Zaon MRX causing radio interference 2

"jcarlyle" wrote in message
...
I did a set of noise experiments using my Zaon MRX and my Icon A6.

The setup for the Zaon was (1) Flight Mode = On, (2) Brt down until
just disappears, (3) Antenna pointed vertically, (4) Power – internal,
external, external w/ 0.01uF ceramic and 0.1uF metal film caps in
parallel across power leads at tip going into Zaon (I couldn’t fit my
1” long by 1/2" diameter non-split ferrite into the test rig).

The setup for the Icom was (1) Frequencies 123.300, 123.075, 122.800,
(2) Internal batteries, (3) Antenna pointed vertically (4) unit on
opposite site of power input to Zaon and external battery.

The testing procedure was (1) Place antennas 3 inches apart, (2)
Reduce squelch from highest value until sound appears, note number,
increase squelch, reduce squelch, note number, repeat until lowest
consistent squelch number is obtained.

Test 1 – Zaon on internal batteries, Test 2 – Zaon on external
battery, no caps, and Test 3 – Zaon on external battery, caps used.

Results:
Test 1 Test 2 Test 3
Internal External Ext w/ caps
123.300 5 18 14
123.075 5 24 21
123.800 5 24 16

It’s clear that the Zaon radiates noise when running on an external
battery. It’s also clear that the 0.01uF ceramic and 0.1uF metal film
caps in parallel across the Zaon power leads reduce the noise the Zaon
is radiating, but they are nowhere near as effective as running the
Zaon on internal batteries.

Any electrical engineers out there who'd like to make some suggestions
for further tests to help me try and get the Zaon noise down?

-John

Not an EE, but it might be interesting to see how a the length of the llne
to the battery affects things. I have a suspicion that the radiating
element is the power lead, rather than the antenna. They could be using a
switching regulator for external power (not unreasonable if you want a wide
input range and decent efficiency).

See if, with the Zaon antenna and power cord at right angles, rotating the
receiver antenna from parallel to the Zaon antenna to parallel to the
power cord makes the problem worse.
Sometimes it's useful to find how to make things worse, and that gives you a
clue as to how to make things better.

A different approach might be to supply your own regulator as a "battery
eliminator" that goes in place of the battery, supplying a filtered nominal
battery voltage.

But if a little is good, a lot may be better. Try paralleling a 10 uF cap
with what you have.
Keep increasing the capacitance until it doesn't help or gets worse.
Some linear regulators will oscillate with too little capacitance on the
input, but I would think Zaon would catch that.

Also, is the power cord through the ferrite as many times as it will fit?
The inductance is non-linear, it's proportional to the number of turns
squared. So managing another turn or two through the toroid may help.

Gosh, it's easy to come up with work I don't have to do myself.

Tim Ward