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Re: [RFI] Quiet Power Supply?

To: rfi@contesting.com
Subject: Re: [RFI] Quiet Power Supply?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Wed, 3 Aug 2016 12:18:08 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Wed,8/3/2016 11:29 AM, Ken Winterling wrote:
Check out the IOTA power supplies.  I have had the IOTA DLS-55 with IQ4
smart charger module for years.  Sometimes it has run 24/7 for months.  The
IOTA units are exceptionally RF clean and have excellent electrical
characteristics.

Hi Ken,

I've scoured the IOTA website and cannot find a single word about EMC compliance, nor even about use with radio equipment. Their "technical library" is largely dedicated to the charging of lead-acid batteries. There are no prices on the website, and clicking on "Ham Radio/Hobby" in the Distributor link directs me to a company that specializes in sales to radio control users (we're talking battery charging for model airplanes here) and another that specializes in SELLING "TOP-OF-THE-LINE Chargers/Power Supplies/converters to Manufacturing and the Public," neither of which gives me a warm fuzzy feeling about RFI.

Whether or not RFI will be observed from any noise source will strongly depend upon what "antennas" are connected to that noise source (AC wiring, DC wiring), the proximity of receiving antennas to the noise source, and the other RF noise present in the environment. Most hams have antennas that are pretty close to their shacks, and most of us have RF noise from other sources in the homes and businesses that surround us. I've seen far too many observations that XYZ product is clean when in reality it is not, or is quiet on some bands and not others, when in reality the noise it produces is covered up by other noise. As a result, I'm VERY skeptical of observations like this, especially when the mfr's published materials make no mention of RFI, when the product is not sold through ham distributors, and when the product is primarily used as a charger. :)

All I can find in IOTA product literature is this statement: "The exceptionally clean DC output of the DLS Series converter promotes longer life for any connected load and virtually eliminates AC ripple that can cause static or premature failure of radio or television equipment." To most power supply designers, "ripple" means power-frequency variations in voltage, not RF noise.

I've tried to use products like this that hams had claimed were "very quiet" and found that they were not. My QTH is quieter than most, but far from dead quiet, because I have neighbors. I've yet to find a switching power supply that is anything approaching quiet on 160M, or that is quiet enough to be run within 30 ft of HF antennas.

So my question is, how quiet is your QTH, and how close are your antennas to your shack?

73, Jim K9YC


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