Need RF Quiet USB Power Source

[John Carlyle]

Can anyone recommend a 12 vdc to 5 vdc USB power source I can use to charge an iPhone in flight that won't break squelch on my glider's radio?

-John, Q3

[jfitch]

On Thursday, June 26, 2014 7:48:50 AM UTC-7, John Carlyle wrote:
> Can anyone recommend a 12 vdc to 5 vdc USB power source I can use to charge an iPhone in flight that won't break squelch on my glider's radio?
>
>
>
> -John, Q3

John - I have not had a problem with using a good quality cigarette lighter convertor. Blue Sea sells a panel mounted version, it seems to be shielded in a can (look on Amazon for Blue Sea USB). I had used a potted 12v->5V convertor with my iPhone 4S, you have to trick it by tying the USB data lines together with a 100K resistor. The same trick will not work with the Lightning connector on the iPhone 5S. You need a real cable and a USB supply that responds to the official protocols.

[Dan Marotta]

Don't know about your radio, but...

I found a dual USB (1 amp and 2 amp) adapter that plugs into a 12 volt
source in the auto section at Wal Mart. I wired in a 12 volt lighter
plug with a toggle switch to control it and glued it to the side of my
panel. It powers my Streak and has a phone charging cable should I need
it. Cheap and effective.

Dan Marotta

[Paul Remde]

Hi John,

It's not exactly what you're looking for, but the 5V batteries I sell work
great for powering an iPhone.
http://www.cumulus-soaring.com/batterypacks5v.htm

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.
_________________________________

"John Carlyle" wrote in message
news:cf7fb615-c1ef-4feb...@googlegroups.com...

[John Carlyle]

Thanks to Jon, Dan and Paul. I asked because the external battery pack I use for my iPhone when I'm not flying creates a whole bunch of noise on my Becker AR4201 radio and on my iCOM A6 when I use it in the glider. I have a 12v adapter for an iPAQ 3950 that makes noise in the glider, too.

I had an old cigarette lighter to iPhone charger. If I can find it, I'll give it a try. Else I guess I'll give the Blue Sea 12V Dual USB Charger Socket a try.

-John, Q3

[Martin Gregorie]

Most of these converters are switch-mode supplies, so can be a bit RF-
unfriendly. The trick for killing the RF interference is to put the
switch-mode PSU in a Faraday Cage and make sure there are ferrite cores
on all wires coming out of the cage and as close as possible to it.

I used an IPAQ 36xx cigarette lighter adapter because that can supply 1.4
amps at 5v. I took it apart and dug the circuit out of it, soldered 12v
supply leads from it to an XLR socket in place of the cigarette lighter
contacts, connected two pins of a D-9 socket to the 5v end and put the
lot in a small metal box with the connectors mounted in holes cut in the
lid plus a push-fit hole for the PSU's LED, which also helps to mount it:
Pritt pads finish the job of holding it in place and insulating its PCB
from the metal box. The box went behind my panel. I put ferrite cores on
the two leads close to the metal box end.

I've used this for some years to drive satnavs of various sorts without
any noticeable RF interference detected by either my original ATR 500
transceiver or the Dittel KRT2 that has just replaced it - anybody in
need of an ATR 500 in good condition should apply here.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

[John Carlyle]

Thanks, Martin.

I found my old iPhone cigarette lighter charger. It puts out enough RF to break squelch on my iCOM A6 if the antenna is within 2 inches of the iPhone. I'll do another test in my glider this weekend to see if the adapter is usable as is before going further.

Your trick of putting the switcher inside a metal box and using chokes on the input and output power lines may be necessary to stifle the switcher...

-John, Q3

[JS]

As in real estate.... three big things are location, location, location.
Jim

[John Carlyle]

True - but in a glider the location choices are a tad constrained...

-John, Q3

[kru...@sbcglobal.net]

On Thursday, June 26, 2014 7:48:50 AM UTC-7, John Carlyle wrote:

> Can anyone recommend a 12 vdc to 5 vdc USB power source I can use to charge an iPhone in flight that won't break squelch on my glider's radio?
>
>
>
> -John, Q3

Take a look at the New Trent Power pak http://www.amazon.com/gp/product/B003ZBZ64Q. Use it myself to charge my tablet and IPHONE but can't speak about RF noise though

[Jim White]

Solution is a choke on the cable.

[John Carlyle]

I have a New Trent model IMP500 battery pack, and it's a huge generator of RF noise. It's so bad it makes noise without even having a cable connected to it! It's why I started looking for a quiet 12 vdc to 5 vdc USB power source...

