[RFI] Quiet Power Supply?

[Christopher Brown]

Not the original responder but am another IOTA user.

It looks like they have reworked their site and material since I last
visited, more shiny, less technical.  In the past there was much more
detailed information, including specific talk about RFI in multiple docs
most detailed as I recall was under the "Marine" section where
interferance to marine SSB rigs was talked about.

New web site is much fluffier.

That being said, IOTA is a long time company that was originally big in
the marine and certain commercial and specialty vehicle markets that got
into RV and Solar related (aux charging PV/other battery bank based
systems).


I have a pair of DLS-55/IQ4 paralleled to charge the shack battery bank
(100% DC shack), a DLS-55 as a portable supply, and a DLS-15/IQ4 as a
charger in a _small_ tent trailer (not a pop-up, tent folds out of the
top and is towed behind the motorcycle.)


These are well made units with a full galvanized steel enclosure.  AC
greenwire is bonded to inside of steel case.  There is a bonding lug on
outside if needed.  DC output is isolated and can be used in
series/parallel configs, if you need to bond DC common it is up to you.


My shack is second story on back of house.  My main HF antenna is a
short cut for 80M inverted L 30ft from shack with a SGC235 at base and
is usable 160M - 10M.  My shack is in the main pattern of the antenna on
all bands.  To make matters worse, the AC feed to the shack (DLS-55/IQ4
pair) runs parallel to upper section of L inside back wall of house,
then parallel to vertical section.  I have to be _very_ careful with
filtering my test gear in the shack.

In the trailer, the DLS15 maintains a pair of 35ah AGMs to run the
IC7000 and SGC237 when camping.  The antenna is <5 feet from the DLS15
and all wiring in trailer (small trailer) and the chassis of the trailer
is part of the radial field for the antenna.


At the time of original install (2009) there was also a rooftop doublet
fed by a balanced tuner about 15ft above shack.  DLS-55 pair has been on
24/7 minus power outages wince 2009.

All of the iotas seem to run a ~ 43khz switching freq.  It is detectable
faintly withing a foot or so of the case and close wiring as one would
expect.

Initially I was unfiltered, just plugged in.  Never had an issue.  While
doing an extensive RF survey I found that both the inverted L and
rooftop doublet could detect the supplies, but only when band conditions
were very, very quiet (band close and NO other RFI present) and was
still at or below floor.  Strongest on 160, where a bit of a background
hum under the static was clearly there, intermittently barely detectable
up on 20.

When the bands were actually usable though, buried in the static.

Had to go below AM band before noise was actually above background levels.

I could have left as is, but I tend to be finicky and I have lots of
line filters and ferrite around.  I put a good 30amp Corcomm filter and
a couple single 2.4" type 31 toroids on the AC feed.

After that, I could not pickup anything on any antenna above about 400khz.

I got rid of my Daiwa, MFJ and Astron switched supplies because while
they are all relatively quite as switchers go, the IOTA was > 10db
quieter, before filtering and that includes testing both while idling
and while running at full output.


Last test (post filtering but nothing special filtering wise) was a
simple one.  I was running a battery bank test so I also connected a 9ft
whip in the middle of the shack and the inverted L to a 2 port switch
connected to the SDR-14

When bank reached 80% discharge, I re-connected IOTA pair and measured
charge current at 110amps @ 13.4VDC.

Then spent the afternoon cycling between antennas and both wide and
narrow on the SDR.

Worst on the L, was weakly detectable below 160M, and there _might_ have
been a very weak hum on 160 and 80 but so weak I am not certain (no
visible impact on waterfall, way below band noise).  No detection
possible after charge current fell below about 60 amps.

On the in-shack whip about 4 feet from the chargers, was detectable up
to 20m but only above background noise on 160 and 80 until charge
current dropped under about 40 amps then audible 80 and down but
at/below background noise levels.

As a side note, while the AC in the shack is proper, H/N/G all run
together with no separations, rolls, etc BUT it is all in-wall romex...
No conduit.  The vertical section runs up from crawl-space to second
floor where it connects to one end of a horizontal run that wraps around
3 walls of shack and the vertical run then continues up to the light
switch and on into attic space and over to room lights.  This setup
makes a wonderful antenna, to the point that _ALL_ of the test gear is
on heavy filtering and the shack is where I take noisy devices to plug
in and test effectiveness of chokes/filters.


Anyway, their new website/technical info sucks, but these are actually
good devices RF wise.  Not completely silent, but as a ref both models
of ham radio marketed Daiwa switcher supplies I had when plugged in to
the same shack wireing and just idleing were > 10db noisier then a pair
of DLS-55 units running flat out at 55amps each.  Since my shack is DC
including the 500watt amp, if I am actually chasing DX, these things are
running hard, amp draws about 90amps and battery back is only a few
hundred amp-hours, so if I turn the amp on, these thingsd are running
hard at the same time I have the headphones on and an struggling to copy
remote stations.


I would suggest that a few of the largest #31 clamps on the AC and maybe
even DC side would not be a bad thing, specially with a very close
(house mounted) HF antenna, but then again coupling is so bad here I
filter and choke _everything_.





On 8/3/16 11:18, Jim Brown wrote:
> 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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