ATS-909 wall wart introduces noise
 

The wall wart supplied with my ATS-909 introduces some noise to the
receiver audio. Are there any ways to suppress the noise? Ferrite
beads in the leads?

The noise is very annoying, since I like using the ATS-909 with an
external power supply. The receiver eats batteries for breakfast, and
SW reception suffers severely as soon as 3/4 or less battery power is
available. When I connect the wall wart, reception and signal strength
improve dramatically, but so does noise. It does not matter when
listening to strong BC signals, but listening to weak signals becomes
a pain.

Many thanks for your tips,

t3000

Tisle kolmetuhatta wrote:

The wall wart supplied with my ATS-909 introduces some noise to the
receiver audio. Are there any ways to suppress the noise? Ferrite
beads in the leads?

The noise is very annoying, since I like using the ATS-909 with an
external power supply. The receiver eats batteries for breakfast, and
SW reception suffers severely as soon as 3/4 or less battery power is
available. When I connect the wall wart, reception and signal strength
improve dramatically, but so does noise. It does not matter when
listening to strong BC signals, but listening to weak signals becomes
a pain.

Many thanks for your tips,

t3000

It's most likely unbypassed diodes. There's a moment when no diode
is conducting, and that removes an RF ground from the radio 120 times
a second, and you're hearing the 120 Hz change in the antenna system.

My own general solution to wall warts is go to NiMH batteries, and just
swap in one set and recharge the other set.

What I use (I may be a few months out of date of state of the art)

The Maha C401FS charger is great for AA and AAA's

The AccuPower20 for those and C's and D's and 9v's.

those both charge cells individually, which is what to look for.
Parallel and series charging isn't so great. It can leave you with
irregularly charged cells.

An ancient CCrane charger though is the only one I have with a cell
charge meter, and that comes in very handy to see what's what with
this or that cell.

NiMH C's and D's unfortunately are pretty costly still.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

In article ,
Ron Hardin wrote:

Tisle kolmetuhatta wrote:

The wall wart supplied with my ATS-909 introduces some noise to the
receiver audio. Are there any ways to suppress the noise? Ferrite
beads in the leads?

The noise is very annoying, since I like using the ATS-909 with an
external power supply. The receiver eats batteries for breakfast, and
SW reception suffers severely as soon as 3/4 or less battery power is
available. When I connect the wall wart, reception and signal strength
improve dramatically, but so does noise. It does not matter when
listening to strong BC signals, but listening to weak signals becomes
a pain.

Many thanks for your tips,

t3000

It's most likely unbypassed diodes. There's a moment when no diode
is conducting, and that removes an RF ground from the radio 120 times
a second, and you're hearing the 120 Hz change in the antenna system.

My own general solution to wall warts is go to NiMH batteries, and just
swap in one set and recharge the other set.

What I use (I may be a few months out of date of state of the art)

The Maha C401FS charger is great for AA and AAA's

The AccuPower20 for those and C's and D's and 9v's.

those both charge cells individually, which is what to look for.
Parallel and series charging isn't so great. It can leave you with
irregularly charged cells.

An ancient CCrane charger though is the only one I have with a cell
charge meter, and that comes in very handy to see what's what with
this or that cell.

NiMH C's and D's unfortunately are pretty costly still.

Good information except for the "when there is no diode conducting"
explanation. When the diode switches off the voltage rises very rapidly
to a large value, which interacts with parasitics of the power supply
wiring generating broadband noise. Bypassing the diode with a capacitor
gives the RF generated voltage spike a short current path around the
diode so that it is less likely to radiate. Better than just a capacitor
would be a series resistor and capacitor across the diode. This little
circuit is called a snubber. Most power supplies use both halves of the
60 Hz sine wave line voltage so the generated noise pulses occur at 120
Hz.

You can also try a common mode choke on the cord from the wall wart. Put
the choke near the wall wart end of the power cord. Keep the radio away
from the wall and the house wiring because the radio could still pick
the same noise up that way.

--
Telamon
Ventura, California