Does anyone have any practical experience with these? Looks deceptively simple, and cheap.
How about a wearable version to improve cell phone and wireless reception?
Barry Latham
A little. I built two maybe 30 years ago just to see how they work. I've also etched a few on PCB's, again for tinkering. In about 2004, I threw one together for testing a UWB prototype. They're useful if you need circular polarization over a very wide bandwidth. Not very useful if you need more gain than you would get with a dipole (about
3-4dBi). If you don't need CP, then a simple bow tie antenna is easier and better.Don't forget to add a broadband balun in order to get the approximately 200 ohms down to 50 ohms.
The rule of thumb for antennas is; Gain, Small size, Wide bandwidth... pick two. In this case, we have only a really wide bandwidth, but are stuck with low gain and a physically big antenna, which might explain why you don't see more of these.
More:
The very last thing one wants in a cell phone is a single antenna for all the RF related devices. The possibility of self-interference is almost guaranteed. The trend is towards small and separate antennas for each band. For example, the new Galaxy S5: with 8 antennas inside.
There's also the necessity of having more than one antenna for Wi-Fi and LTE MIMO. LTE-advance has specs for up to 8x8 MIMO which means 8 LTE antennas in the handset. For spatial diversity to function, they have to be somewhat physically separated. That can probably be done on a laptop or tablet, but not a handset.
The radiation pattern requirements for cellular are a compromise between adequate gain and low radiation in the direction of the head to reduce SAR (specific absorption rate). The result are some rather complex antenna patterns with most of the RF coming out of the back of the phone, and very little in the direction of the users head. A spiral antenna just isn't going to do that.
If you want it wearable, I guess that the spiral can be mounted on top of your head on a mortar board hat, or carried on your back. If you look carefully, todays internal antenna handsets do not have an external antenna connector. There is a test connector (usually under the battery), but that's intentionally designed to NOT lock the mating connector so as not to be easily used for such external antenna schemes. There are loop coupling schemes, but the coupling losses usually make it not worth the effort. The problem is not the external antenna. The problem is coupling the RF to the antenna from the handset.
However, all is not lost. If lack of signal is your problem, you can do much better with a simple corner reflector. For the lowest frequency of 700Mhz, something about 7" high and maybe about 14" wide should work. Bigger is better. Cut a hole in the center for your ear. When talking, simply locate the cell phone at the focus of the corner reflector (or single axis parabolic reflector) and you have more gain than you can possibly get from wearing a coaxial snail antenna.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I have a couple of these... can't recall exactly where I got them.
Any guess as to specs?
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
That's a 2 arm conical log spiral antenna. The outer cone should be 2 spiral copper traces on some manner of flexible microwave printed circuit material. There's a coax cable connecting the N-connector with the two spirals traces at the apex of the cone. There is probably a balun or impedance transformation along the coax cable.
Scaling from the N-connector in the photo (15mm thread diameter), I would guess(tm) that the cone is 60mm base and 150mm height. Assuming a dipole spiral, I count 5 turns per dipole arm. The lowest frequency is set by the length of the spiral or roughly: 60mm / 2 * 5turns = 150 mm For a 1/4 wavelength arm, that's about 500 MHz. Such antennas have fractional bandwidths of at least 10:1 making the upper frequency about 5GHz. If you wrap a string along one of the arms, and measure the arm length more accurately than my guess, I can provide a better estimate.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I still have a couple of those! TNC on the end. Very good for RX, 440 MHz on up.
The spiral nature gives you the bandwidth; shaping it into a cone gives you the directionality.
-- Namaste--
I think I have two of them. I could TDR the pair!
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
They have antenna tuners these days. It makes the phone more frequency agile. The tuners are just high quality caps and switches at the moment. There is noise about using MEMS, but I don't think any production phones have them.
Samsung RF performance is kind of poor. Not Apple shitty, but not like Moto, Nokia, Blackberry, etc. either
I've seen spiral conicals feeding dishes for TX, so some designs are meant for TX.
I don't see much of that. Usually its some manner of ceramic or PCB antenna, with a matching network. Those with one antenna per band seem to work best. Those that try to share antennas usually work badly.
I haven't seen any, yet. My guess(tm) is that it's still smaller, cheaper, and easier to use multiple antennas, than to use a single antenna and tuner. There are also some rather bizarre looking and hopefully functional multiband antennas (in IEEE Ants and Props journal) which are probably as good as any antenna tuner. The downside is that the 700 MHz bandplan in the US is quite different from other parts of the world. Using a dedicated antenna might make the phone US specific and not allow roaming into other parts of the world. An antenna tuner would theoretically not have that problem, making it a desirable feature. I'm still waiting for true SDR handsets, that will work on any carriers system.
Nice but there's a catch. Tx-Rx isolation in the 700MHz band seems to be a problem. The phones I'm seeing have separate tx and rx 700MHz antennas. Combining that to a single antenna is going to require some manner of diplexer, which can be potentially rather large.
Dunno. I haven't run any recent tests. The problem seems to be that the new LTE phones are having problems meeting the SAR requirement. The cell site can theoretically transmit 1 to 2 watts per channel if necessary. Most handsets transmit no more than about 150 milliwatts. If manufacturers reduce the tx power in order to meet SAR requirements, performance will suffer. I haven't had time to check if that's the problem with Samsung or various iPhones.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Paratek chips are in the Z30, which every claims has phenomenal RF. Paratek is owned by Blackberry, but they supply the tuners to other vendors. ST Micro makes them as well.
I'm not sure how you would fine out who uses what, other than if Ifixit has a tear down. But multiple antenna phones are on their way out. Too many bands. With no contract phones being the next phase, you need a phone ready for anything.
