hasn't been good lately.
I just got official permission from the HOA to install an end fed wire
outside. I was thrilled. I put it up. The darn thing wasn't any
better than the attic doublet. Noisy as heck! What a letdown!
So I'm laying in bed last night reflecting on how my little KX1 was the
only Elecraft radio that never had noise problems and seemed to have a
receiver quieter than my K3.
Whoa! The KX1 always ran on batteries...could it be?????
I just took delivery on a brand new Kx33 Low RFI power supply a couple
days ago. It was advertised in the last QST. Previous to that, I've
been using a Samlex 1235M. For the heck of it, I connected my K2
to an
SLA battery and the noise was still there. But when I disconnected the
Kx33 power supply from the wall, the noise level dropped dramatically.
Then I switched to the Samlex and the noise came back. Back on the
battery, the noise dropped again as long as the power supplies were
unplugged and dead.
I have a laptop next to the computer. When I pulled the plug on the
laptop supply, the rest of the noise went away. I was down to S0/S1
and
CW signals were popping out all over the band again. Running the
computer on its internal battery did NOT contribute any noise. It was
the computer power supply.
Now that I am totally on batteries, I also appear to be immune from
both
the gas furnace and the dishwasher motor both of which caused me
problems when using the AC supplies. YES, I HAD CHOKES ON ALL
SUPPLIES,
CABLES, WIRE.
I've been on the air all day with my new outside antenna, on battery
power, making contacts near and far and I feel like I've hit the
jackpot. Since I'm totally QRP and CW, being limited to batteries is
not an issue.
If you're going to check your own supplies out, remember they've got to
be OFF/UNPLUGGED from the wall. Just disconnecting them from the
radio/computer isn't enough. It's RF.
73, Stan WB2LQF
1
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--
---
72,
Rich Hurd / WC3T / DMR: 3142737
PA Army MARS, Northampton County RACES, EPA-ARRL Public Information
Officer
for Scouting
Latitude: 40.761621 Longitude: -75.288988 (40°45.68' N 75°17.33' W)
Grid:
*FN20is*
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