Possible new Noise Threat to Amature Radio.

[Ed/KB1HYS]

Check out the Duracell PowerMat, a inductive battery charger...

http://powermat.com/platform/

I have asked them what frequency and how much power they radiate, let's see what that answer is...  How many watt's of RF have to be pumped out to achieve a charging current in a receive antenna a short distance away???

[gerry_w1id]

You could be right. However, as I understand it, those chargers operate on the inductive principle. The device being charged has to be directly over the charging coil. The frequencies involved are in the range of most switching power supplies. By nature the charging signal must be a sine wave for maximum efficiency as opposed to switching supplies with varying duty cycles and harmonic righ waveforms. The advantage of this system is that you don't have to plug in a whole slew of chargers for your mobile devices, whether phones, tablets, or MP3 players. For example a hotel could have one powermat in every room for charging any brand or type of device by any guest thus there would be no need to take your charger with you. For this system to work, the battery pack in the device has to have technology identifying itself as a compliant device and be able to communicate with the charger. You could not use a powermat to charge just any battery. As I understand it, the standards are still being worked out by a body made up of various mobile device companies as well as semiconductor manufacturers. Semiconductor companies seem to think there is a market for these type chargers. The biggest obstacle they face is relatively low efficiency because they have "discovered" RF is not an efficient way to transmit energy. Thus the need to have the device being charged directly over the coil.

[Tom WA3KLR]

I did a patent search on Powermat Technologies as the Assignee and came up with 2 patents: 8188619 and 8193769.  The pdf files of the patents are attached below.

The quick skim I did through them I spotted no mention of frequency or distance.  The one patent shows the primary coil on the bottom side of a desktop and the secondary coil on the top.  The freqency may be vague because my guess is they have filed in many countries where the allocations are different.  In the U.S, my guess is that they will stay below the bottom end of the AM broadcast band where the radiation limits are higher.  Also in writing a patent you don't want to get so specific as to invite others to horn in without infringing on the patent.  This product is an intentional radiator and I don't remember the implications of this versus an unintentional radiator.

The one patent shows an abstract schematic implementation using an LTC4442 MOSFET gate driver i.c which most class E builders are familiar with.  This i.c. plus external FETs drive the primary coil.  The LTC data sheet shows graphs using the part up to 1 MHz.  Class E hams use it at 75 meters I believe.

My impression: I don't think this is any worse than all of the switching regulators out there already, able to conduct their trash back out onto the power line, which gives us the problems.  Here the radiation should be limited to the primary coil.  If next door to a 505 kHz band experimenter then he could have receive interference.



  

[Opcom]

because of the amount of power to be generally sent, efficiencies, and scale of the couplers, and even the appearance of the pickup area, practical ones being tested are mostly 100KHz to 1MHz. The industry research however extends to 3-5MHz. The schemes are ingenious to include communication between the charger and device so that the device can control the charger to some degree. The only emission that should come from a well designed and efficient one would be an alternating magnetic field some of which could leak past the imperfect coupling so there should not be the typical switching power supply noise (not holding my breath). The smart ones have groups of coils and only the necessary ones need be actuated. If there could be agreement in how to design and use the things, annoyances could be minimized, but every user I know is quite too lazy to be bothered positioning a device precisely, they just want to throw it on the pad.

[WB2EMS]

One concern I have, and I had the opportunity to talk to one of the investors in the system, is that using magnetic fields, it will couple into loop antennas that are primarily sensitive to magnetic fields.

Currently, we can get away from a lot of the noise generated by household devices by using a magnetic loop. I use a pixel RF-1B. But if these devices become ubiquitous, and I think they might, that method of avoiding interference might become useless.

They are looking at versions large enough to charge electric cars. Those will be strong magnetic fields.

If our rechargeable devices become equipped with the receiving antennas by default - in cell phones, tablets, etc then a desktop pad could be handy as heck. But I worry about the noise impact on radio operations.

