[RFI] RFI Report Re: IOTA DLS-45 w/IQ4 Charger-PS

[Christopher E. Brown]

On Mon, 21 Mar 2011, doc at kd4e.com wrote:

> RFI Report Re: IOTA DLS-45 w/IQ4 Charger-PS
>
> The unit arrived today and I made up a cable set and set it to
> work charging a 105 AH @ 20hr rated deep-cycle battery.
>
> I was hearing really strong radio frequency interference on the
> AM broadcast band 20 feet from the IOTA.  The IOTA was sitting
> on a table inside of a 20' steel shipping container and the
> AM-BC receiver was in another room.
>
> The AM-BC receiver was plugged into the AC outlet so I brought
> my little RFI-chasing handheld AM-FM-SW battery-powered receiver
> into the same location as the other receiver and no RFI.
>
> I relocated the AC cord of the IOTA from the AC outlet to the
> "Surge and Noise Protect Outlets" of a Tripp-Lite UPS and the
> RFI that was clobbering the AC-powered AM-BC receiver via the
> AC line went away.
>
> So, just as a heads-up for those considering the IOTA - be
> prepared to provide line-filtering on the AC side as apparently
> the device is not well-filtered there.

I saw similar here on multiples of the switcher freq (43 - 47 khz) up to 
about 1500khz (getting weaker as they went up) until I noted the install 
sheet note on bonding the chassis and used the bonding lug on the outside 
of the chassis.


The green wire in the AC cable bonds the the inside of the steel chassis 
and the circuit board, the chassis bond is on the outside.  Bonding the 
outside lug to the same gnd as the power plug corrected things for me.  I 
can only assume that the field from the transformers is exciting the case 
inside and out, and that bonding the outside of the case helps close the 
current loop.  My bond connections run from the chassis lug across the 
case and are run with the power cable (zipped the the AC cable) the outlet 
where it has a ring term on a screw on the bonded metal face of the 
outlet.