-John, Q3

[Kevin Neave]

I've used...

eBay item number: 251278536206

.. in the past.

Seem to be much quieter (RF) than the usual USB adapters for cigar
lighters

KN

[John Carlyle]

Thanks, Kevin! I'll add that to Jon's Blue Sea recommendation.

The only drawback is that it doesn't say if it works with iPhones. They require some resistors to work, see: http://www.epanorama.net/newepa/2010/08/18/apple-charger-secrets/ There are resistors at the USB end, so maybe it does work with Apple products.

-John, Q3

[jfitch]

Do you have the traditional iPhone connector, or the new one (little thing named Lightning)? Resistors will work for most devices that use the old connector, but may not for the new one. There are some protocols run on the data lines to determine whether the power supply is suitable for the device, and how much power it can supply. The tiny little Lightning connector has electronics in it to do this among other things.

Early on Apple used resistors prior to there being any agreed standard on USB as to how to do this. These methods are sort of grandfathered in, but the newer devices are much more sophisticated. I found some that work work occasionally but not always,etc. The better name brand stuff works all the time.

The Blue Sea version has an aluminum can around the whole thing. They make both a cigarette socket one and a panel mount - it looks to me like the panel mount is just the cigarette one with a plastic housing over it to make it mountable. I have taken apart several of the cigarette lighter adapters, most of them are an ultrasonic welded plastic housing without much shielding. EMI engineering is still a bit of a black art, a copper foil covering (drained to a low impedance ground) and chokes is a good place to start - but don't be terribly surprised if it doesn't solve the whole problem.

[JS]

Powerwerx.com also sell the Blue Sea panel mount USB and a lighter plug version.
Jim

[John Carlyle]

Thank you, Jon, for the suggestion to go with brand name stuff.

Right now I'm using an iPhone 4, but I will upgrade to either the 4.7" or 5.5" model rumored for Fall release. That's why the Blue Sea adapter you suggested earlier in the thread was so interesting to me, since it claimed to meet Apple specifications. I do understand that I might have to shield whatever I buy, but I've done that before so no worries.

Thanks, Jim, for the Powerwerx.com reference for Blue Sea.

-John, Q3

[Six-Seven]

John,

The basic problem is explained by several people above that these power converters* (converting 12vdc to 5vdc) use electronics that can emit high frequency noise which can be picked up by external devices like your ship's radio. The amount of noise is inversely proportional to the price you paid (less $$$ equals more noise).

Multiple people above mentioned adding a "choke" or "ferrite core" or "beads" (one and the same). Great idea. These keep the high frequency noise from getting onto the 12vdc bus and then into other devices.

But these will not help your problem as your external power pack is obviously not connected to the bus. The noise is getting into your radio through the air. This might indicate a poorly designed radio (Becker is one of the better brands) or your coax's shield isn't grounded correctly (check the BNC connector) or a cheap poorly designed external power pack.

Back to Ferrite Cores - You have probably seen some on your laptop's power supply as a thick oblong thingy molded onto the cord. The power wires are routed through these cores. They come in two varies; 1) a solid ring shape (torus) for new installations or 2) a snap on clamp style for retrofits. Route the power wires through at least twice. They are a good idea for all of your devices that connect to your ship's power bus. Here are some links.

http://www.k0bg.com/beads.html
http://en.wikipedia.org/wiki/Ferrite_bead
http://www.ebay.com/itm/5-Pcs-Black-UF50B-6mm-Dia-Clip-On-EMI-RFI-Noise-Ferrite-Core-Filter-/281370901241?pt=LH_DefaultDomain_0&hash=item4183033af9

Good luck. Report back.

- John

* Old power supplies (converters) were "linear" and pretty dumb. Voltage regulation was difficult and they didn't easily handle varying voltage inputs. Any newer power supplies are "switching" and are a major step forward in technology. Pros: Much smaller, more efficient, able to handle multiple voltage inputs (like being able to use 110-220vac or 12-24vdc). Cons: the switching mechanism is high frequency and can be noisy. There is a switching power supply in the Oudie's power/data cable and seems to be very high quality and not very noisy.

http://en.wikipedia.org/wiki/Switched-mode_power_supply

[Dan Marotta]

Having a bit of searching for a battery pack, I found that several units
supply multiple DC voltages in addition to the 5v that everyone is
looking for. I believe it's that 9v or 12v up conversion that's causing
the RF noise. I'd suggest getting a 5v ONLY pack.

Dan Marotta