[Opcom]

Which system is the one you are speaking of where you spoke with the parties involved?

I didn't even want to mention loops but it is obvious and my only salvation might be the RF-1B seen at ham-com. Do you like it?

magnetic field chargers can become a whole new item for FCC enforcement. Maybe easier to pinpoint the offenders. Pads are a convenience but connectors are the right way to respect our "rights" to clean spectrum.

[gerry_w1id]

Perhaps a lot of questions can be answered by going to the Texas Instruments web site (ti.com) and typing in "BQ500210" in the search box. This will take you to the data sheet and other miscellaneous information. The operating voltage for this particular IC is around 3V and the frequency of operation can vary between 100 to 200kHz (spread spectrum) and is definitely a sine wave. It is a very short range system. Several companies have banded together and are working on a standard. At this point it is safe to say the technology is nascent and there is no clear guarantee that this type of technology will even take off. I know personally that the people involved in the chip development are very concerned about unwanted radiation because it limits efficiency and certainly don't want to interfere with any wireless devices in close proximity. They are also very concerned about RF exposure for regulatory purposes. Notice I didn't say they are concerned about causing interference or causing hazards due to high level RF. In the corporate environment, this is how it goes. Certainly this thing bears watching but at this point I don't think it has reached alarming proportions. For all I know it may be some kind of transition to another charging method: energy harvesting. Some people are working on devices that convert vibration to energy. Since most people carry a cell phone on their person, this system would convert vibration and movement associated with walking into energy. Now that would be interesting to see.

[W1ATR]

It's about time they came up with a replacement for the plasma tv. 

[WB2EMS]

Which system is the one you are speaking of where you spoke with the parties involved?

I can't find my notes or bookmarks. It was about a year back and memories fade. The investor was a friend of my siblings and I only had one conversation with him about it. I did express my concerns about interference.

I didn't even want to mention loops but it is obvious and my only salvation might be the RF-1B seen at ham-com. Do you like it?

Fairly well. It does have some sharp nulls for groundwave. I inadvertently had the null on a local AM station that a friend needed to monitor via my online SDR system and he reported the signal was terrible. I moved the rotor 20 degrees and bingo S9+. It didn't make all the other noise artifacts in the environment magically go away, but it did help and my site isn't too noisy. There is one local noise coming from the neighbors that I'd hoped it would cure and it didn't - but it helped. But I think it's the heating controller on her kiln and it excites the power lines for a quarter mile either direction as well and the RF-1B is mounted closer to that source than my other antennas. I might have better luck if I moved it further away from the property line and power lines.

magnetic field chargers can become a whole new item for FCC enforcement. Maybe easier to pinpoint the offenders. Pads are a convenience but connectors are the right way to respect our "rights" to clean spectrum.

I don't see the FCC, or really any other parts of the government, respecting our rights much these days. The way they 'handled' BPL doesn't give me hope and with the crony capitalism happening now....  If Jeff Immelt decides to buy one of these companies and deploy it ubiquitously I'm sure they'll get a green light to go ahead, spectrum be damned. 

[W1AEX]

When I read this story it reminded me of the thread you started Ed. When this gets deployed to every neighborhood I would imagine that it will definitely impact reception for those of us on the HF bands. I'm quite sure it will not get the amazing Part 15 sticker that has protected us so well in the past. Perhaps it could also be used to reduce the local mosquito population?

http://washington.cbslocal.com/2012/06/28/army-developing-laser-that-shoots-lightning/

[Opcom]

Looks like it might be the old scheme of two parallel laser beams powerful enough to ionize the air, and the ionized air columns being made use of as two 'conduits' for an electric discharge spent against the target where the laser beams strike. Any laser can be used as long as its beam will ionize air to conduct the discharge. There is a newer scheme with some mechanicals in the beam path as well.

It would be interesting to see what would happen if the thing were used on a power system having more electricity than the weapon produces. Maybe the juice would flow right back to the 'gun' and burn it out.