More Fractal Madness

OK - - understood, but what about the embedded antennas that are used? They must be small, can that design be incorporated (maybe with some reworK) into an Outernet device the size of the old Lighthouse? Ken

THAT is a good question. I would be acting like an armchair quarterback if I were to say one way or another. However, I have a mil spec gps puck antenna here and I am going to pull it apart and get a look in there. I do know that the gps modules like sold at sparkfun and adafruit are not going to cut it. been there done that.

Smartphone GPS antennas are tiny. Some of the older designs used an inverted F type sort of dipole, but the newer models are mostly tiny microstrip or patch antennas.

GPS transmits 23 watts with antenna gain bumping it to about 500 watts ERP, but path loss of over 180dB. Signal level might be as low as -133dB at the receiver.

I wonder if one of the GPS quadrifilar helix antennas would do any good.

Let’s take a look at those items. I found a company, Aafruit Antennas, seemingly selling products that sound as though they might work with the CHIP, LNA/SDR. They are not that expensive.

Perhaps I’m missing something, @Syed what do you think? Ken

I’m not opposed to incorporating new parts into the design. Faster, better, cheaper–it’s all of those, right? :slight_smile:

Sure - - even if it doesn’t become an Outernet component, but works and is small, I’d go for it. We just don’t want to reinvent the wheel here if you’ve already looked at the item and had a reason to reject it. Please tell us so we can save some time.

For example:

and

are not expensive. I’m game to buy them and test them out here next to the official PATCH, and some fractals I’ve made. Ken

Is this what you mean? Ken

Oh, you’re looking at standard ceramic patches. Yes, the actual GPS ones are not directional enough for us. There are some that provide more gain, which may eventually work themselves into an Outernet product. Adafruit is just a reseller. And Taoglas is way expensive for what such a commodity product.

agreed on the ceramic patch antennas. wasted about 2 days messing with various ones and the data showed it was not directional enough. (re: the ones from Adafruit and Sparkfun etc).

More like this https://store.uputronics.com/index.php?route=product/product&path=60_65&product_id=66

There are some like this that have built in LNA, and also some that are passive. The thing is, they are not directional. QFH antennas are used for GPS, weather satellite, communication satellites, etc.

I’m looking to find some of the ones that used to be in the old HP iPaq GPS module. They were made of a film with copper traces for the elements. Very lightweight and small. Curious as to whether one of these with a mondo LNA might do some Outernet…

Also curious as to all the other L band signals I see when sweeping the patch across the sky. I wonder if those will prevent anything but a fairly directional antenna to work for our purposes.

That Sarantel is -3dBi of gain. The lowest I’ve closed a link against was 3dBi (very shaky frame lock).

I have an idea for a QFH like that, but set in a shallow, wide dish reflector molded into the case.

I think it would great if you were to try that. The more antenna options the better. I’m going to continue exploring fractal designs. Ken

Ken,

I am a total noob when it comes to antenna design: it would be terrific if you could write a tutorial on how to go about designing this kinda fractal antenna? Not in general about fractal antennae, but how does one start with the requisite parameters - freq, target gain, material properties, polarization - and from there, derive antenna dimensions etc?

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I’ll work on that. Right now, I’m a NOOB too here. I need to get better at it before I lead everybody down this garden path!

So far my 2 antennas produce low SNRs when the PATCH is banging away with SNRs over 8. But the designs do get a Frame Lock!

Any help out there in the world would be appreciated :slight_smile: Ken

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I’m not surprised the fractal works, but with low gain. They are designed for wide bandwidth in a compact space. Stacked fractals might give enough of a boost, but there is also the factor of preventing side radiation from other sky sources from getting in the mix. That’s where the reflector is very important.

The other alternative is a compact 4 element yagi. In a finished product, it could be something that “flips” out, uncovering the solar panel. In fact, there could be one on either end of the case serving as protective covers for the solar panel when not in use. That gives an immediate 3dB gain increase over one yagi.

I’ve also made an inquiry for a 4 element patch custom for L-band, just for testing. Another possibility for using as “flip” or “slide” out covers containing antennas.