That would be the Blackberry Z30 STA100-2 FCC ID L6ARFW120LW I count 5 antenna connectors on the PCB. Unfortunately, the antennas are buried inside various shells and the resolution insufficient to identify the Paratek chip. Looks like the phone does
850/1900/2.4GHz/5Ghz/13.56NF which covers all the connectors. Are you sure that the Z30 has an tuner?The cellular vendors usually used 2 year phone contracts to lock in the user to a specific provider (i.e. vendor lock). I don't see any sales advantage to the cellular provider to SDR or no contract as it only increases churn. The trend to no contract phones is simply to improve cash flow by forcing the customer to purchase a no contract phone at full list price in advance instead of spreading the cost out throughout the 2 year contract time. It also makes it somewhat easier for providers to steal customers from other providers. When I see some consolidation among the approximately 1300 Android smartphone mutations, I might believe that provider portability has some benefits.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Well you have bluetooth and wifi, not to mention NFC. So the deal is the number of antennas just for cellular.
Here is a quick look at the Z30: Network (LTE)
700MHz (Band 17) / 850MHz (Band 5) / 1900MHz (Band 2) / AWS (Band 4) / 2600MHz (Band 7)Network (HSPA)
2100MHz (Band I) / 1900MHz (Band II) / AWS (Band IV) /850MHz (Band V)Network (GSM)
850MHz / 900MHz / 1800MHz / 1900MHzLooks like it covers 8 bands.
If you are buying a Nexus phone at Wal-Mart, I would consider that a direct sale. That is, you get a phone and then find a MVNO. But I think Google had put some Nexus phones right in their Play Store. Ah, for example:
Yep, but if you look at the FCC ID page for the Blackberry Z30 STA100-2 at: L6A RFW120LW I see only the usual 800/1900/WiFi/NFC bands, plus 1900. Nothing for
700 and 2100 MHz . Compare with the HTC One at FCC ID: PN0 7120 which 700, 1700, and 1900 MHz. Well, I may have the wrong FCC ID. Under L6A prefix (Blackberry), there are 1100 listings. Got a better number for the Z30 (which hopefully shows a Paratek antenna tuna chip?Yep. Google is likely to rediscover the problem that Intel had when it was selling motherboards at the same time as chips to motherboard vendors. It's not nice to compete with your own customers. We'll see how it plays out. Right now, Google is probably trying to determine if they can make money as a handset vendor.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Here comes "It depends." Most of the Blackberry phones are designed for multiple markets in a way where the bands are set by firmware. For instance, I have the hardware of a CDMA phone on my GSM phone, but the firmware will not allow EDVO or CDMA. So that one phone really does have many many bands.
The cellular vendors will not allow true world phones, well at the moment. The cellular providers have gradually relaxed this. Quad UMTS and QUAD 2G is commonplace these days.
Google dumped Moto,so I guess they figured out that pisses off their competitonl. I wouldn't buy LG anything at the moment, so that takes care of Nexus. Well, I have a LG blueray drive on my PC. So I guess if they are cheap enough, maybe I would buy something from LG
I haven't been paying attention. Paratek was purchased by RIM in
2012. So far, the Z30 is the only phone that uses the chip. I would not expect to see Paratek chips in competitors phones.Looks like the Z30 does have a Paratek antenna tuner. Apparently some users consider it an improvement, although they seem to be comparing it with previous Blackberry phones, which may have had problems. No numbers as usual:
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Blackberry phones have radios like Nokia, i.e. good stuff. Paratek sold these chips to the industry before Blackberry bought them. Blackberry sells all sorts of stuff that isn't captive to their phones. "Documents To Go" for instance. Same goes for QNX (pronounced Q-nicks).
But Qualcom is doing the same thing. I doubt you can patent an antenna tuner. I mean, you make a variable inductor or a variable cap. The roller inductor is kind of tough to do in a phone, so the industry uses caps. The caps at one time were discrete and the networks were switched in and out. The programmable cap is obviously the next generation.
So if I'm have trouble with a call, I might turn 180* and have better reception?
You could try this:
This is quite fashionable;
I'm sorry,
or, you could build it into the shoulders of a shirt,
But definitely not this,
or this
All that and I never found the one I was looking for, it was a yagi mounted on a hat for a fellow flying a remote control airplane. It looked well balanced and comfortable. Mikek
Yes. Put your phone into "field test mode" which will display the receive signal strengths (they're different for voice and data): There are some nifty apps for Android and jailbroken iPhones that will display signal levels. Play with hand position, phone position, and metal reflectors to maximize the signal level.
I like the idea. The biquad antenna is probably for video from the aircraft. Judging by the bright copper color of the PCB material, this is the first time he's used it. If the aircraft is doing aerobatics, I predict a stiff neck, nausea, falling on his face, etc.
Yagi's have too many side lobes to be useful on your head. It's also too close to what's left of your brain to be considered RF safe. I recommend a colander or salad bowl antenna instead: This was originally designed to be hand aimed and to accommodate a USB dongle. However, I believe the basic structure is suitable for mounting on your head using a colander and chin strap.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
The signal levels for voice and data must be a CDMA thing. Every GSM phone I owned only had one level.
I can put my phone in "engineering mode" and see the levels of neighbor cell sites as well as the serving site. I've seen an iphone app for this, so I assume all phones have this ability, though perhaps not available without an app.
I currently have a RSSI -59 RSRP -86 SINR 13.8 BAND 4 LTE
This link has a few screen shots of what is in engineering mode.
That antenna on the head is very "ham sexy."
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